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Methicillin-Resistant Staphylococcus aureus: HELP
Articles by Benjamin P. Howden
Based on 32 articles published since 2010
(Why 32 articles?)
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Between 2010 and 2020, B. P. Howden wrote the following 32 articles about Methicillin-Resistant Staphylococcus aureus.
 
+ Citations + Abstracts
Pages: 1 · 2
1 Review Vancomycin in the treatment of methicillin-resistant Staphylococcus aureus - a clinician's guide to the science informing current practice. 2015

Lee, Jean Yh / Howden, Benjamin P. ·Microbiological Diagnostic Unit Public Health Laboratory, Department of Microbiology and Immunology, The University of Melbourne at the Doherty Institute for Infection and Immunity, Parkville, 3010, Victoria, Australia. ·Expert Rev Anti Infect Ther · Pubmed #25947636.

ABSTRACT: Clinicians treating an infection assess a patient in terms of disease manifestation, causative organism and available antibiotic options with the aim of devising a therapeutic strategy under the creed of 'first, do no harm'. It is often only when treatment is failing or options are limited, as in the scenario of multidrug-resistant organisms, that consideration is given to the interplay that occurs between the microbe and the host. The emergence of Staphylococcus aureus with reduced susceptibility to vancomycin provides a prime example of these dynamic interactions. This review shall explore these concepts in relation to vancomycin for the treatment of methicillin-resistant S. aureus, with the aim of providing an informed approach to the utilization of this drug.

2 Review What's new in the treatment of serious MRSA infection? 2014

Holmes, Natasha E / Howden, Benjamin P. ·aDepartment of Infectious Diseases, Austin Centre for Infection Research, Austin Health, Heidelberg bDepartment of Microbiology and Immunology, Microbiological Diagnostic Unit, University of Melbourne at The Peter Doherty Institute for Infection and Immunity, Parkville cDepartment of Microbiology, Monash University, Clayton, Victoria, Australia. ·Curr Opin Infect Dis · Pubmed #25211361.

ABSTRACT: PURPOSE OF REVIEW: Vancomycin has been the cornerstone of treatment for methicillin-resistant Staphylococcus aureus (MRSA) infections. This review describes new MRSA-active antibiotics that have recently been introduced and highlights emerging resistance. RECENT FINDINGS: Elevations in the vancomycin minimum inhibitory concentration within the susceptible range are associated with treatment failure and mortality in the treatment of MRSA infections. Ceftaroline and ceftobiprole are anti-MRSA cephalosporins and are noninferior to comparator agents in the treatment of acute bacterial skin and skin structure infections (ABSSSIs) and pneumonia. Tedizolid is more potent than linezolid, has improved pharmacokinetics and reduced toxicity and is active against cfr-containing S. aureus. Telavancin now has approval for treatment of hospital-acquired pneumonia, and recent phase 2 trial data showed similar cure rates in S. aureus bacteremia. Dalbavancin and oritavancin are administered once weekly and are noninferior to comparators for acute bacterial skin and skin structure infections. Resistance has emerged against many new anti-MRSA antimicrobials including ceftaroline. Combination therapy of β-lactams with vancomycin or daptomycin is increasing. SUMMARY: Several new MRSA-active agents are now approved for use, although much of the data is derived from treatment of acute bacterial skin and skin structure infections or pneumonia. Further studies are required for more invasive infections, such as bacteremia and endocarditis.

3 Review Vancomycin therapeutics and monitoring: a contemporary approach. 2013

Avent, M L / Vaska, V L / Rogers, B A / Cheng, A C / van Hal, S J / Holmes, N E / Howden, B P / Paterson, D L. ·UQ Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia. m.avent@uq.edu.au ·Intern Med J · Pubmed #23185970.

ABSTRACT: Vancomycin remains a clinically useful antibiotic despite the advent of several alternative drugs. Optimising vancomycin therapy with therapeutic drug monitoring is widely recommended. The aim of therapeutic drug monitoring is to help the clinician to achieve target pharmacodynamic parameters in the case of vancomycin, an area under the concentration time curve/minimum inhibitory concentration ratio of ≥400. Vancomycin monitoring methods can be categorised into four categories: empiric trough concentrations; linear regression analysis (one-compartment model), population methods and Bayesian estimation procedures. Although the empiric trough concentrations and population methods are easy to use and require minimal resources, there are large differences in the published vancomycin model parameters. This demonstrates that there is great variance in pharmacokinetic parameters between the models and a single vancomycin model cannot be applied to all patient populations. The linear regression and Bayesian methods recommended more accurate dosage regimens; however, they require additional resources such as information technology and healthcare personnel with background training in pharmacokinetics. The Bayesian methods offered additional advantages such as calculation of doses based on a single-serum concentration and optimisation of the patient's previous pharmacokinetic data to determine subsequent dosage regimens. Computerised programs, utilising the Bayesian estimation procedures, are able to achieve target concentrations in a greater percentage of patients earlier in the course of therapy than the empiric trough concentrations and population methods. We recommend the use of these programs providing there is appropriate expertise available to make appropriate recommendations.

4 Review Antimicrobial resistance: Not community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA)! A clinician's guide to community MRSA - its evolving antimicrobial resistance and implications for therapy. 2011

Chua, Kyra / Laurent, Frederic / Coombs, Geoffrey / Grayson, M Lindsay / Howden, Benjamin P. ·Infectious Diseases, Austin Health, Heidelberg, Victoria, Australia. ·Clin Infect Dis · Pubmed #21148528.

ABSTRACT: There is significant diversity in methicillin-resistant Staphylococcus aureus (MRSA) clones arising in the community worldwide, with considerable geographical differences in typical antimicrobial resistance profiles. Many community clones of MRSA have a non-multidrug resistant antimicrobial profile, providing increased options for empirical and directed therapy of infections caused by these strains. However, the recent description of increasing non-β lactam resistance in community clones of MRSA, especially USA300, provides a timely warning for clinicians making decisions about therapy for patients potentially infected with these strains. Continued monitoring of global epidemiology and emerging drug resistance data is critical for the effective management of these infections.

5 Article Effect of Vancomycin or Daptomycin With vs Without an Antistaphylococcal β-Lactam on Mortality, Bacteremia, Relapse, or Treatment Failure in Patients With MRSA Bacteremia: A Randomized Clinical Trial. 2020

