Emergence of the community-acquired methicillin-resistant Staphylococcus aureus USA300 clone in a Japanese child, demonstrating multiple divergent strains in Japan

In 2008 we isolated methicillin-resistant Staphylococcus aureus (MRSA) from an 11-month-old Japanese girl who lived in Saitama, Japan, and suffered from cellulitis of the lower thigh and sepsis. The MRSA (strain NN47) belonged to multilocus sequence type (ST) 8 and exhibited spa363 (t024), agr1, staphylococcal cassette chromosome mec (SCCmec) type IVa, and coagulase type III. It was positive for Panton–Valentine leukocidin (PVL) and the arginine catabolic mobile element (ACME). Pulsed-field gel electrophoresis (PFGE) demonstrated that the MRSA was the USA300 clone, which is the predominant community-acquired MRSA (CA-MRSA) in the US. Strain NN47 was divergent, in terms of the spa type and patterns of PFGE and plasmids, from the USA300-0114 type strain or USA300 strain NN36, previously isolated from a visitor (Indian girl) from the US. Strain NN47 was resistant to erythromycin, in addition to β-lactam agents (e.g., oxacillin). These data demonstrate the first emergence of the USA300 clone in Japanese children who have never been abroad and have had no contact with foreigners (and therefore, the first USA300 spread in Japan), and also emergence of multiple divergent strains of the USA300 clone in Japan. Because the USA300 clone is highly transmissible and virulent, surveillance of the USA300 clone is needed.     

Genotyping of skin and soft tissue infection (SSTI)-associated methicillin-resistant Staphylococcus aureus (MRSA) strains among outpatients in a teaching hospital in Japan: application of a phage-open reading frame typing (POT) kit

We aimed to elucidate the current epidemiological features of outpatient skin and soft tissue infection (SSTI)-associated methicillin-resistant Staphylococcus aureus (MRSA) in Japan. Altogether, we evaluated the performance of a phage-open reading frame typing (POT) kit for genotyping these MRSA strains. We collected 57 MRSA strains from all outpatients with SSTIs attending a teaching hospital in Japan. Drug susceptibility measurement and genotyping including SCCmec typing, spa typing, multilocus sequence typing, pulsed-field gel electrophoresis, and commercial POT-kit were performed. The majority of strains (39 strains, 68 %) had the SCCmec-II element. Seventeen strains (30 %) with SCCmec-IV accounted for the second largest population. Strains with SCCmec-IV and SCCmec-V appeared multiclonal, and a predominance of Panton–Valentine leukocidin (PVL) gene-negative CC8/spa-CC008 strains, as well as the first isolate of an ST93 strain in Japan, was observed among them. Only one USA300 strain was identified. Strains with SCCmec-IV and SCCmec-V were significantly susceptible to antimicrobials. The PVL gene was found in 5 SCCmec-IV strains and 1 SCCmec-V strain. The POT-kit successfully predicted the SCCmec type in 54 strains (95 %), and typing by POT1 scores was highly concordant with SCCmec typing and spa typing. Moreover, three PVL-positive strains fell into a particular POT type (POT scores, 106–77–113). Simpson’s index of the POT-kit was 0.977. In conclusion, the present study clarified the multiclonal nature of outpatient SSTI-associated MRSA in a teaching hospital in Japan. These data also underscore the utility of the POT-kit for non-outbreak surveillance through its simple platform consisting of two multiplex PCRs without sequencing.     

Survey of methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> from neonates and the environment in the NICU

Methicillin-resistant Staphylococcus aureus (MRSA) is a risk factor of nosocomial infection with compromised hosts including neonates. Currently, the prevalence of MRSA carriers among children is increasing in Japan. There are some reports of nosocomial infection caused by MRSA in a pediatric ward or neonatal intensive care unit (NICU). During 6 months (from January 2001 to June 2001), 37 MRSA strains were isolated from 37 neonates who were admitted in the NICU and 52 MRSA were strains isolated from NICU environments. We performed DNA typing of MRSA using an arbitrary primed-PCR method on these isolates. Thirty-seven clinical isolates were classified into four types (A type, 14; B type, 4; C type, 4; D type, 3; and others, 12). The A-type strains of MRSA continued to be isolated for more than 6 months. In the NICU environment, the detection rate of the A-type MRSA was 23.1% (12/52). The A-type strains were frequently isolated from environments around patients. The A-type strains of MRSA were prevalent in the NICU, probably due to nosocomial infection. Although none of the neonatal patients developed severe MRSA infection, the same genotype strains were persistently isolated during a period of more than 6 months from patients and the NICU environment around patients. Environmental control around neonatal patients is important to prevent nosocomial infection in the NICU.     

