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1.
J Clin Microbiol ; 59(1)2020 12 17.
Article in English | MEDLINE | ID: mdl-33087430

ABSTRACT

Staphylococcus aureus ST45 is a major global MRSA lineage with huge strain diversity and a high clinical impact. It is one of the most prevalent carrier lineages but also frequently causes severe invasive disease, such as bacteremia. Little is known about its evolutionary history. In this study, we used whole-genome sequencing to analyze a large collection of 451 diverse ST45 isolates from 6 continents and 26 countries. De novo-assembled genomes were used to understand genomic plasticity and to perform coalescent analyses. The ST45 population contained two distinct sublineages, which correlated with the isolates' geographical origins. One sublineage primarily consisted of European/North American isolates, while the second sublineage primarily consisted of African and Australian isolates. Bayesian analysis predicted ST45 originated in northwestern Europe about 500 years ago. Isolation time, host, and clinical symptoms did not correlate with phylogenetic groups. Our phylogenetic analyses suggest multiple acquisitions of the SCCmec element and key virulence factors throughout the evolution of the ST45 lineage.


Subject(s)
Methicillin-Resistant Staphylococcus aureus , Staphylococcal Infections , Australia/epidemiology , Bayes Theorem , Europe/epidemiology , Humans , Methicillin-Resistant Staphylococcus aureus/genetics , Phylogeny , Staphylococcal Infections/epidemiology , Staphylococcus aureus/genetics
2.
J Antimicrob Chemother ; 75(9): 2594-2598, 2020 09 01.
Article in English | MEDLINE | ID: mdl-32585694

ABSTRACT

OBJECTIVES: Implementation of EUCAST susceptibility testing in an Australian hospital laboratory demonstrated higher rates of aminopenicillin and amoxicillin/clavulanate resistance in Haemophilus influenzae than previously recognized. This study aimed to better define the variability in the detection of ß-lactam resistance based on EUCAST and CLSI disc diffusion (DD) methodology, by comparison with the recommended reference method, broth microdilution (BMD), and by concordance with genomic analysis. METHODS: A total of 100 random H. influenzae isolates were assessed for ampicillin and amoxicillin/clavulanate susceptibility by EUCAST and CLSI DD and BMD. WGS was used to analyse the ftsI gene of a subset of isolates with ß-lactam resistance, other than that due to isolated ß-lactamase production. RESULTS: Of the 100 isolates, 32 were categorized as either ß-lactamase negative, ampicillin resistant (BLNAR) (n = 18) or ß-lactamase positive, amoxicillin/clavulanate resistant (BLPACR) (n = 14) by EUCAST DD. All 18 EUCAST BLNAR isolates were genotypically confirmed by WGS. Five of 18 BLNAR isolates were concordant by CLSI DD, 12 by EUCAST BMD and 4 by CLSI BMD. Nine of 14 EUCAST BLPACR isolates were confirmed by WGS; the remaining 5 were 1 mm below the EUCAST DD breakpoint. Only one isolate was detected as BLPACR by CLSI DD. Group III mutations associated with high-level ampicillin resistance were identified in 10/32 isolates. CONCLUSIONS: The EUCAST DD susceptibility method is more reliable than either CLSI or BMD for the detection of genotypically defined BLNAR resistance. However, accurate categorization of amoxicillin/clavulanate resistance remains problematic. Continuous and reproducible surveillance of resistance is needed; for this to be possible, robust susceptibility methods are required.


Subject(s)
Haemophilus Infections , Haemophilus influenzae , Amoxicillin-Potassium Clavulanate Combination/pharmacology , Anti-Bacterial Agents/pharmacology , Australia , Haemophilus influenzae/genetics , Humans , Microbial Sensitivity Tests , beta-Lactamases/genetics
3.
Epidemiol Infect ; 148: e153, 2020 04 23.
Article in English | MEDLINE | ID: mdl-32321605

ABSTRACT

This study presents enhanced surveillance data from 2004 to 2018 for all community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) specimens collected in Western Australia (WA), and describes the changing epidemiology over this period. A total of 57 557 cases were reviewed. Annual incidence rates increased from 86.2 cases per 100 000 population to 245.6 per 100 000 population (IRR = 2.9, CI95 2.7-3.0). The proportion of isolates carrying Panton-Valentine leucocidin (PVL)-associated genes increased from 3.4% to 59.8% (χ2 test for trend 7021.9, P < 0.001). The emergence of PVL-positive, 'Queensland CA-MRSA' (ST93-IV) and 'WA 121' (ST5-IV) accounted for the majority of increases in CA-MRSA across the study period. It is unclear why some clones are more prolific in certain regions. In WA, CA-MRSA rates increase as indices of temperature and humidity increase after controlling for socioeconomic disadvantage. We suggest climatic conditions may contribute to transmission, along with other socio-behavioural factors. A better understanding of the ability for certain clones to form ecological niches and cause outbreaks is required.


