医院获得性耐甲氧西林金黄色葡萄球菌57株的葡萄球菌染色体mec基因盒基因分型及耐药性分析

Genotyping of staphylococcal cassette chromosome mec and antimicrobial resistance of 57 hospital-acquired-methicilin-resistant Staphylococcus aureus

目的了解上海长征医院临床分离的医院获得性耐甲氧西林金黄色葡萄球菌(HA-MRSA)的葡萄球菌染色体mec基因盒(SCCmec)的基因分型及耐药状况。方法收集上海长征医院2010年8月—2011年8月从医院获得性肺炎下呼吸道分离的57株HA-MRSA。应用聚合酶链反应(PCR)检测mecA基因,多重PCR方法对HA-MRSA进行SCCmec基因分型。采用标准的K-B纸片扩散法测定HA-MRSA对β内酰胺类抗生素(青霉素、苯唑西林、头孢西丁、头孢曲松)和非β内酰胺类抗生素[环丙沙星、左氧氟沙星、红霉素、克林霉素、利福平、万古霉素、替考拉宁、利奈唑胺和复方磺胺甲基异口恶唑(TMP-SMZ)]的敏感性。结果 57株HA-MRSA的mecA基因均为阳性,有39株明确分型,其中SCCmecⅡ型11株(19.3%),SCCmecⅢ型19株(33.3%),SCCmecⅣb型1株(1.7%),SCCmecⅣc型1株(1.7%),SCCmecⅣd型7株(12.3%),未发现SCCmecⅠ型和SCCmecⅤ型。另有18株(31.6%)mecA基因阳性菌株未能分型。全部57株对青霉素、苯唑西林、头孢西丁、头孢曲松耐药;55株(96.5%)对左氧氟沙星耐药,1株中度敏感,1株敏感;56株(98.2%)对环丙沙星耐药,1株敏感;54株(94.7%)对红霉素耐药,1株中度敏感,2株敏感;47株(82.5%)对克林霉素耐药,2株中度敏感,8株敏感;25株(43.9%)对TMP-SMZ耐药,1株中度敏感,31株敏感;10株(17.5%)对利福平耐药,47株敏感;57株对替考拉宁、万古霉素、利奈唑胺均敏感,耐药率为0。结论上海长征医院临床分离HA-MRSA的SCCmec基因型以Ⅲ型、Ⅱ型为主,除1株携带SCCmecⅣb型的HA-MRSA外,其余56株(包括SCCmecⅡ、Ⅲ、Ⅳc、Ⅳd型)均具有多重耐药的特征。

Objective To investigate genotype characteristics of staphylococcal cassette chromosome mec （SCCmec） and antimicrobial resistance of hospital-acquired rnethicillin-resistant Staphy/ococcus aureus （HA-MRSA） isolated from Shanghai Changzheng Hospital. Methods A total of 57 strains of HA-MRSA were isolated from various specimens of lower respiratory tract of the inpatients with hospital-acquired pneumonia between August 2010 and August 2011. The polymerase chain reaction （PCR） was used to detect mecA gene. Multiplex PCR was used to detect the SCOmec genotype. Antimicrobial susceptibility of 13 antibiotics （^-Iactams.- penicillin, oxacillin, cefoxitin, and ceftriaxone, non-β-Iactams; ciprofloxacin, levofloxacin, erythromycin, clindamycin, rifampicin, vancomycin, teicoplanin, linezolid and trimethoprin-sulfamethoxazole） was determined by agar diffusion method. Results All of the 57 strains were positive for mecA gene. SCCmec Ⅱ was identified in Ⅱ（19.3%） isolates, SCCmecⅢ in 19 （33.3%）, SCCmecⅣ＇b in 1 （1.7%）, SOCmecⅣ＇c in 1（1.7%） and SCCmec lVd in 7 （ 12.3 % ）. No SCCmec Ⅰ or SCOmec Ⅴ was found. Another 18 HA-MRSA strains （31.6 % ） can not be classified. All the strains were resistant to penicillin, oxacillin, cefoxitin and ceftriaxone and susceptible to teicoplanin, vancomycin and linezolid. Fifty-five strains （96. 5%） were resistant to levofloxacin. Fifty-six strains （98.2%） were resistant to ciprofloxacin. Fifty-four strains （94.7%） were resistant to erythromycin. Forty-seven strains （82.5%） were resistant to clindamycin. Twenty-five strains （43.9%） were resistant to trimethoprin-sulfamethoxazole. Ten strains （17.5%） were resistant to rifampicin. Conclusion SCCmecⅢ and SOOmecⅡ are the main genotypes of HA-MRSA from Shanghai Changzheng Hospital. All of the strains （SOCrnecⅡ, Ⅲ, Ⅳc and Ⅳd） are multi-resistant to tested antibiotics except for the one with SCOrnecⅣb. [Key words] Methicillin-resistant Staphylococcus aureus; Staphylococcal cassette chromosome mec; Polymerase chain reaction; Drug resistance