Tong, Steven Y C / Lye, David C / Yahav, Dafna / Sud, Archana / Robinson, J Owen / Nelson, Jane / Archuleta, Sophia / Roberts, Matthew A / Cass, Alan / Paterson, David L / Foo, Hong / Paul, Mical / Guy, Stephen D / Tramontana, Adrian R / Walls, Genevieve B / McBride, Stephen / Bak, Narin / Ghosh, Niladri / Rogers, Benjamin A / Ralph, Anna P / Davies, Jane / Ferguson, Patricia E / Dotel, Ravindra / McKew, Genevieve L / Gray, Timothy J / Holmes, Natasha E / Smith, Simon / Warner, Morgyn S / Kalimuddin, Shirin / Young, Barnaby E / Runnegar, Naomi / Andresen, David N / Anagnostou, Nicholas A / Johnson, Sandra A / Chatfield, Mark D / Cheng, Allen C / Fowler, Vance G / Howden, Benjamin P / Meagher, Niamh / Price, David J / van Hal, Sebastiaan J / O'Sullivan, Matthew V N / Davis, Joshua S / Anonymous3491127. ·Victorian Infectious Disease Service, Royal Melbourne Hospital, and University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia. · Menzies School of Health Research, Charles Darwin University, Casuarina, Northern Territory, Australia. · National Centre for Infectious Diseases, Singapore. · Institute of Infectious Diseases and Epidemiology, Tan Tock Seng Hospital, Singapore. · Yong Loo Lin School of Medicine, National University of Singapore, Singapore. · Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore. · Rabin Medical Center, Beilinson Hospital, Petah Tikva, Israel. · Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel. · Nepean Clinical School, University of Sydney, Sydney, New South Wales, Australia. · Nepean Hospital, Kingswood, New South Wales, Australia. · Royal Perth Hospital, Perth, Western Australia, Australia. · Fiona Stanley Hospital, Murdoch, Western Australia, Australia. · Pathwest Laboratory Medicine WA, Murdoch, Western Australia, Australia. · Antimicrobial Resistance and Infectious Diseases Research Laboratory, School of Veterinary and Life Sciences, Murdoch University, Murdoch, Western Australia, Australia. · Division of Infectious Diseases, National University Hospital, Singapore. · Department of Medicine, National University of Singapore, Singapore. · Australasian Kidney Trials Network, University of Queensland, Brisbane, Australia. · Eastern Health Clinical School, Monash University, Box Hill, Victoria, Australia. · Centre for Clinical Research, University of Queensland, Herston, Australia. · Department of Microbiology and Infectious Diseases, NSW Health Pathology, Liverpool, New South Wales, Australia. · Rambam Health Care Campus, Haifa, Israel. · Technion-Israel Institute of Technology, Haifa, Israel. · Footscray Hospital, Western Health, Footscray, Victoria, Australia. · Department of Infectious Diseases, Middlemore Hospital, Auckland, New Zealand. · Royal Adelaide Hospital, Adelaide, South Australia, Australia. · Wollongong Public Hospital, Wollongong, New South Wales, Australia. · School of Clinical Sciences at Monash Health, Monash University, Clayton, Victoria, Australia. · Monash Infectious Diseases, Monash Medical Centre, Clayton, Victoria, Australia. · Division of Medicine, Royal Darwin Hospital, Tiwi, Northern Territory, Australia. · Department of Infectious Diseases, Blacktown Hospital, Blacktown, New South Wales, Australia. · Centre for Infectious Diseases and Microbiology, Westmead Hospital, University of Sydney, Sydney, New South Wales, Australia. · Department of Microbiology and Infectious Diseases, Concord Repatriation General Hospital, Concord, New South Wales, Australia. · Faculty of Medicine and Health, University of Sydney, Sydney, New South Wales, Australia. · Department of Infectious Diseases, Austin Health, Austin Centre for Infection Research, Heidelberg, Victoria, Australia. · Cairns Hospital, Cairns, Queensland, Australia. · The Queen Elizabeth Hospital, Woodville, South Australia, Australia. · University of Adelaide, Adelaide, South Australia, Australia. · Department of Infectious Diseases, Singapore General Hospital, Singapore. · Duke-NUS Medical School, Singapore. · Infection Management Services, Princess Alexandra Hospital, Brisbane, Queensland, Australia. · Southern Clinical School, Faculty of Medicine, University of Queensland, Brisbane, Australia. · St Vincent's Public Hospital Sydney, Darlinghurst, New South Wales, Australia. · School of Medicine, University of Notre Dame, Darlinghurst, New South Wales, Australia. · Flinders Medical Centre, Adelaide, South Australia, Australia. · School of Public Health and Preventive Medicine, Monash University, Melbourne, Victoria, Australia. · Infection Prevention and Healthcare Epidemiology Unit, Alfred Health, Melbourne, Victoria, Australia. · Division of Infectious Diseases, Department of Medicine, Duke University Medical Center, Durham, North Carolina. · Duke Clinical Research Institute, Duke University Medical Center, Durham, North Carolina. · Microbiological Diagnostic Unit Public Health Laboratory, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia. · Victorian Infectious Diseases Reference Laboratory Epidemiology Unit, Royal Melbourne Hospital, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia. · Centre for Epidemiology and Biostatistics, University of Melbourne, Melbourne, Victoria, Australia. · Department of Microbiology and Infectious Disease, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia. · New South Wales Health Pathology, Westmead Hospital, Westmead, Australia. · Department of Infectious Diseases, John Hunter Hospital, Newcastle, New South Wales, Australia. ·JAMA · Pubmed #32044943.

ABSTRACT: Importance: Methicillin-resistant Staphylococcus aureus (MRSA) bacteremia is associated with mortality of more than 20%. Combining standard therapy with a β-lactam antibiotic has been associated with reduced mortality, although adequately powered randomized clinical trials of this intervention have not been conducted. Objective: To determine whether combining an antistaphylococcal β-lactam with standard therapy is more effective than standard therapy alone in patients with MRSA bacteremia. Design, Setting, and Participants: Open-label, randomized clinical trial conducted at 27 hospital sites in 4 countries from August 2015 to July 2018 among 352 hospitalized adults with MRSA bacteremia. Follow-up was complete on October 23, 2018. Interventions: Participants were randomized to standard therapy (intravenous vancomycin or daptomycin) plus an antistaphylococcal β-lactam (intravenous flucloxacillin, cloxacillin, or cefazolin) (n = 174) or standard therapy alone (n = 178). Total duration of therapy was determined by treating clinicians and the β-lactam was administered for 7 days. Main Outcomes and Measures: The primary end point was a 90-day composite of mortality, persistent bacteremia at day 5, microbiological relapse, and microbiological treatment failure. Secondary outcomes included mortality at days 14, 42, and 90; persistent bacteremia at days 2 and 5; acute kidney injury (AKI); microbiological relapse; microbiological treatment failure; and duration of intravenous antibiotics. Results: The data and safety monitoring board recommended early termination of the study prior to enrollment of 440 patients because of safety. Among 352 patients randomized (mean age, 62.2 [SD, 17.7] years; 121 women [34.4%]), 345 (98%) completed the trial. The primary end point was met by 59 (35%) with combination therapy and 68 (39%) with standard therapy (absolute difference, -4.2%; 95% CI, -14.3% to 6.0%). Seven of 9 prespecified secondary end points showed no significant difference. For the combination therapy vs standard therapy groups, all-cause 90-day mortality occurred in 35 (21%) vs 28 (16%) (difference, 4.5%; 95% CI, -3.7% to 12.7%); persistent bacteremia at day 5 was observed in 19 of 166 (11%) vs 35 of 172 (20%) (difference, -8.9%; 95% CI, -16.6% to -1.2%); and, excluding patients receiving dialysis at baseline, AKI occurred in 34 of 145 (23%) vs 9 of 145 (6%) (difference, 17.2%; 95% CI, 9.3%-25.2%). Conclusions and Relevance: Among patients with MRSA bacteremia, addition of an antistaphylococcal β-lactam to standard antibiotic therapy with vancomycin or daptomycin did not result in significant improvement in the primary composite end point of mortality, persistent bacteremia, relapse, or treatment failure. Early trial termination for safety concerns and the possibility that the study was underpowered to detect clinically important differences in favor of the intervention should be considered when interpreting the findings. Trial Registration: ClinicalTrials.gov Identifier: NCT02365493.