Subject(s)
Community-Acquired Infections/microbiology , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Staphylococcal Infections/epidemiology , Staphylococcal Infections/microbiology , Adolescent , Adult , Aged , Aged, 80 and over , Bacterial Toxins/genetics , Bacterial Toxins/metabolism , Child , Child, Preschool , Community-Acquired Infections/epidemiology , Exotoxins/genetics , Exotoxins/metabolism , Female , Genotype , Humans , Incidence , Infant , Leukocidins/genetics , Leukocidins/metabolism , Male , Methicillin-Resistant Staphylococcus aureus/classification , Middle Aged , Retrospective Studies , Risk Factors , Western Australia/epidemiology , Young Adult
4.
Sci Rep ; 7(1): 5273, 2017 07 13.
Article in English | MEDLINE | ID: mdl-28706213

ABSTRACT

Pigs have been recognised as a reservoir of livestock associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in Europe, Asia and North America. However, little is known about the presence and distribution of MRSA in the Australian pig population and pig industry. This study describes the presence, distribution and molecular characteristics of the human adapted Australian CA-MRSA ST93 isolated from pigs, people, and the environment within a piggery. Isolates were subjected to antibiotic susceptibility testing, DNA microarray, whole genome sequencing, multi locus sequence typing, virulence and resistance gene characterization and phylogenetic analysis. MRSA were isolated from 60% (n = 52) of farm workers where 84% of isolates returned ST93 and the rest ST398. Of the thirty-one pig isolates tested further, an equal number of ST398 and ST93 (15 each) and one as ST30-V were identified. Four of six environmental isolates were identified as ST93 and two as ST398. This study has identified for the first time in Australia the occurrence of CA-MRSA ST93 and LA-MRSA ST398 amongst farm workers, pigs, and the farm environment. Comparative genome analysis indicates that ST398 is likely to have been introduced into Australia from Europe or North America. This study also reports the first linezolid resistant MRSA isolated in Australia.


Subject(s)
Community-Acquired Infections/microbiology , Disease Reservoirs/veterinary , Farmers/statistics & numerical data , Livestock/microbiology , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Staphylococcal Infections/veterinary , Virulence , Animals , Australia , Community-Acquired Infections/epidemiology , Cross-Sectional Studies , Drug Resistance, Microbial , Humans , Methicillin-Resistant Staphylococcus aureus/genetics , Multilocus Sequence Typing , Staphylococcal Infections/epidemiology , Staphylococcal Infections/microbiology , Swine , Whole Genome Sequencing
5.
J Glob Antimicrob Resist ; 6: 95-101, 2016 09.
Article in English | MEDLINE | ID: mdl-27530849

ABSTRACT

The evolution of meticillin-resistant Staphylococcus aureus (MRSA) from meticillin-susceptible S. aureus has been a result of the accumulation of genetic elements under selection pressure from antibiotics. The traditional classification of MRSA into healthcare-associated MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA) is no longer relevant as there is significant overlap of identical clones between these groups, with an increasing recognition of human infection caused by livestock-associated MRSA (LA-MRSA). Genomic studies have enabled us to model the epidemiology of MRSA along these lines. In this review, we discuss the clinical relevance of genomic studies, particularly whole-genome sequencing, in the investigation of outbreaks. We also discuss the blurring of each of the three epidemiological groups (HA-MRSA, CA-MRSA and LA-MRSA), demonstrating the limited relevance of this classification.


