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ABSTRACT: The purpose of this paper is to determine the prevalence of the toxic shock toxin gene (tst) and to enumerate the circulating strains of methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) in Australian isolates collected over two decades. The aim was to subtype these strains using the binary genes pvl, cna, sdrE, pUB110 and pT181. Isolates were assayed using real-time polymerase chain reaction (PCR) for mecA, nuc, 16S rRNA, eight single-nucleotide polymorphisms (SNPs) and for five binary genes. Two real-time PCR assays were developed
for tst. The 90 MRSA isolates belonged to CC239 (39 in 1989, 38 in 1996 and ten in 2003), CC1 (two in 2003) and CC22 (one in 2003).
The majority of the 210 MSSA isolates belonged to CC1 (26), CC5 (24) and CC78 (23). Only 18 isolates were tst-positive and only 15 were pvl-positive. Nine MSSA isolates belonged to five binary types of ST93, including two pvl-positive types. The proportion of tst-positive and pvl-positive isolates was low and no significant increase was demonstrated. Dominant MSSA clonal complexes were similar to those
seen elsewhere, with the exception of CC78. CC239 MRSA (AUS-2/3) was the predominant MRSA but decreased significantly in prevalence,
while CC22 (EMRSA-15) and CC1 (WA-1) emerged. Genetically diverse ST93 MSSA predated the emergence of ST93-MRSA (the Queensland
clone).
European Journal of Clinical Microbiology 04/2012; 28(10):1183-1189. · 2.86 Impact Factor
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ABSTRACT: Staphylococcus aureus is the most common cause of skin and soft tissue infections (SSTIs). Such infections have increased in several countries recently and at a time when community-associated methicillin-resistant S. aureus (CA-MRSA) strains have emerged globally. We examined changes in Australian hospitalisations for the treatment of cutaneous abscesses between 1999 and 2008, a period when increased numbers of CA-MRSA infections were being reported. National hospitalisation data for cutaneous abscess treatment (1999-2008) were examined. Hospitalisation numbers were collated and age-specific admission rates calculated and examined for changes over time. Yearly admissions for the treatment of cutaneous abscesses increased by 48%, from 8,849 (1999-2000) to 13,126 (2007-2008). The crude annual hospitalisation rate per 100,000 population rose from 46 to 62 respectively. However, increases in admission rates were limited to the 10 to 54 years age range. Incidence rate ratios (IRRs) for final versus baseline year admission rates for these age groups ranged from 1.36 (95% confidence interval [CI] 1.04-1.78) for those aged 10-14 years to 1.64 (95% CI 1.26-2.12) for those aged 45-49 years; p<0.05. Increases in hospitalisation for cutaneous abscess treatment have occurred in Australia during the last decade. Research into the underlying causes and prevention of these infections is a public health priority.
European Journal of Clinical Microbiology 05/2011; 31(1):93-6. · 2.86 Impact Factor
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ABSTRACT: The Sequenom MassARRAY iPLEX single-nucleotide polymorphism (SNP) typing platform uses matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) coupled with single-base extension PCR for high-throughput multiplex SNP detection. In this study, we investigated the use of iPLEX MassARRAY technology for methicillin-resistant Staphylococcus aureus (MRSA) genotyping. A 16-plex MassARRAY iPLEX GOLD assay (MRSA-iPLEX) was developed that targets a set of informative SNPs and binary genes for MRSA characterization. The method was evaluated with 147 MRSA isolates, and the results were compared with those of an established SYBR Green-based real-time PCR system utilizing the same SNP-binary markers. A total of 2352 markers belonging to 44 SNP-binary profiles were analysed by both real-time PCR and MRSA-iPLEX. With real-time PCR as the reference standard, MRSA-iPLEX correctly assigned 2298 of the 2352 (97.7%) markers. Sequence variation in the MRSA-iPLEX primer targets accounted for the majority of MRSA-iPLEX erroneous results, highlighting the importance of primer target selection. MRSA-iPLEX provided optimal throughput for MRSA genotyping, and was, on a reagent basis, more cost-effective than the real-time PCR methods. The 16-plex MRSA-iPLEX is a suitable alternative to SYBR Green-based real-time PCR typing of major sequence types and clonal complexes of MRSA.
