Occurrence of II and V staphylococcal cassette chromosome mec types among coagulase-negative staphylococci from Northeastern part of India

Introduction: Coagulase Negative Staphylococci, the most commonly isolated pathogen are becoming emerging threats to the community as well as to the nosocomial environment. The present study underscores the distribution of Staphylococcal cassette chromosome mec (SCCmec) types among Methicillin resistant Coagulase Negative Staphylococci from the environmental origin. Methods and Materials: Environmental and food sample (n = 460) from different location of northeastern region of India were collected for a period of one year and were phenotypically and genotypically screened using cefoxitin disc and PCR techniques for mecA and mecC gene detection. All the MR-CoNS isolates possessing mecA gene were subjected to 16srDNA sequencing for species identification. SCCmec typing was determined by evaluating using primer sets from type I to type V. Antibiotic susceptibility testing was performed for all the isolates. Statistical analysis with chi-square test using SPSS-21 statistical software. Results: Methicillin resistance shown by one hundred forty three isolates were carried out for molecular analysis, among them 53.84% serves as mecA carrier. Distribution of Staphylococcus haemolyticus was more frequent and was found that SCCmec types II and V were predominant among the study isolates. Linezolid was the drug of choice for the CoNS isolates. Statistical analysis showed an insignificant result for the tested antibiotics and SCCmec types. Conclusion: This study therefore interprets the relative importance of SCCmec types among MR-CoNS isolates.

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.

SCCmec resistant mechanism, toxicity and prevalence in livestock-associate methicillin-resistant Staphylococcus aureus / 中国人兽共患病学报

Staphylococcus aureus is one of the most frequently encountered zoonotic pathogens.This bacterium produces the notable virulence factors such as hemolysin,panton-valentine leucocidin,exfoliative toxins and enterotoxin,which can cause invasive disease in humans and animals.Methicillin-resistant S.aureus (MRSA) is a multidrug-resistant bacterium which acquired the staphylococcal chromosome cassette mec (SCCmec).SCCmec is one of the key reasons for the antibiotic resistance of MRSA.As for MRSA resistance,the β-1actam resistance is mediated by mecA gene,and the drug-resistance genes inserted in the variable area of the SCCmec element play an important role in the multidrug resistance of MRSA.In recent years,it has been reported in Europe,North America and other countries that the multidrug resistance MRSA was detected in aquaculture environment and livestock.Besides,MRSA poses a serious threat to public health,and it can colonize and cause invasive disease in humans through aquaculture environment or other ways.This review summarizes drug resistance change of S.aureus and analysis of SCCmec resistance elements,toxicity and prevalence of livestock-associate MRSA,which would have theoretical and practical significance to understand S.aureus drug resistance,SCCmec typing,as well as control and prevent LA-MRSA transmission and infection between animals and humans.

Detection of Integrons and Staphylococcal Cassette Chromosome mec Types in Clinical Methicillin-resistant Coagulase Negative Staphylococci Strains

OBJECTIVES: Integrons are thought to play an important role in the spread of antibiotic resistance. This study investigates class 1 and 2 integron-positive methicillin-resistant coagulase-negative staphylococci strains isolated in Iran and characterizes their patterns of antimicrobial resistance. METHODS: Hundred clinical isolates of coagulase-negative staphylococci were characterized for integron content and staphylococcal cassette chromosome mec (SCCmec) type. RESULTS: Sixteen isolates carried class 1 (intI1) integrons and four isolates carried class 2 (intI2) integrons. One resistance gene array was identified among the class 1 integrons (aadA1 cassette). The distribution of SCCmec types in 50 methicillin-resistant coagulase-negative staphylococci strains showed that SCCmec types III and V dominated among the tested strains. CONCLUSION: This is the first report of methicillin-resistant coagulase-negative staphylococci strains that carry two mobile genetic elements, including class 1 and 2 integrons and SCCmec, in Iran.