Subject(s)
Methicillin-Resistant Staphylococcus aureus/genetics , Staphylococcal Infections/epidemiology , Animals , Community-Acquired Infections/microbiology , Genomics , Humans , Livestock/microbiology
6.
J Antimicrob Chemother ; 71(12): 3372-3375, 2016 12.
Article in English | MEDLINE | ID: mdl-27566311

ABSTRACT

BACKGROUND: In Western Australia (WA), clonal complex 5, ST835, community-associated (CA) MRSA is isolated almost exclusively from aged care facilities. In WA four different staphylococcal cassette chromosome (SCC) mec (SCCmec) elements have been identified in this ST, indicating high genetic activity in the SCCmec region. OBJECTIVES: To investigate the SCC region of ST835 CA-MRSA WA MRSA-40 and determine the distribution of an SCCsorbitol element found within the region. RESULTS: The SCC region contained a composite island, SCCmecWA MRSA-40-CI, that was composed of three elements, ΨSCCpls, SCCsorbitol and SCCmecVT (5C2&5). This is the first time that a sorbitol operon has been reported in an SCC element. CONCLUSIONS: Generation of SCCmecWA MRSA-40-CI has involved multiple genetic events and recombination with CoNS has occurred during evolution of the SCC elements. While Staphylococcus aureus is renowned for its ability to utilize mobile genetic elements to disseminate antimicrobial resistance, the SCC region of WA MRSA-40 shows that this clone has also utilized SCC elements to acquire extra virulence and possibly adapt to a niche environment.


Subject(s)
Chromosomes, Bacterial , Community-Acquired Infections/microbiology , Genomic Islands , Homes for the Aged , Methicillin-Resistant Staphylococcus aureus/genetics , Nursing Homes , Staphylococcal Infections/microbiology , Aged , Evolution, Molecular , Genotype , Humans , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Recombination, Genetic , Western Australia
7.
N Z Vet J ; 64(4): 253-6, 2016 Jul.
Article in English | MEDLINE | ID: mdl-26850500

ABSTRACT

CASE HISTORY: A 14-year-old neutered male Sealyham terrier was referred for assessment of a persistent pyoderma. It had experienced numerous episodes of dermatitis involving pododermatitis, pyoderma and otitis over the previous 6 years. CLINICAL FINDINGS: Superficial, focally deep and mucocutaneous pyoderma were present, with yellow mucoid exudate on both nares and the lower lips crusted with haemopurulent exudate. Epidermal collarettes were present on the dorsal and lateral trunk. There were peri-anal crusts and mild erythema was present on the concave aspect of both pinnae. MICROBIOLOGICAL FINDINGS: Culture and microbiological testing identified Staphylococcus pseudintermedius as the infecting organism. Kirby-Bauer disc susceptibility testing revealed the isolate was resistant to numerous antimicrobials including oxacillin. PCR testing of the isolate identified the presence of the mecA gene which confers resistance to ß-lactam antimicrobials. Pulsed field gel electrophoresis typing suggested the isolate was not related to the methicillin-resistant S. pseudintermedius that had been reported to be associated with canine infections in Western Australia. DIAGNOSIS: Superficial, deep and mucus membrane pyoderma associated with a multi-drug resistant S. pseudintermedius. CLINICAL RELEVANCE: This is the first recorded case of canine pyoderma involving methicillin-resistant multidrug-resistant S. pseudintermedius in New Zealand. Treatment of such cases is difficult because the number of effective and available antimicrobials is limited. This finding should raise the awareness of the veterinary and medical professions to the presence of such organisms in New Zealand and stimulate a discussion about possible biosecurity barriers, treatment strategies and prevention of zoonotic and nosocomial infections.


Subject(s)
Bacterial Proteins/metabolism , Dog Diseases/microbiology , Drug Resistance, Multiple, Bacterial , Staphylococcal Skin Infections/veterinary , Staphylococcus/drug effects , Animals , Bacterial Proteins/genetics , Dog Diseases/epidemiology , Dogs , Male , New Zealand/epidemiology , Staphylococcal Skin Infections/epidemiology , Staphylococcal Skin Infections/microbiology , Staphylococcus/classification
8.
J Hosp Infect ; 92(2): 183-90, 2016 Feb.
Article in English | MEDLINE | ID: mdl-26778134