6 Article Australia's response to the global threat of antimicrobial resistance: past, present and future. 2019

Davis, Joshua S / Jones, Cheryl A / Cheng, Allen C / Howden, Benjamin P. ·Menzies School of Health Research, Darwin, NT. · John Hunter Hospital, Newcastle, NSW. · University of Sydney, Sydney, NSW. · Monash University, Melbourne, VIC. · Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, VIC. · Austin Health, Melbourne, VIC. ·Med J Aust · Pubmed #31313300.

ABSTRACT: -- No abstract --

7 Article Antibiotic resistance and host immune evasion in 2019

Jiang, Jhih-Hang / Bhuiyan, Md Saruar / Shen, Hsin-Hui / Cameron, David R / Rupasinghe, Thusitha W T / Wu, Chun-Ming / Le Brun, Anton P / Kostoulias, Xenia / Domene, Carmen / Fulcher, Alex J / McConville, Malcolm J / Howden, Benjamin P / Lieschke, Graham J / Peleg, Anton Y. ·Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, VIC 3800, Australia. · Department of Materials Science and Engineering, Faculty of Engineering, Monash University, Clayton, VIC 3800, Australia. · Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC 3800, Australia. · Metabolomics Australia, Bio21 Institute of Molecular Science and Biotechnology, Parkville, VIC 3010, Australia. · Scientific Research Division, National Synchrotron Radiation Research Center, 30076 Hsinchu, Taiwan. · Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Kirrawee DC, NSW 2232, Australia. · Department of Chemistry, University of Bath, Claverton Down, BA2 7AY Bath, United Kingdom. · Chemistry Research Laboratory, University of Oxford, OX1 3TA Oxford, United Kingdom. · Monash Micro Imaging, Monash University, Clayton, VIC 3100, Australia. · Department of Biochemistry and Molecular Biology, Bio21 Institute of Molecular Science and Biotechnology, The University of Melbourne, Parkville, VIC 3010, Australia. · Microbiological Diagnostic Unit Public Health Laboratory, Department of Microbiology and Immunology, The University of Melbourne at The Doherty Institute for Infection and Immunity, Melbourne, VIC 3000, Australia. · Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia. · Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, VIC 3800, Australia; anton.peleg@monash.edu. · Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Melbourne, VIC 3004, Australia. ·Proc Natl Acad Sci U S A · Pubmed #30808758.

ABSTRACT:

8 Article Daptomycin selects for genetic and phenotypic adaptations leading to antibiotic tolerance in MRSA. 2018

Berti, Andrew D / Shukla, Neehal / Rottier, Aaron D / McCrone, J Sue / Turner, Hannah M / Monk, Ian R / Baines, Sarah L / Howden, Benjamin P / Proctor, Richard A / Rose, Warren E. ·Pharmacy Practice Division, University of Wisconsin-Madison, Madison, WI, USA. · Department of Pharmacy Practice, Wayne State University, Detroit, MI, USA. · Doherty Applied Microbial Genomics, Department of Microbiology and Immunology, The University of Melbourne at the Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia. · Microbiological Diagnostic Unit Public Health Laboratory, Department of Microbiology and Immunology, The University of Melbourne at the Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia. · Infectious Diseases Department, Austin Health, Melbourne, Victoria, Australia. · Department of Medicine, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, USA. · Department of Medical Microbiology/Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, USA. ·J Antimicrob Chemother · Pubmed #29718242.

ABSTRACT: Objectives: Daptomycin non-susceptibility in Staphylococcus aureus can emerge via the accumulation of single or multiple mutations, each resulting in a slight increase in the daptomycin MIC. The daptomycin-non-susceptible phenotype may include other features such as daptomycin tolerance. This study identifies S. aureus genomic regions that frequently develop mutations following prolonged daptomycin exposure but have not been previously associated with daptomycin non-susceptibility. Methods: Sequence variations in the same eight loci independently observed following 28 day parallel serial passages of S. aureus J01 in daptomycin were introduced in isolation into S. aureus J01. MICs were determined by microbroth dilution. Daptomycin killing and tolerance were determined by kill curve analysis. Results: Single mutations in snoF, hmp1, sspA, rimP, hepT, rsh, map1 and amaP had only a modest impact on the daptomycin MIC (≤2-fold). In contrast, individual mutation in several of these regions resulted in pronounced changes to daptomycin tolerance. Conclusions: This study demonstrates that less characterized mutations in S. aureus following daptomycin exposure do not result in significant daptomycin susceptibility changes, but rather allow for enhanced survival characteristics during treatment. This sheds new light on genetic adaptations that may play a role in persistent infection. Further studies are needed to elucidate the prevalence of these mutations in clinical isolates.

9 Article Mobile phones and computer keyboards: unlikely reservoirs of multidrug-resistant organisms in the tertiary intensive care unit. 2018

Smibert, O C / Aung, A K / Woolnough, E / Carter, G P / Schultz, M B / Howden, B P / Seemann, T / Spelman, D / McGloughlin, S / Peleg, A Y. ·Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Melbourne, Victoria, Australia. Electronic address: oliviasmibert@gmail.com. · Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Melbourne, Victoria, Australia. · Melbourne Diagnostic Unit, Doherty Institute, University of Melbourne, Victoria, Australia. · Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Melbourne, Victoria, Australia; Infection and Immunity Program, Biomedicine Discovery Institute, Department of Microbiology, Monash University, Clayton, Victoria, Australia. ·J Hosp Infect · Pubmed #29501730.

ABSTRACT: Few studies have used molecular epidemiological methods to study transmission links to clinical isolates in intensive care units. Ninety-four multidrug-resistant organisms (MDROs) cultured from routine specimens from intensive care unit (ICU) patients over 13 weeks were stored (11 meticillin-resistant Staphylococcus aureus (MRSA), two vancomycin-resistant enterococci and 81 Gram-negative bacteria). Medical staff personal mobile phones, departmental phones, and ICU keyboards were swabbed and cultured for MDROs; MRSA was isolated from two phones. Environmental and patient isolates of the same genus were selected for whole genome sequencing. On whole genome sequencing, the mobile phone isolates had a pairwise single nucleotide polymorphism (SNP) distance of 183. However, >15,000 core genome SNPs separated the mobile phone and clinical isolates. In a low-endemic setting, mobile phones and keyboards appear unlikely to contribute to hospital-acquired MDROs.

