Nationwide surveillance for Staphylococcus aureus with reduced susceptibility to vancomycin in Korea

Methicillin-resistant Staphylococcus aureus (MRSA) accounts for more than 70% of S. aureus isolates from tertiary hospitals in Korea. Clinical isolates of S. aureus were collected from eight provincial, university-affiliated hospitals during the period from June 1999 to January 2001 for nationwide surveillance. All isolates were screened for reduced susceptibility to vancomycin by using brain heart infusion agar containing 4 micro g of vancomycin per milliliter. Population analysis and the determination of the MIC of vancomycin were done for the isolates which grew on the screening agar plates. Of 682 total isolates, MRSA accounted for 64% (439 of 682). Of 27 (4%) isolates that grew on the screening agar plates, none showed the heteroresistance phenotype. No strains with reduced susceptibility to vancomycin were identified.     

Prevalence and clinical implications of Staphylococcus aureus with a vancomycin MIC of 4 microg/ml in Korea

In addition to vancomycin-intermediate Staphylococcus aureus (VISA), S. aureus with a vancomycin MIC of 4 microg/ml has been reported to be the cause of therapeutic failure. This study was designed to determine the prevalence of methicillin-resistant S. aureus (MRSA) with a vancomycin MIC of 4 microg/ml and to clarify the clinical characteristics of infections caused by these isolates. During the 8-week period from April to May, 2001, 27 hospitals participated in a nationwide surveillance program for VISA and vancomycin-resistant S. aureus (VRSA) in Korea. After screening on brain-heart infusion agar containing 4 microg/ml of vancomycin as previously described, 100 isolates with confluent growth were tested. The medical records of the patients involved were reviewed. Even though VISA or VRSA was not detected among 3,756 MRSA isolates, 18 (0.5%) had a vancomycin MIC of 4 microg/ml. The infections in 12 of these patients, excluding 5 that were colonized, were 8 chronic osteomyelitis, 1 surgical site infection, 1 pneumonia, 1 intra-abdominal infection, and 1 catheter-related infection. Although 11 cases were exposed to glycopeptides for a long time (median 56 days), the site of infection became culture-negative in only 1 case. Two patients died of their S. aureus infections. MRSA with a vancomycin MIC of 4 microg/ml was rare. Chronic osteomyelitis was the most common type of infection, and prolonged exposure to glycopeptides was associated with reduced susceptibility to vancomycin.     

Colonization with vancomycin-intermediate Staphylococcus aureus strains containing the vanA resistance gene in a tertiary-care center in north India

A nasal carriage survey for methicillin-resistant Staphylococcus aureus (MRSA) in an intensive care unit detected four strains of MRSA with reduced susceptibility to vancomycin. The vanA gene was found in two of these vancomycin-intermediate Staphylococcus aureus (VISA) strains. The absence of selective vancomycin pressure might have resulted in reduced expression of the resistant gene.     

Vancomycin susceptibility trends and prevalence of heterogeneous vancomycin-intermediate Staphylococcus aureus in clinical methicillin-resistant S. aureus isolates

Due to the rise in methicillin-resistant Staphylococcus aureus (MRSA) infections and widespread use of vancomycin, MRSA isolates with reduced susceptibility to vancomycin are emerging (i.e., MIC creep). However, the prevalence of heterogeneous vancomycin-intermediate S. aureus (hVISA) is unknown due to the difficulty in detecting this phenotype. Recently, Etest glycopeptide resistance detection (GRD) strips have been developed to detect hVISA. This study assessed vancomycin susceptibility in MRSA isolates and determined the prevalence of hVISA by Etest GRD and population analysis profile-area under the curve ratio (PAP-AUC). The genetic backgrounds of 167 MRSA isolates collected from 2000 to 2008 were identified by pulsed-field gel electrophoresis. Vancomycin MICs were determined using Etest and two broth microdilution assays, MicroScan and Sensititre. Etest GRD was performed on all isolates, and those exhibiting a hVISA phenotype were further tested by PAP-AUC. The vancomycin MIC modes remained consistent at 1 μg/ml, as assessed by Sensititre and MicroScan. Etest reported a significant increase (mode MIC = 1.5 μg/ml) in the MIC between 2000 and 2008 (P < 0.01); however, this increase did not reflect a ≥ 2-fold change. In addition, the slight MIC increase did not increase linearly from 2000 to 2008, suggesting biological fluctuation, and is inconsistent with the concept of MIC creep. Etest GRD identified six hVISA isolates, two of which were confirmed to be hVISA by PAP-AUC. In conclusion, reduced vancomycin susceptibility was not detected in our hospital over a 9-year period using three different MIC methodologies, and the hVISA incidence was 1.2%, as determined by Etest GRD and PAP-AUC.     

