Genotyping of community-associated methicillin resistant Staphylococcus aureus (CA-MRSA) in a tertiary care centre in Mysore,South India: ST2371-SCCmec IV emerges as the major clone

The burden of community-associated methicillin resistant Staphylococcus aureus (CA-MRSA) is on the rise in population and clinical settings on account of the adaptability and virulence traits of this pathogen. We characterized 45 non-duplicate CA-MRSA strains implicated mainly in skin and soft tissue infections (SSTIs) in a tertiary care hospital in Mysore, South India. All the isolates were genotyped by staphylococcal cassette chromosome mec (SCCmec) typing, staphylococcal protein A (spa) typing, accessory gene regulator (agr) typing, and multi-locus sequence typing (MLST). Four sequence types (STs) belonging to three major clonal complexes (CCs) were identified among the isolates: CC22 (ST2371 and ST22), CC1 (ST772) and CC8 (ST8). The majority (53.3%) of the isolates was of the genotype ST2371-t852-SCCmec IV [sequence type-spa type-SCCmec type], followed by ST22-t852-SCCmec IV (22.2%), ST772-t657-SCCmec V (13.3%) and ST8-t008-SCCmec IV (11.1%). ST237I, a single locus variant of ST22 (EMRSA-15 clone), has not been reported previously from any of the Asian countries. Our study also documents for the first time, the appearance of ST8-SCCmec IV (USA300) strains in India. Representative strains of the STs were further analyzed by pulsed field gel electrophoresis (PFGE). agr typing detected type I or II alleles in the majority of the isolates. All the isolates were positive for the leukotoxin gene, pvl (Panton–Valentine leukocidin) and the staphylococcal enterotoxin gene cluster, egc. Interestingly, multidrug resistance (resistance to ⩾3 classes of non-beta-lactam antibiotics) was observed in 77.8% (n = 35) of the isolates. The highest (75.5%) resistance was recorded for ciprofloxacin, followed by erythromycin (53.3%), and quinupristin–dalfopristin (51.1%). Inducible clindamycin-resistance was identified in 37.7% of the isolates and it was attributed to the presence of erm(A), erm(C) and a combination of erm(A) and erm(C) genes. Isolates which showed a phenotypic pattern of M^R/L^S (macrolide-resistance/lincosamide-sensitivity) harbored the msr(A) gene. In conclusion, we report a high rate of multidrug resistance among Indian strains of CA-MRSA and the emergence of the lineages ST2371 and ST8 in India.     

Community-associated strains of methicillin-resistant Staphylococccus aureus as the cause of healthcare-associated infection.

OBJECTIVE: Methicillin-resistant Staphylococcus aureus (MRSA) isolates from patients with community-associated infection have been described as strains genetically distinct from the strains isolated from patients with healthcare-associated infection. This study examines the hypothesis that community-associated MRSA (CA-MRSA) strains now cause serious infections in hospitalized patients. METHODS: Thirty-seven clinical MRSA isolates were randomly selected from blood isolates obtained from July 2003 through June 2004. Strains were tested for staphylococcal chromosomal cassette mec (SCCmec) type, pulsed-field gel electrophoresis (PFGE) type, and presence of Panton-Valentine leukocidin (PVL) genes. Medical records review and epidemiologic classification was performed by an investigator blinded to the results of the bacterial strain analysis. Episodes of bloodstream infection were independently classified as either community-associated or healthcare-associated infections, and bacterial isolates were independently classified as either CA-MRSA strains or healthcare-associated MRSA (HA-MRSA) strains, according to established definitions. SETTING: A tertiary care Veterans Affairs Medical Center. RESULTS: Twenty-four (65%) of 37 MRSA isolates were SCCmec type IV, a genetic type characteristic of CA-MRSA strains; 22 of these 24 isolates belonged to the CA-MRSA clone USA300 and carried PVL genes. Thirteen (35%) of the 37 strains were SCCmec type II, of which 12 were USA100-ST5 and 12 lacked PVL genes. Thirty patients (81%) had healthcare-associated infections; 18 (60%) of these 30 were infected with isolates carrying markers of CA-MRSA strains. Of 7 patients with CA-MRSA infections, 6 were infected with isolates belonging to the USA300 clone. Patients with healthcare-associated bloodstream infections were as likely to be infected with a CA-MRSA strain as patients with a community-associated infection (P = .38). CONCLUSIONS: MRSA strains with molecular characteristics of CA-MRSA strains have emerged as an important cause of serious healthcare-associated infection in our hospital.     