10 Article A phylogenomic framework for assessing the global emergence and evolution of clonal complex 398 methicillin-resistant 2017

Gonçalves da Silva, Anders / Baines, Sarah L / Carter, Glen P / Heffernan, Helen / French, Nigel P / Ren, Xiaoyun / Seemann, Torsten / Bulach, Dieter / Kwong, Jason / Stinear, Timothy P / Howden, Benjamin P / Williamson, Deborah A. ·1​Doherty Applied Microbial Genomics, Department of Microbiology & Immunology, The University of Melbourne at The Doherty Institute for Infection and Immunity, Melbourne, Australia. · 2​Microbiological Diagnostic Unit Public Health Laboratory, Department of Microbiology & Immunology, The University of Melbourne at The Doherty Institute for Infection and Immunity, Melbourne, Australia. · 3​Institute of Environmental Science and Research, Wellington, New Zealand. · 4​Infectious Disease Research Centre, Massey University, Palmerston North, New Zealand. · 5​Victorian Life Sciences Computation Initiative, Melbourne, Australia. ·Microb Genom · Pubmed #28348878.

ABSTRACT: Distinct clones of methicillin-resistant

11 Article Genomic analysis of ST88 community-acquired methicillin resistant 2017

Kpeli, Grace / Buultjens, Andrew H / Giulieri, Stefano / Owusu-Mireku, Evelyn / Aboagye, Samuel Y / Baines, Sarah L / Seemann, Torsten / Bulach, Dieter / Gonçalves da Silva, Anders / Monk, Ian R / Howden, Benjamin P / Pluschke, Gerd / Yeboah-Manu, Dorothy / Stinear, Timothy. ·Department of Bacteriology, Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana; Department of Molecular Parasitology and Immunology, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland. · Department of Microbiology and Immunology, Doherty Applied Microbial Genomics, Doherty Institute for Infection and Immunity, University of Melbourne , Melbourne, VIC , Australia. · Department of Bacteriology, Noguchi Memorial Institute for Medical Research, University of Ghana , Accra , Ghana. · Department of Microbiology and Immunology, Doherty Applied Microbial Genomics, Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, VIC, Australia; University of Melbourne, Victorian Life Sciences Computation Initiative, Melbourne, VIC, Australia. · Department of Microbiology and Immunology, Doherty Applied Microbial Genomics, Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, VIC, Australia; Department of Microbiology and Immunology, Microbiological Diagnostic Unit Public Health Laboratory, Doherty Institute for Infection & Immunity, University of Melbourne, Melbourne, VIC, Australia; Department of Infectious Diseases, Austin Health, Heidelberg, VIC, Australia. · Department of Molecular Parasitology and Immunology, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland. ·PeerJ · Pubmed #28265515.

ABSTRACT: BACKGROUND: The emergence and evolution of community-acquired methicillin resistant METHODS: We first established a complete ST88 reference genome (AUS0325) using PacBio SMRT sequencing. We then used comparative genomics to assess relatedness among 17 ST88 CA-MRSA isolates recovered from patients attending Buruli ulcer treatment centres in Ghana, three non-African ST88s and 15 other MRSA lineages. RESULTS: We show that Ghanaian ST88 forms a discrete MRSA lineage (harbouring SCC DISCUSSION: This study reveals that

12 Article Australian Group on Antimicrobial Resistance Australian Staphylococcus aureus Sepsis Outcome Programme annual report, 2014. 2016

Coombs, Geoffrey W / Daley, Denise A / Thin Lee, Yung / Pearson, Julie C / Robinson, J Owen / Nimmo, Graeme R / Collignon, Peter / Howden, Benjamin P / Bell, Jan M / Turnidge, John D / Anonymous1760878. ·Australian Collaborating Centre for Enterococcus and Staphylococcus Species (ACCESS) Typing and Research, School of Veterinary and Life Sciences, Murdoch University, Murdoch, Western Australia. · Department of Microbiology and Infectious Diseases, PathWest Laboratory Medicine-WA, Fiona Stanley Hospital, Murdoch, Western Australia. · Australian Group on Antimicrobial Resistance, Fiona Stanley Hospital, Murdoch, Western Australia. · Division of Microbiology, Pathology Queensland Central Laboratory, Queensland. · Griffith University School of Medicine, Gold Coast, Queensland. · Department of Microbiology and Infectious Diseases, The Canberra Hospital, Australian Capital Territory. · School of Clinical Medicine, Australian National University, Australian Capital Territory. · Microbiological Diagnostic Unit Public Health Laboratory, Department of Microbiology and Immunology, The University of Melbourne at the Doherty Institute for Infection and Immunity, Victoria. · SA Pathology, Department of Microbiology and Infectious Diseases, Women's and Children's Hospital, North Adelaide, South Australia. · Departments of Pathology, Paediatrics and Molecular and Biomedical Sciences, University of Adelaide, Adelaide, South Australia. ·Commun Dis Intell Q Rep · Pubmed #27522136.

ABSTRACT: From 1 January to 31 December 2014, 27 institutions around Australia participated in the Australian Staphylococcal Sepsis Outcome Programme (ASSOP). The aim of ASSOP 2014 was to determine the proportion of Staphylococcus aureus bacteraemia (SAB) isolates in Australia that are antimicrobial resistant, with particular emphasis on susceptibility to methicillin and to characterise the molecular epidemiology of the isolates. Overall, 18.8% of the 2,206 SAB episodes were methicillin resistant, which was significantly higher than that reported in most European countries. The 30-day all-cause mortality associated with methicillin-resistant SAB was 23.4%, which was significantly higher than the 14.4% mortality associated with methicillin-sensitive SAB (P <0.0001). With the exception of the beta-lactams and erythromycin, antimicrobial resistance in methicillin-sensitive S. aureus remains rare. However in addition to the beta-lactams, approximately 50‰ of methicillin-resistant S. aureus (MRSA) were resistant to erythromycin and ciprofloxacin and approximately 15% were resistant to co-trimoxazole, tetracycline and gentamicin. When applying the European Committee on Antimicrobial Susceptibility Testing breakpoints, teicoplanin resistance was detected in 2 S. aureus isolates. Resistance was not detected for vancomycin or linezolid. Resistance to non-beta-lactam antimicrobials was largely attributable to 2 healthcare-associated MRSA clones; ST22-IV [2B] (EMRSA-15) and ST239-III [3A] (Aus-2/3 EMRSA). ST22-IV [2B] (EMRSA-15) has become the predominant healthcare associated clone in Australia. Sixty per cent of methicillin-resistant SAB were due to community-associated (CA) clones. Although polyclonal, almost 44% of community-associated clones were characterised as ST93-IV [2B] (Queensland CA-MRSA) and ST1-IV [2B] (WA1). CA-MRSA, in particular the ST45-V [5C2&5] (WA84) clone, has acquired multiple antimicrobial resistance determinants including ciprofloxacin, erythromycin, clindamycin, gentamicin and tetracycline. As CA-MRSA is well established in the Australian community it is important that antimicrobial resistance patterns in community and healthcare-associated SAB is monitored as this information will guide therapeutic practices in treating S. aureus sepsis.

