Staphylococcal cassette chromosome mec (SCCmec) and arginine catabolic mobile element (ACME) in Staphylococcus epidermidis isolated from prosthetic joint infections

The aim of the present study was to characterise the staphylococcal cassette chromosome mec (SCCmec) in Staphylococcus epidermidis isolated from prosthetic joint infections (PJIs) and, if possible, assign them to any of the presently known SCCmec types. In addition, the isolates were examined for the presence of the arginine catabolic mobile element (ACME). Sixty-one S. epidermidis isolates obtained from PJIs and 24 commensal S. epidermidis isolates were analysed. The mecA gene was detected in 49 of the 61 (80 %) PJI isolates and in four of the 24 (17 %) commensal isolates, and the composition of the SCCmec was further analysed. SCCmec types I and IV were the most common types among the PJI isolates. However, for over half (57 %) of the isolates, it was not possible to assign an SCCmec type. ACME was detected in eight (13 %) of the PJI isolates and in 14 (58 %) of the commensal isolates. The characterisation of the SCCmec elements revealed a large heterogeneity, with a high frequency of isolates carrying more than one type of the ccr gene complex. ACME was more common among the commensal isolates and may represent a survival benefit for S. epidermidis colonising healthy individuals in the community.     

Molecular characterization of nasal methicillin resistant Staphylococcus aureus isolates from workers of an automaker company in southeast Iran

Colonization of methicillin resistant Staphylococccus aureus (MRSA) can occur more commonly in healthy people who live in close together or are in close physical contact with each other. Having knowledge about the molecular characteristics of these strains provides considerable discernment into the epidemiology of this important microorganism. A total of 806 nasal swabs were collected from healthy workers of an automaker company in the southeast of Iran and were analyzed to detect MRSA isolates. Multilocus sequence typing (MLST), spa typing, and detection of staphylococcal cassette chromosome mec (SCCmec) were performed. The presence of genes encoding Panton‐Valentine Leukocidin (PVL) and Arginine Catabolic Mobile Element (ACME) were also investigated. Carriage rate of S. aureus was 20%. Among 10 identified MRSA, no acme was found while high prevalence of pvl (60%) was of great concern. Seven different spa types including five new ones were identified. The most frequent sequence type was the novel one; ST 3373 (n = 3), followed by each of ST22, ST88, ST859 (n = 2) and ST1955 (n = 1). MRSA isolates were clustered into two main clonal complexes; CC22 (n = 6) and CC88 (n = 4). Low genetic diversity with the dominance of CC22, SCCmecIV was found. Distribution of previously found hospital‐associated MRSA was demonstrated among our isolates.     

Emergence of Panton-Valentine leucocidin-positive ST8-methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> (USA300 clone) in Korea causing healthcare-associated and hospital-acquired bacteraemia

Panton-Valentine leucocidin (PVL)-positive sequence type (ST)8-MRSA-SCCmec IVa (USA300) is the epidemic strain of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in North America. USA300 is extremely rare in South Korea, and PVL-negative ST72 SCCmec type IVc is the predominant CA-MRSA clone. In a multicentre, prospective cohort study of S. aureus bacteraemia, we identified PVL-positive ST8-MRSA isolates by performing multilocus sequence typing and PCR for PVL. We analyzed the clinical characteristics of patients with PVL-positive ST8-MRSA bacteraemia, and performed SCCmec, spa, and agr typing, PCR for arginine catabolic mobile element (ACME), virulence gene profiling, and pulsed-field gel electrophoresis (PFGE). Among a total of 818 MRSA isolates, we identified ten isolates of PVL-positive ST8-MRSA (USA300) (3 from Hospital D, 4 from Hospital G, and 3 from Hospital A), all of which involved exclusively healthcare-associated (5 isolates) and hospital-acquired bacteraemia (5 isolates). This strain accounted for 8~10 % of the hospital-acquired MRSA bacteraemia in Hospitals D and G. Bacteraemia of unknown origin was the most common type of infection followed by pneumonia. All the isolates were SCCmec type IVa, spa type t008, and agr group I. Eight of the isolates harboured ACME. In a PFGE analysis, four isolates were identical to the USA300 control strain, five differed by a single band, and the remaining one differed by two bands. All the isolates were pulsed-field type USA300. This is the first report of healthcare-associated and hospital-acquired bacteraemia caused by USA300 in South Korea. USA300 seems to be an emerging hospital clone in this country.     