Emergence of staphylococcal cassette chromosome mec type Ⅰ with high-level mupirocin resistance among methicillin-resistant Staphylococcus aureus

Objective: To investigate the molecular epidemiology and antimicrobial resistance patterns of methicillin-resistant Staphylococcus aureus (MRSA) among healthcare workers and patients. Methods: MRSA isolates were recovered from nasal swabs collected at a tertiary care hospital of Nepal and confirmed on the basis of Gram staining, conventional biochemical tests, and PCR amplification of mecA gene. PCRs were also used for detection of the different resistance genes and staphylococcal cassette chromosome (SCC) mec types. Antibiotic susceptibility patterns of isolates were assessed by disc diffusion method and minimum inhibitory concentrations were determined by E-test. Results: A total of 29 MRSA were isolated from 536 nasal swabs (5.4%) of health care workers and patients at a tertiary care hospital in Nepal. All isolates were susceptible to amikacin, gentamicin, vancomycin (minimal inhibitory concentrations1024μg/mL). Fourteen isolates were found harboring the mupA gene and one isolate was found carrying the novel mupB gene. High prevalence (68%) of SCCmec I type was found, followed by SCCmec V (13%) and SCCmec III (3%) among all the MRSA isolates. Conclusions: We found the emergence of SCCmec type Ⅰ with high-level mupirocin resistance among MRSA in Nepal. Data also suggest that MRSA SCCmec type V strain has spread from the community to the hospital.

Study on the antibiotic resistance of Staphylococcus aureus isolated from hospitalized children with respiratory tract infections / 中华实用儿科临床杂志

Objective To investigate the antimicrobial resistance and genotype distribution of staphylococcal cassette chromosome mec (SCCmec) of staphylococcus aureus (S.aureus) isolated from children hospitalized at Pediatric People's Hospital of Zhongjiang County.Methods Seventy-seven strains of S.aureus were collected by nasopharyngeal swabs at the Pediatric Department of People's Hospital of Zhongjiang County from January to December 2015.Methicillin-resistant staphylococcus aureus (MRSA) and methicillin-susceptible staphylococcus aureus (MSSA) were identified by cefoxitin disc diffusion and detection of mecA method.The minimum inhibitory concentrations (MIC) of antibiotics were determined by E-test method.SCCmec typing on MRSA strains was performed by using multiplex PCR.Results MRSA accounted for 54.5％ (42 strains) strains of 77 strains.All MRSA strains were resistant to Penicillin,and the rates of antibiotic resistance to Cefuroxime,Ceftriaxone,Erythromycin were 78.6％,95.2％ and 97.6％,respectively.The rates of antibiotic resistance of 35 MSSA to Penicillin and Erythromycin were 97.1％ and 62.9％,and they were also sensitive to other antibiotics.In 42 strains of MRSA,SCCmec type Ⅳa was the predominant type (27 strains,64.3 ％),which was followed by type Ⅳ g and Ⅴ (each 5 strains,11.9％),type Ⅳ c and Ⅳh (each 1strain,2.4％).Non-susceptibility rate of SCCmec Ⅳ to cefuroxime was significantly higher than that of other SCCmec types (P ＜ 0.05).Conclusions All strains from children hospitalized in People's Hospital of Zhongjiang County are often resistant to Penicillin and Erythromycin.The proportion of MRSA isolated from hospitalized children was high.SCCmec type Ⅳa is the main genotype of MRSA.

Emergence of staphylococcal cassette chromosome mec type I with high-level mupirocin resistance among methicillin-resistant Staphylococcus aureus

