Antimicrobial Resistance and Molecular Characteristics of Nasal Staphylococcus aureus Isolates From Newly Admitted Inpatients.
ABSTRACT: Staphylococcus aureus, or methicillin-resistant S. aureus (MRSA), is a significant pathogen in both nosocomial and community infections. Community-associated MRSA (CA-MRSA) strains tend to be multi-drug resistant and to invade hospital settings. This study aimed to assess the antimicrobial resistance and molecular characteristicsof nasal S. aureus among newlyadmitted inpatients.In the present study, 66 S. aureus isolates, including 10 healthcare-associated MRSA (HA-MRSA), 8 CA-MRSA, and 48 methicillin-sensitive S. aureus (MSSA) strains, were found in the nasal cavities of 62 patients by screening 292 newlyadmitted patients. Antimicrobial resistance and molecular characteristics of these isolates, including spa-type, sequence type (ST) and SCCmec type, were investigated. All isolates were sensitive to linezolid, teicoplanin, and quinupristin/dalfopristin, but high levels of resistance to penicillin and erythromycin were detected. According to D-test and erm gene detection results, the cMLS(B) and iMLS(B) phenotypes were detected in 24 and 16 isolates, respectively. All 10 HA-MRSA strains displayed the cMLS(B) phenotypemediated by ermA or ermA/ermC, while the cMLS(B) CA-MRSA and MSSA strains carried the ermB gene. Molecular characterization revealedall 10 HA-MRSA strains were derived from the ST239-SCCmec III clone, and four out of eight CA-MRSA strains were t437-ST59-SCCmec V. The results suggest that patients play an indispensable role in transmitting epidemic CA-MRSA and HA-MRSA strains.
Project description:Several studies have shown that patients with bacteremia caused by methicillin-resistant Staphylococcus aureus (MRSA) have worse outcomes than those with bacteremia caused by methicillin-susceptible S. aureus (MSSA). However, only a limited number of studies have stratified the MRSA isolates into healthcare-associated (HA-) and community-associated (CA-) MRSA strains in such a comparison. This three-year retrospective cohort study, enrolling adult patients with nosocomial S. aureus bacteremia (SAB), was designed to investigate whether CA-MRSA and/or HA-MRSA strains were associated with different outcomes in comparison to MSSA in such a setting. The drug susceptibilities and staphylococcal cassette chromosome mec (SCCmec) types were determined for all of the causative isolates available. The MRSA bacteremia was further categorized into those caused by CA-MRSA strains (CA-MRSA-S bacteremia) when the causative isolates carried the type IV or V SCCmec element, those caused by HA-MRSA strains (HA-MRSA-S bacteremia) when the isolates carried the type I, II, or III SCCmec element, or unclassified MRSA bacteremia when the isolates were not available. The relevant demographic, clinical, and laboratory data were collected by reviewing the patients' charts. The primary outcome was all-cause in-hospital mortality. A total of 353 patients were studied. The overall in-hospital mortality rate was 32.6%, with 23.3% in MSSA, 30.5% in CA-MRSA-S, 47.5% in HA-MRSA-S, and 35.3% in unclassified MRSA bacteremia, respectively. The multivariate analysis showed that HA-MRSA-S, but not CA-MRSA-S, bacteremia was associated with a significantly worse outcome compared with MSSA. The other risk factors independently associated with all-cause in-hospital mortality included the Charlson co-morbidity index, septic shock, thrombocytopenia, and persistent bacteremia. Resistance to linezolid and daptomycin was found among the MRSA isolates. The present study showed that bacteremia caused by HA-MRSA-S, but not CA-MRSA-S, was an independent risk factor for all-cause in-hospital mortality in patients with nosocomial SAB. Continuous monitoring regarding the susceptibilities of MRSA to linezolid and daptomycin is necessary.