Carriage of methicillin-resistant Staphylococci and their SCCmec types in a long-term-care facility

Following an outbreak caused by staphylococcal cassette chromosome mec (SCCmec) type V methicillin (meticillin)-resistant Staphylococcus aureus (MRSA), a point-prevalence survey of the nasal carriage of staphylococci was conducted in a long-term-care facility in northern Finland in 2004. The focus was directed at methicillin-resistant coagulase-negative staphylococci (MR-CNS) and their SCCmec elements. A nasal swab was taken from 76 of the 80 residents 6 months after the onset of the outbreak. Staphylococcal isolates were identified by conventional methods and the GenoType Staphylococcus test, and their SCCmec elements were analyzed. Of the 76 individuals, 24 (32%) carried S. aureus and 67 (88%) CNS in their nostrils. Of the CNS carriers, 41 (61%) had at least one mecA-positive MR-CNS, and two individuals (3%) had both MRSA and methicillin-resistant Staphylococcus epidermidis (MRSE). Among the 61 MR-CNS isolates identified, 49 (80%) were MRSE. The distribution of the SCCmec types was diverse: 20 (33%) were of type IV, 11 (18%) of type V, 4 (6%) of type I or IA, 3 (4%) of type II, and 23 (38%) of new types (with six different combinations of ccr and other mec genes or only mecA). Both of the individuals with MRSA and MRSE shared SCCmec type V among their isolates. Nasal MR-CNS carriage was common among the residents of this long-term-care facility. A variety of SCCmec types, including many new types, were identified among the MR-CNS strains. The horizontal transfer of SCCmec elements is speculated based on the sharing of SCCmec type V between MRSA and MRSE.     

Comparative Whole-Genome Mapping To Determine Staphylococcus aureus Genome Size,Virulence Motifs,and Clonality

Despite being a clonal pathogen, Staphylococcus aureus continues to acquire virulence and antibiotic-resistant genes located on mobile genetic elements such as genomic islands, prophages, pathogenicity islands, and the staphylococcal chromosomal cassette mec (SCCmec) by horizontal gene transfer from other staphylococci. The potential virulence of a S. aureus strain is often determined by comparing its pulsed-field gel electrophoresis (PFGE) or multilocus sequence typing profiles to that of known epidemic or virulent clones and by PCR of the toxin genes. Whole-genome mapping (formerly optical mapping), which is a high-resolution ordered restriction mapping of a bacterial genome, is a relatively new genomic tool that allows comparative analysis across entire bacterial genomes to identify regions of genomic similarities and dissimilarities, including small and large insertions and deletions. We explored whether whole-genome maps (WGMs) of methicillin-resistant S. aureus (MRSA) could be used to predict the presence of methicillin resistance, SCCmec type, and Panton-Valentine leukocidin (PVL)-producing genes on an S. aureus genome. We determined the WGMs of 47 diverse clinical isolates of S. aureus, including well-characterized reference MRSA strains, and annotated the signature restriction pattern in SCCmec types, arginine catabolic mobile element (ACME), and PVL-carrying prophage, PhiSa2 or PhiSa2-like regions on the genome. WGMs of these isolates accurately characterized them as MRSA or methicillin-sensitive S. aureus based on the presence or absence of the SCCmec motif, ACME and the unique signature pattern for the prophage insertion that harbored the PVL genes. Susceptibility to methicillin resistance and the presence of mecA, SCCmec types, and PVL genes were confirmed by PCR. A WGM clustering approach was further able to discriminate isolates within the same PFGE clonal group. These results showed that WGMs could be used not only to genotype S. aureus but also to identify genetic motifs in MRSA that may predict virulence.     