ABSTRACT

BACKGROUND: Two meticillin-resistant Staphylococcus aureus (MRSA) clones, sequence type (ST) 22 and ST239, have successfully spread globally. Across Australia, ST22 has supplanted ST239 as the main healthcare-associated MRSA. To understand the reasons underlying this shift, the epidemiology and clinical features of infections due to ST22 and ST239 MRSA isolates from a tertiary hospital in Melbourne, Australia were compared. METHODS: Over six months, consecutive MRSA isolates with clinical data were collected from specimens referred to Alfred Health Pathology (AHP). Isolates were genotyped by a multi-locus-sequence-typing-based high-resolution melting method. FINDINGS: Three hundred and twenty-eight of 1079 (30%) S. aureus isolated by AHP were MRSA. Of these, 313 were genotyped; 78 (25%) were clonal complex (CC) 22 (representing ST22) and 142 (45%) were CC239 (representing ST239). Common clinical syndromes included skin or soft tissue, respiratory tract and osteo-articular infections. On multi-variate logistic regression, compared with CC239, CC22 was associated with older patients [adjusted odds ratio (aOR) 1.04 for each year increase, 95% confidence interval (CI) 1.02-1.07)], and patients from subacute hospitals (aOR 2.7, 95% CI 1.2-5.8) or long-term care facilities (LTCFs; aOR 5.5, 95% CI 2.0-14.5). Median time from patient admission to MRSA isolation was nine days for CC239 and one day for CC22 (P < 0.01). MRSA strain epidemiology varied according to hospital unit. CONCLUSIONS: CC22 and CC239 MRSA have differing ecological niches. CC22 is associated with elderly patients in LTCFs, and CC239 is associated with nosocomial acquisition. Infection control strategies involving LTCFs and their residents will likely be required to achieve continued MRSA control.


Subject(s)
Cross Infection/epidemiology , Cross Infection/microbiology , Genotype , Methicillin-Resistant Staphylococcus aureus/classification , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Staphylococcal Infections/epidemiology , Staphylococcal Infections/microbiology , Age Factors , Aged , Aged, 80 and over , Australia/epidemiology , Cross Infection/pathology , Ecosystem , Female , Humans , Infection Control , Male , Methicillin-Resistant Staphylococcus aureus/genetics , Middle Aged , Multilocus Sequence Typing , Staphylococcal Infections/pathology , Staphylococcus aureus , Tertiary Care Centers
9.
Clin Microbiol Infect ; 21(5): 444-50, 2015 May.
Article in English | MEDLINE | ID: mdl-25708549

ABSTRACT

Typing of healthcare-associated methicillin-resistant Staphylococcus aureus (MRSA) from Australia in the 1970s revealed a novel clone, ST2249-MRSA-III (CC45), present from 1973 to 1979. This clone was present before the Australian epidemic caused by the recombinant clone, ST239-MRSA-III. This study aimed to characterize the genome of ST2249-MRSA-III to establish its relationship to other MRSA clones. DNA microarray analysis was conducted and a draft genome sequence of ST2249 was obtained. The recombinant structure of the ST2249 genome was revealed by comparisons to publicly available ST239 and ST45 genomes. Microarray analysis of genomic DNA of 13 ST2249 isolates showed gross similarities with the ST239 chromosome in a segment around the origin of replication and with ST45 for the remainder of the chromosome. Recombination breakpoints were precisely determined by the changing pattern of nucleotide polymorphisms in the genome sequence of ST2249 isolate SK1585 compared with ST239 and ST45. One breakpoint was identified to the right of oriC, between sites 1014 and 1065 of the gene D484_00045. Another was identified to the left of oriC, between sites 1185 and 1248 of D484_01632. These results indicate that ST2249 inherited approximately 35.3% of its chromosome from an ST239-like parent and 64.7% from an ST45-like parent. ST2249-MRSA-III resulted from a major recombination between parents that resemble ST239 and ST45. Although only limited Australian archival material is available, the oldest extant isolate of ST2249 predates the oldest Australian isolate of ST239 by 3 years. It is therefore plausible that these two recombinant clones were introduced into Australia separately.


