Department of Oncology, Hematology, and Infectious Diseases, Fukuoka University School of Medicine, Fukuoka, Japan.
J Infect Chemother. 2012 Apr;18(2):199-206. doi: 10.1007/s10156-011-0313-3. Epub 2011 Oct 19.
Methicillin-resistant Staphylococcus aureus (MRSA) infections have been the most common cause of nosocomial infections in Japan, but their genetic characteristics related to bloodstream infections have not been well studied. The aim of this study was to investigate a comprehensive molecular characterization of MRSA blood isolates during the historical 18-year study period between 1987 and 2004 in a tertiary care university hospital. A total of 137 MRSA isolates recovered from the blood of inpatients at Fukuoka University Hospital were analyzed. Clinical information and antimicrobial susceptibility profiles were reviewed, and staphylococcal chromosomal cassette mec (SCCmec), accessory gene regulator (agr), and a battery of bacterial genes were tested by PCR-based assays. The relatedness of these isolates was determined by the repetitive sequence-based PCR (rep-PCR) and pulsed-field gel electrophoresis (PFGE). Although low numbers of agr type III/SCCmec type IV isolates circulated between 1987 and 1992, agr type II/SCCmec type II isolates started circulating in 1993 and were responsible for the increased MRSA isolates until 2004. The rep-PCR and PFGE identified 104 epidemic and 33 sporadic isolates. Among the 104 epidemic isolates, six major rep-PCR/PFGE types were identified, which occupied 67.3% of epidemic isolates. The SCCmec type II and agr type II isolates were observed in significantly higher proportion in epidemic isolates than in sporadic isolates (P = 0.0318, P = 0.0123, respectively). In contrast, SCCmec type IV strains were observed in significantly higher proportion in sporadic isolates than in epidemic isolates (P = 0.0494). Although isolates with sec were detected in higher rates in epidemic isolates (P = 0.0397), seh was detected in higher rates in sporadic isolates (P = 0.0350). Multivariate logistic regression analysis with forward stepping revealed that SCCmec type II was independently associated with epidemic isolates (P = 0.0067; odds ratio, 1.75; 95% confidence interval, 1.17-2.64). These data indicated that SCCmec type II MRSA isolates were responsible for the increased MRSA bloodstream infections for inpatients during the 18-year study period in the hospital.
耐甲氧西林金黄色葡萄球菌（MRSA）感染一直是日本医院感染的最常见原因，但它们与血流感染相关的遗传特征尚未得到很好的研究。本研究旨在调查在 1987 年至 2004 年期间在一家三级保健大学医院进行的 18 年历史研究中，MRSA 血培养分离株的全面分子特征。对从福冈大学医院住院患者血液中分离出的 137 株 MRSA 进行了分析。回顾了临床信息和抗菌药物敏感性谱，并通过基于 PCR 的检测方法检测了葡萄球菌染色体盒 mec（SCCmec）、辅助基因调节剂（agr）和一系列细菌基因。通过重复序列基元 PCR（rep-PCR）和脉冲场凝胶电泳（PFGE）确定这些分离株的相关性。尽管 1987 年至 1992 年间循环的 agr 型 III/SCCmec 型 IV 分离株数量较少，但 1993 年开始循环 agr 型 II/SCCmec 型 II 分离株，并导致 2004 年 MRSA 分离株增加。rep-PCR 和 PFGE 鉴定出 104 个流行株和 33 个散发病例。在 104 个流行株中，鉴定出 6 种主要的 rep-PCR/PFGE 型，占流行株的 67.3%。在流行株中，SCCmec 型 II 和 agr 型 II 分离株的比例明显高于散发病例（P=0.0318，P=0.0123）。相反，在散发病例中，SCCmec 型 IV 株的比例明显高于流行株（P=0.0494）。尽管在流行株中检测到 sec 的分离株比例较高（P=0.0397），但在散发病例中，seh 的分离株比例较高（P=0.0350）。逐步向前的多变量逻辑回归分析显示，SCCmec 型 II 与流行株独立相关（P=0.0067；优势比，1.75；95%置信区间，1.17-2.64）。这些数据表明，SCCmec 型 II MRSA 分离株是导致该医院 18 年研究期间住院患者 MRSA 血流感染增加的原因。