First report of methicillin-resistant Staphylococcus aureus with reduced susceptibility to vancomycin in Thailand

To investigate whether there are methicillin-resistant Staphylococcus aureus (MRSA) strains with reduced susceptibility to vancomycin in Thailand, a total of 155 MRSA strains isolated from patients hospitalized between 1988 and 1999 in university hospitals in Thailand were tested for glycopeptide susceptibility. All the strains were classified as susceptible to vancomycin and teicoplanin when judged by NCCLS criteria for glycopeptide susceptibility using the agar dilution MIC determination. Vancomycin MICs at which 50 and 90% of the isolates tested were inhibited (MIC50 and MIC(90), respectively) were 0.5 and 1 microg/ml, respectively, with a range of 0.25 to 2 microg/ml. For teicoplanin, MIC50 and MIC90 were 2 microg/ml, with a range of 0.5 to 4 microg/ml. However, one-point population analysis identified three MRSA strains, MR135, MR187, and MR209, which contained subpopulations of cells that could grow in 4 microg of vancomycin per ml. The proportions of the subpopulations were 2 x 10(-4), 1.5 x 10(-6), and 4 x 10(-7), respectively. The subsequent performance of a complete population analysis and testing for the emergence of mutants with reduced susceptibility to vancomycin (MIC > or = 8 microg/ml) confirmed that these strains were heterogeneously resistant to vancomycin. Two of these strains caused infection that was refractory to vancomycin therapy. Pulsed-field gel electrophoresis showed that the two strains had identical SmaI macrorestriction patterns and that they were one of the common types of MRSA isolated in the hospital. This is the first report of heterogeneous resistance to vancomycin in Thailand and an early warning for the possible emergence of vancomycin resistance in S. aureus in Southeast Asia.     

Evolution of a vancomycin-intermediate Staphylococcus aureus strain in vivo: multiple changes in the antibiotic resistance phenotypes of a single lineage of methicillin-resistant S. aureus under the impact of antibiotics administered for chemotherapy

A number of methicillin-resistant Staphylococcus aureus (MRSA) isolates were recovered over a period of several weeks from blood samples and from the heart valve of a patient who underwent extensive vancomycin chemotherapy for persistent S. aureus bacteremia. Consecutive isolates showed gradually decreasing growth rates during in vitro cultivation and increasing vancomycin MICs, from an MIC of 1 micro g/ml for the initial isolate to an MIC of 8 micro g/ml for the final MRSA isolates, which also became tolerant to vancomycin. Major changes were observed in the oxacillin resistance phenotype of several of the isolates-apparently related to in vivo exposure to imipenem, which was also used during a period of chemotherapy. Both the gradually increasing vancomycin MICs and the changes in oxacillin resistance could be reproduced by appropriate exposure of the initial MRSA isolate to antibiotics in vitro. All isolates had the same pulsed-field gel electrophoresis pattern, spaA type, and multilocus sequence type (MLST), which was identified as a single-locus variant of ST5, the MLST characteristic of previously characterized MRSA isolates with reduced susceptibility to vancomycin in the United States and Japan.     

Increased vancomycin MICs for Staphylococcus aureus clinical isolates from a university hospital during a 5-year period

Staphylococcus aureus is one of the most commonly isolated organisms in nosocomial infections. While the prevalence of methicillin-resistant S. aureus (MRSA) continues to increase worldwide, there is concern about an increase in vancomycin MICs among S. aureus strains. The prevalence of MRSA and vancomycin MIC trends in S. aureus from patients in a university hospital were analyzed. Clinical Laboratory Standards Institute (CLSI, formerly NCCLS) reference broth microdilution MIC testing was performed on all clinically relevant S. aureus isolates from January 2000 through December 2004. A total of 6,003 S. aureus isolates were analyzed. No vancomycin-resistant S. aureus isolates were detected. One MRSA isolate had a vancomycin MIC of 8 mug/ml and was confirmed as vancomycin-intermediate S. aureus. Among the 6,002 remaining isolates, a shift in vancomycin MICs from 相似文献   

Relationship of MIC and bactericidal activity to efficacy of vancomycin for treatment of methicillin-resistant Staphylococcus aureus bacteremia