Subject(s)
Cross Infection/epidemiology , Cross Infection/microbiology , Genotype , Methicillin-Resistant Staphylococcus aureus/classification , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Recombination, Genetic , Staphylococcal Infections/epidemiology , Australia/epidemiology , Chromosomes, Bacterial , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , Evolution, Molecular , Genome, Bacterial , Humans , Methicillin-Resistant Staphylococcus aureus/genetics , Microarray Analysis , Sequence Analysis, DNA , Staphylococcal Infections/microbiology
10.
J Antimicrob Chemother ; 70(3): 649-52, 2015 Mar.
Article in English | MEDLINE | ID: mdl-25411186

ABSTRACT

OBJECTIVES: To describe a family of conjugative plasmids isolated from colonizing community Staphylococcus aureus and determine their ability to mobilize unrelated antimicrobial resistance/virulence plasmids, not encoding mobilization functions. METHODS: Plasmid pWBG749 was labelled with Tn551 (pWBG749e) to enable laboratory manipulation. Plasmid pWBG749e was conjugated into S. aureus of seven different lineages that harboured unrelated plasmids and mobilization experiments were performed. Plasmids were screened by EcoRI restriction and hybridization with probes prepared from unique pWBG749 conjugation genes. RESULTS: Conjugative plasmids pWBG745, pWBG748 and pWBG749 belong to the same conjugative-plasmid family as the vancomycin resistance plasmid pBRZ01. Plasmid pWBG749e mobilized five unrelated plasmids. Mobilized plasmid pWBG744 is a pIB485-family plasmid that was also found in international S. aureus. CONCLUSIONS: Plasmid pWBG749e can mobilize unrelated S. aureus plasmids whose means of dissemination have not previously been understood.


Subject(s)
Conjugation, Genetic , Gene Transfer, Horizontal , Plasmids , Staphylococcus aureus/genetics , Community-Acquired Infections/microbiology , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , Gene Order , Genes, Bacterial , Humans , Molecular Sequence Data , Sequence Analysis, DNA , Staphylococcal Infections/microbiology , Staphylococcus aureus/isolation & purification
11.
Clin Microbiol Infect ; 20(7): 597-604, 2014 Jul.
Article in English | MEDLINE | ID: mdl-24891110

ABSTRACT

The clinical and molecular epidemiology of Staphylococcus aureus disease has changed considerably over the past two decades, particularly with the emergence and spread of community-associated methicillin-resistant S. aureus (CA-MRSA) clones. Indeed, some of the first global descriptions of CA-MRSA were from remote indigenous communities in Western Australia, and from Pacific Peoples in New Zealand. The epidemiology of S. aureus infections in the South West Pacific has several unique features, largely because of the relative geographical isolation and unique indigenous communities residing in this region. In particular, a number of distinct CA-MRSA clones circulate in Australia and New Zealand, such as sequence type (ST) 93 methicillin-resistant S. aureus (MRSA) (Queensland clone) and clonal complex 75 S. aureus (Staphylococcus argenteus) in Australia, and ST30 MRSA (Southwest Pacific clone) in New Zealand. In addition, there is a disproportionate burden of S. aureus disease in indigenous paediatric populations, particularly in remote Aboriginal communities in Australia, and in Pacific Peoples and Maori in New Zealand. In this review, we provide a contemporary overview of the clinical and molecular epidemiology of S. aureus disease in the South West Pacific region, with a particular focus on features distinct to this region.


Subject(s)
Community-Acquired Infections/epidemiology , Community-Acquired Infections/microbiology , Staphylococcal Infections/epidemiology , Staphylococcal Infections/microbiology , Staphylococcus aureus/classification , Staphylococcus aureus/genetics , Australia/epidemiology , Humans , Molecular Epidemiology , New Zealand/epidemiology , Pacific Islands/epidemiology , Staphylococcus aureus/isolation & purification
12.
Epidemiol Infect ; 142(8): 1713-21, 2014 Aug.
Article in English | MEDLINE | ID: mdl-24534254

ABSTRACT

Our aim was to describe the epidemiology and incidence of community-onset invasive S. aureus disease in children presenting to our hospital, and to compare the clonal complexes and virulence genes of S. aureus strains causing invasive and non-invasive disease. The virulence gene repertoire of invasive disease isolates was characterized using DNA microarray and compared with the virulence gene repertoire of non-invasive S. aureus isolates. Over the study period, 163 children had an invasive S. aureus infection. There was no difference in the distribution of clonal complexes or in the prevalence of genes encoding virulence factors between invasive and non-invasive isolates. Future research should include a strong focus on identifying the host and environmental factors that, along with organism virulence factors, are contributing to the patterns of invasive S. aureus disease observed in New Zealand.