13 Article CAMERA2 - combination antibiotic therapy for methicillin-resistant Staphylococcus aureus infection: study protocol for a randomised controlled trial. 2016

Tong, Steven Y C / Nelson, Jane / Paterson, David L / Fowler, Vance G / Howden, Benjamin P / Cheng, Allen C / Chatfield, Mark / Lipman, Jeffrey / Van Hal, Sebastian / O'Sullivan, Matthew / Robinson, James O / Yahav, Dafna / Lye, David / Davis, Joshua S / Anonymous10000863. ·Menzies School of Health Research, Charles Darwin University, Darwin, NT, Australia. · Royal Darwin Hospital, Darwin, NT, Australia. · University of Queensland, Centre for Clinical Research, Herston, QLD, Australia. · Division of Infectious Diseases, Department of Medicine, Duke University Medical Center, Durham, NC, USA. · Duke Clinical Research Institute, Duke University Medical Center, Durham, NC, USA. · Microbiological Diagnostic Unit Public Health Laboratory, The University of Melbourne, at The Doherty Institute, Melbourne, VIC, Australia. · Infection Prevention and Healthcare Epidemiology Unit, Alfred Health, Melbourne, VIC, Australia. · Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, VIC, Australia. · Burns, Trauma Critical Care Research Centre, The University of Queensland, Brisbane, QLD, Australia. · Faculty of Health, Queensland University of Technology, Brisbane, QLD, Australia. · Department of Microbiology and Infectious Disease Royal Prince Alfred Hospital, Sydney, NSW, Australia. · Centre for Infectious Diseases and Microbiology, Westmead Hospital, Sydney, NSW, Australia. · Marie Bashir Institute for Infectious Diseases and Biosecurity, University of Sydney, Sydney, NSW, Australia. · Department of Microbiology and Infectious Diseases, Pathwest Laboratory Medicine WA, Royal Perth Hospital and Fiona Stanley Hospital, Perth, WA, Australia. · Australian Collaborating Centre for Enterococcus and Staphylococcus Species (ACCESS) Typing and Research, School of Veterinary and Life Sciences, Murdoch University, Perth, WA, Australia. · Faculty of Medicine, Tel Aviv University, Ramat Aviv, Israel. · Rabin Medical Center, Petah Tikvah, Israel. · Institute of Infectious Diseases and Epidemiology, Tan Tock Seng Hospital, Singapore, Singapore. · Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. · Menzies School of Health Research, Charles Darwin University, Darwin, NT, Australia. Joshua.Davis@menzies.edu.au. · John Hunter Hospital, Newcastle, NSW, Australia. Joshua.Davis@menzies.edu.au. ·Trials · Pubmed #27029920.

ABSTRACT: BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia is a serious infection resulting in 20-50 % 90-day mortality. The limitations of vancomycin, the current standard therapy for MRSA, make treatment difficult. The only other approved drug for treatment of MRSA bacteraemia, daptomycin, has not been shown to be superior to vancomycin. Surprisingly, there has been consistent in-vitro and in-vivo laboratory data demonstrating synergy between vancomycin or daptomycin and an anti-staphylococcal β-lactam antibiotic. There is also growing clinical data to support such combinations, including a recent pilot randomised controlled trial (RCT) that demonstrated a trend towards a reduction in the duration of bacteraemia in patients treated with vancomycin plus flucloxacillin compared to vancomycin alone. Our aim is to determine whether the addition of an anti-staphylococcal penicillin to standard therapy results in improved clinical outcomes in MRSA bacteraemia. METHODS/DESIGN: We will perform an open-label, parallel-group, randomised (1:1) controlled trial at 29 sites in Australia, New Zealand, Singapore, and Israel. Adults (aged 18 years or older) with MRSA grown from at least one blood culture and able to be randomised within 72 hours of the index blood culture collection will be eligible for inclusion. Participants will be randomised to vancomycin or daptomycin (standard therapy) given intravenously or to standard therapy plus 7 days of an anti-staphylococcal β-lactam (flucloxacillin, cloxacillin, or cefazolin). The primary endpoint will be a composite outcome at 90 days of (1) all-cause mortality, (2) persistent bacteraemia at day 5 or beyond, (3) microbiological relapse, or (4) microbiological treatment failure. The recruitment target of 440 patients is based on an expected failure rate for the primary outcome of 30 % in the control arm and the ability to detect a clinically meaningful absolute decrease of 12.5 %, with a two-sided alpha of 0.05, a power of 80 %, and assuming 10 % of patients will not be evaluable for the primary endpoint. DISCUSSION: Key potential advantages of adding anti-staphylococcal β-lactams to standard therapy for MRSA bacteraemia include their safety profile, low cost, and wide availability. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02365493 . Registered 24 February 2015.

14 Article Combination of Vancomycin and β-Lactam Therapy for Methicillin-Resistant Staphylococcus aureus Bacteremia: A Pilot Multicenter Randomized Controlled Trial. 2016

Davis, Joshua S / Sud, Archana / O'Sullivan, Matthew V N / Robinson, James O / Ferguson, Patricia E / Foo, Hong / van Hal, Sebastiaan J / Ralph, Anna P / Howden, Benjamin P / Binks, Paula M / Kirby, Adrienne / Tong, Steven Y C / Anonymous8210841 / Anonymous8220841 / Tong, Steven / Davis, Joshua / Binks, Paula / Majumdar, Suman / Ralph, Anna / Baird, Rob / Gordon, Claire / Jeremiah, Cameron / Leung, Grace / Brischetto, Anna / Crowe, Amy / Dakh, Farshid / Whykes, Kelly / Kirkwood, Maria / Sud, Archana / Menon, Mahesh / Somerville, Lucy / Subedi, Shrada / Owen, Shirley / O'Sullivan, Matthew / Liu, Eunice / Zhou, Fei / Robinson, Owen / Coombs, Geoffrey / Ferguson, Patrician / Ralph, Anna / Liu, Eunice / Pollet, Simon / Van Hal, Sebastian / Foo, Hong / Van Hal, Sebastian / Davis, Rebecca. ·Global and Tropical Health Division, Menzies School of Health Research. · Department of Infectious Diseases, John Hunter Hospital, Newcastle. · Department of Infectious Diseases, Nepean Hospital and University of Sydney. · Marie Bashir Institute for Infectious Diseases and Biosecurity, University of Sydney. · Centre for Infectious Diseases and Microbiology, Westmead Hospital. · Department of Microbiology and Infectious Diseases, PathWest Laboratory Medicine WA, Royal Perth Hospital and Fiona Stanley Hospital. · Australian Collaborating Centre for Enterococcus and Staphylococcus Species (ACCESS) Typing and Research, School of Veterinary and Life Sciences, Murdoch University and School of Biomedical Sciences, Curtin University, Perth, Western Australia. · Department of Infectious Diseases, Blacktown Hospital. · Department of Microbiology and Infectious Diseases, Liverpool Hospital. · Department Microbiology and Infectious Diseases, Royal Prince Alfred Hospital, Sydney, New South Wales. · Department of Infectious Diseases, Royal Darwin Hospital, Darwin, Northern Territory. · Department of Microbiology and Immunology, Microbiological Diagnostic Unit, The University of Melbourne at the Doherty Institute for Infection and Immunity. · Departments of Microbiology and Infectious Diseases, Austin Health. · Department of Microbiology, Monash University, Melbourne, Victoria, Australia. · National Health and Medical Research Council Clinical Trials Centre, University of Sydney. ·Clin Infect Dis · Pubmed #26349552.