Objective To investigate the molecular epidemiology and antimicrobial resistance patterns of methicillin-resistant Staphylococcus aureus (MRSA) among healthcare workers and patients. Methods MRSA isolates were recovered from nasal swabs collected at a tertiary care hospital of Nepal and confirmed on the basis of Gram staining, conventional biochemical tests, and PCR amplification of mecA gene. PCRs were also used for detection of the different resistance genes and staphylococcal cassette chromosome (SCC) mec types. Antibiotic susceptibility patterns of isolates were assessed by disc diffusion method and minimum inhibitory concentrations were determined by E-test. Results A total of 29 MRSA were isolated from 536 nasal swabs (5.4%) of health care workers and patients at a tertiary care hospital in Nepal. All isolates were susceptible to amikacin, gentamicin, vancomycin (minimal inhibitory concentrations  1 024 μg/mL). Fourteen isolates were found harboring the mupA gene and one isolate was found carrying the novel mupB gene. High prevalence (68%) of SCCmec I type was found, followed by SCCmec V (13%) and SCCmec III (3%) among all the MRSA isolates. Conclusions We found the emergence of SCCmec type I with high-level mupirocin resistance among MRSA in Nepal. Data also suggest that MRSA SCCmec type V strain has spread from the community to the hospital.

Molecular epidemiology of coagulase-negative bloodstream isolates: detection of Staphylococcus epidermidis ST2, ST7 and linezolid-resistant ST23

Abstract The mechanisms contributing to persistence of coagulase-negative staphylococci are diverse; to better understanding of their dynamics, the characterization of nosocomial isolates is needed. Our aim was to characterize phenotypic and molecular characteristics of Staphylococcus epidermidis and Staphylococcus haemolyticus human blood isolates from two tertiary care hospitals in Mexico, the Hospital Universitario in Monterrey and the Hospital Civil in Guadalajara. Antimicrobial susceptibility was determined. Biofilm formation was assessed by crystal violet staining. Detection of the ica operon and Staphylococcal Cassette Chromosome mec typing were performed by PCR. Clonal relatedness was determined by Pulsed-fiel gel electrophoresis and Multi locus sequence typing. Methicillin-resistance was 85.5% and 93.2% for S. epidermidis and S. haemolyticus, respectively. Both species showed resistance >70% to norfloxacin, clindamycin, levofloxacin, trimethoprim/sulfamethoxazole, and erythromycin. Three S. epidermidis and two S. haemolyticus isolates were linezolid-resistant (one isolate of each species was cfr+). Most isolates of both species were strong biofilm producers (92.8% of S. epidermidis and 72.9% of S. haemolyticus). The ica operon was amplified in 36 (43.4%) S. epidermidis isolates. SCCmec type IV was found in 47.2% of the S. epidermidis isolates and SCCmec type V in 14.5% of S. haemolyticus isolates. No clonal relatedness was found in either species. Resistance to clindamycin, levofloxacin, erythromycin, oxacillin, and cefoxitin was associated with biofilm production for both species (p < 0.05). A G2576T mutation in 23S rRNA gene was detected in an S. haemolyticus linezolid-resistant isolate. All linezolid-resistant S. epidermidis isolates belonged to ST23; isolate with SCCmec type IV belonged to ST7, and isolate with SCCmec type III belonged to ST2. This is the first report of ST7 in Mexico. There was a high genetic diversity in both species, though both species shared characteristics that may contibute to virulence.

Distribution of genes encoding aminoglycoside‑modifying enzymes among clinical isolates of methicillin‑resistant staphylococci.

The objective of this study was to determine the distribution of genes encoding aminoglycoside‑modifying enzymes (AMEs) and staphylococcal cassette chromosome mec (SCCmec) elements among clinical isolates of methicillin‑resistant staphylococci (MRS). Antibiotic susceptibility test was done using Kirby–Bauer disk diffusion method. The presence of SCCmec types and AME genes, namely, aac (6’)‑Ie‑aph (2’’), aph (3’)‑IIIa and ant (4’)‑Ia was determined using two different multiplex polymerase chain reaction. The most encountered AME genes were aac (6′)‑Ie‑aph (2’’) (55.4%) followed by aph (3’)‑IIIa (32.3%) and ant (4’)‑Ia gene (9%). SCCmec type I (34%) was predominant in this study. In conclusion, the aac (6’)‑Ie‑aph (2’’) was the most common AME gene and SCCmec type I was most predominant among the MRS isolates.