Subject(s)
Community-Acquired Infections/epidemiology , Community-Acquired Infections/pathology , Staphylococcal Infections/epidemiology , Staphylococcal Infections/pathology , Staphylococcus aureus/classification , Staphylococcus aureus/genetics , Adolescent , Child , Child, Preschool , Cluster Analysis , Community-Acquired Infections/microbiology , Cross-Sectional Studies , Genotype , Humans , Incidence , Infant , Infant, Newborn , Microarray Analysis , Molecular Epidemiology , Molecular Typing , New Zealand/epidemiology , Retrospective Studies , Staphylococcal Infections/microbiology , Staphylococcus aureus/isolation & purification , Virulence Factors/genetics
13.
Clin Microbiol Infect ; 20(6): 530-5, 2014 Jun.
Article in English | MEDLINE | ID: mdl-24224545

ABSTRACT

To compare the management and outcome of methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia in patients known to be MRSA-colonized/infected (C-patients) with the management and outcome in those not known to be colonized/infected (NC-patients), we conducted a 10-year retrospective review of MRSA bacteraemia in an adult tertiary hospital. Clinical data were obtained by chart review, and mortality data from linked databases. Prior MRSA colonization/infection status was available to treating clinicians at the time of the bacteraemia as a 'Micro-Alert' tag on the patient's labels, in medical charts, and in electronic information systems. C-patients accounted for 35.4% of all MRSA bacteraemia episodes. C-patients were more likely to be indigenous, to be diabetic, or to have a history of previous S. aureus infection. Markers of illness severity (Simplified Acute Physiology Score (SAPS)-II, need for admission to the intensive-care unit, length of stay, and metastatic seeding) were similar in both groups. Empirical therapy included a glycopeptide in 49.3% of C-patients vs. 18.9% of NC-patients (p <0.01), and contained an antibiotic to which the MRSA isolate tested susceptible in vitro in 56.7% of C-patients vs. 45.1% of NC-patients (p 0.13). All-cause 7-day and 30-day mortality were 7.5% vs. 18.9% (p 0.04), and 22.4% vs. 31.1% (p 0.20), in the C-patient and NC-patient groups, respectively. Knowing MRSA colonization status was significantly associated with lower 30-day mortality in Cox regression analysis (p <0.01). These data suggest that mortality from MRSA bacteraemia is lower in C-patients, which may reflect the earlier use of glycopeptides. The low use of empirical glycopeptides in septic patients known to be previously MRSA-colonized/infected may represent a missed opportunity for infection control to positively impact on clinical management.


Subject(s)
Anti-Bacterial Agents/therapeutic use , Bacteremia/drug therapy , Glycopeptides/therapeutic use , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Staphylococcal Infections/drug therapy , Adolescent , Adult , Aged , Aged, 80 and over , Bacteremia/diagnosis , Bacteremia/mortality , Carrier State/diagnosis , Child , Female , Humans , Male , Middle Aged , Retrospective Studies , Staphylococcal Infections/diagnosis , Staphylococcal Infections/mortality , Survival Analysis , Treatment Outcome , Young Adult
14.
Epidemiol Infect ; 142(3): 501-11, 2014 Mar.
Article in English | MEDLINE | ID: mdl-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-ß-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.


Subject(s)
Community-Acquired Infections/epidemiology , Staphylococcal Infections/epidemiology , Staphylococcus aureus/isolation & purification , Adult , Anti-Bacterial Agents/pharmacology , Community-Acquired Infections/drug therapy , Community-Acquired Infections/microbiology , Drug Resistance, Bacterial , Humans , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Methicillin-Resistant Staphylococcus aureus/pathogenicity , Middle Aged , Polymerase Chain Reaction , Prevalence , Severity of Illness Index , Staphylococcal Infections/drug therapy , Staphylococcal Infections/microbiology , Staphylococcus aureus/pathogenicity , Victoria/epidemiology , Virulence
15.
Eur J Clin Microbiol Infect Dis ; 31(9): 2421-8, 2012 Sep.
Article in English | MEDLINE | ID: mdl-22382823