Molecular genetic characterization of methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> isolates recovered from Moscow clinics

Methicillin-resistant Staphylococcus aureus (MRSA) is the causative agent of nosocomial infections observed worldwide. The goal of this work was to study the genetic variations in MRSA isolates recovered from Moscow clinics and compare various methods of molecular typing (multiplex PCR, SNP genotyping based on the determination of single-nucleotide polymorphisms). A total of 62 epidemiologically unrelated hospital-acquired MRSA isolates were studied. A previously described multiplex PCR assay was utilized for the molecular typing of staphylococcal cassette chromosome mec (SCCmec). SNP genotyping that targets the seven sequences in five housekeeping genes (arcC162, arcC210, aroE132, gmk123, tpi241, tpi243, and yqiL333) was employed. Primer extension was used to screen single nucleotide variants followed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Multilocus sequence typing (MLST) was used as a reference assay. Most MRSA isolates (93.6%) were assigned to the clonal complex (CC) 8 disseminated worldwide. Three MRSA isolates (4.8%) proved to belong to CC1. The following correlation was established in this study between SCCmec cassette types and sequence types (STs): ST8-MRSA carried SCCmec type IV and ST239-MRSA carried type-III a SCCmec. Four SNP groups associated with certain SCCmec types were also identified. The developed SNP genotyping assay aided by MALDI-MS enables the rapid genotyping of S. aureus isolates according to their clonal types.     

High prevalence of mec complex C and ccrC is independent of SCCmec type V in Staphylococcus haemolyticus

Staphylococcus haemolyticus is one of the most clinically relevant coagulase-negative staphylococci (CoNS), particularly in immunocompromised patients; however, little is known regarding its molecular epidemiology. In this work, we characterized the genetic background and the SCCmec region of 36 methicillin-resistant S. haemolyticus (MRSHae) and 10 methicillin-susceptible S. haemolyticus (MSSHae) collected from neutropenic patients in Tunisia between 2002 and 2004. The molecular characterization of MRSHae by pulsed-field gel electrophoresis (PFGE) showed that the great majority of the isolates (77.8%) belonged to only four types. SCCmec typing by polymerase chain reaction (PCR) and Southern hybridization showed that isolates belonging to each PFGE type could carry either one or two SCCmec types. SCCmec V was the most common, but mec complex C was frequently associated to ccr allotypes other than ccrC. The mec complex class C was predominant in MRSHae (47%) and ccrC was predominant among both methicillin-resistant and -susceptible isolates (31 and 50%, respectively). Interestingly, one half (50%) of the MRSHae isolates analyzed lacked the known ccr complexes (ccrAB and ccrC), although they carried the mecA. Conversely, all MSSHae carrying a ccrC complex were multidrug-resistant, although they lack the mecA. The results suggest that ccrC and mec complex C are frequent and may exist autonomously and independently of SCCmec type V in S. haemolyticus. Moreover, the data obtained suggest that small chromosomal rearrangements promoting the loss or structural variation of mec and ccr complex appear to occur frequently, which probably provide S. haemolyticus with a specialized means for SCCmec trapping and/or diversification.     

Countrywide molecular survey of methicillin-resistant Staphylococcus aureus strains in Poland

The present investigation was undertaken to assess the proportion of methicillin-resistant Staphylococcus aureus (MRSA) strains among hospital-acquired isolates and to determine the clones of MRSA currently circulating in Poland by using a number of molecular techniques. Between January and May 2005, methicillin resistance was investigated among a total of 915 S. aureus isolates collected from 39 hospitals. A total of 208 (22.7%) isolates were positive for the mecA gene by PCR. The molecular characterization of MRSA isolates was carried out by the multiple-locus variable-number tandem repeat fingerprinting, pulsed-field gel electrophoresis, multilocus sequence typing, and staphylococcal chromosomal cassette mec (SCCmec) typing methods. The Hungarian (PFGE B; ST239, SCCmec type III [ST239-III]), Iberian (ST247-I), and Berlin (ST45-IV) clones were predominant, representing approximately 52.9, 11.5, and 10.0% of the MRSA isolates, respectively. A decline in the proportion of earlier MRSA clones, such as ST5-IV (a Pediatric clone), ST80-IV) (a Mediterranean clone), ST239-III (a Polish and Brazilian clone), and ST30-IV (a southwest Pacific clone) was observed. Additionally, the emergence of an MRSA clone with SCCmec type V, possibly representing a community-acquired strain, was observed in two hospitals during this study.     

