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In 2012, the Australian Group on Antimicrobial Resistance (AGAR) conducted a community-onset period-prevalence survey of clinical Staphylococcus aureus isolated from hospital outpatients and general practice patients including nursing homes, long term care facilities and hospice patients. Day surgery and dialysis patients were excluded. Twenty-nine medical microbiology laboratories from all state and mainland territories participated. Isolates were tested by Vitek2® (AST-P612 card). Results were compared with previous AGAR community surveys. Nationally, the proportion of S. aureus that were methicillin-resistant S. aureus (MRSA) increased significantly from 11.5% in 2000 to 17.9% in 2012 (P<0.0001). Resistance to the non-ß-lactam antimicrobials varied between regions. No resistance was detected to vancomycin, teicoplanin or linezolid. Resistance in methicillin susceptible S. aureus was rare apart from erythromycin (12.8%) and was absent for vancomycin, teicoplanin, linezolid and daptomycin. The proportion of S. aureus characterised as health care-associated MRSA (HA-MRSA) was 5.1%. Three HA-MRSA clones were characterised, with 72.9% and 26.4% of HA-MRSA classified as ST22-IV [2B] (EMRSA-15) and ST239-III [3A] (Aus-2/3 EMRSA) respectively. Multi-clonal community-associated MRSA (CA-MRSA) accounted for 12.5% of all S. aureus. Regional variation in resistance in MRSA was primarily due to the differential distribution of the 2 major HA-MRSA clones; ST239-III [3A] (Aus-2/3 EMRSA), which is resistant to multiple non-ß-lactam antimicrobials, and ST22-IV [2B] (EMRSA-15), which is resistant to ciprofloxacin and typically erythromycin. Although the majority of CA-MRSA were non-multi-resistant, a significant expansion of Panton-Valentine leukocidin (PVL) positive CA-MRSA clones has occurred nationally. The mean age of patients (31.7 years, 95% CI 28.9-34.5) with a PVL positive CA-MRSA infection was significantly lower (P<0.0001), than the mean age of patients with a PVL negative CA-MRSA infection (55.7 years, 95% CI 50.7-60.6). This shift in the molecular epidemiology of MRSA clones in the Australian community will potentially increase the number of young Australians with skin and soft tissue infections requiring hospitalisation., (copyright@health.gov.au)

The Australian Group on Antimicrobial Resistance (AGAR) performs regular period-prevalence studies to monitor changes in antimicrobial resistance in selected enteric Gram-negative pathogens. The 2010 survey focussed on community-onset infections, examining isolates from urinary tract infections from patients presenting to outpatient clinics, emergency departments or to community practitioners. Two thousand and ninety-two Escherichia coli, 578 Klebsiella species and 268 Enterobacter species were tested using a commercial automated method (Vitek 2, BioMérieux) and results were analysed using Clinical and Laboratory Standards Institute breakpoints from January 2012. Of the key resistances, non-susceptibility to the third-generation cephalosporin, ceftriaxone, was found in 3.2% of E. coli and 3.2%-4.0% of Klebsiella spp. Non-susceptibility rates to ciprofloxacin were 5.4% for E. coli, 1.0%-2.3% for Klebsiella spp., and 2.5%-6.6% in Enterobacter spp, and resistance rates to piperacillin-tazobactam were 2.8%, 3.2%-6.9%, and 16.8%-18.0% for the same 3 groups respectively. Only 3 strains, 2 Klebsiella spp. and 1 Enterobacter spp, were shown to harbour a carbapenemase (IMP-4)., (This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without prior written permission from the Commonwealth. Requests and inquiries concerning reproduction and rights should be addressed to the Commonwealth Copyright Administration, Attorney General's Department, Robert Garran Offices, National Circuit, Barton ACT 2600 or posted at http://www.ag.gov.au/cca.)

Background: It is uncertain whether particular clones causing invasive community-onset methicillin-resistant and methicillin-sensitive Staphylococcus aureus (cMRSA/cMSSA) infection differ in virulence., Methods: Invasive cMRSA and cMSSA cases were prospectively identified. Principal component analysis was used to derive an illness severity score (ISS) from clinical data, including 30-day mortality, requirement for intensive hospital support, the presence of bloodstream infection, and hospital length of stay. The mean ISS for each S. aureus clone (based on MLST) was compared with its DNA microarray-based genotype., Results: Fifty-seven cMRSA and 50 cMSSA infections were analyzed. Ten clones caused 82 (77%) of these infections and had an ISS calculated. The enterotoxin gene cluster (egc) and the collagen adhesin (cna) gene were found in 4 of the 5 highest-ranked clones (ST47-MSSA, ST30-MRSA-IV[2B], ST45-MSSA, and ST22-MRSA-IV[2B]) compared with none and 1 of the lowest 5 ranked clones, respectively. cMSSA clones caused more severe infection than cMRSA clones. The lukF/lukS Panton-Valentine leukocidin (PVL) genes did not directly correlate with the ISS, being present in the second, fourth, and 10th most virulent clones., Conclusions: The clinical severity of invasive cMRSA and cMSSA infection is likely to be attributable to the isolates' entire genotype rather than a single putative virulence determinant such as PVL.