ABSTRACT

To determine the impact of infectious diseases consultation (IDC) in Staphylococcus aureus bacteraemia. All MRSA bacteraemia and a random subset of MSSA bacteraemia were retrospectively analysed. Out of 599 SAB episodes, 162 (27%) were followed by an IDC. Patients with IDC were younger and more frequently intravenous drug users, but fewer resided in a long-term care facility or were indigenous. Hospital length of stay was longer (29.5 vs 17 days, p < 0.001), and endocarditis (19.1% vs 7.3%, p < 0.001) and metastatic seeding (22.2% vs 10.1%, p < 0.001) were more frequent in the IDC group; however, SAPS II scores were lower in the IDC group (27 vs 37, p < 0.001). ICU admission rates in the two groups were similar. The isolate tested susceptible to empirical therapy more frequently in the IDC group (88.9% vs 78.0%, p = 0.003). Seven-day (3.1 vs 16.5%), 30-day (8.0% vs 27.0%) and 1-year mortality (22.2% vs 44.9%) were all lower in the IDC group (all p < 0.001). Multivariate analysis showed that effective initial therapy was the only variable associated with the protective effect of IDC. In patients with SAB, all-cause mortality was significantly lower in patients who had an IDC, because of the higher proportion of patients receiving effective initial antibiotics.


Subject(s)
Bacteremia/diagnosis , Bacteremia/mortality , Referral and Consultation/statistics & numerical data , Staphylococcal Infections/diagnosis , Staphylococcal Infections/mortality , Staphylococcus aureus/isolation & purification , Adolescent , Adult , Aged , Aged, 80 and over , Anti-Bacterial Agents/administration & dosage , Bacteremia/drug therapy , Child , Critical Care/statistics & numerical data , Endocarditis, Bacterial/epidemiology , Female , Humans , Length of Stay , Male , Middle Aged , Retrospective Studies , Staphylococcal Infections/drug therapy , Survival Analysis , Treatment Outcome , Young Adult
16.
Eur J Clin Microbiol Infect Dis ; 31(6): 1067-72, 2012 Jun.
Article in English | MEDLINE | ID: mdl-21909648

ABSTRACT

Due to a longstanding comprehensive "search and destroy policy", methicillin-resistant Staphylococcus aureus (MRSA) is not endemic in Western Australian (WA) acute care hospitals. As the prevalence of MRSA in the community has increased, healthcare workers (HCW) are at risk of importing MRSA into hospitals. We aimed to determine the prevalence of and risk factors for nasal MRSA colonization in our HCW population. A period prevalence study was conducted at an 850-bed tertiary hospital. Basic demographics and a nasal swab were obtained. A total of 1,542 HCWs employed in our centre were screened for MRSA, of whom 3.4% (n = 52) were colonized. MRSA colonization was more common in patient care assistants (6.8%) and nurses (5.2%) than in allied health professionals (1.7%) and doctors (0.7%) (p < 0.01). Working in "high-risk" wards that cared for MRSA colonized/infected patients was the strongest risk factor for HCW MRSA colonization (p < 0.001). ST1-IV and ST78-IV (the most common community clones in the region) were the most frequently identified clones. In conclusion, MRSA colonization of HCWs occurs primarily in HCWs caring for patients colonized or infected with MRSA. Surveillance screening of HCWs should be regularly performed on wards with patients with high MRSA colonization prevalence to prevent further spread in the hospital.


Subject(s)
Carrier State/epidemiology , Health Personnel , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Nose/microbiology , Staphylococcal Infections/epidemiology , Adolescent , Adult , Aged , Carrier State/microbiology , Female , Hospitals , Humans , Male , Middle Aged , Prevalence , Risk Factors , Staphylococcal Infections/microbiology , Western Australia/epidemiology , Young Adult
17.
Clin Microbiol Infect ; 17(12): 1804-10, 2011 Dec.
Article in English | MEDLINE | ID: mdl-21595795

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.


Subject(s)
Methicillin-Resistant Staphylococcus aureus/classification , Methicillin-Resistant Staphylococcus aureus/genetics , Molecular Typing/methods , Polymorphism, Single Nucleotide , Real-Time Polymerase Chain Reaction/methods , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/methods , Staphylococcal Infections/microbiology , Costs and Cost Analysis , Humans , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Real-Time Polymerase Chain Reaction/economics , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/economics
18.
Eur J Clin Microbiol Infect Dis ; 29(8): 1025-33, 2010 Aug.
Article in English | MEDLINE | ID: mdl-20549534

ABSTRACT

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.