Epidural abscess caused by community-associated methicillin-resistant Staphylococcus aureus strain USA300 in Japan

We report a case of epidural abscess caused by community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strain USA300 in a previously healthy 25-year-old American woman who lived in Japan for more than 1 year. She started to complain of severe headache that continued for about 10 days after improvement of subcutaneous abscesses caused by MRSA. Computed tomography (CT) and magnetic resonance imaging (MRI) showed epidural abscess. As epidural abscess was not improved by treatment with vancomycin and ceftriaxone, craniotomy and drainage were performed, and the severe headache disappeared. Characteristics of the MRSA strain isolated from the abscess were identical to those of strain USA300; multilocus sequence typing sequence type 8, staphylococcal cassette chromosome mec type IVa, Panton–Valentine leukocidin positive, arginine catabolic mobile element positive, and pulsed-field gel electrophoresis type USA300. This may be the first report of epidural abscess caused by USA300 strain in Japan. Because CA-MRSA strains, including USA300, have begun to spread in Japan, epidural abscess should be taken into account in the diagnosis of previously healthy patients with persistent headache accompanied by skin lesions.     

Molecular typing of methicillin-resistant Staphylococcus aureus: Comparison of PCR-based open reading frame typing,multilocus sequence typing,and Staphylococcus protein A gene typing

The recently developed PCR-based open reading frame typing (POT) method is a useful molecular typing tool. Here, we evaluated the performance of POT for molecular typing of methicillin-resistant Staphylococcus aureus (MRSA) isolates and compared its performance to those of multilocus sequence typing (MLST) and Staphylococcus protein A gene typing (spa typing). Thirty-seven MRSA isolates were collected between July 2012 and May 2015. MLST, spa typing, and POT were performed, and their discriminatory powers were evaluated using Simpson's index analysis. The MRSA isolates were classified into 11, 18, and 33 types by MLST, spa typing, and POT, respectively. The predominant strains identified by MLST, spa typing, and POT were ST8 and ST764, t002, and 93-191-127, respectively. The discriminatory power of MLST, spa typing, and POT was 0.853, 0.875, and 0.992, respectively, indicating that POT had the highest discriminatory power.Moreover, the results of MLST and spa were available after 2 days, whereas that of POT was available in 5 h. Furthermore, POT is rapid and easy to perform and interpret. Therefore, POT is a superior molecular typing tool for monitoring nosocomial transmission of MRSA.     

Emergence of the community-acquired methicillin-resistant Staphylococcus aureus USA300 clone in Japan

We isolated methicillin-resistant Staphylococcus aureus (MRSA) from a 3-month-old Indian girl who was born in the United States, moved to Japan, and suffered from subcutaneous abscesses in 2007. The MRSA (strain NN36) belonged to multilocus sequence type (ST) 8, exhibited agr1, staphylococcal cassette chromosome mec (SCCmec) type IVa, and coagulase type III, and was positive for Panton-Valentine leukocidin (PVL) and the arginine catabolic mobile element (ACME), just like the USA300 clone, which is the predominant community-acquired MRSA (CA-MRSA) in the United States. Strain NN36 shared an identical pulsed-field gel electrophoresis (PFGE) pattern with the USA300 clone. Although the USA300 clone is of spa1, strain NN36 possessed spa985. Strain NN36 was resistant to erythromycin and kanamycin, in addition to β-lactam agents (e.g., oxacillin). The data suggest that the USA300 clone has emerged in Japan. Because the USA300 clone has recently spread to European countries, surveillance of the USA300 clone should be actively performed in Japan.     