We attempted to find a relationship between the microbiological properties of bloodstream isolates of methicillin-resistant Staphylococcus aureus (MRSA) and the efficacy of vancomycin in the treatment of bacteremia. Vancomycin susceptibility testing was performed, and bactericidal activity was determined for 30 isolates from 30 different patients with MRSA bacteremia for whom clinical and microbiological outcome data were available. The majority of these patients had been previously enrolled in multicenter prospective studies of MRSA bacteremia refractory to conventional vancomycin therapy. Logistic regression found a statistically significant relationship between treatment success with vancomycin and decreases in both vancomycin MICs (< or =0.5 microg/ml versus 1.0 to 2.0 microg/ml; P = 0.02) and degree of killing (reduction in log(10) CFU/milliliter) by vancomycin over 72 h of incubation in vitro (P = 0.03). For MRSA isolates with vancomycin MICs < or = 0.5 microg/ml, vancomycin was 55.6% successful in the treatment of bacteremia whereas vancomycin was only 9.5% effective in cases in which vancomycin MICs for MRSA were 1 to 2 microg/ml. Patients with MRSA that was more effectively killed at 72 h by vancomycin in vitro had a higher clinical success rate with vancomycin therapy in the treatment of bacteremia (log(10) < 4.71 [n = 9], 0%; log(10) 4.71 to 6.26 [n = 13], 23.1%; log(10) > 6.27 [n = 8], 50%). We conclude that a significant risk for vancomycin treatment failure in MRSA bacteremia begins to emerge with increasing vancomycin MICs well within the susceptible range. Elucidating the mechanisms involved in intermediate-level glycopeptide resistance in S. aureus should begin by examining bacteria that begin to show changes in vancomycin susceptibility before the development of obvious resistance. Prognostic information for vancomycin treatment outcome in MRSA bacteremia may also be obtained by testing the in vitro bactericidal potency of vancomycin.     

First report of vancomycin-intermediate resistance in sequence type 72 community genotype methicillin-resistant Staphylococcus aureus

Vancomycin-intermediate resistance has not been previously reported among sequence type 72 (ST72) methicillin-resistant Staphylococcus aureus (MRSA) isolates of SCCmec type IV (ST72-MRSA-IV), which are distinctive community genotype strains in Korea. We report the first case of vancomycin treatment failure due to development of vancomycin-intermediate resistance in infection caused by an ST72-MRSA-IV isolate.     

In vitro activities of eight antibiotics against methicillin-resistant S. aureus and S. epidermidis strains isolated in Korea

Staphylococcus aureus and Staphylococcus epidermidis strains isolated at eight large medical centers in Korea were examined for methicillin resistance and resistance to eight other antibiotics; cefazolin, cefamandole, cefuroxime, cefoxitin, cefotaxime, moxalactam, penicillin G and vancomycin. Methicillin resistance was found in 296 of 1225 strains (24.2%) of S. aureus and 126 of 348 strains (36.2%) of S. epidermidis. Methicillinresistant strains were isolated from all sources with the frequency of isolation ranging from 11% to 60%. From pleural effusion, throat swab and blood, methicillin-resistant strains of S. aureus were more frequently isolated with statistical significance (Chi-squared test, 95% confidence). Almost all of Methicillin-resistant S. aureus (MRSA) and S. epidermidis (MRSE) strains were multiply resistant to one or more tested eight antibiotics. However only 7(2.4%) of 296 MRSA strains and 2(1.6%) of 126 MRSE strains were resistant to vancomycin. Vancomycin was the most effective antibiotic against staphylococcal isolates as well as MRSA and MRSE.     

Antibiotics resistance of meticilline-resistant Staphylococcus aureus: detection of the first glycopeptides low sensibility strains in Tunisia

The adaptation of Staphylococcus aureus to the hospital environment led to the acquisition of resistance to all antibiotics available in clinical practice. The aim of this study was to investigate the methicillin-resistant Staphylococcus aureus (MRSA) strains isolated in the F. Bourguiba hospital of Monastir (Tunisia). We determined the antibiotype of all Staphylococcus aureus strains identified. Susceptibility rates to fosfomycin, chloramphenicol, rifampicin and pristinamycin were 7%, 3%, 2% and 0%, respectively. The prevalence of MRSA was 15.5% (96 strains); their susceptible to gentamicin progressively increased. The minimum inhibitory concentration (MICs) of oxacillin, vancomycin and teicoplanin were evaluated for the 96 MRSA strains. We identified two MRSA strains (M4 and M41) showing reduced glycopeptides susceptibility. Further analysis revealed that M4 and M41 harbor the gene encoding the class S and class F proteins specific for the Panton-Valentine Leukocidin (PVL). The mecA gene was detected only in strain M41 which harbors the Staphylococcal Cassette Chromosome (SCCmec) type III. This is the first reported MRSA showing reduced susceptibility to glycopeptides in Tunisia. Regulatory surveillance of susceptibility to antibiotics is needed to reduce the morbidity and the mortality rates as well as societal costs of S. aureus infections.     