Study on antibiotic resistance and staphylococcal chromosomal cassette mec molecular epidemiology of methicillin resistant coagulase negative staphylococci in children / 中华实用儿科临床杂志

Objective To learn about the antibiotic resistance status of methicillin resistant coagulase negative staphylococcus(MRCNS),and to investigate the distribution and resistant feature of different staphylococcal chromosomal cassette mec(SCCmec) genotypes of children in Anhui,so as to guide clinical medication.Methods Resistance phenotype screening was conducted in coagulase negative staphylococcus,which were isolated from clinical strains in children in Anhui from 2010 to 2014 each year in September.MecA gene was detected by using PCR method in order to collect MRCNS.Minimal inhibitory concentrations (MIC) of 16 antibiotics were determined by adopting agar dilution method.Vacomycin-resistant strains were identified with population analysis and the Brain Heart Infusion vancomycin screen agar dilution method recommended by Clinical and Laboratory Standards Institute in 2013.Van gene and SCCmec types were detected by using PCR method.Results A total of 148 MRCNS strains were detected through the resistance phenotype screening and the detection of mecA gene.There were methicillin resistant staphylococcus epidermidis,methicillin resistant staphylococcus haemolyticus,methicillin resistant staphylococcus hominis,and other kinds of MRCNS,and the proportions of them were 44.59％ (66/148 cases),25.68％ (38/148 cases),19.59％ (29/148 cases) and 10.14％ (15/148 cases),respectively.The analysis of antibiotic resistance showed the antimicrobial resistant rates of MRCNS to Penicillin,Cefoperazone,Cefotaxime,Ceftriaxone,lmipenem and Meropenem were all 100％,to Erythromycin and Azithromycin,Ciprofloxacin,Clindamycin,Gentamicin,Lewofloxacin,Rifampincin,Chloramphenicol,Teicoplanin and Vancomycin were 92.57％,97.98％,83.78％,79.05％,43.24％,35.81％,24.32％,8.78％,2.03％ and 0.68％,respectively.There was 1 heterogeneous Vancomycin-resistant strain,which was resistant to both Vancomycin and Teicoplanin (with MIC 32.00 mg/L and 64.00 mg/L).No vanA,vanB,vanC1 or vanC2/3 gene was detected from heterogeneous Vancomycin-resistant strain by PCR.Ⅰ to Ⅴ SCCmec genotypes were detected from 148 MRCNS strains,and the major SCCmec type was SCCmec type Ⅲ,which was followed by hybrid type.Three subtypes of SCCmec type Ⅳ were identified,including Ⅳa,Ⅳc and Ⅳd.There were 148 MRCNS strains that showed different resistant phenotypes to various antibiotics.Conclusions The MRCNS strains of children in Anhui province showed multiple resistance to antibiotics.It should be on alert when heterogeneous Vaneomycin-resistant strain appeared.There were several different SCCmec types among several kinds of MRCNS,and SCCmec Ⅲ genotype was the major epidemic isolate.There was no significant correlation between the different resistance rates of non-β-lactamase antibiotics and SCCmec genotypes in MRCNS.

Molecular epidemiology of methicillin resistant staphylococcus aureus colonizing the anterior Nares of school children of Udupi Taluk.