Molecular epidemiology of methicillin-resistant Staphylococcus aureus in a Spanish hospital over a 4-year period: clonal replacement,decreased antimicrobial resistance,and identification of community-acquired and livestock-associated clones

This study was carried out on 189 methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates collected in a third-level hospital in Valladolid, Spain, between 2005 and 2008 in order to investigate the changes in molecular epidemiology and genetic backgrounds associated with the changes in resistance phenotypes produced over time. The MRSA isolates were classified as belonging to 10 different clones, including the identification of a novel MRSA clone, ST2422-MRSA-IV, belonging to CC121; 1 CA-MRSA strain from a USA300 clone; another from ST97-MRSA-IV, associated with clones adapted to livestock (LA-MRSA); and 2 strains belonging to a new spa type (t10258) related to the ST8-MRSA-IV clone. Sixty-two percent of the strains belonging to Spanish-prevalent MRSA sequence type ST125 harboured composite or multiple SCCmec elements including SCCmec type IV plus ccrA/B4 (ST125-SCCmec IV/VI). In the years studied, it was observed that ST125-SCCmec IV/VI replaced the multiresistant ST228-SCCmec I previously prevalent, and, as a consequence, decreased gentamicin and clindamycin resistance was further observed.     

Immediate control of a methicillin-resistant Staphylococcus aureus outbreak in a neonatal intensive care unit

An outbreak of methicillin-resistant Staphylococcus aureus (MRSA) colonization occurred from November 2001 in the neonatal intensive care unit (NICU) of our hospital. Since the establishment of our NICU in 1991, some MRSA has been detected in NICU patients. For MRSA infection preventive measures, utilization of the following items was implemented: mupirocin ointment, diluted povidone iodine, methylrosaniline chloride, and disposable rubber gloves. Patients in whom MRSA was detected received intranasal administration of the mupirocin ointment three times daily and were bathed in, or their entire body was wiped with diluted povidone iodine once daily for the first 3 days in each week. In addition, they received an intraoral application of methylrosaniline chloride daily. All therapy was done until MRSA strains were undetectable for 3 continuous weeks. Genotypes of 13 MRSA strains isolated from eight inpatients and one mother were analyzed by pulsed-field gel electrophoresis (PFGE). All PFGE patterns were identical, except for one, which had one distinct migrating fragment. These data suggested that this MRSA outbreak was caused by the same strain, which was derived from the mother of a low-birth-weight infant born on October 30, 2001. Gradually, the number of inpatients carrying MRSA decreased, until finally MRSA was no longer observed, in April 2002. Fortunately, we controlled the MRSA outbreak immediately, and none of the inpatients developed severe MRSA infection. We think that in our NICU, which is isolated from other hospital wards, it is important to prevent the entrance of MRSA-carrying mothers.     

Increase in the frequency of community-acquired methicillin-resistant Staphylococcus aureus clones among inpatients of acute care hospitals in the Kyoto and Shiga regions,Japan

BackgroundSpecific epidemic clones of hospital-acquired methicillin-resistant Staphylococcus aureus (HA-MRSA) are responsible for the worldwide spread of MRSA. However, in recent years, the isolation of community-acquired MRSA (CA-MRSA) clones has been increasing. We investigated the latest molecular epidemiology trends of HA-MRSA and CA-MRSA clones in the Kyoto and Shiga regions, Japan.Materials and methodsAll nonduplicate MRSA isolates obtained from the clinical specimens of inpatients at four acute care hospitals in the Kyoto and Shiga regions between 2014 and 2019 were typed using the PCR-based open reading frame typing (POT) method. CA-MRSA and HA-MRSA were classified according to the POT1 values. We performed whole-genome sequencing analysis for representative isolates displaying common POT types.ResultsA total of 2413 isolates were included in the study, comprising 1730 nosocomial and 683 nonnosocomial isolates. The rates of HA-MRSA decreased from 50.2% in 2014 to 19.0% in 2019, while those of CA-MRSA increased from 44.7% to 76.4% (p < 0.001). Isolates belonging to the most common 10 POT types (CA-MRSA, n = 6; HA-MRSA, n = 4) accounted for 42% of the isolates studied and were obtained from 3 or more hospitals. Whole-genome sequencing analysis showed that the common CA-MRSA isolates with POT types 106-137-80, 106-9-80, 106-9-2, and 106-137-2, those with POT types 106-183-37 and 106-129-5, and HA-MRSA isolates with POT types 93-191-103, 93-157-127, 93-137-103, and 93-223-111 belonged to ST8-SCCmecIV, ST1-SCCmecIV, and ST764-SCCmecII, respectively.ConclusionA recent clonal shift from HA-MRSA to CA-MRSA occurred, and specific regional clones were prevalent among inpatients in the Kyoto and Shiga regions.     