ABSTRACT: BACKGROUND: In vitro laboratory and animal studies demonstrate a synergistic role for the combination of vancomycin and antistaphylococcal β-lactams for methicillin-resistant Staphylococcus aureus (MRSA) bacteremia. Prospective clinical data are lacking. METHODS: In this open-label, multicenter, clinical trial, adults with MRSA bacteremia received vancomycin 1.5 g intravenously twice daily and were randomly assigned (1:1) to receive intravenous flucloxacillin 2 g every 6 hours for 7 days (combination group) or no additional therapy (standard therapy group). Participants were stratified by hospital and randomized in permuted blocks of variable size. Randomization codes were kept in sealed, sequentially numbered, opaque envelopes. The primary outcome was the duration of MRSA bacteremia in days. RESULTS: We randomly assigned 60 patients to receive vancomycin (n = 29), or vancomycin plus flucloxacillin (n = 31). The mean duration of bacteremia was 3.00 days in the standard therapy group and 1.94 days in the combination group. According to a negative binomial model, the mean time to resolution of bacteremia in the combination group was 65% (95% confidence interval, 41%-102%; P = .06) that in the standard therapy group. There was no difference in the secondary end points of 28- and 90-day mortality, metastatic infection, nephrotoxicity, or hepatotoxicity. CONCLUSIONS: Combining an antistaphylococcal β-lactam with vancomycin may shorten the duration of MRSA bacteremia. Further trials with a larger sample size and objective clinically relevant end points are warranted. Australian New Zealand Clinical Trials Registry: ACTRN12610000940077 (www.anzctr.org.au).

15 Article Convergent adaptation in the dominant global hospital clone ST239 of methicillin-resistant Staphylococcus aureus. 2015

Baines, Sarah L / Holt, Kathryn E / Schultz, Mark B / Seemann, Torsten / Howden, Brian O / Jensen, Slade O / van Hal, Sebastiaan J / Coombs, Geoffrey W / Firth, Neville / Powell, David R / Stinear, Timothy P / Howden, Benjamin P. ·Department of Biochemistry and Molecular Biology, Bio 21, Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, Victoria, Australia. · Microbiological Diagnostic Unit Public Health Laboratory, Department of Microbiology & Immunology, The University of Melbourne at The Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia. · Microbiology and Infectious Diseases, School of Medicine, Ingham Institute for Applied Medical Research, University of Western Sydney, Sydney, New South Wales, Australia. · School of Biological Sciences, University of Sydney, Sydney, New South Wales, Australia. · bhowden@unimelb.edu.au. ·mBio · Pubmed #25736880.

ABSTRACT: IMPORTANCE: Methicillin-resistant Staphylococcus aureus (MRSA) is responsible for innumerable drug-resistant health care-associated infections globally. This study, the first to investigate the evolutionary response of hospital-associated MRSA (HA-MRSA) over many decades, demonstrates how MRSA can persist in a region through the reintroduction of a previously unrecognized distinct clade. This study also demonstrates the crucial adaptive responses of HA-MRSA to the highly selective environment of the health care system, the evolution of MRSA isolates to even higher levels of antibiotic resistance at the cost of attenuated virulence. However, in vivo persistence is maintained, resulting in a clone of HA-MRSA able to resist almost all antimicrobial agents and still cause invasive disease in the heavily compromised hosts found in modern health care settings.

16 Article Hyperexpression of α-hemolysin explains enhanced virulence of sequence type 93 community-associated methicillin-resistant Staphylococcus aureus. 2014

Chua, Kyra Y L / Monk, Ian R / Lin, Ya-Hsun / Seemann, Torsten / Tuck, Kellie L / Porter, Jessica L / Stepnell, Justin / Coombs, Geoffrey W / Davies, John K / Stinear, Timothy P / Howden, Benjamin P. ·Department of Microbiology and Immunology, University of Melbourne, Melbourne, Victoria 3052, Australia. benjamin.howden@austin.org.au. ·BMC Microbiol · Pubmed #24512075.

ABSTRACT: BACKGROUND: The community-associated methicillin-resistant S. aureus (CA-MRSA) ST93 clone is becoming dominant in Australia and is clinically highly virulent. In addition, sepsis and skin infection models demonstrate that ST93 CA-MRSA is the most virulent global clone of S. aureus tested to date. While the determinants of virulence have been studied in other clones of CA-MRSA, the basis for hypervirulence in ST93 CA-MRSA has not been defined. RESULTS: Here, using a geographically and temporally dispersed collection of ST93 isolates we demonstrate that the ST93 population hyperexpresses key CA-MRSA exotoxins, in particular α-hemolysin, in comparison to other global clones. Gene deletion and complementation studies, and virulence comparisons in a murine skin infection model, showed unequivocally that increased expression of α-hemolysin is the key staphylococcal virulence determinant for this clone. Genome sequencing and comparative genomics of strains with divergent exotoxin profiles demonstrated that, like other S. aureus clones, the quorum sensing agr system is the master regulator of toxin expression and virulence in ST93 CA-MRSA. However, we also identified a previously uncharacterized AraC/XylS family regulator (AryK) that potentiates toxin expression and virulence in S. aureus. CONCLUSIONS: These data demonstrate that hyperexpression of α-hemolysin mediates enhanced virulence in ST93 CA-MRSA, and additional control of exotoxin production, in particular α-hemolysin, mediated by regulatory systems other than agr have the potential to fine-tune virulence in CA-MRSA.

17 Article Adaptive change inferred from genomic population analysis of the ST93 epidemic clone of community-associated methicillin-resistant Staphylococcus aureus. 2014

Stinear, Timothy P / Holt, Kathryn E / Chua, Kyra / Stepnell, Justin / Tuck, Kellie L / Coombs, Geoffrey / Harrison, Paul Francis / Seemann, Torsten / Howden, Benjamin P. ·Department of Microbiology and Immunology, University of Melbourne, Victoria, Australia. ·Genome Biol Evol · Pubmed #24482534.

ABSTRACT: Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has emerged as a major public health problem around the world. In Australia, ST93-IV[2B] is the dominant CA-MRSA clone and displays significantly greater virulence than other S. aureus. Here, we have examined the evolution of ST93 via genomic analysis of 12 MSSA and 44 MRSA ST93 isolates, collected from around Australia over a 17-year period. Comparative analysis revealed a core genome of 2.6 Mb, sharing greater than 99.7% nucleotide identity. The accessory genome was 0.45 Mb and comprised additional mobile DNA elements, harboring resistance to erythromycin, trimethoprim, and tetracycline. Phylogenetic inference revealed a molecular clock and suggested that a single clone of methicillin susceptible, Panton-Valentine leukocidin (PVL) positive, ST93 S. aureus likely spread from North Western Australia in the early 1970s, acquiring methicillin resistance at least twice in the mid 1990s. We also explored associations between genotype and important MRSA phenotypes including oxacillin MIC and production of exotoxins (α-hemolysin [Hla], δ-hemolysin [Hld], PSMα3, and PVL). High-level expression of Hla is a signature feature of ST93 and reduced expression in eight isolates was readily explained by mutations in the agr locus. However, subtle but significant decreases in Hld were also noted over time that coincided with decreasing oxacillin resistance and were independent of agr mutations. The evolution of ST93 S. aureus is thus associated with a reduction in both exotoxin expression and oxacillin MIC, suggesting MRSA ST93 isolates are under pressure for adaptive change.