The evolution of Staphylococcus aureus

A broad variety of infections, ranging from minor infections of the skin to post-operative wound infections can be caused by Staphylococcus aureus. The adaptive power of S. aureus to antibiotics leaded, in the early 1960s, to the emergence of methicillin-resistant S. aureus (MRSA). The cause of resistance to methicillin and all other β-lactam antibiotics is the mecA gene, which is situated on a mobile genetic element, the staphylococcal cassette chromosome mec (SCCmec). Seven major variants of SCCmec, type I to VII, are distinguished. The most important techniques used to investigate the molecular epidemiology of S. aureus are pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), S. aureus protein A (spa) typing and SCCmec typing (only for MRSA). These techniques have been used to study the evolution of the MRSA clones that have emerged since the early 1960s, and to study their subsequent worldwide dissemination. The early MRSA clones were hospital-associated (HA-MRSA). However, from the late 1990s, community-associated MRSA (CA-MRSA) clones emerged worldwide. CA-MRSA harbors SCCmec type IV, V or VII, the majority belong to other S. aureus lineages compared to HA-MRSA, and CA-MRSA is often associated with the presence of the toxin Panton-Valentine leukocidin (PVL). However, during recent years, the distinction between HA-MRSA and CA-MRSA has started to disappear, and CA-MRSA is now endemic in many US hospitals. MRSA probably originated trough the transfer of SCCmec into a limited number of methicillin-sensitive S. aureus (MSSA) lineages. This review describes the latest observations about the structure of SCCmec, the techniques used to study the molecular epidemiology and evolution of S. aureus as well as some challenges that researchers face in the future.     

Clinical and molecular characteristics of nosocomial meticillin-resistant Staphylococcus aureus skin and soft tissue isolates from three Indian hospitals

We analysed risk factors for nosocomial meticillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infections (SSTIs) in three Indian hospitals. We also determined antimicrobial resistance patterns and genotypic characteristics of MRSA isolates using pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and staphylococcal cassette chromosome (SCCmec) typing. Medical records of 709 patients admitted to three tertiary hospitals with nosocomial S. aureus SSTIs were clinically evaluated. Antimicrobial susceptibility testing of patient isolates was performed in accordance with Clinical and Laboratory Standards Institute guidelines, with meticillin and mupirocin resistance confirmed by multiplex polymerase chain reaction. PFGE analysis of 220 MRSA isolates was performed, followed by MLST and SCCmec typing of a selected number of isolates. MRSA was associated with 41%, 31% and 7.5% of infections at the three hospitals, respectively. Multiple logistic regression analysis identified longer duration of hospitalisation [odds ratio (OR): 1.78; OR: 2.83 for ≥20 days], intra-hospital transfer (OR: 1.91), non-infectious skin conditions (3.64), osteomyelitis (2.9), neurological disorders (2.22), aminoglycoside therapy (1.74) and clindamycin therapy (4.73) as independent predictors for MRSA SSTIs. MRSA isolates from all three hospitals were multidrug resistant, with fifteen clones (I–XV) recognised. A majority of the strains possessed type III cassette. The common sequence type (ST) 239 was considered the signature MLST sequence for PFGE clone III. This major MRSA clone III was closely related to the UK EMRSA-1 and was significantly more resistant to antibiotics. Dissemination of multidrug-resistant MRSA clones warrants continuous tracking of resistant genotypes in the Indian subcontinent.     

Molecular characterization of invasive Staphylococcus aureus strains isolated from patients with diabetes in Iran: USA300 emerges as the major type

There have been few studies focused on the molecular characterization of invasive Staphylococcus aureus strains in patients with diabetes in Iran. In the present study, 20 invasive S. aureus strains recovered from the patients with diabetes characterized by the virulence and resistance analysis, biofilm formation, staphylocoagulase (SC) typing, S. aureus protein A locus (spa) typing staphylococcal cassette chromosome mec (SCCmec) typing, and multilocus sequence typing (MLST). Virulence gene detection indicated a high prevalence of strains encoding the pvl genes (50%), a low prevalence of the tst and seg gene (each of them was 5%) and a markedly high prevalence of fnbB (95%), fnbA (85%), icaD (75%), icaA (65%). A total of 3 coagulase types (III, 85%; II, 10%; V, 5%), 2 agr types (I, 90%; II 10%) and 2 SCCmec types (IV, 65%; III, 35%) and four different clones namely ST8-MRSA-IV/t008 (50%) (USA300), ST239-MRSA-III/t030 (35%), ST5-MRSA-IV/t002 (10%), and ST45-MRSA-IV/t038 (5%) were detected in this study. Eighty-five percent of the isolates were biofilm producers. All the 4 high-level mupirocin resistance (HLMUPR) strains belonged to CC/ST8-MRSA-IV/t008 clone and carried mupA gene. Fusidic acid-resistant isolate belonged to ST239-SCCmec III/t030 clone. One vancomycin-intermediate resistance isolates was detected in our study, which belonged to ST5-MRSA-IVt002. Circulating clone in MRSA strains (USA300) isolated from the patients with diabetes highlighting the possibility of transmission of these microorganisms' clones between hospital, community, and environments. However, further studies require providing critical insights into the importance of continued controlling and treatment of S. aureus infections in patients with diabetes.     