Methicillin‐resistant and vancomycin‐intermediate Staphylococcus aureus colonizing patients and intensive care unit environment: virulence profile and genetic variability

This study aims to determine the prevalence of Staphylococcus aureus colonizing patients and ICU environment of a teaching hospital, the virulence and antimicrobial susceptibility profile of the isolates, and to evaluate the genetic relationship among them. A total of 536 swabs (134 of patients and 402 of ICU environment) were collected and analyzed to detect S. aureus. The antimicrobial susceptibility of the isolates was determined by disk diffusion test, and the detection of the mecA and virulence factors genes was performed by PCR, in addition to SCCmec typing. The genetic similarity of the isolates was determined by PFGE. Staphylococcus aureus was isolated in 12.7% of the swabs. The prevalence of colonization was 13.4% in patients and 12.4% in the environmental samples. The multidrug resistance was determined in 82.4% of the isolates. The prevalence of methicillin‐resistant S. aureus was 20.6%, with 50.0% classified as SCCmec IV. The intermediate resistance to vancomycin was detected in 5.9% and 4.4% of the isolates obtained from patients and environment, respectively. Identical isolates obtained from different patients and sources were grouped into several clusters. The results showed dissemination of multidrug‐resistant strains between patients and fomites and the persistence of MRSA and VISA isolates in the ICU environment.     

Clinical isolates of Staphylococcus aureus from the Arkhangelsk region,Russia: antimicrobial susceptibility,molecular epidemiology,and distribution of Panton‐Valentine leucocidin genes

A total of 91 consecutive clinical isolates of Staphylococcus aureus were collected at the Regional Hospital of Arkhangelsk, Russia, from May to December 2004, and examined for antimicrobial susceptibility, methicillin resistance and presence of Panton‐Valentine leucocidin (PVL) genes. Epidemiological typing was performed by pulsed‐field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Methicillin‐resistant S. aureus (MRSA) isolates were examined by staphylococcal cassette chromosome mec (SCCmec) typing. High‐to‐moderate rates of resistance to penicillin (β‐lactamase production; 93%), tetracycline (40%), erythromycin and clindamycin (32%) were observed. Forty out of ninety‐one (44%) isolates were positive for PVL genes. Thirty‐six (40%) PVL‐positive methicillin‐susceptible S. aureus (MSSA) strains were shown by PFGE and MLST typing (ST121, ST681, ST837) to be part of a nosocomial outbreak caused by clonal complex (CC) 121. PFGE, MLST and SCCmec typing revealed three MRSA clones. Sequence type (ST) 239‐III (n=11), ST1097‐III (n=1) and ST8‐IV (n=3) belong to CC8 of epidemic multiresistant MRSA, whereas ST426‐MRSA‐IV/CC395 (n=1) has not been reported previously. All MRSA strains were PVL negative. The overall results underline the necessity of microbiological sampling, antimicrobial susceptibility testing, and epidemiological typing as a rational basis for antimicrobial treatment of S. aureus infections, and infection control measures to limit the spread of multiresistant MRSA and epidemic MSSA clones.     

Presence of arginine catabolic mobile element among community‐acquired meticillin‐resistant staphylococcus aureus is linked to a specific genetic background

The prevalence of arginine catabolic mobile element (ACME) among diverse and heterogeneous community‐associated methicillin‐resistant Staphylococcus aureus community‐associated Methicillin‐resistant S. aureus (CA‐MRSA) (n = 114) in a low‐endemic area, i.e. Sweden, was investigated. Among the CA‐MRSA, represented by 47 different spa types, ACME was only found in 10 isolates with a common genetic background [t008, SCCmec type IV, Panton‐Valentine leukocidin (PVL) positive, and indistinguishable or closely related pulsed‐field gel electrophoresis (PFGE)‐patterns] corresponding to USA300. This strain does not seem to be established in our area as most of the patients contracted the CA‐MRSA abroad. Presence of ACME does not seem to be associated with colonization, long‐term carriership, or intra‐familiar transmission in a higher extent than CA‐MRSA in general.     

Current status of oxacillin-susceptible mecA-positive Staphylococcus aureus infection in Shanghai,China: A multicenter study