Clinical Microbiology and Infection 03/2011; 17(12):1804-10. · 4.54 Impact Factor
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ABSTRACT: Surveillance cultures may detect colonisation with drug-resistant Gram-negative bacteria and can be hypothesised to guide appropriate initial antibiotic treatment for intensive care unit (ICU) patients. We investigated the microbiological data of 228 episodes of nosocomial bloodstream infection (BSI) due to Gram-negative bacteria in an ICU in which piperacillin/tazobactam or meropenem was used empirically for serious infections, to evaluate the contribution of surveillance cultures to an appropriate choice of initial antibiotic therapy. Surveillance cultures were taken in advance of BSI in 218 (95.6%) of 228 episodes. Concordant organisms with identical identification and susceptibilities were found in prior surveillance cultures and subsequent blood cultures in 65 (29.8%) of 218 episodes. Surveillance cultures predicted resistance in 52.9% and 51.4% of BSIs caused by resistant pathogens to piperacillin/tazobactam and meropenem, respectively. The negative predictive value of surveillance cultures negative for a resistant organism also exceeded 90% for piperacillin/tazobactam and meropenem. Given that the overall resistant rates of BSI pathogens of our study were 11.3% to piperacillin/tazobactam and 16.4% to meropenem, surveillance cultures in our setting may provide important information on the probability of drug resistance of the causative pathogens and some utility in aiding empiric antibiotic therapy for ICU patients who subsequently develop BSI.
European Journal of Clinical Microbiology 01/2011; 30(6):739-44. · 2.86 Impact Factor
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ABSTRACT: The purpose of this study was to determine the extent of the spread of epidemic clones of non-multiresistant methicillin-resistant Staphylococcus aureus (nmMRSA) and the epidemiology of resultant infections throughout the state of Queensland. We collected a sample of clinical isolates of nmMRSA from laboratories serving public hospitals and clinics throughout the state. Three hundred isolates were typed and tested for the presence of Panton-Valentine leukocidin (PVL) genes and demographic and clinical data were collected from associated cases. Fifteen percent of S. aureus isolates were nmMRSA and 69% of these belonged to PVL-positive clones, predominantly ST93 and CC30. Low numbers of USA300- and USA400-like isolates were also present. Infections due to PVL-positive strains were much less frequently acquired in hospital (3.4%) than those due to PVL-negative nmMRSA (23.7%). Thirty-seven percent of cases were in indigenous people who make up only 3.6% of the general population. The proportion of cases with PVL-positive, but non-negative isolates decreased progressively with age, suggesting that immunity to PVL might be an important determinant of protection. nmMRSA strains are present throughout Queensland and cause infections in both community and healthcare settings.
European Journal of Clinical Microbiology 10/2010; 29(10):1253-9. · 2.86 Impact Factor
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S Schlebusch,
G R Price,
S Hinds,
C Nourse,
J M Schooneveldt,
M H Tilse,
H G Liley,
T Wallis,
F Bowling,
D Venter, G R Nimmo
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ABSTRACT: The purpose of this brief report is to describe the first outbreak of a community-associated nonmultiresistant and PVL-positive MRSA strain (CC30) in a neonatal intensive care unit in Australia. The utility of matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS) for microbial typing is compared with single nucleotide polymorphism (SNP) plus binary gene analysis. The composite correlation index analysis of the MALDI-TOF-MS data demonstrated the similar inter-strain relatedness found with the SNP-plus-binary gene typing used to confirm the outbreak. The evolving spread of MRSA emphasizes the importance of surveillance, infection control vigilance and the ongoing investigation of rapid typing methods for MRSA.
European Journal of Clinical Microbiology 10/2010; 29(10):1311-4. · 2.86 Impact Factor
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ABSTRACT: Given variability in the epidemiology of candidaemia and a relative paucity of contemporary longitudinal data, a passive laboratory-based surveillance study was performed to assess the epidemiology of candidaemia in all public healthcare facilities in Queensland, Australia over the period 1999-2008. Demographic and microbiological data on all candidaemia episodes, together with appropriate denominators (admissions and patient-days), were collected from laboratory and administrative information systems. From 1999 to 2008, 1137 episodes occurred (overall incidence-density: 0.45 per 10 000 patient-days) with a 3.5-fold increase in density (P<0.0001 for trend). Candidaemia episodes originating in traditional high-risk areas either decreased (haemato-oncology and paediatric wards) or remained stable (intensive care units). Episodes on adult medical/surgical wards increased significantly over time, accounting for 60% of the total by 2008. The relative proportion caused by Candida albicans decreased and Candida parapsilosis increased (both P<0.01). The proportion of fluconazole-resistant isolates did not change. The increasing occurrence of candidaemia outside traditional high-risk areas and the emergence of C. parapsilosis present new challenges for preventive and early intervention strategies.