MRSA in children presenting to hospitals in Birmingham, UK

Meticillin-resistant Staphylococcus aureus (MRSA) isolates from children presenting to Birmingham hospitals were characterized using molecular methods. The study was performed on MRSA isolates from children aged 相似文献   

Clinical and laboratory features of community-associated methicillin-resistant Staphylococcus aureus: is it really new?

OBJECTIVE: To review the epidemiologic and molecular characteristics of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in Detroit, Michigan, to assess the risk factors for infection and the response to therapy. DESIGN: Prospective clinical and laboratory study of 2003-2004 CA-MRSA isolates. Molecular features were compared with CA-MRSA isolates from 1980. SETTING: A 600-bed urban academic medical center. PATIENTS: Twenty-three patients with CA-MRSA infections from 2003-2004 were evaluated. In addition, laboratory analysis was performed on 13 CA-MRSA isolates from 1980. MAIN OUTCOME MEASURES: Laboratory analysis of isolates included antimicrobial susceptibility testing, pulsed-field genotyping, testing for Panton-Valentine leukocidin (PVL) genes, and staphylococcal cassette chromosome mec typing. RESULTS: Patients were predominantly young African American males and presented with skin and soft-tissue infections. All isolates were resistant to erythromycin and highly susceptible to other agents. Patients were generally treated successfully with combination incision and drainage and systemic antibiotics. Among the 23 isolates, 20 (87%) were the same strain. This strain carried the staphylococcal cassette chromosome mec type IV and PVL genes and is genetically identical to USA 300. Thirteen isolates of patients from our community who presented with CA-MRSA infections in 1980 represented a single clone that is unique compared with the 2003-2004 isolates. This strain carried staphylococcal cassette chromosome mec type IVA but did not carry the PVL genes. CONCLUSIONS: In our community, CA-MRSA is largely due to a single clone with a type IV mec gene and PVL gene. The type IV staphylococcal cassette chromosome mec type can be demonstrated in CA-MRSA isolates from a remote period, suggesting that earlier outbreaks were not related to healthcare exposure.     

Methicillin-Resistant Staphylococcus aureus (MRSA) Detected at Four U.S. Wastewater Treatment Plants

Background: The incidence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections is increasing in the United States, and it is possible that municipal wastewater could be a reservoir of this microorganism. To date, no U.S. studies have evaluated the occurrence of MRSA in wastewater.Objective: We examined the occurrence of MRSA and methicillin-susceptible S. aureus (MSSA) at U.S. wastewater treatment plants.Methods: We collected wastewater samples from two Mid-Atlantic and two Midwest wastewater treatment plants between October 2009 and October 2010. Samples were analyzed for MRSA and MSSA using membrane filtration. Isolates were confirmed using biochemical tests and PCR (polymerase chain reaction). Antimicrobial susceptibility testing was performed by Sensititre® microbroth dilution. Staphylococcal cassette chromosome mec (SCCmec) typing, Panton-Valentine leucocidin (PVL) screening, and pulsed field gel electrophoresis (PFGE) were performed to further characterize the strains. Data were analyzed by two-sample proportion tests and analysis of variance.Results: We detected MRSA (n = 240) and MSSA (n = 119) in 22 of 44 (50%) and 24 of 44 (55%) wastewater samples, respectively. The odds of samples being MRSA-positive decreased as treatment progressed: 10 of 12 (83%) influent samples were MRSA-positive, while only one of 12 (8%) effluent samples was MRSA-positive. Ninety-three percent and 29% of unique MRSA and MSSA isolates, respectively, were multidrug resistant. SCCmec types II and IV, the pvl gene, and USA types 100, 300, and 700 (PFGE strain types commonly found in the United States) were identified among the MRSA isolates.Conclusions: Our findings raise potential public health concerns for wastewater treatment plant workers and individuals exposed to reclaimed wastewater. Because of increasing use of reclaimed wastewater, further study is needed to evaluate the risk of exposure to antibiotic-resistant bacteria in treated wastewater.     