BackgroundOxacillin-susceptible mecA-positive Staphylococcus aureus (OS-MRSA) represents an important issue, as its oxacillin susceptibility has contributed to misidentification by conventional susceptibility tests and consequently potential therapeutic failure, but limited data on the current status of OS-MRSA infection in Chinese hospitals are available.MethodsThis multicenter study performed a battery of susceptibility tests and diagnostic tests for 956 S. aureus isolates from 10 hospitals, including automated susceptibility testing on VITEK 2, broth microdilution, disk diffusion, and detection of PBB2a, mecA gene and mecC gene. For all identified OS-MRSA, multi-locus sequence typing (MLST), together with spa typing, SCCmec typing and PVL detecting, was carried out.ResultsOS-MRSA, most of which were from pediatric inpatients, represented 1.8% (17/956) of total isolates. Of these 17 OS-MRSA, 10 were ST59, followed by ST965 (3/17), and 11 carried SCCmec type IV, while 5 carried SCCmec type V, but only one was Panton–Valentine leucocidin (PVL)-positive, also, 16 had one or two point mutations within mecA promoter. OS-MRSA had inducible oxacillin resistance and significantly lower MDR (Multi-Drug Resistant) rate. We observed that the VITEK 2 system exhibited some deficiency in OS-MRSA detection, whereas cefoxitin disk diffusion was shown to be a reliable and cost-saving alternative and should be supplemented in detecting S. aureus with borderline oxacillin susceptible MICs.ConclusionThis study has characterized phenotypically and molecularly OS-MRSA in China, and provided insights into more effective management of OS-MRSA.     

Heterogeneity of methicillin-resistant Staphylococcus aureus strains at a German university hospital during a 1-year period

Heterogeneous methicillin-resistant Staphylococcus aureus (MRSA) strains, including community-acquired MRSA strains, have been observed in Central Europe. The purpose of this study was to characterize by molecular methods MRSA isolated during the period 2002–2003 at the Otto-von-Guericke University Hospital in Magdeburg, Germany, and at a nearby chronic care facility. Strains were analyzed for their resistance phenotype. Selected isolates were typed by multilocus sequence typing (MLST), by a multiplex polymerase chain reaction (PCR) for the staphylococcal cassette chromosome mec (SCCmec), by an allele-specific PCR for the staphylococcal accessory gene regulator (agr), and by PCR for the presence of toxin genes (sea–sej, tsst-1, hlgA, C, and B, lukE/D, and luk-pvl). Of the 2,731 S. aureus isolates studied, 199 (7.3%) were MRSA, with a prevalence of 21.6%, 19.6%, and 12% in the department of dermatology, the chronic care facility, and the intensive care units. Six different sequence types (ST247, ST228, ST22, ST22a, ST225, and ST45) were observed. Of these, ST22, ST22a, and ST45 dominated (>50%) in the department of dermatology and the chronic care facility. Strains with these sequence types were usually not resistant to gentamicin and were associated with agr group I, the SCCmec type IV element, and the presence of the sec and sed toxin genes. ST228 strains were found mainly in the intensive care units and had a broader resistance phenotype and were associated with agr group II and the SCCmec type I element. All luk-pvl-positive MRSA isolates (n=8) belonged to agr group I and were typed as ST22 or ST45 and contained the SCCmec type I (n=1), type III (n=1), or type IV (n=6) element. The main observations of this study are in concordance with previously reported findings showing dissemination of MRSA in Central Europe. Through the multitude of applied methods, the data from this study contribute to a more precise knowledge about the heterogeneity of MRSA in a clinical setting. Rapid dissemination of MRSA clones at a university hospital was demonstrated, indicating that dissemination may depend on the environmental conditions within the individual departments.     

Molecular Investigation of Staphylococcal Cassette Chromosome Mec Types and Genotypic Relations of Methicillin-Resistant Staphylococci Isolated from Before and after Hospital Exposed Students

Background: Reservoir of methicillin resistance genes called staphylococcal cassette chromosome mec (SCCmec), plasmids and genomic characterisations of isolates have been widely investigated in epidemiologic research. However, the extent to which these organisms are transported by patients or hospital staff is not entirely clear. Aim: This study aims to investigate the molecular relatedness and plasmid profiles of MR staphylococci isolated from nursing students before and after hospital training, to find out the possible source. Materials and Methods: This study examined 39 methicillin-resistant (MR) staphylococci and 2 inducible clindamycin-resistant, methicillin-susceptible Staphylococcus aureus. Specimens were collected before and after 4 months of hospital training from the hands and nares of 75 nursing students. A polymerase chain reaction technique was used to confirm the existence of mecA gene and identify SCCmec types; total DNA was digested by SmaI endonuclease restriction to monitorise clonal relatedness by pulsed-field gel electrophoresis (PFGE); plasmid profiles were monitorised on agarose gel. Results: All 39 isolates tested positive for mecA; SCCmec type III was observed most frequently. Interestingly, in one isolate of Staphylococcus epidermidis, four different types of SCCmec elements were observed. There were 23 different types of plasmids, whose sizes ranged from 1.4 to 46.0 kb. After PFGE dendogram analysis, two strains were classified as indistinguishable; six were closely related. Most of the isolates obtained after hospital training showed clonal similarity and seven had multiple SCCmec elements require further investigation for the possible mechanism. Conclusion: Most of the isolates obtained after hospital training showed clonal similarity and seven had multiple SCCmec elements require further investigation for the possible mechanism.     

