Antimicrobial resistance features and molecular typing of clinically isola-ted m ethicillin-resistant Staphylococcus aureus / 中国感染控制杂志

Objective To study antimicrobial resistance and genotyping of methicillin-resistant Staphylococcus au-reus(MRSA). Methods A total of 967 no-repetitive strains of Staphylococcus aureus(S.aureus)isolated from a hospital between January 2014 and November 2015 were collected,antimicrobial susceptibility testing,mecA gene,and Panton-Valentine leukocidin gene(PVL gene)were detected;staphylococcal cassette chromosome mec(SCCmec)typing,multilocus sequence typing(MLST),S.aureus protein A(spa)gene typing,and S.aureus ac-cessory gene regulator(agr)typing were performed with multiplex polymerase chain reaction. Results Of 967 strains of S.aureus,210(21.72%)were MRSA;detection rate of MRSA from sputum specimen was higher than that of skin and soft tissue specimen(68.09% vs 1 1.83% ,P<0.05);vancomycin- and linezolid-resistant S.aureus strains were not found,susceptibility rates of MRSA to gentamicin,tetracycline,erythromycin,clindamycin,levo-floxacin,ciprofloxacin,moxifloxacin,nitrofurantoin,and rifampicin were all lower than those of methicillin-sensi-tive Staphylococcus aureus(MSSA),differences were all statistically significant(all P<0.05);antimicrobial sus-ceptibility rate of MRSA to compound sulfamethoxazole was higher than MSSA,difference was significant(P<0.05). Susceptibility rates of MRSA isolated from skin and soft tissue to gentamicin,levofloxacin,ciprofloxacin,moxifloxacin,and rifampicin were 86.90% -95.24%,while MRSA isolated from sputum were only 1.56% -15.63%.Of 967 strains of S.aureus,210 harbored mecA gene,10 harbored PVL gene,8(3.81%)of 210 MRSA strains weren't typed. The main types of MLST,SCCmec,spa,and agr were ST 239(n= 177 strains),type Ⅲ(n= 177 strains),t 030(n= 177 strains),and typeⅠ(n= 196 strains)respectively.Conclusion The main epidemic clone of MRSA strain in this hospital is ST239-MRSA-SCCmec III-t030,antimicrobial resistance is serious,monitoring on drug-resistant strains in hospital should be strengthened.

Prevalence and molecular proifle of theStaphylococcus aureus strains harboring tstand/or pvl genes / 中国感染与化疗杂志

Objective To investigate the prevalence, accessory gene regulator (agr) and staphylococcal cassette chromosome mec (SCCmec, only for methicillin resistantS. aureus, MRSA) types of theS. aureus strains carrying toxic shock syndrome toxin-1 (tst) and/or panton-valentine leukocidin (pvl) genes.Methods Nine hundred and sixteen isolates ofS. aureus were collected from seven hospitals in Shanghai and Zhejiang Province and subjected to detection oftst,pvl,mecA andmecC genes by polymerase chain reaction (PCR). Theagr and SCCmec (only for MRSA) types were determined in thetst orpvl gene positive isolates.Results Of the 916 isolates, 208 carriedtst gene (22.7%), 35 harboredpvl gene (3.8%), and 665 weremecA positive (MRSA). No isolate was mecC positive. Out of the 665 MRSA isolates, 198 hosted thetst gene (29.8%). The most commonagr and SCCmec types were agr 2 (97.0%) and SCCmec II (94.4%), respectively. For thepvl gene, only 14 isolates were positive (2.1%). Theagr 1 (85.7%), SCCmecIII (42.9%) and SCCmec IVa (28.6%) were the most commonagr type and SCCmec type. In the 251 methicillin-sensitiveS. aureus (MSSA) isolates, 10 carriedtst gene (4.0%) and 21 carriedpvl gene (8.4%). The prevalence oftst gene in MRSA was higher than that in MSSA, while the prevalence ofpvlgene was just the opposite. However, the prevalence ofpvlgene in MRSA isolates from Zhejiang Province was higher than that in the MRSA isolates from Shanghai (P severeS. aureus infections.