Multiple-locus variable-number tandem-repeat analysis of meticillin-resistant Staphylococcus aureus discriminates within USA pulsed-field gel electrophoresis types

Many isolates of meticillin-resistant Staphylococcus aureus (MRSA) are indistinguishable when compared using the standard pulsed-field gel electrophoresis (PFGE) typing method. This may present a problem when investigating local outbreaks of MRSA transmission in a healthcare setting. It also impedes investigation of the widely disseminated community-acquired MRSA (USA 300-0114) in the inpatient setting, which is displacing other traditional hospital-acquired PFGE types. Combination of methods, including multiple-locus sequence typing (MLST), spa typing and staphylococcal cassette chromosome mec (SCCmec) typing, have been used with, or in place of, PFGE to characterise MRSA for epidemiological purposes. These methods are technically challenging, time-consuming and expensive and are rarely feasible except in large laboratories in tertiary care medical centres. Another method, which is simpler and with faster turnaround time, is multiple-locus variable-number tandem-repeat analysis (MLVA). We investigated the utility of MLVA to distinguish common PFGE types. The results suggest that MLVA can be used to identify unrelated strains with identical PFGE patterns or confirm close genetic composition of linked isolates. MLVA could potentially be used in conjunction with PFGE to validate relationships, but further prospective evaluation of these relationships will be required in order to define the proper role, if any, for use of this method in hospital epidemiology.     

Three-year survey of community-acquired methicillin-resistant Staphylococcus aureus producing Panton-Valentine leukocidin in a French university hospital

A retrospective survey was conducted at Bicêtre Hospital, France from January 2001 to September 2003 to screen for S. aureus isolates with a typical phenotype previously involved in necrotizing pneumonia in France. They were resistant to oxacillin and kanamycin, of intermediate susceptibility to fusidic acid, and susceptible to tobramycin and fluoroquinolones. Seventeen isolates were found and 16 were viable. The Panton-Valentine leukocidin (PVL) genes, various toxin genes and SCCmec IV and agr3 alleles were detected in all isolates. The clonal origin of these isolates was demonstrated by pulsed-field gel electrophoresis. Fourteen isolates were community-acquired methicillin-resistant Staphylococcus (CA-MRSA) isolated from previously healthy patients with skin or soft tissue infections. Three infections were of nosocomial origin, underlining that these PVL-producing CA-MRSA strains may also be hospital acquired. Five CA-MRSA isolates with an identical resistance phenotype collected in a neighbouring teaching hospital (H?pital Pitié-Salpétrière, Paris, France) were also PVL positive. Three isolates were clonally related to those of the Bicêtre Hospital whereas two were not. This retrospective study identified PVL-producing CA-MRSA in two Parisian hospitals. The incidence at Bicêtre Hospital was 0.8% of all S. aureus and 2% of all MRSA isolated. Our data indicate that these MRSA isolates might become hospital acquired.     

Characterization of Streptococcus pneumoniae invasive serotype 19A isolates recovered in Colombia

The aim of this study was to determine the molecular characterization of invasive penicillin non-susceptible Streptococcus pneumoniae serotype 19A isolates, collected in Colombia between 1994 and 2012. A total of 115 isolates serotype 19A were analyzed. Genetic relationship of 80 isolates with minimal inhibitory concentration (MIC) to penicillin ≥0.125 μg/was determined by pulsed-field gel electrophoresis (PFGE) and selected strains were studied by multilocus sequence typing (MLST). Among the 115 isolates, resistance to penicillin in meningitis was 64.2%, in non-meningitis 32.2% were intermediate and 1.1% were high resistance. The most frequent sequence types were ST320 (33.7%), ST276 (21.5%), and ST1118 (11.2%). Five isolates were associated with the Spain^9V-ST156 clone, and two isolates were related to Colombia^23F-ST338 clone. S. pneumoniae serotype 19A increased in Colombia was associated with the spread of isolates genetically related to ST320 and ST276, and emergence of capsular variants of worldwide-disseminated clones.     