Use of surveillance cultures and enteral vancomycin to control methicillin-resistant Staphylococcus aureus in a paediatric intensive care unit

This study assessed the effects of throat and gut surveillance, combined with enteral vancomycin, on gut overgrowth, transmission of methicillin-resistant Staphylococcus aureus (MRSA), infections and mortality in patients admitted to a paediatric intensive care unit (PICU). A 4-year prospective observational study was undertaken with 1241 children who required ventilation for >or=4 days. Patients identified as MRSA carriers following surveillance cultures of throat and rectum received enteral vancomycin. Twenty-nine (2.4%) children carried MRSA, 19 on admission and nine during treatment in the PICU; one patient was not able to be evaluated. Overgrowth was present in 22 (75%) of the carriers. Ten (0.8%) children developed 21 MRSA infections (15 exogenous infections in eight children at a median of 8 days (IQR 3-10.5); five primary endogenous infections at a median of 3 days (IQR 1-25) in three children when they were in overgrowth status; one child developed both types of infection). Enteral vancomycin reduced gut overgrowth significantly, completely preventing secondary endogenous infections. Transmission occurred on nine occasions over a period of 4 years. Four patients died, two (5.9%) with MRSA infection, giving a mortality (11.8%) similar to the study population (9.8%). No emergence of vancomycin-resistant enterococci or S. aureus with intermediate susceptibility to vancomycin was detected. A policy based on throat and gut surveillance, combined with enteral vancomycin, for critically-ill children who were MRSA carriers was found to be effective and safe, and challenges the recommended guidelines of nasal swabbing followed by topical mupirocin.     

Molecular Epidemiology of Oxacillin-resistant Staphylococcus aureus and in vitro Activity of Glycopeptides against Staphylococcus species

Oxacillin resistant Staphylococcus aureus and coagulase negative Staphylococcus species (MRSA and MRSCoN)have become major pathogens in nosocomial infections.The first MRSA isolate in the world was identified in En gland in 1961 [1]. Since that tim…     

Antimicrobial resistance of <Emphasis Type="Italic">Staphylococcus</Emphasis> from otorrhea in chronic suppurative otitis media and comparison with results of all isolated <Emphasis Type="Italic">Staphylococci</Emphasis>

Staphylococcus is one of the most important pathogenic bacteria in chronic suppurative otitis media (CSOM). The prevalence of pathogenic bacteria in patients with CSOM has not been compared with the prevalence rates in patients from other fields of medicine. We investigated the pathogenic bacteria in CSOM throughout Korea and annual isolation rates of methicillin-resistant Staphylococcus aureus (MRSA) over 6 years. Routine culture results and susceptibility data of CSOM isolated from 2000 to 2005 were collected from six general hospitals in Korea, along with the results of all clinically isolated Staphylococci from one tertiary care teaching hospital. Of the 1,162 bacteria identified in 1,360 CSOM patients, 628 (54.0%) were Staphylococci in CSOM. Of the latter, 288 (45.9%) were MRSA, which accounted for 24.8% of identified bacteria. Of the 5,988 clinically isolated Staphylococci from one tertiary care hospital, 3,712 (61.9%) were MRSA. All MRSA isolated from CSOM patients were sensitive to vancomycin and teicoplanin, and 88.2% were sensitive to sulfamethoxazole/trimethoprim. In contrast, these strains showed little or no sensitivity to oxacillin, clindamycin, penicillin, and erythromycin. Annual MRSA isolation rates showed no tendencies to increase or decrease. MRSA was the most frequently identified Staphylococcus in patients with otorrhea. The isolation rate of MRSA has not changed over 6 years. Continuous and periodic surveillance of MRSA is necessary to reduce the spread of antibiotic-resistant pathogens and to guide appropriate antibacterial therapy.     