Molecular epidemiological analysis of methicillin-resistant staphylococci in a neonatal intensive care unit

To investigate the contamination by and transmission of MRSA/MRCNS in the old NICU of Hospital A and the relocated NICU (new NICU), we isolated and evaluated staphylococci from nurses' palms, towels under the heads of neonates, infant incubators (including portholes and infant covers), and room air. Detection rates of MRSA/MRCNS isolated from different sample locations were 52.6% in the old NICU and 53.4% in the new NICU, which demonstrates that the nurses' palms in both the old and new NICUs and indoor environment were contaminated with MRSA/MRCNS. In the old NICU, numerous MRSA and MRCNS strains (Log 3.17 ± 0.19 cfu/10 cm2) were identified from towels, and the implementation of improvement plans resulted in a decrease in the number of MRSA/MRCNS isolates (Log 1.95 ± 0.57 cfu/10cm2) from the towels used in the new NICU. A homology study of MRSA/MRCNS strains by PFGE DNA restriction patterns identified genotypes that showed similar patterns in the nurses' palms, towels, infant incubators, and room air.     

Efficacy of PCR-based open reading frame typing assay for outbreak investigation of metallo-β-lactamase-producing Pseudomonas aeruginosa in hematology unit

We investigated the efficacy of the PCR-based open reading frame typing (POT) assay for outbreak investigation of metallo-β-lactamase (MBL)-producing Pseudomonas aeruginosa (MBL-PA). A total of 53 P. aeruginosa isolates were detected between January 2010 and December 2012 on a hematology ward, of which 6 were identified as MBL-PA with the bla_IMP-1 gene. The POT assay revealed the same genotype (207-41) in 3 of 6 MBL-PA, suggesting an outbreak caused by a single strain. Environmental investigation of bathroom samples revealed the same POT genotype (207-41) as those of the clinical isolates and no other MBL-PA strains. Genetic relatedness of the MBL-PA isolates was confirmed by the DiversiLab repetitive-sequence-based PCR typing system, suggesting the POT type 207-41 as a genetically identical clone. The POT assay can be successfully applied to MBL-PA genotyping.     

Evidence of Multiple Virulence Subtypes in Nosocomial and Community-Associated MRSA Genotypes in Companion Animals from the Upper Midwestern and Northeastern United States

Objective: Not much is known about the zoonotic transmission of methicillin-resistant Staphylococcus aureus (MRSA) in companion animals in the United States. We report the rate of prevalence of S. aureus and MRSA recovered from clinical samples of animals requiring treatment at veterinary clinics throughout the upper midwestern and northeastern United States.Design: We compared phenotypes, genotypes, and virulence profiles of the MRSA isolates identified in companion animals, such as cats, dogs, horses, and pigs, with typical human nosocomial and community-associated MRSA (CA-MRSA) genotypes to assess implied zoonotic transmission or zooanthroponosis. Five hundred thirty-three coagulase-positive staphylococci (CPS) isolates recovered between 2006 and 2008 from a variety of animal-source samples were screened for S. aureus by S. aureus-specific 16S rDNA primers and were screened for methicillin-resistance. All MRSA isolates were genotyped by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and spa typing. They were also screened for common staphylococcal enterotoxin and adhesion genes by multiplex and singleplex PCR.Results: Among the 533 CPS isolates recovered, 66 (12.4%) were determined to be S. aureus and 24 (4.5%) were MRSA. The percent of animals that were positive for S. aureus were as follows: 6.6% (32 of 487) dogs, 39.6% (19 of 48) cats, 83.3% (10 of 12) horses, and 100% of pigs, rabbits, hamsters and rats. Notably, 36.4% of all S. aureus identified were MRSA. Methicillin-resistant S. aureus was present in clinical samples from 12 of 487 dogs (2.5%), 6 of 48 cats (12.5%), 5 of 12 horses (42%), and 1 of 2 pigs (50%). The 24 MRSA isolates resolved into 4 PFGE clones: USA100 (50%), USA300 (16.7%), USA500 (20.8%) and USA800 (12.5%) and 6 sequence types (ST5, ST8, ST105, ST830, and ST986) or 2 clonal complexes, CC5 and CC8. Five major virulence profiles (clusters A to E) were observed in these MRSA isolates. Genotypic and virulence profiles of cats and dogs were more similar to each other than to those of horses. A Panton-Valentine leukocidin positive isolate with ST8:USA300 background was identified in a pig causing skin and soft infection.Conclusion: The presence of human MRSA clones in these animals suggests possible reverse zoonotic transmission. This study reports the first case of a USA300 genotype in a pig. Presence of multiple virulence profiles within a MRSA genotype in these animals suggests the potential of emergence of new MRSA clones by gaining or losing additional virulence genes.     