Context: Community associated methicillin resistant Staphylococcus aureus (CA‑MRSA) cause serious skin and soft tissue infections including necrotizing fasciitis and necrotizing pneumonia. Production of Panton Valentine Leucocidine (PVL) toxin is implicated in its enhanced virulence. A variant of epidemic MRSA‑15 (EMRSA‑15) which produces PVL toxin has been isolated and characterized by pulsed-field gel electrophoresis (PFGE) method from the Indian population both in hospital and community settings. Aims: Identify the epidemiological type of MRSA colonizing the anterior nares of school children in Udupi taluk. Settings and Design: The study population included children of the age group of 5-16 years belonging to the Udupi taluk of Karnataka, India. A total of 1503 children were screened for MRSA colonization during July 2009 to December 2010. Materials and Methods: PVL assay, Staphylococcal Cassette Chromosome (SCC) mec typing and PFGE typing were carried out with all the MRSA isolates. Statistical Analysis Used: Frequency distribution of different variables was assessed by SPSS. Results: Among the 1.1% of MRSA, 58.8% (10/17) of isolates were positive for pvl and 41.7% (7/17) were identified as SCC mec type IV. PFGE patterns of all the strains were identical with Indian variant EMRSA‑15; however they were different from classical EMRSA‑15 in 3-4 bands. Conclusions: The Indian variant EMRSA‑15 gains much epidemiological relevance owing to the acquisition of pvl gene. In spite of low prevalence of nasal colonization of MRSA, emergence of the virulent Indian variant EMRSA‑15 in our community is a worrisome fact to be reckoned with.

Molecular characterization of St ap hy lococcus aureus in Yanbian / 中国感染与化疗杂志

Objective To investigate the molecular epidemiology of Staphylococcus aureus in Yanbian area .Methods From March 2011 to June 2012 ,a total of 101 consecutive and non-duplicate strains of Staphylococcus aureus were collected from Yanbian Hospital .Genotypes of SCCmec ,spa,and multilocus sequence typing (MLST) were determined by PCR combined with DNA sequencing analysis .The pvl gene was detected by PCR .Results The most prevalent SCCmec type was type II (65 .0% ,39/60) ,followed by SCCmec type III (26 .7% ,16/60) .A total of 11 Spa types were identified for the MRSA strains ,including t2460 (55 .0% ,33/60) ,t030 (18 .3% ,11/60) ,t002 ,t324 ,and t632 (5 .0% ,3/60 each) .A total of 29 Spa types were identified for MSSA strains ,including t796 (14 .6% ,6/41) ,t309 (9 .8% ,4/41) ,and t126 (7 .3% ,3/41) . The pvl gene was identified in 5 stains .MRSA strains were classified into three types based on multilocus sequence typing (MLST) ,namely ST5 ,ST239 and ST72 .MLST-based MSSA types were more diverse ,including ST5 ,ST 25 ,ST 15 ,ST 59 ,ST 1 ,ST 7 ,ST 45 ,ST 22 ,and ST 188 .Conclusions ST5-MRSA-SCCmecII-t2460 and ST239-MRSA-SCCmecIII-t030 are the most prevalent MRSA clones in Yanbian area .Multiple prevalent MSSA clones are identified.

Characterization of Community-Associated Methicillin-Resistant Staphylococcus aureus in Gwangju, Korea

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important nosocomial pathogens worldwide. This study was performed to investigate the characterization of MRSA isolated from healthy persons in Gwangju area. A total of 404 nasal swab samples was collected during October 2011 and May 2012 in Gwangu, Korea. A survey on MRSA was conducted with meat distributors (n=230), pre-school children (n=108), officers (n=66), respectively. To confirm the MRSA, polymerase chain reaction (PCR) for the S. aureus specific gene and mecA gene was performed. A total of 34 (8.4%) MRSA isolates was isolated from 404 nasal swab samples: 6.1% (14/230) from meat distributors, 16.7% (18/108) from pre-school children, and 3.0% (2/66) from officers samples, respectively. The most prevalent antimicrobial resistance observed in the MRSA isolates was to ampicillin 100% (34/34), followed by penicillin 97.1% (33/34), oxacillin 94.1% (32/34) and erythromycin 52.9% (18/34). All MRSA isolates were then characterized by panton-valentine leukocidin (pvl) gene detected by PCR, staphylococcal cassette chromosome mec (SCCmec) typing, and pulsed-field gel electrophoresis (PFGE) with Sma I digestion. 34 MRSA isolates from nasal carriage were pvl gene negative, SCCmec type IV; 73.5% (25/34), type II; 17.6% (6/34), type III; 2.9% (1/34), and untypable; 5.9% (2/34), respectively. 34 MRSA isolates showed 16 PFGE patterns. These results indicated that isolation rates of community-associated methicillin-resistant S. aureus (CA-MRSA) from healthy persons were low (8.4%), but continuous surveillance and monitoring should be performed to prevent the spread of MRSA in the community.