The Journal of hospital infection 04/2010; 76(1):46-51. · 3.01 Impact Factor
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ABSTRACT: Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections are emerging in southeast Queensland, Australia, but the incidence of carriage of CA-MRSA strains is unknown. The aim of this study was to assess the nasal carriage rate of S. aureus, including CA-MRSA strains, in the general adult population of southeast Queensland. 396 patients presenting to general practices in two Brisbane suburbs and 303 volunteers randomly selected from the electoral rolls in the same suburbs completed a medical questionnaire and had nasal swabs performed for S. aureus. All isolates of S. aureus underwent antibiotic susceptibility testing and single-nucleotide polymorphism (SNP) and binary typing, including determination of Panton-Valentine leukocidin (PVL). The nasal carriage rate of methicillin-susceptible S. aureus (MSSA) was 202/699 (28%), a rate similar to that found in other community-based nasal carriage studies. According to multivariate analysis, nasal carriage of S. aureus was associated with male sex, young adult age group and Caucasian ethnicity. Only two study isolates (one MSSA and one CA-MRSA) carried PVL. The nasal carriage rate of MRSA was low, at 5/699 (0.7%), and only two study participants (0.3%) had CA-MRSA strains. CA-MRSA is an emerging cause of infection in southeast Queensland, but as yet the incidence of carriage of CA-MRSA in the general community is low.
Clinical Microbiology and Infection 02/2009; 15(2):149-55. · 4.54 Impact Factor
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ABSTRACT: The epidemiology of meticillin-resistant S. aureus (MRSA) infection has changed remarkably in recent years with the appearance of new MRSA strains causing infections in the community. These strains have now begun to cause healthcare-associated infections. The ability to track such changes is necessary to guide clinical and public health action. Here we report passive surveillance of all public laboratory susceptibility data in Queensland to track changes in MRSA phenotypes corresponding to the major epidemic strains from 2000 to 2006. The inpatient rate of MRSA isolation from pus, tissue and fluid (PTF) and blood culture (BC) specimens declined by 26% and 35%, respectively. The rate of isolation of the AUS-2/3-like phenotype (corresponding to ST239-MRSA-III) decreased from 651 to 242 isolates per million accrued patient days in inpatient PTF and BC, whereas that for non-multiresistant MRSA (nmMRSA, corresponding to community MRSA strains) increased from 71 to 315. The overall outpatient rate of MRSA isolation from PTF and BC increased by 224% and 31%, respectively. The rate of AUS-2/3-like isolates in outpatient PTF decreased from 131 to 60 per million outpatient occasions of service while the nmMRSA rate increased from 52 to 490. Surveillance of phenotypes derived from routine susceptibility data is a useful tool for tracking changes in the epidemiology of MRSA over large geographical regions.
Journal of Hospital Infection 10/2008; 70(4):305-13. · 3.39 Impact Factor
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ABSTRACT: Non-multiresistant methicillin-resistant Staphylococcus aureus (nmMRSA) infections are emerging worldwide and are often community-associated. This prospective case-cohort study compares features of 96 nmMRSA clinical isolates with 96 matched multiresistant MRSA (mMRSA) and 192 matched methicillin-susceptible S. aureus (MSSA) clinical isolates. Seventy-four percent of nmMRSA infections were healthcare-associated. nmMRSA infections were much more likely to involve skin and soft tissue (skin and soft tissue infections; SSTIs) and were much less likely to be treated appropriately with antibiotics than MSSA or mMRSA infections. Panton-Valentine leukocidin (PVL) genes were detected in 55% of nmMRSA, 16% of MSSA and 2% of mMRSA isolates. Independent of the methicillin-resistance phenotype, 59% of PVL-positive SSTIs presented as furunculosis compared to only 10% of PVL-negative SSTIs. Patients with PVL-positive infections were much younger than patients with PVL-negative infections. The proportion of PVL-positive infections peaked in the 10-29 years old age group, followed by a linear decline.
European Journal of Clinical Microbiology 06/2008; 27(5):355-64. · 2.86 Impact Factor
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The Medical journal of Australia 07/2001; 174(12):617-8. · 2.81 Impact Factor
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ABSTRACT: Australian isolates of vancomycin-resistant enterococci (VRE) have been widely scattered geographically, predominantly polyclonal and of the VanB phenotype. Forty-nine VRE were isolated from 47 patients in our hospital from October 1996 to December 1999. Forty-four of these VRE were Enterococcus faecium with a vanA glycopeptide resistance genotype. Four isolates were pathogenic. Thirty-five VRE were from an outbreak in the Renal and Infectious Diseases Units over a four-month period. Pulsed-field gel electrophoresis (PFGE) demonstrated that 41 of the 49 VRE were indistinguishable or closely related. Enhanced environmental cleaning, strict contact isolation of colonized patients and reducing inpatient admissions terminated the epidemic. Cohorting of methicillin-resistant Staphylococcus aureus (MRSA)-positive patients was restricted because VRE patients occupied the isolation facilities. This resulted in a statistically significant increase in MRSA infections across the hospital. VRE epidemics have the ability to influence the epidemiology of other nosocomial pathogens when infection control resources are exhausted.