Molecular characterization and antibiotic resistance of clinical isolates of methicillin‐resistant Staphylococcus aureus obtained from Southeast of Iran (Kerman)

Staphylococcus aureus infections, particularly infections caused by methicillin‐resistant S. aureus (MRSA) strains, are emerging as a major public health problem. The aim of this study was to determine the prevalence of MRSA, antibiotic resistance profile and staphylococcal cassette chromosome mec (SCCmec) type of MRSA isolates obtained from clinical samples. Totally, 162 S. aureus isolates were obtained from clinical samples at three university hospitals in Kerman, Iran from March 2011 to February 2012. All isolates were identified as S. aureus by phenotypic methods and confirmed by PCR amplification of the nuc gene . MRSA isolates were screened by phenotypic tests and confirmed by presence of mecA gene. The minimum inhibitory concentrations (MICs) of the MRSA isolates against antibacterial agents were determined by E‐test. All isolates were analyzed by PCR for the presence of mecA and pvl genes. SCCmec typing of MRSA isolates was performed by multiplex PCR assay. Strain typing was carried out with REP‐PCR. Using mecA gene PCR and phenotypic methods, 56.8% of the isolates were identified as MRSA. All MRSA isolates were susceptible to vancomycin and linezolid. The sensitivity of MRSA isolates to trimethoprim‐sulfamethoxazole, clindamycin, ciprofloxacin, gentamicin, and erythromycin was 70.66, 66.53, 42.4, 38.05, and 29.35%, respectively. The most frequent SCCmec types were type III (48.31%) followed by type V (19.1%), type I (16.85%), and type IV (3.37%). The pvl gene was detected in 3.08% of isolates (two MRSA and three MSSA isolates). REP‐PCR typing divided the 92 MRSA isolates into 10 distinct clusters. Our results indicate that vancomycin and linezolid are the most effective antibacterial agents against MRSA isolates and SCCmec type III is predominant in MRSA strains in this area.     

Clonal spreading of methicillin-resistant SCCmec Staphylococcus aureus with specific spa and dru types in central Taiwan

The goal of this study was to delineate the molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) in Taiwan. Ninety-six MRSA isolates were collected from the blood cultures of different patients during the period July to December of 2008. The spa typing, staphylococcal chromosomal cassette (SCCmec) typing, mec-associated direct repeat unit (dru) copy numbers, and toxin genes (sea, seb, sec, tst, lukS/F) of each isolate were determined. Thirty-eight, 28, 18, and 12 MRSA isolates were SCCmec type II, SCCmec type III, SCCmec type IV, and SCCmec type V, respectively. Most (31/38, 81.6%) of the SCCmec type II isolates were of spa t002 with four dru repeats. Some of them also carried the sec or tst toxin gene (67.7 and 80.6%, respectively). Of the 28 SCCmec type III MRSA isolates, 15 (53.6%) were of t037 with 14 dru repeats, and all also carried the sea gene. Of the 18 SCCmec type IV MRSA isolates, 13 (72.2%) were of t437 with nine dru repeats, and ten of them also had the seb gene. Among the SCCmec type V MRSA isolates, nine were type V_T. Five (55.6%) of them were of t437 with 11 dru repeats, and all contained the lukS/F gene. The clonal spreading of SCCmec MRSA strains with specific spa and dru types was found. Further longitudinal, multiple-site surveillance is required in order to define the MRSA evolution in Taiwan.     