Project description:OBJECTIVES: Staphylococcus aureus or methicillin-resistant Staphylococcus aureus (MRSA) has been an important pathogen causing bloodstream infections. Our study aimed to investigate the epidemiological and genetic diversity of clinical S. aureus isolates from patients with bloodstream infection in four hospitals of Shanghai from 2009 to 2011. METHODS: A collection of S. aureus isolates causing bloodstream infection from four hospitals in the central part of Shanghai was carried out. Antimicrobial susceptibility testings of collected isolates were performed according to the Clinical and Laboratory Standards Institute (CLSI) guidelines, and spa-type, multi-locus sequence typing, agr type and toxin gene profiling were performed to explore the molecular diversity. Moreover, MRSA strains were also characterized by Staphylococcal cassette chromosome mec (SCCmec) typing. RESULTS: The drugs such as linezolid, teicoplanin and vancomycin were efficacious for treating S. aureus including MRSA bloodstream infection. Methicillin-sensitive Staphylococcus aureus (MSSA) strains displayed distinct diversity in molecular characterization and toxin genes, and three virulent MSSA strains encoding at least five toxins were detected. Five community-associated MRSA (CA-MRSA) strains were found, but the majority (88.7%) of MRSA strains belonged to two epidemic clones (ST239-MRSA- III and ST5-MRSA- II) with different toxin gene profiles among patients with bloodstream infection. CONCLUSIONS: Healthcare-associated MRSA (HA-MRSA) strains were still the main pathogen causing bloodstream infections in spite of the emergence of CA-MRSA strains in hospital setting.
Project description:<h4>Background</h4>Staphylococcus aureus (S. aureus), especially methicillin-resistant Staphylococcus aureus (MRSA), is considered a common zoonotic pathogen, causing severe infections. The objective of this study was to investigate the antimicrobial susceptibility, resistance genes and molecular epidemiology among MRSA and methicillin-susceptible Staphylococcus aureus (MSSA) isolated from food animals in Sichuan Province, China.<h4>Methods</h4>This study was conducted on 236 S. aureus isolates. All isolates were subjected to antimicrobial susceptibility testing by using a standard microbroth dilution method. The Polymerase Chain Reaction (PCR) was performed to identify genes encoding the β-lactams resistance (blaZ, mecA), macrolides (ermA, ermB, ermC) and aminoglycosides (aacA-aphD). The molecular structures and genomic relatedness of MRSA isolates were determined by staphylococcal chromosome cassette mec (SCCmec) typing and pulsed-field gel electrophoresis (PFGE), respectively.<h4>Results</h4>Among 236 isolates, 24 (10.17 %) were recognized as MRSA. MRSA isolates showed different resistance rates to 11 antimicrobials ranging from 33.33 to 100 %, while for MSSA isolates the rates varied from 8.02 to 91.51 %. Multi-drug resistance phenotype was found in all MRSA isolates. The ermC gene encoding macrolides-lincosamides-streptogramin B was the most prevalent gene detected in 87.29 % of the S. aureus isolates, followed by ermB (83.05 %), blaZ (63.98 %), aacA-aphD (44.07 %), ermA (11.44 %) and mecA (11.02 %) genes. The prevalence of resistance genes in MRSA isolates was significantly higher than that of MSSA. Regarding the molecular morphology, SCCmec III (12/24, 50 %) was the most common SCCmec type. Furthermore, the PFGE typing showed that 24 MRSA were divided into 15 cluster groups (A to O), the major pulsotype J encompassed 25 % of MRSA isolates.<h4>Conclusions</h4>The S. aureus isolates from food animals in Sichuan province of China have severe antimicrobials resistance with various resistance genes, especially MRSA isolates. Additionally, the genetic pool of MRSA isolates is diverse and complex, and further investigation is necessary.