A novel multiplex PCR for molecular characterization of methicillin resistant Staphylococcus aureus recovered from Jeddah, Kingdom of Saudi Arabia.

Background: Molecular characterization of staphylococcal cassette chromosome mec (SCCmec) types of methicillin-resistant Staphylococcus aureus (MRSA) is very essential for studying the epidemiology of MRSA. Objectives: This study reports two multiplex PCR for molecular typing of MRSA collected from Jeddah, Kingdom of Saudi Arabia. Materials and Methods: A total of 101 clinical isolates of strains were collected from major hospital laboratories and public health centres, Jeddah, Kingdom of Saudi Arabia during the period from August 2009 to May 2011. All the strains were tested phenotypically by conventional methods and genotypically by a novel multiplex PCR targeting at the same time S. aureus 16S rRNA, Panton - valentine leucocidin (PVL) and mecA resistance genes. All the strains were tested also by multiplex PCR for typing of SCC mec types. Results: All the 101 strains previously identified phenotypically as S. aureus with bacteriological examination were positive for amplification of 756 base pair fragments specific for 16S rRNA of S. aureus. Moreover, all the strains were positive for amplification of 1339 base pair fragments specific for mecA gene, while only 38 strains (37.6%) showed positive amplification of 433 base pair fragments specific for PVL gene. The most predominant SCC mec type among the examined isolates is type V 43 (42.5) followed by SCCmec type III 39 (38.6%). Conclusion: The newly modified multiplex PCR is rapid and sensitive method for detection of MRSA. Moreover, the most predominant SCC mec type among the examined isolates from Jeddah, King Saudi Arabia is type V (42.5%), followed by Type III (38.6%).

Distribution of Staphylococcus aureus strains colonized in healthy community population and molecular epidemiological characteristics for MRSA strains / 中华流行病学杂志

Objective To investigate the nasal colonization of Staphylococcus (S.) aureus strains among medical university students in Shenyang and to study the molecular epidemiological characteristics of methicillin resistant S. aureus (MRSA) strains. Methods Sterilized nasal swabs were used to collect nasal bacteria from both nares of the students. Nasal specimens were further identified as S. aureus strains, sensitive or resistant to methicillin through a series of tests. Molecular related methods including staphylococcal cassette chromosome mec (SCCmec) typing, pulsed- field gel electrophoresis (PFGE) , coagulase isotyping and minimum inhibitory concentration (MIC) determination etc. were used to characterize the isolates. Prevalence of the panton-valentine leukocidin (pvl) genes (lukS and F-PV) among the isolates was also assessed. Results Staphylococci were found in 488 specimens from 977 participants through the surveillance program, conducted in 2009. Of the 488 specimens being tested, 364 were identified as coagulase-negative staphylococci (CoNS) and 124 as S. aureus. MRSA strain among the S. aureus isolates was accounted for 3.4%. In the surveillance program conducted in 2010, staphylococci grew in 310 specimens fiom 657 participants. Of the 310 specimens tested, 195 were identified as CoNS and 115 as S. aureus. The percentage of MRSA strains among the S. aureus isolates was 7.7%. In total, 239 students carried S.aureus, and the percentage of MRSA carriers among the total specimens tested in this study was 5.1%.Most of the MRSA strains could be classified into one of the five types of SCCmec elements. Type Ⅳ a SCCmec strains were most frequent seen overall (10 isolates). A total of 11 pulsotypes were identified among the MRSA strains and were classified into 7 major groups (A to G) by the mutual correlations of their banding patterns. Ten MRSA strains were identified as pvl positive strains. Conclusion An MRSA clone (Ⅳ a SCCmec pulsotype A) carrying pvl toxin gene was found to be prevalent in the nares of the healthy university students.