18 Article Antibiotics and Staphylococcus aureus--more than meets the MIC. 2014

Howden, Benjamin P. ·Austin Centre for Infection Research (ACIR), Infections Diseases Department, and Department of Microbiology, Austin Health, Heidelberg, Melbourne, Australia, Benjamin.Howden@austin.org.au. ·J Mol Med (Berl) · Pubmed #24337505.

ABSTRACT: -- No abstract --

19 Article Community-onset Staphylococcus aureus infections presenting to general practices in South-eastern Australia. 2014

Bennett, C M / Coombs, G W / Wood, G M / Howden, B P / Johnson, L E A / White, D / Johnson, P D R. ·The University of Melbourne, Melbourne, Australia. · Department of Microbiology and Infectious Diseases, PathWest Laboratory Medicine-WA, Royal Perth Hospital, Australia. · Austin Health, Melbourne, Australia. ·Epidemiol Infect · Pubmed #23866772.

ABSTRACT: Community-acquired Staphylococcus aureus infections are a public health concern, yet little is known about infections that do not present to hospital. We identified community-onset S. aureus infections via specimens submitted to a community-based pathology service. Referring doctors confirmed eligibility and described infection site, severity and treatment. Isolates were characterized on antibiotic resistance, PFGE, MLST/SCCmec, and Panton-Valentine leukocidin (PVL), representing 106 community-onset infections; 34 non-multiresistant methicillin-resistant S. aureus (nmMRSA) (resistant to <3 non-β-lactam antibiotics), 15 multiply antibiotic-resistant MRSA (mMRSA) and 57 methicillin-sensitive S. aureus (MSSA). Most (93%) were skin and soft tissue infections. PVL genes were carried by 42% of nmMRSA isolates [95% confidence interval (CI) 26-61] and 15% of MSSA (95% CI 8-28). PVL was associated with infections of the trunk, head or neck (56·4% vs. 24·3%, P=0·005) in younger patients (23 vs. 52 years, P<0·001), and with boils or abscesses (OR 8·67, 95% CI 2·9-26·2), suggesting underlying differences in exposure and/or pathogenesis.

20 Article Analysis of the small RNA transcriptional response in multidrug-resistant Staphylococcus aureus after antimicrobial exposure. 2013

Howden, Benjamin P / Beaume, Marie / Harrison, Paul F / Hernandez, David / Schrenzel, Jacques / Seemann, Torsten / Francois, Patrice / Stinear, Timothy P. ·Austin Centre for Infection Research, Infectious Diseases Department, Austin Health, Heidelberg, Victoria, Australia. Benjamin.Howden@austin.org.au ·Antimicrob Agents Chemother · Pubmed #23733475.

ABSTRACT: The critical role of noncoding small RNAs (sRNAs) in the bacterial response to changing conditions is increasingly recognized. However, a specific role for sRNAs during antibiotic exposure has not been investigated in Staphylococcus aureus. Here, we used Illumina RNA-Seq to examine the sRNA response of multiresistant sequence type 239 (ST239) S. aureus after exposure to four antibiotics (vancomycin, linezolid, ceftobiprole, and tigecycline) representing the major classes of antimicrobials used to treat methicillin-resistant S. aureus (MRSA) infections. We identified 409 potential sRNAs and then compared global sRNA and mRNA expression profiles at 2 and 6 h, without antibiotic exposure and after exposure to each antibiotic, for a vancomycin-susceptible strain (JKD6009) and a vancomycin-intermediate strain (JKD6008). Exploration of this data set by multivariate analysis using a novel implementation of nonnegative matrix factorization (NMF) revealed very different responses for mRNA and sRNA. Where mRNA responses clustered with strain or growth phase conditions, the sRNA responses were predominantly linked to antibiotic exposure, including sRNA responses that were specific for particular antibiotics. A remarkable feature of the antimicrobial response was the prominence of antisense sRNAs to genes encoding proteins involved in protein synthesis and ribosomal function. This study has defined a large sRNA repertoire in epidemic ST239 MRSA and shown for the first time that a subset of sRNAs are part of a coordinated transcriptional response to specific antimicrobial exposures in S. aureus. These data provide a framework for interrogating the role of staphylococcal sRNAs in antimicrobial resistance and exploring new avenues for sRNA-based antimicrobial therapies.

21 Article Decreased vancomycin susceptibility in Staphylococcus aureus caused by IS256 tempering of WalKR expression. 2013

McEvoy, Christopher R E / Tsuji, Brian / Gao, Wei / Seemann, Torsten / Porter, Jessica L / Doig, Kenneth / Ngo, Dung / Howden, Benjamin P / Stinear, Timothy P. ·Department of Microbiology and Immunology, University of Melbourne, Parkville, Victoria, Australia. ·Antimicrob Agents Chemother · Pubmed #23629723.

ABSTRACT: Vancomycin-intermediate Staphylococcus aureus (VISA) strains often arise by mutations in the essential two-component regulator walKR; however their impact on walKR function has not been definitively established. Here, we investigated 10 MRSA strains recovered serially after exposure of vancomycin-susceptible S. aureus (VSSA) JKD6009 to simulated human vancomycin dosing regimens (500 mg to 4,000 mg every 12 h) using a 10-day hollow fiber infection model. After continued exposure to the vancomycin regimens, two isolates displayed reduced susceptibility to both vancomycin and daptomycin, developing independent IS256 insertions in the walKR 5' untranslated region (5' UTR). Quantitative reverse transcription-PCR (RT-PCR) revealed a 50% reduction in walKR gene expression in the IS256 mutants compared to the VSSA parent. Green fluorescent protein (GFP) reporter analysis, promoter mapping, and site-directed mutagenesis confirmed these findings and showed that the IS256 insertions had replaced two SigA-like walKR promoters with weaker, hybrid promoters. Removal of IS256 reverted the phenotype to VSSA, showing that reduced expression of WalKR did induce the VISA phenotype. Analysis of selected WalKR-regulated autolysins revealed upregulation of ssaA but no change in expression of sak and sceD in both IS256 mutants. Whole-genome sequencing of the two mutants revealed an additional IS256 insertion within agrC for one mutant, and we confirmed that this mutation abolished agr function. These data provide the first substantial analysis of walKR promoter function and show that prolonged vancomycin exposure can result in VISA through an IS256-mediated reduction in walKR expression; however, the mechanisms by which this occurs remain to be determined.

22 Article Vancomycin minimum inhibitory concentration, host comorbidities and mortality in Staphylococcus aureus bacteraemia. 2013

Holmes, N E / Turnidge, J D / Munckhof, W J / Robinson, J O / Korman, T M / O'Sullivan, M V N / Anderson, T L / Roberts, S A / Warren, S J C / Gao, W / Johnson, P D R / Howden, B P. ·Austin Centre for Infection Research, Department of Infectious Diseases, Austin Health, Heidelberg, Vic., Australia; Department of Medicine, University of Melbourne, Parkville, Vic., Australia. ·Clin Microbiol Infect · Pubmed #23441652.