Project description:Widespread infections with community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA) have occurred in the United States with the dissemination of the USA300 strain beginning in 2000. We examined 105 isolates obtained from children treated at the University of Chicago from 1994 to 1997 (75 methicillin-susceptible S. aureus [MSSA] and 30 MRSA isolates) in order to investigate for possible evidence of USA300 during this period. Infections were defined epidemiologically based on medical record review. The isolates underwent multilocus sequence typing (MLST), as well as assays for the Panton-Valentine leukocidin (PVL) genes, the protein A gene (spa), and arcA and opp3, proxy markers for the arginine catabolic mobile element (ACME), characteristic of USA300 MRSA. MRSA isolates also underwent staphylococcal cassette chromosome mec (SCCmec) typing and pulsed-field gel electrophoresis (PFGE) subtyping. MSSA isolates belonged to 17 sequence type (ST) groups. The 12 epidemiologically defined CA-MRSA infection isolates were either ST1 (n = 4) or ST8 (n = 8). They belonged to 3 different PFGE types: USA100 (n = 1), USA400 (n = 5), and USA500 (n = 6). Among the CA-MRSA infection isolates, 8 (67%) were PVL(+). None of the MRSA or MSSA isolates contained arcA or opp3. Only one MRSA isolate was USA300 by PFGE. This was a health care-associated (HA) MRSA isolate, negative for PVL, that carried SCCmec type II. USA300 with its characteristic features was not identified in the collection from the years 1994 to 1997.
Project description:Since the late 1990s, changes in the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) were recognized with the emergence of community-associated MRSA (CA-MRSA). CA-MRSA belonging to clonal complex 152 (CC152), carrying the small staphylococcal cassette chromosome mec (SCCmec) type V and encoding the Panton-Valentine leukocidin (PVL), has been observed in Europe. The aim of this study was to investigate its origin, evolution, and dissemination. Whole-genome sequencing was performed on a global collection of 149 CC152 isolates spanning 20?years (93 methicillin-susceptible S. aureus [MSSA] and 56 MRSA isolates). Core genome phylogeny, Bayesian inference, in silico resistance analyses, and genomic characterization were applied. Phylogenetic analysis revealed two major distinct clades, one dominated by MSSA and the other populated only by MRSA. The MSSA isolates were predominately from sub-Saharan Africa, whereas MRSA was almost exclusively from Europe. The European MRSA isolates all harbored an SCCmec type V (5C2&5) element, whereas other SCCmec elements were sporadically detected in MRSA from the otherwise MSSA-dominated clade, including SCCmec types IV (2B), V (5C2), and XIII (9A). In total, 93% of the studied CC152 isolates were PVL positive. Bayesian coalescent inference suggests an emergence of the European CC152-MRSA in the 1990s, while the CC152 lineage dates back to the 1970s. The CA-MRSA CC152 clone mimics the European CC80 CA-MRSA lineage by its emergence from a PVL-positive MSSA ancestor from North Africa or Europe. The CC152 lineage has acquired SCCmec several times, but acquisition of SCCmec type V (5C2&5) seems associated with expansion of MRSA CC152 in Europe.IMPORTANCE Understanding the evolution of CA-MRSA is important in light of the increasing importance of this reservoir in the dissemination of MRSA. Here, we highlight the story of the CA-MRSA CC152 lineage using whole-genome sequencing on an international collection of CC152. We show that the evolution of this lineage is novel and that antibiotic usage may have the potential to select for the phage-encoded Panton-Valentine leukocidin. The diversity of the strains correlated highly to geography, with higher level of resistance observed among the European MRSA isolates. The mobility of the SCCmec element is mandatory for the emergence of novel MRSA lineages, and we show here distinct acquisitions, one of which is linked to the successful clone found throughout Europe today.