Background: Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) was first reported in remote regions of Western Australia and is now the predominant MRSA isolated in the state. The objective of this study is to determine the genetic relatedness of Western Australian CA-MRSA clones within different multilocus sequence type (MLST) clonal clusters providing an insight into the frequency of S. aureus SCCmec acquisition within a region., Results: The CA-MRSA population in Western Australia is genetically diverse consisting of 83 unique pulsed-field gel electrophoresis strains from which 46 MLSTs have been characterised. Forty five of these sequence types are from 18 MLST clonal clusters and two singletons. While SCCmec IV and V are the predominant SCCmec elements, SCCmec VIII and several novel and composite SCCmec elements are present. The emergence of MRSA in diverse S. aureus clonal clusters suggests horizontal transmission of the SCCmec element has occurred on multiple occasions. Furthermore DNA microarray and spa typing suggests horizontal transfer of SCCmec elements has also occurred within the same CC. For many single and double locus variant CA-MRSA clones only a few isolates have been detected., Conclusions: Although multiple CA-MRSA clones have evolved in the Western Australian community only three clones have successfully adapted to the Western Australian community environment. These data suggest the successful evolution of a CA-MRSA clone may not only depend on the mobility of the SCCmec element but also on other genetic determinants.

Differences between the features of invasive community-onset methicillin-resistant Staphylococcus aureus (cMRSA) and methicillin-susceptible S. aureus (cMSSA) infections are incompletely understood. Fifty-seven patients with invasive cMRSA infection were prospectively identified at two teaching hospitals; for each cMRSA case, two cases of invasive cMSSA infection acted as controls. The primary outcome was 30-day all-cause mortality. Patients with invasive cMRSA infection were more likely to be Aboriginal (25% vs. 14%, age-adjusted odds ratio [OR] 2.5, p = 0.037), reside in a long-term care facility and/or have been hospitalised in the previous year (51% vs. 34%, p = 0.04) and less likely to have endocarditis (2% vs. 12%, p = 0.02) or require admission to an intensive care unit or high-dependency area (7% vs. 21%, p = 0.02). All-cause mortality at 30 days was similar in the cMRSA and cMSSA groups (9% vs. 7%, p = 0.68). Panton-Valentine leukocidin (PVL) genes were detected in a similar proportion of cMRSA and cMSSA isolates (32% vs. 27%, p = 0.49) and the presence of PVL genes was associated with younger age (35 years vs. 55 years, p < 0.001), Aboriginal ethnicity (38% vs. 10%, p < 0.001), skin and soft-tissue infection (54% vs. 19%, p < 0.001), lower illness severity at presentation (SAPS II score 9 vs. 21, p = 0.001) and shorter hospitalisation (9 days vs. 24 days, p < 0.001). Patients with "PVL-positive" and "PVL-negative" S. aureus infection had similar 30-day all-cause mortality (4% vs. 9%, p = 0.28). Few clinical features differentiated patients with invasive cMRSA infection from those with infection caused by cMSSA. Invasive "PVL-positive" S. aureus infection was associated with less morbidity but similar mortality to "PVL-negative" infection.

Clonal complex 59 (CC59) community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strains were characterized using pulsed-field gel electrophoresis, spa typing, multilocus sequence typing, diagnostic DNA microarrays, and PCRs targeting staphylococcal cassette chromosome mec (SCCmec) elements and Panton-Valentine leukocidin (PVL). Six distinct groups within CC59 were characterized. At least seven different variants of SCCmec elements were identified (IVa [2B], IVb [2B], IVd [2B], IV variant [2B], IVa [2B&5], V variant [5C2], and V [5C2&5]). (The structural type is indicated by a Roman numeral, with a lowercase letter indicating the subtype, and the ccr complex and the mec complex are indicated by an Arabic numeral and an uppercase letter, respectively. Where there is an extra ccr element, this is indicated by "&" and an Arabic numeral designating the ccr type.) The first group is similar to the American sequence type 59 (ST59) MRSA-IV CA-MRSA strain USA1000. The second group includes a PVL-negative ST87 strain with an SCCmec element of subtype IVb (2B). The third group comprises PVL-variable ST59 MRSA-IV strains harboring multiple SCCmec IV subtypes. PVL-negative ST59 MRSA strains with multiple or composite SCCmec elements (IVa [2B&5]) form the fourth group. Group 5 corresponds to the internationally known "Taiwan clone," a PVL-positive strain with a variant SCCmec element (V [5C2&5]). This strain proved to be the most common CC59 MRSA strain isolated in Western Australia. Finally, group 6 encompasses the ST59 MRSA-V variant (5C2). The differentiation of CC59 into groups and strains indicates a rapid evolution and spread of SCCmec elements. Observed differences between groups of strains as well as intrastrain variability within a group facilitate the tracing of their spread.