ABSTRACT: We reported an association between elevated vancomycin MIC and 30-day mortality in patients with Staphylococcus aureus bacteraemia (SAB), including patients with methicillin-susceptible S. aureus (MSSA) treated with flucloxacillin. A detailed analysis of comorbidities and disease severity scores in the same cohort of patients was performed to ascertain if unknown clinical parameters may have influenced these results. The association between elevated vancomycin MIC and 30-day mortality in SAB remained significant (p 0.001) on multivariable logistic regression analysis even when accounting for clinical factors. In addition, the association persisted when restricting analysis to patients with MSSA bacteraemia treated with flucloxacillin. This suggests that elevated vancomycin MIC is associated with but not causally linked to an organism factor that is responsible for increased mortality.

23 Article The RpoB H₄₈₁Y rifampicin resistance mutation and an active stringent response reduce virulence and increase resistance to innate immune responses in Staphylococcus aureus. 2013

Gao, Wei / Cameron, David R / Davies, John K / Kostoulias, Xenia / Stepnell, Justin / Tuck, Kellie L / Yeaman, Michael R / Peleg, Anton Y / Stinear, Timothy P / Howden, Benjamin P. ·Infectious Diseases Department, Austin Centre for Infection Research, University of Melbourne, Australia. ·J Infect Dis · Pubmed #23255563.

ABSTRACT: The occurrence of mutations in methicillin-resistant Staphylococcus aureus (MRSA) during persistent infection leads to antimicrobial resistance but may also impact host-pathogen interactions. Here, we investigate the host-pathogen consequences of 2 mutations arising in clinical MRSA during persistent infection: RpoB H₄₈₁Y, which is linked to rifampicin resistance, and RelA F₁₂₈Y, which is associated with an active stringent response. Allelic exchange experiments showed that both mutations cause global transcriptional changes, leading to upregulation of capsule production, with attenuated virulence in a murine bacteremia model and reduced susceptibility to both antimicrobial peptides and whole-blood killing. Disruption of capsule biosynthesis reversed these impacts on innate immune function. These data clearly link MRSA persistence and reduced virulence to the same mechanisms that alter antimicrobial susceptibility. Our study highlights the wider consequences of suboptimal antimicrobial use, where drug resistance and immune escape mechanisms coevolve, thus increasing the likelihood of treatment failure.

24 Article The molecular epidemiology of the highly virulent ST93 Australian community Staphylococcus aureus strain. 2012

Coombs, Geoffrey W / Goering, Richard V / Chua, Kyra Y L / Monecke, Stefan / Howden, Benjamin P / Stinear, Timothy P / Ehricht, Ralf / O'Brien, Frances G / Christiansen, Keryn J. ·Australian Collaborating Centre for Enterococcus and Sdtaphylococcus Species (ACCESS) Typing and Research, PathWest Laboratory Medicine-Western Australia, Royal Perth Hospital, Western Australia, Australia. Geoffrey.coombs@health.wa.gov.au ·PLoS One · Pubmed #22900085.

ABSTRACT: In Australia the PVL-positive ST93-IV [2B], colloquially known as "Queensland CA-MRSA" has become the dominant CA-MRSA clone. First described in the early 2000s, ST93-IV [2B] is associated with skin and severe invasive infections including necrotizing pneumonia. A singleton by multilocus sequence typing (MLST) eBURST analysis ST93 is distinct from other S. aureus clones. To determine if the increased prevalence of ST93-IV [2B] is due to the widespread transmission of a single strain of ST93-IV [2B] the genetic relatedness of 58 S. aureus ST93 isolated throughout Australia over an extended period were studied in detail using a variety of molecular methods including pulsed-field gel electrophoresis, spa typing, MLST, microarray DNA, SCCmec typing and dru typing. Identification of the phage harbouring the lukS-PV/lukF-PV Panton Valentine leucocidin genes, detection of allelic variations in lukS-PV/lukF-PV, and quantification of LukF-PV expression was also performed. Although ST93-IV [2B] is known to have an apparent enhanced clinical virulence, the isolates harboured few known virulence determinants. All PVL-positive isolates carried the PVL-encoding phage ΦSa2USA and the lukS-PV/lukF-PV genes had the same R variant SNP profile. The isolates produced similar expression levels of LukF-PV. Although multiple rearrangements of the spa sequence have occurred, the core genome in ST93 is very stable. The emergence of ST93-MRSA is due to independent acquisitions of different dru-defined type IV and type V SCCmec elements in several spa-defined ST93-MSSA backgrounds. Rearrangement of the spa sequence in ST93-MRSA has subsequently occurred in some of these strains. Although multiple ST93-MRSA strains were characterised, little genetic diversity was identified for most isolates, with PVL-positive ST93-IVa [2B]-t202-dt10 predominant across Australia. Whether ST93-IVa [2B] t202-dt10 arose from one PVL-positive ST93-MSSA-t202, or by independent acquisitions of SCCmec-IVa [2B]-dt10 into multiple PVL-positive ST93-MSSA-t202 strains is not known.

25 Article Comparison of the bacterial isolates and antibiotic resistance patterns of elderly nursing home and general community patients. 2012

Xie, C / Taylor, D McD / Howden, B P / Charles, P G P. ·Department of Medicine, University of Melbourne, Melbourne, Victoria, Australia. ·Intern Med J · Pubmed #21241444.

ABSTRACT: BACKGROUND: Nursing home-acquired infections may differ from general community-acquired infections in bacteriology and antibiotic resistance. However, there are currently limited data on this topic in the Australian setting. AIMS: To compare bacterial isolates and antibiotic resistance patterns, from pathology specimens of nursing home and community patients, and to comment on the suitability of empiric antibiotic guidelines for nursing home-acquired infection. METHODS: This was a retrospective cohort study of patients, aged ≥ 65 years, who resided in either nursing homes or the general community. Patients with a hospital admission in the previous 28 days were excluded. Positive specimen cultures, collected between July 2003 and June 2008 in the Emergency Department and Outpatient Clinics of the Austin Hospital (Melbourne), were examined. The main outcome measures were the bacterial isolates, and their antibiotic resistance patterns, of patients from nursing homes and the general community. RESULTS: Specimens of blood (638), sputum (425), urine (4044) and wound cultures (785) were examined. The bacteriology of blood culture isolates did not differ between the two groups (P= 0.3). However, the bacteriology of sputum, urine and wound cultures differed significantly between the groups (P= 0.025, P < 0.001, P= 0.004 respectively). There were also higher proportions of antibiotic resistance among some bacteria in nursing home patients, especially methicillin resistance among Staphylococcus aureus isolates across all specimen types, and resistance to several empiric antibiotics among Enterobacteriaceae isolates in urine cultures. CONCLUSION: Empiric antibiotic guidelines appear adequate to treat nursing home-acquired septicaemia and pneumonia. However, guidelines for urinary tract infections and wound infections may need to be refined.

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