Project description:Studies on the molecular epidemiologic characteristics of methicillin-resistant Staphylococcus aureus (MRSA) strains have demonstrated their genetic and geographical diversity. In addition, it has been reported that there are genetic differences between community-associated (CA) and health care-associated (HA) MRSA strains. Therefore, we investigated the major epidemiologic characteristics of CA MRSA isolates in South Korea and compared them with those of HA MRSA strains. Distributions of staphylococcal chromosome cassette mec (SCCmec) types and other molecular features, including the Panton-Valentine leukocidin (PVL) gene, were studied in 138 invasive MRSA isolates. Multiplex type IVA SCCmec was identified as the major CA MRSA infection type (53.1%), with a significantly higher prevalence than in HA MRSA (P < 0.001). One major group of type IVA strains carried a larger atypical class B mec element and new subtypes of ccrA2 (96% amino acid homology). The PVL gene was detected in one USA300-like isolate only. Seven major clone types determined by combinational grouping (genetic background SCCmec typing) showed representative patterns of antimicrobial susceptibilities. We concluded that less multi-drug-resistant strains of clone types B-I and D-1 (genetic background, B and D complexes; type IVA SCCmec) predominate in CA MRSA and that international PVL-positive strains have not spread in South Korea as yet.
Project description:Macrolides, lincosamides, and type B streptogramins (MLS<sub>B</sub>) are important therapeutic options to treat methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) infections; however, resistance to these antibiotics has been emerging. In Chile, data on the MLS<sub>B</sub> resistance phenotypes are scarce in both community-(CA) and hospital-acquired (HA) MRSA isolates. Antimicrobial susceptibility to MLS<sub>B</sub> was determined for sixty-eight non-repetitive isolates of each HA-(32) and CA-MRSA (36). Detection of SCC<i>mec</i> elements, <i>ermA</i>, <i>ermB</i>, <i>ermC</i>, and <i>msrA</i> genes was performed by PCR. The predominant clones were SCC<i>mec</i> I-ST5 (HA-MRSA) and type IVc-ST8 (CA-MRSA). Most of the HA-MRSA isolates (97%) showed resistance to clindamycin, erythromycin, azithromycin, and clarithromycin. Among CA-MRSA isolates, 28% were resistant to erythromycin, azithromycin, and 25% to clarithromycin. All isolates were susceptible to linezolid, vancomycin, daptomycin and trimethoprim/sulfamethoxazole, and over 97% to rifampicin. The <i>ermA</i> gene was amplified in 88% of HA-MRSA and 17% of CA-MRSA isolates (<i>p</i> < 0.001). The <i>ermC</i> gene was detected in 6% of HA-SARM and none of CA-SARM isolates, whereas the <i>msrA</i> gene was only amplified in 22% of CA-MRSA (<i>p</i> < 0.005). Our results demonstrate the prevalence of the cMLSB resistance phenotype in all HA-MRSA isolates in Chile, with the <i>ermA</i> being the predominant gene identified among these isolates.
Project description:Genetic characteristics were analysed for recent clinical isolates of methicillin-resistant and -susceptible Staphylococcus aureus (MRSA and MSSA respectively) in Kathmandu, Nepal. MRSA isolates harbouring Panton-Valentine leukocidin (PVL) genes were classified into ST1, ST22 and ST88 with SCCmec-IV and ST772 with SCCmec-V (Bengal Bay clone), while PVL-positive MSSA into ST22, ST30 and ST772. ST22 isolates (PVL-positive MRSA and MSSA, PVL-negative MRSA) possessed a variant of elastin binding protein gene (ebpS) with an internal deletion of 180 bp, which was similar to that reported for ST121 S. aureus previously outside Nepal. Phylogenetic analysis indicated that the ebpS variant in ST22 might have occurred independently of ST121 strains. This is the first report of ST772 PVL-positive MRSA in Nepal and detection of the deletion variant of ebpS in ST22 S. aureus.