USA300 methicillin-resistant Staphylococcus aureus bacteremia and the risk of severe sepsis: is USA300 methicillin-resistant Staphylococcus aureus associated with more severe infections?

USA300 methicillin-resistant Staphylococcus aureus (MRSA) is increasing as a cause of severe community-associated bacteremic infections. We assessed severe sepsis in response to infection in patients with USA300 MRSA compared to non-USA300 MRSA bacteremia. A cohort study was conducted from 1997 to 2008 comparing sepsis in response to infection in 271 patients with MRSA bacteremia from 4 VA hospitals. Sixty-seven (25%) patients with MRSA bacteremia were USA300 MRSA; 204 (75%) were non-USA300 MRSA. The proportion of MRSA bacteremia caused by USA300 MRSA increased over time (χ2 P < 0.0001). Adjusting for age and nosocomial infection, patients with USA300 MRSA bacteremia were more likely to have severe sepsis or septic shock in response to infection than patients with non-USA300 MRSA bacteremia (adjusted relative risk = 1.82; 95% confidence interval, 1.16-2.87; P = 0.01). This suggests that patients with USA300 MRSA are more likely to develop severe sepsis in response to their infection, which could be due to host or bacterial differences.     

Effects of Low-Dose Amoxicillin on Staphylococcus aureus USA300 Biofilms

Previous studies showed that sub-MIC levels of β-lactam antibiotics stimulate biofilm formation in most methicillin-resistant Staphylococcus aureus (MRSA) strains. Here, we investigated this process by measuring the effects of sub-MIC amoxicillin on biofilm formation by the epidemic community-associated MRSA strain USA300. We found that sub-MIC amoxicillin increased the ability of USA300 cells to attach to surfaces and form biofilms under both static and flow conditions. We also found that USA300 biofilms cultured in sub-MIC amoxicillin were thicker, contained more pillar and channel structures, and were less porous than biofilms cultured without antibiotic. Biofilm formation in sub-MIC amoxicillin correlated with the production of extracellular DNA (eDNA). However, eDNA released by amoxicillin-induced cell lysis alone was evidently not sufficient to stimulate biofilm. Sub-MIC levels of two other cell wall-active agents with different mechanisms of action—d-cycloserine and fosfomycin—also stimulated eDNA-dependent biofilm, suggesting that biofilm formation may be a mechanistic adaptation to cell wall stress. Screening a USA300 mariner transposon library for mutants deficient in biofilm formation in sub-MIC amoxicillin identified numerous known mediators of S. aureus β-lactam resistance and biofilm formation, as well as novel genes not previously associated with these phenotypes. Our results link cell wall stress and biofilm formation in MRSA and suggest that eDNA-dependent biofilm formation by strain USA300 in low-dose amoxicillin is an inducible phenotype that can be used to identify novel genes impacting MRSA β-lactam resistance and biofilm formation.     