Molecular Typing and Epidemiology of Human Listeriosis Cases,Denmark, 2002–2012

Denmark has a high incidence of invasive listeriosis (0.9 cases/100,000 population in 2012). We analyzed patient data, clinical outcome, and trends in pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) of Listeria monocytogenes strains isolated in Denmark during 2002–2012. We performed 2-enzyme PFGE and serotyping on 559 isolates and MLST on 92 isolates and identified some correlation between molecular type and clinical outcome and patient characteristics. We found 178 different PFGE types, but isolates from 122 cases belonged to just 2 closely related PFGE types, clonal complex 8 and sequence type 8. These 2 types were the main cause of a peak in incidence of invasive listeriosis during 2005–2009, possibly representing an outbreak or the presence of a highly prevalent clone. However, current typing methods could not fully confirm these possibilities, highlighting the need for more refined discriminatory typing methods to identify outbreaks within frequently occurring L. monocytogenes PFGE types.     

Community-acquired methicillin-resistant Staphylococcus aureus carrying Panton-Valentine leukocidin genes: worldwide emergence

Infections caused by community-acquired (CA)-methicillin--resistant Staphylococcus aureus (MRSA) have been reported worldwide. We assessed whether any common genetic markers existed among 117 CA-MRSA isolates from the United States, France, Switzerland, Australia, New Zealand, and Western Samoa by performing polymerase chain reaction for 24 virulence factors and the methicillin-resistance determinant. The genetic background of the strain was analyzed by pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). The CA-MRSA strains shared a type IV SCCmec cassette and the Panton-Valentine leukocidin locus, whereas the distribution of the other toxin genes was quite specific to the strains from each continent. PFGE and MLST analysis indicated distinct genetic backgrounds associated with each geographic origin, although predominantly restricted to the agr3 background. Within each continent, the genetic background of CA-MRSA strains did not correspond to that of the hospital-acquired MRSA.     

Emergence of methicillin-resistant,vancomycin-intermediate Staphylococcus aureus among patients associated with group A Streptococcal pharyngitis infection in southern India

Beyond Staphylococcus aureus being an etiological agent for several serious clinical complications, the foot prints of S. aureus in pharyngitis infection has also been recently recognized. With due response to the fact, a prospective study was conducted between 2009 and 2010 to describe the molecular epidemiology of S. aureus in throat swabs of pharyngitis patients. A total of 63 methicillin-resistant S. aureus (MRSA) and 102 methicillin-susceptible S. aureus (MSSA) isolates were recovered from 265 throat swabs, representing a community-acquired outpatient population from Tamil Nadu, India. Molecular characterization of MRSA was done by two conventional multiplex PCR assays including Panton-Valentine leukocidin (PVL), mecA and nuc genes, and staphylococcal cassette chromosome mec (SCCmec) typing. Among 165 S. aureus isolates, methicillin resistance was observed in 38.2% (n = 63), in which 69.8% (n = 44/63) of the MRSA along with 55.9% (n = 57/102) of MSSA harbored PVL toxin genes. SCCmec typing showed 50.8% of isolates as SCCmec V (n = 32), 44.4% as SCCmec III (n = 28), and 1.6% as SCCmec types I, II and IVa (n = 1). Multilocus sequence typing performed for 26 selected MRSA isolates resulted in 12 different sequence types (ST), including a novel ST2129/SCCmec III, PVL-positive. Ten MRSA isolates were categorized as ST772 (38.5%)/SCCmec V, PVL-positive, and three isolates as ST368 (11.5%)/SCCmec III, PVL-negative. Though the prominent clones of ST772/SCCmec V were multidrug-susceptible worldwide, they were highly multidrug-resistant in the current study, including four clones intermediate to vancomycin. Totally, 10 (15.9%) out of 63 MRSA isolates were documented as vancomycin-intermediate S. aureus (VISA). Collectively, the present study for the first time portrayed the high prevalence of active MRSA pharyngitis infection and also emphasizes an alarming need for discrimination of pharyngeal-asymptomatic carriers of S. aureus from those with an active S. aureus pharyngitis infection.     