Identification of the first vancomycin intermediate-resistant Staphylococcus aureus (VISA) isolate from a hospital in Portugal

A clinical isolate of methicillin-resistant Staphylococcus aureus (MRSA) with intermediate resistance to vancomycin (minimal inhibitory concentration [MIC] of 4 mug/ml) was isolated in 2006 from a surgical wound of a patient hospitalized at the orthopedics ward of Hospital de S?o Marcos--Braga, in the town of Braga. A combination of molecular typing methods, including pulsed-field gel electrophoresis (PFGE), spa typing, multilocus sequence typing, and staphylococcal chromosomal cassette mec typing, identified the vancomycin intermediate-resistant S. aureus VISA-BRAGA as a derivative of the epidemic MRSA (EMRSA)-15 clone, which has been isolated with increasing frequency from several Portuguese hospitals recently. Compared to another EMRSA-15 isolate with the same genetic background (including PFGE subtype) the VISA-BRAGA isolate exhibited relatively high oxacillin MIC, slow growth, loss of hemolytic activity, and increased resistance to vancomycin and to daptomycin although neither of these two antibiotics was used in therapy. The VISA-BRAGA isolate described here appears to represent the first S. aureus with decreased susceptibility to vancomycin identified in a Portuguese hospital.     

Resistance mechanisms of gram-positive bacteria

The introduction and increasing use of antibiotics for antibacterial therapy has initiated a rapid development and expansion of antibiotic resistance in microorganisms, particularly in human pathogens. Additionally, a shift to an increase in number and severity of Gram-positive infections has been observed the last decades. Common to these pathogens is their tendency to accumulate multiple resistances under antibiotic pressure and selection. Methicillin-resistant Staphylococcus aureus (MRSA), that have acquired multiresistance to all classes of antibiotics, have become a serious nosocomial problem. Recently, the emergence of the first MRSA with reduced vancomycin susceptibility evoked the specter of a totally resistant S. aureus. Problems with multiresistance expand also to penicillin-resistant Streptococcus pneumoniae that are partially or totally resistant to multiple antibiotics, and to vancomycin-resistant Enterococcus ssp., completely resistant to all commonly used antibiotics. The rapid development of resistance is due to mutational events and/or gene transfer and acquisition of resistance determinants, allowing strains to survive antibiotic treatment.     

Is Vancomycin MIC “Creep” Method Dependent? Analysis of Methicillin-Resistant Staphylococcus aureus Susceptibility Trends in Blood Isolates from North East Scotland from 2006 to 2010

This study investigated "creep" in vancomycin and daptomycin MICs among methicillin-resistant Staphylococcus aureus (MRSA) isolates from blood cultures over a 5-year period in a hospital in the United Kingdom, using different susceptibility testing methods. Trends in vancomycin and daptomycin susceptibility were evaluated by using Etest performed prospectively on isolates in routine clinical practice from December 2007 to December 2010 (n = 102). Comparison was made to results from prospective testing of subcultures at the Scottish MRSA Reference Laboratory, using an automated system (Vitek 2) and retrospective testing (Etest and CLSI reference broth microdilution [BMD] method) of stored isolates from 2006 to 2010 (n = 208). Spearman's rank correlations revealed a significant increase in vancomycin MIC (P = 0.012) and a significant decrease in daptomycin MIC (P = 0.03) by year of study for Etest results from the time of isolation. However, neither trend was replicated in MICs from automated or retrospective testing. The Friedman test revealed a significant difference between vancomycin MICs obtained from the same samples by different testing methods (χ(2) [3 degrees of freedom] = 97; P < 0.001). MICs from automated testing and Etest analysis of stored isolates were significantly lower than those from Etest analysis at the time of isolation for both antibiotics (P < 0.001). Effects of storage on the MIC appeared within the first 6 months of storage. Inconsistent evidence on vancomycin MIC creep and the relevance of the MIC to clinical outcome may arise from differences in susceptibility testing methods, including storage of isolates. There is a need to standardize and streamline susceptibility testing of vancomycin against MRSA.     