An outbreak of severe infectious diseases caused by methicillin-resistant Staphylococcus aureus USA300 clone among hospitalized patients and nursing staff in a tertiary care university hospital

The USA300 clone, which produces Panton-Valentine leukocidin (PVL), is a major highly pathogenic community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) clone that is spreading throughout the world. Although the prevalence of the USA300 clone in Japan was very limited a decade ago, its incidence has been increasing in both community and hospital settings in recent years. There is great concern that the USA300 clone will cause more complicated diseases and become a serious threat to immunocompromised patients in hospital settings. Here, we report an outbreak of severe infectious diseases in a tertiary care university hospital involving the incidence of deep infections, including bacteremia, and continuous and frequent isolation of MRSA strains for five months from six patients and a healthy nursing staff member in the same ward. The genotype of all MRSA isolates was identical to that of the USA300 clone. Furthermore, pulsed-field gel electrophoresis analysis indicated that all MRSA had the same patterns. These data demonstrate that a USA300 clone outbreak had occurred in the hospital. Fortunately, this outbreak was terminated subsequent to the interventions of the infection control team and all patients recovered following the appropriate therapies. Our report demonstrates that patients carrying highly pathogenic CA-MRSA have the potential to become a source of nosocomial outbreaks that can spread to healthy healthcare workers. Therefore, stricter standard precautions should be applied for all patients at the time of admission to prevent such nosocomial outbreaks.     

Methicillin-resistant Staphylococcus aureus transmission and hospital-acquired bacteremia in a neonatal intensive care unit in Greece

BackgroundStaphylococcus aureus is a common pathogen causing hospital acquired infections (HAIs) in neonates. In this study, the epidemiology of methicillin-resistant S. aureus (MRSA) colonization and infections in a 30-bed, level III university-affiliated neonatal intensive care unit (NICU) located in a children's hospital was retrospectively investigated for the period 2014–2018.MethodsGenes encoding Panton-Valentine Leukocidin (lukS/lukF-PV, PVL), toxic shock syndrome toxin (tst), exfoliative toxins (eta, etb), and the resistance genes mecA, mecC and fusB, were defined in 46 representative strains by PCRs. Relatedness of strains was assessed by MLST.ResultsOf 1538 neonates, 77 (5%) had a positive culture for MRSA (23/77 were NICU-acquired and 54/77 imported cases). Four MRSA bacteremias occurred. Most isolates were multi-resistant. One major clone was identified, ST225, among 40 tested neonatal strains (23/40, 58%). Of these, 14/23 were imported from the same maternity hospital (MH). Another clone, ST217, was predominant (4/6) among health care workers (HCWs), found colonized. Four isolates classified as ST80 were PVL-positive. Additional four strains carried tst (10%), belonging to ST30 and ST225 (two strains each), and two etb. The implicated MH was notified for the problem, decolonization treatment was successfully performed in HCWs and neonates. Strengthening of infection control measures with emphasis on hand hygiene was applied.ConclusionsUncovering reservoirs for on-going MRSA transmission in NICUs has proved challenging. Well known nosocomial MRSA clones are being constantly introduced and transmitted via MHs and HCWs. Effective infection prevention and control requires constant vigilance.     

Nasal carriage of methicillin-resistant Staphylococcus aureus among preclinical medical students: epidemiologic and molecular characteristics of methicillin-resistant S. aureus clones

Between May 2008 and October 2009, a total of 2103 interns were randomly tested for nasal colonization of S. aureus and methicillin-resistant Staphylococcus aureus (MRSA). The prevalence of S. aureus among staphylococci specimens was 23.1%, and among the total S. aureus the MRSA prevalence was 9.4%. MRSA isolates were further subtyped using genetic element staphylococcal cassette chromosome mec (SCCmec) typing, pulsed-field gel electrophoresis (PFGE) band pattern, and multilocus sequence typing. SCCmec type IVa was the most prevalent strain, at 45.4 %. Eleven PFGE patterns were identified in MRSA strains, with 1 predominant (pulsotype A, 45.5%). Eight strains which belonged to clonal complex 78 carried type IVa SCCmec and produced type 3 coagulase. Panton–Valentine leukocidin (PVL) genes (lukS and F-PV) were identified in 10 (45.4%) MRSA strains; these predominately carried ?Sa2958type and ?Sa108PVL-like type PVL phages. After inducing prophages, 8 strains infected other S. aureus isolates and could generate novel PVL-positive strains of S. aureus. The present study demonstrates that interns can carry certain MRSA strains asymptomatically and contribute to the spread of MRSA between the community and hospital.     