2017-2018年江西地区耐甲氧西林金黄色葡萄球菌的分子流行特征

目的 了解江西各地区耐甲氧西林金黄色葡萄球菌（MRSA）的分子特征及主要流行克隆型别,探讨流行克隆可能的竞争优势,为后续的机制研究提供资料。方法 收集2017年1月-2018年12月江西省11个地市11所三甲医院临床分离的MRSA,同时应用mecA+femB双重PCR法鉴定为MRSA菌株后纳入研究,应用spa分型、SCCmec分型、PFGE和MLST进行分子分型,采用PCR方法检测杀白细胞素（PVL）毒力基因。结果 spa分型主要为t437（74株,占31.22%）、t030（32株,占13.50%）;不同地区的spa型存在很大差异,南昌地区以t030为主,其余地区以t437为主。SCCmecIVa为优势型别（占66.67%）,SCCmecⅢ占15.19%;除南昌地区以SCCmecⅢ为主要型别外（占59.38%）,其余各地区均以SCCmecIVa为主要优势型别。经PFGE分型和MLST,优势克隆型别为ST239、ST59、ST1和ST338;优势克隆群为CC239、CC59和CC1。共检出32株（13.19%）PVL阳性菌,其中鹰潭地区PVL检出率最高（29.63%,8/27）,其次为景德镇地区（26.32%,5/19）。结论 ST59-MRSA-IVa-t437为江西地区的主要优势流行克隆型,且各地区之间存在一定程度的克隆播散。ST239-MRSA-Ⅲ-t30为次要优势流行克隆型,主要在南昌地区多见,其他地区散发。江西地区PVL阳性菌株的主要型别为ST59-MRSA-t437-IVa型。     

Molecular epidemiology of methicillin-resistant Staphylococcus aureus, rural southwestern Alaska

USA300 is the dominant strain responsible for community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA) infections in most of the United States. We examined isolates from outbreaks of MRSA skin infections in rural southwestern Alaska in 1996 and 2000 (retrospective collection) and from the hospital serving this region in 2004-2006 (prospective collection). Among 36 retrospective collection isolates, 92% carried Panton-Valentine leukocidin (PVL) genes; all carried staphylococcal chromosomal cassette mec (SCCmec) type IV. None belonged to clonal complex (CC) 8, the CC associated with USA300; 57% were sequence type (ST) 1, and 26% were ST30; 61% were clindamycin resistant. In the prospective collection, 42 isolates were PVL+ and carried SCCmec type IV; 83.3% were ST1, 9.5% were ST30, and 7.1% were ST8. Among 120 prospective isolates, 57.5% were clindamycin resistant. CA-MRSA epidemiology in southwestern Alaska differs from that in the lower 48 states; ST8 strains were rarely identified and clindamycin resistance was common.     

Community-associated methicillin-resistant Staphylococcus aureus isolates causing healthcare-associated infections

We noted a marked increase in healthcare-associated (HA) methicillin-resistant Staphylococcus aureus (MRSA) infections caused by isolates phenotypically consistent with community-associated (CA)-MRSA strains. To study this trend, we retrospectively examined all HA-MRSA isolates from patients in our institution during 1999-2004. An isolate was considered an SCCmecIV phenotype if it had antimicrobial drug susceptibilities consistent with typical CA-MRSA isolates. Our phenotypic definition was validated in a limited subset of isolates by SCCmec genotype, pulsed-field gel electrophoresis, and multilocus sequence typing. Among 352 patients with HA-MRSA isolates, SCCmecIV phenotype increased from 17% in 1999 to 56% in 2003 (p < 0.0001). Antimicrobial drug-susceptibility phenotype and genotype were consistent in 21 (91%) of 23 isolates. In a multivariate model, the SCCmec type IV phenotype was independently associated with wound culture source, later year of collection, and MRSA isolated earlier during hospitalization. In conclusion, MRSA isolates phenotypically similar to CA strains have become the predominant isolates associated with HA-MRSA in our hospital.     

Changes in the epidemiology of meticillin-resistant Staphylococcus aureus associated with the emergence of EMRSA-16 at a university hospital

This study investigated the molecular epidemiology of meticillin-resistant Staphylococcus aureus (MRSA) in the University Hospital of the Canary Islands (HUC) in order to evaluate epidemiological changes over a six-year period. Clinical and epidemiological data were collected between May 2000 and December 2003, and isolates were subjected to pulsed-field gel electrophoresis (PFGE), multi-locus sequence typing (MLST), SCCmec typing and spa typing. Since 2000, the rate of MRSA infections has increased at the HUC, coinciding with the emergence and spread of the EMRSA-16 clone (ST36-MRSA-II) and replacement of the Iberian clone (ST247-MRSA-I). Genotypic changes were associated with changes in the epidemiological profile. The mean age and proportion of patients over 60 years old (P=0.01) and the proportion of respiratory infections (P=0.001) increased significantly. Gentamicin and tetracycline susceptibility of MRSA isolates increased (P<0.001) following the emergence of EMRSA-16. Combining PFGE, SCCmec and MLST has been instrumental in understanding these changes and defining the clones circulating in the HUC patient population.