Typing methods and DL MRSA Library database in study of MRSA causing nosocomial infection / 中华临床感染病杂志

Objective To investigate the drug resistance,source and molecular epidemiology of methicillin-resistant Staphyloccus aureus(MRSA)causing nosocomial infection. Methods Fifty-seven pathogenic MRSA strains were isolated from Beijing Tongren Hospital during 2007 and 2008.K-B method,MIC assay,multiple PCR,automatic repetitive element sequence-based PCR(REP-PCR)typing platform and DL MRSA Library were used to identify the resistant phenotypes,Panton-Valentine leukocidin gene (pvl)and REP-PCR types of the MRSA.Results All strains were classified as 6 antibiotic resistant phenotypes(a-f)based on the resistance to rifampin,clindamycin,levofloxacin and cotrimoxazole.The MRSAs with Staphylococcal cassette chromosome mec(SCCmec)Ⅲ and SCCmec Ⅱ accounted for 91.23% (52/57)and 5.26%(3/57)of all strains,respectively.Only one strain was pvl positive.All strains were typed as REP-A-F(6 types)and three single clones by automatic REP-PCR typing platform,in which REP-C was predominant(30/57,52.63%).Three out of 6 REP-D strains were from laryngology wards.The REP-C-SCCmec Ⅲ were genetically most close to the Brazilian clone-SCCmec Ⅲ in DL MRSA Library.Conclusion s REP-C-SCCmec Ⅲ-a type are the major epidemic hospital-associated MRSA and the REP-D-SCCmec Ⅲ-d is usually isolated from patients received laryngeal surgery. Automatic REP-PCR typingplatform combined with DL MRSA Library database is an effective approach to study the nosocomial infection.

Drug resistance and genotype of methicillin-resistant Staphylococcus in Tianjin / 中华临床感染病杂志

Objective To investigate the drug resistance and genotype of methicillin-resistant Staphylococcus (MRS), and to study the epidemiology of drug resistance in Staphylococcus. Methods Drug susceptibility tests were performed for 138 Staphylococcus strains clinically isolated, and mecA gene was detected with PCR. For mecA positive strains, Staphylococcal cassette chromosome mec (SCCmec) gene was detected by two multiplex PCR assays. Results Seven (10.8%) out of 65 Staphylococcus aureus strains were methicillin-resistant Staphylococcus aureus (MRSA) strains, and 44 (60.3%) out of 73 coagulase negative Staphylococcus strains were methicillin-resistant coagulase negative Staphylococcus (MRCNS)strains. There was statistical significance on the difference of isolation rates (x2 = 37. 05, P ＜0.01). No vancomycin or nitrofurantoin resistant strain was found. There were 52 (52/138, 37.7%) mecA positive strains, including 16 SCCmec type Ⅰ strains, 1 type Ⅱ strain, 13 type Ⅲ strains, 9 type Ⅳ strains and 4 type Ⅴ strains. Conclusions Drug resistance in MRS is increasingly serious. MRCNS strains are more popular than MRSA in clinic, and SCCmec Ⅰ and Ⅲ may account for most infections.

Drug-resistance and genotyping of methicillin-resistant Staphylococcus aureus isolated from intensive care unit / 中华临床感染病杂志

Objective To investigate drug resistance and genotypes of methicillin-resistant Staphylococcus aureus (MRSA) isolated from intensive care unit (ICU). Methods MRSA strains were isolated from patients, medical staff and environment of hospital ICUs. Disk diffusion (K-B method) was used for drug resistance testing; Staphylococcal cassette chromosome mec (SCCmec) and Staphylococcal protein A (spa) typing methods were used for genotyping and identifying the homology. Results There were 78 strains of Staphylococcus aureus isolated including 62 isolates of MRSA, which were mainly from the burn ICU (22, 35.48%). Among 62 MRSA strains, 50 were hospital acquired strains, in which 43 isolates were of SCCmec Ⅲ, 4 of SCCmec Ⅰ and 3 of SCCmec Ⅱ. Twelve isolates could not be typed. Twenty-eight out of 37 hospital acquired isolates were typed by spa typing as SCCmec Ⅲ-t030, which belonged to the same clone. Conclusion MRSA in ICU is multi-drug resistant and SCCmec Ⅲ-t030 is the most prevalent genotype, which indicates that clinical MRSA strains and environmental MRSA strains may be homologous.