Staphylococcus aureus nasal carriage among outpatients attending primary health care centers: a comparative study of two cities in Saudi Arabia and Egypt

Epidemiological and molecular data on community acquired methicillin resistant Staphylococcus aureus (CA-MRSA) are still scarce in both Egypt and Saudi Arabia. There is almost no data regarding methicillin resistant Staphylococcus aureus (MRSA) prevalence in both countries. This study was conducted to investigate the prevalence and molecular epidemiology of S. aureus and MRSA nasal carriage among outpatients attending primary health care centers in two big cities in both countries. A total of 206 nasal swabs were obtained, 103 swabs from each country. S. aureus isolates were characterized by antibiotic susceptibility, presence of mecA and PVL genes, SCCmec-typing and spa typing, the corresponding Multi locus sequence typing clonal complex was assigned for each spa type based on Ridom StaphType database. MRSA was detected in 32% of the Egyptian outpatients while it was found in 25% of the Saudi Arabian outpatients. All MRSA isolates belonged to SCCmec type V and IVa, where some isolates in Saudi Arabia remained nontypeable. Surprisingly PVL+ isolates were low in frequency: 15% of MRSA Egyptian isolates and 12% of MRSA isolates in Saudi Arabia. Two novel spa types were detected t11839 in Egypt, and t11841 in Saudi Arabia. We found 8 spa types among 20 isolates from Egypt, and 12 spa types out of 15 isolates from Saudi Arabia. Only two spa types t008 and t223 coexisted in both countries. Four clonal complexes (CC5, CC8, CC22, and CC80) were identified in both Egypt and Saudi Arabia. However, the data collected lacked a representation of isolates from different parts of each country as only one health center from each country was included, it still partially illustrates the CA-MRSA situation in both countries. In conclusion a set of control measures is required to prevent further increase in MRSA prevalence.

Genetic location of SCCmec-associated psm-mec in Staphylococcus hominis from blood culture / 国际检验医学杂志

Objective To investigate the genetic location of SCCmec-associated psm-mec in Staphylococcus hominis isolated from blood culture,and to lay a foundation for further functional studies of psm-mec in Staphylococcus hominis.Methods 25 strains of Staphylococcus hominis isolated from positive blood culture were collected.mecA and psm-mec gene were amplified by PCR,and the SCCmec types were determined by the results of multiplex PCR assay.For analyzing the genetic location characteristic of psm-mec in SCCmec,three pair special PCR primers were used to measure mecR1/psm-mec,psm-mec/xylR and fudoh respectively.Results There were 21 strains of methicillin-resistant Staphylococcus hominis and 4 strains of methicillin-sensitive Staphylococcus hominis. The positive rate of psm-mec gene in methicillin-resistant Staphylococcus hominis was 47.6%,and no psm-mec gene was found in methicillin-sensitive Staphylococcus hominis.Among psm-mec positive strains,2 strains belonged to SCCmecⅢ,5 strains belonged to SCCmecⅢ-like,and 3 strains belonged to new SCCmec types.All of the 10 psm-mec positive strains were mecR1/psm-mec,psm-mec/xylR and fudoh gene positive.Conclusion SCCmec-associated psm-mec extensively exists in methicillin-resistant Staphylococ-cus hominis isolated from positive blood culture,which distributes mainly in typical SCCmecⅢ,SCCmecⅢ-like and new SCCmec types and locates between mecR1 and xylR gene.

Molecular typing and drug resistance of methicillin-resistant Staphylococcus aureus in Zhejiang province / 中华临床感染病杂志

Objective To investigate molecular types and drug resistance of methicillin-resistant Staphylococcus aureus (MRSA) in Zhejiang province.Methods One hundred and fourty-seven clinical MRSA isolates were collected from 11 grade A tertiary hospitals during January 2009 and December 2010 in Zhejiang province.Minimal inhibitory concentrations (MICs) of 13 antimicrobial agents were determined by agar dilution.Multilocus sequence typing (MLST),staphylococcal cassette chromosome mec (SCCmec) typing and spa typing were used to examine the homology of the strains,and drug resistance patterns were compared among different molecular types.Simpson index was used to determine the discriminatory power of three typing methods.Results Fourteen STs were identified in 147 MRSA isolates,of which ST239 (75 isolates),ST5 (24 isolates) and ST59 (23 isolates) were the most prevalent clones.Four SCCmec types (types Ⅱ to Ⅴ) were identified in 141 isolates,and 6 isolates were not typed.SCCmec type Ⅲ was the predominant type (76 isolates),which was followed by type Ⅳ (32 isolates),type Ⅱ (24 isolates) and type Ⅴ (9 isolates).All MRSA isolates yielded 23 spa types,in which t030 (57 strains),t437 (17 strains),t002 (15 strains) and t037 (12 strains) were the predominant spa types.MRSA strains were sensitive to linezolid,teicoplanin,vancomycin and norvancomycin,but were highly resistant to other antibacterial agents,especially in strains carrying clone ST239 or of SCCmec type Ⅲ.The discriminatory power of MLST,SCCmec and spa typing were 0.6885,0.6577 and 0.8165,respectively.Conclusion The predominant clone of MRSA strains in Zhejiang province was ST239-SCCmec Ⅲ-t030-MRSA,and these strains are highly resistant to most antibacterial agents,so that the surveillance of MRSA in hospital should be strengthened.