The VISA/GISA problem: therapeutic implications

The emergence of vancomycin intermediate resistant Staphylococcus aureus (VISA) isolates in Japan, USA, France, Hong Kong and Korea among methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates, is of great concern. Vancomycin has been the drug of choice for the treatment of multiresistant MRSA infections in the last three decades, but the management of invasive MRSA infections will become a serious problem if VISA strains become widespread. VISA isolates reported to date have a vancomycin MIC of 8 mg/L, and were isolated from patients with underlying diseases whose long-term vancomycin treatment apparently failed. Since many VISA isolates also have been resistant to teicoplanin, the term glycopeptide-intermediate S. aureus (GISA) is more appropriate. The frequency of GISA isolates appears to be extremely low; to date, only 10 GISA infections have been reported worldwide. However, heterogeneous resistance to glycopeptides (h-GISA) have been reported in Japan, Europe and Thailand. These h-GISA strains showed vancomycin MICs ranging from 1 to 4 mg/L, but had subpopulations that could grow on agar plates containing 4–8 mg/L, which may represent the first step in the development of GISA strains. Although GISA isolates have shown resistance to many antimicrobials, all GISA isolates remain susceptible to co-trimoxazole and some of them to other common antimicrobials. Currently, there are no recommended therapy guidelines for GISA infections, although in recent studies, several new drugs have shown promising activity against GISA strains. In addition, synergy between glycopeptides and β-lactams against GISA strains was observed in some in vivo and in vitro studies. Specific MRSA/GISA control programs, rational antibiotic policies, including the reduction of glycopeptide use, and rapid laboratory detection of GISA and h-GISA strains are the key measures in preventing the spread of these strains.     

Effectiveness of hydroxyapatite-vancomycin bone cement in the treatment of Staphylococcus aureus induced chronic osteomyelitis

In the field of local application of antimicrobials, a number of novel drugs and/or new drug delivery systems have been developed in recent years. The present study aimed to investigate hydroxyapatite cement (HAC) as a carrier for vancomycin in the treatment of chronic osteomyelitis due to Staphylococcus aureus strains with various mechanisms of resistance. The release of vancomycin from standard test cylinders was determined in vitro and the efficacy of the delivery system was measured in vivo using a rabbit model of chronic osteomyelitis. First, powdered HAC was mixed with vancomycin at 80, 160 and 240 mg/g. After hardening, formed cylinders were eluted in phosphate buffer and antibiotic release was measured by agar diffusion. High levels of release (1512+/-318 to 1937+/-336 microg/ml) were obtained for 12 to 20 days depending on the dosage of vancomycin. Additionally, bone infection was induced in the tibia of 30 New Zealand white rabbits by injecting either a methicillin-resistant S. aureus strain (MRSA) or a S. aureus strain with a small colony variant (SCV) phenotype. After 3 weeks (chronic infection), all animals were treated by debridement. Moreover, group 1 (challenged with SCVs) and group 2 (challenged with MRSA) were treated by filling the marrow with HAC alone, whereas in groups 3 (SCVs) and 4 (MRSA) the marrow was filled with HAC/vancomycin (160 mg/g). After 6 weeks all animals were sacrificed. At 3 weeks, pathogens were detected in 24 of 30 animals. All swabs of the control groups, positive for S. aureus on day 21, were also positive on day 42 and S. aureus strains recovered were shown to be clonal to the strains used for induction of osteomyelitis. By contrast, no growth was found in the treatment group following 7 days of incubation in BHI bouillon. HAC/vancomycin-treated animals showed no histological evidence of infection on day 42. In the other groups, different stages of chronic osteomyelitis were found histologically. No local or systemic side effects due to HAC or vancomycin were seen. HAC is an effective carrier material for antibiotic compounds even in refractory infections due to MRSA or S. aureus SCVs.     

Typing and antimicrobial susceptibilities of methicillin resistant Staphylococcus aureus (MRSA) strains isolated in a hospital in Korea

Methicillin-resistant Staphylococcus aureus (MRSA) strains may cause serious nosocomial infections, including pneumonia and septicemia. The rate of methicillin-resistance among S. aureus isolates in Korea is over 50%. In this study, 90 MRSA isolates from Kyung Hee University Hospital were characterized employing bacteriophage typing, pulsed-field gel electrophoresis (PFGE), and antimicrobial susceptibility testing. Eighty percent of the strains could be phage-typed. The largest group or 40% of the strains belonged to lyso group III, followed by 32% of the isolates which produced a reaction with regional additional phages. Phage type 83A was most frequently encountered, followed by phage type D11. PFGE patterns confirmed the presence of two major clusters, which comprise the isolates belonging to lyso group III and the strains that were typable with regional additional phages. The latter group also contained a number of strains that were nontypable with bacteriophages. The resistance rates to ciprofloxacin, erythromycin, tetracycline, gentamicin and clindamycin were over 94%. Strains with intermediate resistance to vancomycin strains or resistance to mupirocin were not found. In conclusion, this study demonstrates that the results of phage typing are confirmed and supplemented by PFGE data.