Functional Research of Cassette Chromosome Recombinase C Mediated Staphylococcal Cassette Chromosome mec Istand Excision / 中国医科大学学报

Objective To construct 2 recombinant plasmids carrying cassette chromosome recombinase C(ccrC)and ccrAB respectively and introduce the plasmids into methicillin-resistant Staphlococcus aureus(MRSA)strain 81/0432,and to observe the precise excision of Staphylococcal cassette chromosome mec(SCCmec)island from bacterial chromosome.Methods ccrC and ccrAB genes were amplified with chromosomal DNAs isolated from MRSA strains 81/0342 and N31S as PCR templates.We constructed recombinant plasmids pSR5C and pSR2AB by cloning ccrC and ccrAB genes into temperature-sensitive plasmid pYI3,after introducing them into MRSA strains 81/0432 and N315 by electroporation.PCR was performed to identify SCCmec excision from the bacterial chromosome.The transformants were serial passaged for 10 days,and then the drug resistance of these rransformants was detected by replica experiment.Results The fragment length of ccrC gene was 1.9 kb,smaller than the fragment length of ccrAB from N315.The recombinant plasmids of pSR5C and pSR2AB were successfully constructed.After these 2 recombinant plasmids were introduced into MRSA strain 81/0342,type-V SCCmec island was excised from the chromosome and formed a closed circular structure in the bacteria.However,type-Ⅱ SCCmec island could be excised only in N31S strain after the expression of pSR2AB.Replica experiment verified that transformed strains of 0342(pSR2AB),0342(pSR5C),and N315 (pSR2AB)were mostly susceptible to ceftizoxim or tobramycin after the excision of SCCmec island.Conclusion cciC could serve as a recombinase as ccrAB,which could mediate precise excision of SCCmec island from the chromosome of type-V MRSA strain.This study shows that type-V SCCmec island is widely disseminated between Staphylococcus aweus strains in community setting.

Research on genotyping of methicillin-resistant Staphylococcus aureus in China / 中华流行病学杂志

Objective To investigate the source and genetic background of methicillin-resistant Staphylococcus aureus in the year of 2006,in China. Methods From January to December 2006,a total number of 302 consecutive and non-repetitive methicillin-resistant Staphylococcus aureus were collected from 17 Teaching hospitals in 15 areas. Genotypes of SCCmec were determined by multiplex PCR and multilocus sequence typing (MLST) was used to type the house-keeping genes. The implementation of the spa typing method was straightforward,and the results obtained were reproducible,unambiguous,and easily interpreted. Results All areas but Dalian harbored SCCmec Ⅲ while Dalian harbored SCCmec Ⅱ most. There were two strains in Guangzhou,harboring SCCmec Ⅳ. There were four strains of sequence type(ST),with ST239 accounted for 46.7% and ST5 accounted for 44.4%. ST59 accounted for 6.7% and ST88 accounted for 2.2%. There were fourteen strains of Spa typing,with t30 accounted for 52.6% ; t37 accounted for 27.2% ; t2 accounted for 12.9% ; t632 accounted for 2.3% ; t437 accounted for 1.3% ; t570,t601 accounted for 0.7% ; t377,t459,t796,t899,t1152,t2649 accounted for 0.3% ; no-typing accounted for 0.3%,respectively,pvl gene was not detected. Conclusion The main clone strains were ST239-MRSA-SCCmec Ⅲ-t30,ST5-MRSA-SCCmec Ⅱ-t2,with unique geographic distributions across the whole nation.