Subject(s)
Community-Acquired Infections/microbiology , Community-Acquired Infections/pathology , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Staphylococcal Infections/microbiology , Staphylococcal Infections/pathology , Adolescent , Adult , Age Factors , Aged , Aged, 80 and over , Bacterial Toxins/genetics , Case-Control Studies , Child , Child, Preschool , Community-Acquired Infections/mortality , Ethnicity , Exotoxins/genetics , Female , Hospitalization/statistics & numerical data , Hospitals, Teaching , Humans , Leukocidins/genetics , Male , Methicillin-Resistant Staphylococcus aureus/classification , Methicillin-Resistant Staphylococcus aureus/genetics , Middle Aged , Prospective Studies , Risk Factors , Staphylococcal Infections/mortality , Virulence Factors/genetics , Young Adult
19.
J Antimicrob Chemother ; 64(4): 684-93, 2009 Oct.
Article in English | MEDLINE | ID: mdl-19713400

ABSTRACT

OBJECTIVES: Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) was first reported in remote regions of Western Australia (WA) in 1992 and is now the predominant MRSA isolated in the State. To gain insights into the emergence of CA-MRSA, 2146 people living in 11 remote WA communities were screened for colonization with S. aureus. METHODS: Antibiogram analysis, contour-clamped homogeneous electric field electrophoresis, multilocus sequence typing, Panton-Valentine leucocidin determinant detection and accessory genetic regulator typing were performed to characterize the isolates. MRSA was further characterized by staphylococcal cassette chromosome mec typing. RESULTS: The S. aureus population consisted of 13 clonal complexes and two Singleton lineages together with 56 sporadic isolates. Five lineages contained MRSA; however, these were not the predominant methicillin-susceptible S. aureus (MSSA) lineages. There was greater diversity amongst the MSSA while the MRSA appeared to have emerged clonally following acquisition of the staphylococcal cassette chromosome mec. Three MRSA lineages were considered to have been endemic in the communities and have subsequently become predominant lineages of CA-MRSA in the wider WA community. People colonized with MSSA tended to harbour clones of a different genetic lineage at each anatomical site while people colonized with MRSA tended to harbour clones of the same lineage at each site. Overall, the isolates were resistant to few antimicrobials. CONCLUSIONS: Although the evidence suggests that in WA CA-MRSA strains arose in remote communities and have now disseminated into the wider community, there is no evidence that they arose from the predominant MSSA clones in these communities.


Subject(s)
Carrier State/microbiology , Community-Acquired Infections/microbiology , Methicillin-Resistant Staphylococcus aureus/classification , Methicillin-Resistant Staphylococcus aureus/drug effects , Staphylococcal Infections/microbiology , Bacterial Proteins/genetics , Bacterial Toxins/genetics , Bacterial Typing Techniques , Cluster Analysis , DNA Fingerprinting , DNA, Bacterial/genetics , Electrophoresis, Gel, Pulsed-Field , Exotoxins/genetics , Humans , Leukocidins/genetics , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Microbial Sensitivity Tests , Molecular Epidemiology , Polymerase Chain Reaction , Rural Population , Sequence Analysis, DNA , Trans-Activators/genetics , Western Australia
20.
Eur J Clin Microbiol Infect Dis ; 28(4): 353-61, 2009 Apr.
Article in English | MEDLINE | ID: mdl-18850122

ABSTRACT

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.


Subject(s)
Bacteremia/epidemiology , Community-Acquired Infections/epidemiology , Cross Infection/epidemiology , Methicillin-Resistant Staphylococcus aureus , Staphylococcal Infections/epidemiology , Adolescent , Adult , Aged , Aged, 80 and over , Anti-Bacterial Agents/pharmacology , Bacteremia/drug therapy , Bacteremia/microbiology , Bacteremia/mortality , Child , Community-Acquired Infections/drug therapy , Community-Acquired Infections/microbiology , Community-Acquired Infections/mortality , Cross Infection/drug therapy , Cross Infection/microbiology , Cross Infection/mortality , Female , Humans , Male , Methicillin-Resistant Staphylococcus aureus/drug effects , Methicillin-Resistant Staphylococcus aureus/genetics , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Microbial Sensitivity Tests , Middle Aged , Prognosis , Retrospective Studies , Risk Factors , Staphylococcal Infections/drug therapy , Staphylococcal Infections/microbiology , Staphylococcal Infections/mortality , Statistics, Nonparametric
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