Background: Bacterial pneumonia is a well described complication of influenza. In recent years, community-onset methicillin-resistant Staphylococcus aureus (cMRSA) infection has emerged as a contributor to morbidity and mortality in patients with influenza. Since the emergence and rapid dissemination of pandemic A(H1N1)2009 influenzavirus in April 2009, initial descriptions of the clinical features of patients hospitalized with pneumonia have contained few details of patients with bacterial co-infection., Methodology/principal Findings: Patients with community-acquired pneumonia (CAP) caused by co-infection with pandemic A(H1N1)2009 influenzavirus and cMRSA were prospectively identified at two tertiary hospitals in one Australian city during July to September 2009, the period of intense influenza activity in our region. Detailed characterization of the cMRSA isolates was performed. 252 patients with pandemic A(H1N1)2009 influenzavirus infection were admitted at the two sites during the period of study. Three cases of CAP due to pandemic A(H1N1)2009/cMRSA co-infection were identified. The clinical features of these patients were typical of those with S. aureus co-infection or sequential infection following influenza. The 3 patients received appropriate empiric therapy for influenza, but inappropriate empiric therapy for cMRSA infection; all 3 survived. In addition, 2 fatal cases of CAP caused by pandemic A(H1N1)2009/cMRSA co-infection were identified on post-mortem examination. The cMRSA infections were caused by three different cMRSA clones, only one of which contained genes for Panton-Valentine Leukocidin (PVL)., Conclusions/significance: Clinicians managing patients with pandemic A(H1N1)2009 influenzavirus infection should be alert to the possibility of co-infection or sequential infection with virulent, antimicrobial-resistant bacterial pathogens such as cMRSA. PVL toxin is not necessary for the development of cMRSA pneumonia in the setting of pandemic A( H1N1) 2009 influenzavirus co-infection.

The objective was to compare the epidemiology and outcome of healthcare- (HA-) and community-associated (CA-) MRSA bacteraemia. A 10-year retrospective study of MRSA bacteraemia was carried out. Episodes were classified according to established criteria. Molecular typing was performed on a subset of isolates. Of 197 MRSA bacteraemia episodes, 178 (90.4%) were classified as HA-MRSA and 19 (9.6%) as CA-MRSA. All-cause 7- and 30-day mortality rates were similar in the HA and CA-MRSA bacteraemia groups; however, 1-year mortality was higher in the HA-MRSA bacteraemia group (48.3% vs 21.1% [p = 0.023]). Thirty-day all-cause mortality was significantly lower if empiric antimicrobial therapy included agent(s) to which the isolate tested susceptible, compared with patients receiving "inactive" therapy (19% vs 35.1% [p = 0.011]). The majority of MRSA bacteraemia episodes were caused by clones known to circulate in the community. All-cause mortality is as high in HA- as in CA-MRSA bacteraemia. Thirty-day mortality was significantly reduced if the patient received an antibiotic with activity against the MRSA isolate.

Community-associated methicillin-resistant Staphylococcus aureus (MRSA) was first reported in Western Australia in the early 1990s from indigenous peoples living in remote areas. Although a statewide policy of screening all hospital patients and staff who have lived outside the state for MRSA has prevented the establishment of multidrug-resistant epidemic MRSA, the policy has not prevented SCCmec type IV and type V MRSA clones from becoming established. Of the 4,099 MRSA isolates analyzed (referred to the Gram-positive Bacteria Typing and Research Unit) from July 2003 to December 2004, 77.5% were community-associated MRSA (CA-MRSA). Using multilocus sequence/staphylococcal chromosome cassette mec typing, 22 CA-MRSA clones were characterized. Of these isolates, 55.5% were resistant to >1 non-beta-lactam antimicrobial drug. Five Panton-Valentine leukocidin (PVL)-positive CA-MRSA clones were identified. The emergence of multidrug-resistant CA-MRSA clones and the detection of PVL toxin genes in clones previously reported as PVL negative is a major public health concern.

Background: Community-onset infections caused by methicillin-resistant Staphylococcus aureus (COMRSA) are being increasingly reported worldwide., Methods: A retrospective study was performed of 14 patients with 15 episodes of COMRSA bacteremia (COMRSAB) admitted to the Royal Darwin Hospital, Northern Territory, Australia from 1998 to 2001. Isolates from COMRSAB episodes underwent extended susceptibility testing and molecular typing by pulsed field gel electrophoresis and allotyping of the staphylococcal cassette chromosome mec (SCCmec) region by polymerase chain reaction., Results: The proportion of community-onset S. aureus bacteremia episodes that were due to COMRSA increased from 9% in 1998 to 20% in 2001. The clinical features of COMRSAB were similar to those seen with methicillin-susceptible strains, including sepsis, endocarditis and metastatic infection. Ineffective empiric antimicrobial therapy was administered in the majority (80%) of episodes. All COMRSAB isolates tested contained allotype IV SCCmec, which is commonly found in community isolates of MRSA and rarely found in isolates from healthcare-associated MRSA infection., Conclusion: The increasing incidence of COMRSAB in our region has resulted in the addition of vancomycin to standard empiric therapy in certain patients with suspected S. aureus bacteremia acquired in the community.