Trends of β-lactam antibiotic susceptibility in blood-borne methicillin-resistant Staphylococcus aureus (MRSA) and their linkage to the staphylococcal cassette chromosome mec (SCC mec ) type

We investigated trends of beta-lactam antibiotic susceptibility in a total of 218 strains of blood-borne methicillin-resistant Staphylococcus aureus (MRSA) isolated from 1978 through 2002 at a middle-size geriatric hospital in Tokyo; the strains were classified by the MRSA marker, staphylococcal cassette chromosome mec (SCCmec). The minimum growth inhibitory concentration (MIC) of cloxacillin at which 50% of the strains were inhibited (MIC50) was 2 microg/ml in the strains isolated in 1978-1984 and 32 to 64 microg/ml in the strains isolated subsequently. Similarly, the MIC50 values of cefazolin and imipenem in the 1978-1984 isolates were 16 and 相似文献   

JIC Award 2006

We report here an outbreak of β-lactam-induced vancomycin-resistant methicillin- resistant Staphylococcus aureus (MRSA; BIVR) at one of the Cancer-Institute-affiliated hospitals in Tokyo. We examined a total of 500 strains (100 per year) of clinically isolated MRSA from 1998 to 2002. The detection rates of BIVR in the years 1998, 1999, 2000, 2001, and 2002 were 10%, 9%, 49%, 15%, and 19%, respectively. To investigate the cause of the high incidence of BIVR detection in the year 2000, we carried out pulsed-field gel electrophoresis (PFGE) of the SmaI-digested chromosomal DNA of BIVR and MRSA. The results showed that 96% of the BIVR strains isolated in 2000 were classified as an identical DNA type “A”, while only 47% of the MRSA strains were classified as this type. We concluded, based on these results, that this hospital had a nosocomial infection of BIVR in the year 2000. An important message given by this study would be that nosocomial BIVR infection could occur in any hospital where MRSA infection is treated with vancomycin and β-lactam antibiotics.     

Ceftaroline activity against organisms isolated from respiratory tract infections in USA hospitals: results from the AWARE program, 2009–2011

The Assessing Worldwide Antimicrobial Resistance Evaluation Program monitors the activity of ceftaroline and comparator agents tested against pathogens causing either respiratory or skin and soft tissue infections. A total of 7733 isolates from patients in 80 medical centers across the United States (USA) identified as respiratory tract pathogens by the infection type and/or specimen site recorded by the submitting laboratory during 2009–2011 were evaluated. There were 3360 isolates of Streptococcus pneumoniae, 1799 Haemophilus influenzae, 1087 Staphylococcus aureus, 678 Moraxella catarrhalis, 459 Klebsiella pneumoniae, 223 Escherichia coli, and 127 Klebsiella oxytoca. Annual penicillin resistance among S. pneumoniae ranged from 21.9 to 24.3%. All S. pneumoniae strains were inhibited at a ceftaroline MIC of ≤0.5 μg/mL with 100.0% of isolates categorized as susceptible. Ceftaroline was 16-fold more active than ceftriaxone and 32-fold more active than amoxicillin-clavulanate against penicillin-resistant pneumococci. Only 49.8% of the penicillin-resistant isolates were susceptible to ceftriaxone. There were a total of 1087 S. aureus (48.9% methicillin-resistant S. aureus [MRSA]) isolates, and the yearly MRSA rate ranged from 47.9 to 49.7%. The ceftaroline MIC_50/90 for S. aureus was at 0.25/1 μg/mL; 98.2% susceptible and no resistant strains (≥4 μg/mL). Ceftaroline activity against methicillin-susceptible S. aureus (MSSA) isolates (MIC₅₀ and MIC₉₀, 0.25 and 0.25 μg/mL, respectively; 100% susceptible) was 2- to 4-fold greater than for MRSA (MIC_50/90, 0.5/1 μg/mL; 96.2% susceptible). The ceftriaxone MIC₉₀ for MSSA was 4 μg/mL. Ceftaroline was active against H. influenzae (MIC_50/90 ≤0.015/0.03 μg/mL; 100.0% susceptible) and against M. catarrhalis (MIC_50/90, 0.06/0.12 μg/mL). Ceftaroline was active against non–extended spectrum β-lactamase (ESBL) phenotype strains of Enterobacteriaceae but not against ESBL-positive phenotype strains. In summary, ceftaroline was highly active against a large collection of bacterial pathogens isolated from patients with respiratory tract infections in the USA during 2009 through 2011.