Akoğlu Hadim, Zarakolu Pınar, Altun Belgin, Ünal Serhat
Hacettepe Üniversitesi Tıp Fakültesi, İç Hastalıkları Anabilim Dalı, Enfeksiyon Hastalıkları Ünitesi, Ankara, Türkiye.
Mikrobiyol Bul. 2010 Jul;44(3):343-55.
The aim of this study was to determine the epidemiological and molecular characteristics of hospital-acquired (HA)-methicillin-resistant Staphylococcus aureus (MRSA) isolates by investigating the distribution of clinical samples according to the hospital wards, antibiotic susceptibility patterns, staphylococcal chromosome cassette mec (SCCmec) types and the presence of Panton-Valentine Leukocidin (PVL) genes. A total of 110 MRSA isolates obtained from various clinical samples of inpatients at Hacettepe University Adult Hospital between January 2004 and December 2005 were included in the study. The identification of the isolates was done by BD Sceptor automated system (Becton Dickinson, USA). The mecA gene, SCCmec types and PVL genes were detected by polymerase chain reaction (PCR). Pulsed field gel electrophoresis (PFGE) was performed to examine the clonal relatedness. The susceptibility testing was performed for some antibiotics by E-test (AB Biodisk, Sweden) and for the others by disk diffusion methods according to the Clinical and Laboratory Standards Institute (CLSI) recommendations. The clinical samples (35 blood, 37 pus, 23 deep tracheal aspiration, 5 catheter, and 10 other samples) that yielded the MRSA strains were isolated from patients (71.5%) at intensive care units and surgical wards. All the isolates were positive for mecA gene. Of the isolates, 68 (61.8%) were harboring SCCmec type III, 38 (34.5%) SCCmec variant IIIB, and 3 (2.7%) SCCmec type IV. One isolate which was mecA gene positive could not be classified in any of the SCCmec types. PVL was positive in 14 (12.7%) of the isolates. All MRSA strains were susceptible to tigecycline, linezolid, vancomycin and teicoplanin; however, exhibited high rates (> 90%) of resistance to gentamicin, ciprofloxacin and rifampin. Susceptibility rates to trimethoprim/sulfamethoxazole was 90%, clindamycin 53% and erythromycin 32%. Eight pulsotypes were distinguished on the basis of PFGE (A, B, C, D, K, L, N, O). Of the total isolates, 92.7% belonged to pulsotype A. HA-MRSA strains predominantly isolated from pus and blood samples of inpatients at intensive care units and surgical wards in our hospital were multi-resistant. Majority of these isolates were SCCmec III, or variant IIIB type. Although PVL is known as a common virulence factor of community-acquired MRSA, HA-MRSA isolates in our center have a considerable rate of PVL positivity pointing out the importance of surveillance of the changing epidemiology of MRSA.
本研究的目的是通过根据医院病房调查临床样本分布、抗生素敏感性模式、葡萄球菌染色体盒式mec（SCCmec）类型以及杀白细胞素（PVL）基因的存在情况，来确定医院获得性（HA）耐甲氧西林金黄色葡萄球菌（MRSA）分离株的流行病学和分子特征。纳入了2004年1月至2005年12月在哈杰泰佩大学成人医院从住院患者各种临床样本中获得的110株MRSA分离株。分离株的鉴定通过BD Sceptor自动化系统（美国BD公司）进行。通过聚合酶链反应（PCR）检测mecA基因、SCCmec类型和PVL基因。采用脉冲场凝胶电泳（PFGE）检测克隆相关性。根据临床和实验室标准协会（CLSI）的建议，部分抗生素通过E-test（瑞典AB生物盘公司）进行药敏试验，其他抗生素通过纸片扩散法进行药敏试验。产生MRSA菌株的临床样本（35份血液、37份脓液、23份深部气管吸出物、5份导管样本和10份其他样本）从重症监护病房和外科病房的患者中分离得到（71.5%）。所有分离株的mecA基因均为阳性。其中，68株（61.8%）携带SCCmec III型，38株（34.5%）为SCCmec变异型IIIB，3株（2.7%）为SCCmec IV型。1株mecA基因阳性的分离株无法归入任何一种SCCmec类型。14株（12.7%）分离株的PVL呈阳性。所有MRSA菌株对替加环素、利奈唑胺、万古霉素和替考拉宁敏感；然而，对庆大霉素、环丙沙星和利福平的耐药率较高（>90%）。对甲氧苄啶/磺胺甲恶唑的敏感率为90%，克林霉素为53%，红霉素为32%。根据PFGE区分出8种脉冲型（A、B、C、D、K、L、N、O）。在所有分离株中，92.7%属于脉冲型A。我院重症监护病房和外科病房住院患者的脓液和血液样本中主要分离出的HA-MRSA菌株具有多重耐药性。这些分离株大多数为SCCmec III型或变异型IIIB型。虽然PVL是社区获得性MRSA的常见毒力因子，但我们中心的HA-MRSA分离株中PVL阳性率相当高，这指出了监测MRSA流行病学变化的重要性。