Project description:This study aimed to investigate the clinical and molecular epidemiology and biofilm formation of Staphylococcus aureus (SA) isolated from pediatricians in China.SA strains were isolated from Beijing Children's hospital from February 2016 to January 2017. Isolates were typed by multilocus sequence typing (MLST), spa and SCCmec typing (for Methicillin-resistant SA [MRSA] only). Antimicrobial susceptibility testing was performed by agar dilution method except sulphamethoxazole/trimethoprim (E-test method). Biofilm formation and biofilm associated genes were detected.Totally 104 children (41 females and 63 males; median age, 5.2 months) were enrolled in this study, in which 60 patients suffered from MRSA infection. Among the 104 cases, 54.8% were categorized as community associated SA (CA-SA) infections. The children under 3 years were more likely to occur CA-SA infections compared with older ones (P?=?0.0131). ST59-SCCmec IV-t437 (61.7%) was the most prevalent genotype of MRSA, and ST22-t309 (18.2%), ST5-t002 (9.1%), ST6-t701 (9.1%), ST188-t189 (9.1%) were the top four genotypes of methicillin-sensitive SA (MSSA). All the present isolates were susceptible to linezolid, vancomycin, trimethoprim-sulfamethoxazole, mupirocin, tigecyclin, fusidic acid. No erythromycin-susceptible isolate was determined, and only a few isolates (3.8%) were identified as susceptible to penicillin. Multi-drug resistant isolates were reponsible for 83.8% of the ST59-SCCmec IV-t437 isolates. The isolates with strong biofilm formation were found in 85% of MRSA and 53.2% of MSSA, and in 88.7% of ST59-SCCmec IV-t437 isolates. Biofilm formation ability varied not only between MRSA and MSSA (P?= 0.0053), but also greatly among different genotypes (P?<?0.0001). The prevalence of the biofilm associated genes among ST59-SCCmec IV-t437 clone was: icaA (100.0%), icaD (97.3%), fnbpA (100.0%), fnbpB (0), clfA (100%), clfB (100%), cna (2.7%), bbp (0), ebpS (88.5%), sdrC (78.4%), sdrD (5.4%), and sdrE (94.5%).These results indicated strong homology of the MRSA stains isolated from Chinese children, which was caused by spread of multiresistant ST59-SCCmec IV-t437 clone with strong biofilm formation ability. The MSSA strains, in contrast, were very heterogeneity, half of which could produce biofilm strongly.
Project description:<h4>Background</h4>Several studies have addressed the epidemiology of community-associated Staphylococcus aureus (CA-SA) in Europe; nonetheless, a comprehensive perspective remains unclear. In this study, we aimed to describe the population structure of CA-SA and to shed light on the origin of methicillin-resistant S. aureus (MRSA) in this continent.<h4>Methods and findings</h4>A total of 568 colonization and infection isolates, comprising both MRSA and methicillin-susceptible S. aureus (MSSA), were recovered in 16 European countries, from community and community-onset infections. The genetic background of isolates was characterized by molecular typing techniques (spa typing, pulsed-field gel electrophoresis and multilocus sequence typing) and the presence of PVL and ACME was tested by PCR. MRSA were further characterized by SCCmec typing. We found that 59% of all isolates were associated with community-associated clones. Most MRSA were related with USA300 (ST8-IVa and variants) (40%), followed by the European clone (ST80-IVc and derivatives) (28%) and the Taiwan clone (ST59-IVa and related clonal types) (15%). A total of 83% of MRSA carried Panton-Valentine leukocidin (PVL) and 14% carried the arginine catabolic mobile element (ACME). Surprisingly, we found a high genetic diversity among MRSA clonal types (ST-SCCmec), Simpson's index of diversity = 0.852 (0.788-0.916). Specifically, about half of the isolates carried novel associations between genetic background and SCCmec. Analysis by BURP showed that some CA-MSSA and CA-MRSA isolates were highly related, suggesting a probable local acquisition/loss of SCCmec.<h4>Conclusions</h4>Our results imply that CA-MRSA origin, epidemiology and population structure in Europe is very dissimilar from that of USA.