Journal of Hospital Infection 06/2001; 48(1):43-54. · 3.39 Impact Factor
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ABSTRACT: Community-acquired methicillin-resistant Staphylococcus aureus (MRSA) susceptible to gentamicin has been reported in a number of countries in the 1990s. To study the acquisition of gentamicin-sensitive MRSA (GS-MRSA) in southeast Queensland and the relatedness of GS-MRSA to other strains of MRSA, 35 cases of infection due to GS-MRSA from October 1997 through September 1998 were examined retrospectively to determine the mode of acquisition and risk factors for MRSA acquisition. Thirty-one isolates from the cases were examined using a variety of methods (antibiotyping, phage typing, pulsed-field gel electrophoresis [PFGE] fingerprinting, and coagulase typing by restriction analysis of PCR products) and were compared with strains of local hospital-acquired gentamicin-resistant MRSA (GR-MRSA) and of Western Australian MRSA (WA-MRSA). Only 6 of 23 cases of community-acquired GS-MRSA had risk factors for MRSA acquisition. Twenty of 21 isolates from cases of community-acquired infection were found to be related by PFGE and coagulase typing and had similar phage typing patterns. Hospital- and nursing home-acquired GS-MRSA strains were genetically and phenotypically diverse. Community-acquired GS-MRSA strains were not related to nosocomial GR-MRSA or WA-MRSA, but phage typing results suggest that they are related to GS-MRSA previously reported in New Zealand.
Journal of Clinical Microbiology 12/2000; 38(11):3926-31. · 4.15 Impact Factor
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Journal of Clinical Microbiology 11/2000; 38(10):3902. · 4.15 Impact Factor
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The Medical journal of Australia 02/2000; 172(1):42-3. · 2.81 Impact Factor
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ABSTRACT: One hundred and ninety-five multi-resistant strains of Klebsiella pneumoniae were isolated at Princess Alexandra Hospital (PAH) between December 1991 and June 1995. All these organisms produced extended spectrum beta-lactamases (ESBLs) as detected by the double disc synergy test (DDST). Between June 1994 and June 1995, a second population of 67 multi-resistant but DDST negative strains was isolated. Twenty multi-resistant Klebsiella pneumoniae strains (16 DDST positive and four DDST negative) and one susceptible strain were selected for further study. These were tested for production of ESBLs by two double disc synergy methods and agar dilution minimum inhibitory concentrations (MICs) with and without clavulanic acid. Detected ESBLs were further characterised by isoelectric focusing. The confirmed DDST positive K. pneumoniae strains all produced ESBLs that focused at an isoelectric point (pI) of 7.6, suggesting the presence of SHV-2, SHV-2a, SHV-6, SHV-7 or SHV-8 enzymes. The multi-resistant DDST negative strains showed no clavulanic acid synergy and thus no evidence of the presence of ESBLs.
Pathology 06/1998; 30(2):164-8. · 2.38 Impact Factor
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The Lancet 12/1996; 348(9036):1250. · 38.28 Impact Factor
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ABSTRACT: To assess the changes in antibiotic resistances in Staphylococcus aureus, both methicillin-susceptible and methicillin-resistant strains, in Australia.
Retrospective review of data collected annually.
Twenty metropolitan teaching hospitals in the six States of Australia and the Australian Capital Territory from 1988 to 1994.
Changes in prevalence and resistance rates of methicillin-resistant S. aureus (MRSA) and methicillin-susceptible strains, based on antibiotic susceptibility testing of clinical isolates of S. aureus.
Prevalence of MRSA has remained constant on the eastern seaboard of Australia. A distinctive strain of MRSA emerged in Western Australia which had different antimicrobial susceptibilities. Resistances emerged in MRSA strains from eastern Australia, principally to ciprofloxacin and rifampicin, while resistance to fusidic acid remained stable and resistance to chloramphenicol significantly declined. Resistances in methicillin-susceptible strains remained fairly stable, except for a decline in resistance levels for tetracycline. High levels of resistance were seen to penicillin, moderate levels to erythromycin and low levels to trimethoprim and fusidic acid in methicillin-susceptible strains.
The continued high prevalence of and increasing resistance in MRSA in some Australian hospitals have meant that some strains are now untreatable with oral antibiotics.
The Medical journal of Australia 02/1996; 164(2):68-71. · 2.81 Impact Factor
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Medical Journal of Australia. 172(1):42-43.
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