Positive predictive value of the Xpert MRSA assay diagnostic for universal patient screening at hospital admission: influence of the local ecology

The purpose of this study was to assess the accuracy of the Xpert MRSA assay (XP) for the detection of methicillin-resistant Staphylococcus aureus (MRSA) carriage upon hospital admission. Nasal swabs were prospectively collected for MRSA screening from 1,891 patients admitted to a teaching hospital. XP results were compared to chromogenic agar culture results. MRSA was cultured in 61 specimens (3%). Compared with culture, XP had a sensitivity, specificity, positive, and negative predictive value of 60.7, 97.3, 37.8, and 98.9%, respectively. The median turnaround time (TAT) for the results was 3 h. Of 24 MRSA isolated from XP-negative samples, three harbored composite SCCmec. Among 61 samples with culture-negative but XP-positive results, 15 methicillin-susceptible S. aureus (MSSA) isolates tested positive by XP on pure colony lysates. These MSSA included: (i) strains with SCCmec deletion encompassing mecA and (ii) multilocus sequence typing (MLST) clonal complex (CC) 1 strains harboring a chromosomal sequence homologous to one of the orfX–SCCmec junction sequences targeted by XP. On account of the low sensitivity and positive predictive value in a hospital patient population with moderate prevalence of MRSA, culture still appears to be necessary in order to confirm polymerase chain reaction (PCR) results. The emergence of new SCCmec variants and the presence of MSSA harboring cross-reactive SCCmec-like elements may challenge the successful implementation of such detection systems.     

High frequency of multidrug‐resistant Staphylococcus aureus with SCCmec type III and Spa types t037 and t631 isolated from burn patients in southwest of Iran

Methicilin resistance Staphylococcus aureus (MRSA) infections are the major challenges in hospitals, especially in the burn units. The use of molecular typing methods is essential for tracking the spread of S. aureus infection and epidemiological investigations. The aim of this study was to find the profile of the spa types and also the prevalence of each SCCmec type of S. aureus strains in a central burn hospital in southwest of Iran. A total of 81 non‐duplicate S. aureus were isolated from burn patients between April 2011 and February 2012. The susceptibility of the isolates against 13 different antibiotics was tested by disk agar diffusion (DAD) method. MRSA strains were identified by amplification of mecA gene. Multiplex‐polymerase chain reaction (PCR) technique was used to determine the SCCmec types of MRSA strains and all the S. aureus isolates were typed by spa typing method. Detection of mecA gene showed that 70 (86.4%) of the isolates were MRSA. The highest rate of resistance was observed for penicillin (97.5%) and erythromycin (77.8%). None of the isolates were resistant to vancomycin. Sixty‐seven of the 70 MRSA isolates harbored only SCCmec type III and three untypeable isolates. Five different spa types were detected. The most common spa types were t037 (42.5%) and t631 (34.5%) and were only found in MRSA isolates. Only SCCmec type III was found in burn patients which emphasizes the HA‐MRSA origin of these strains. Only five different spa types identified in this study are in accordance with one SCCmec type which indicates that a limited number of bacterial colons are circulated in the burn unit in this hospital.     

Coagulase-negative staphylococci in very-low-birth-weight infants: inability of genetic markers to distinguish invasive strains from blood culture contaminants

Selected coagulase-negative staphylococci from the blood of very-low-birth-weight infants in the Neonatal Intensive Care Unit at the Royal Women’s Hospital, Melbourne, collected over a 5-year period were examined. Isolates were classified as invasive or contaminants, speciated, typed by pulsed-field gel electrophoresis, and examined for biofilm genes (icaA, icaC, and icaD), adhesion genes (atlE, fbe), and the number of copies of IS256. Of the 24 isolates studied, there were 13 contaminants and 11 invasive isolates. The collection included 15 Staphylococcus epidermidis, eight Staphylococcus capitis, and one each of Staphylococcus warneri and Staphylococcus haemolyticus. Two small clusters of S. epidermidis that belonged to the same molecular type were identified. All S. capitis isolates belonged to the same molecular type or subtype, suggesting that a particular clone was circulating in the unit. There was no significant difference in the species found, the presence of icaA, icaC, icaD, atlE, or fbe, or the number of copies of IS256 between invasive isolates and contaminants. A series of nasal isolates from nonhospitalized adults differed from hospital isolates in the absence of IS256 and the low prevalence of icaC. There was no evidence of IS256-mediated insertion into ica genes as a mechanism of phase variation. These findings suggest that contaminants and invasive isolates derived from the same pool of hospital strains capable of causing sepsis in compromised hosts and that other mechanisms of phase variation exist, apart from IS256 insertion into ica genes.