Centre for Infectious Diseases and Microbiology, Sydney Medical School and Sydney Emerging Infections and Biosecurity Institute, University of Sydney, Westmead Hospital, New South Wales, Australia.
J Clin Microbiol. 2013 Jan;51(1):112-6. doi: 10.1128/JCM.01406-12. Epub 2012 Oct 24.
Knowledge concerning stability is important in the development and assessment of microbial molecular typing systems and is critical for the interpretation of their results. Typing system stability is usually measured as the fraction of isolates that change type after several in vivo passages, but this does not necessarily reflect in vivo stability. The aim of this study was to utilize survival analysis to provide an informative quantitative measure of in vivo stability and to compare the stabilities of various techniques employed in typing methicillin-resistant Staphylococcus aureus (MRSA). We identified 100 MRSA pairs (isolated from the same patient ≥ 1 month apart) and typed them using multilocus sequence typing (MLST), phage-derived open reading frame (PDORF) typing, toxin gene profiling (TGP), staphylococcal cassette chromosome mec (SCCmec) subtyping, pulsed-field gel electrophoresis (PFGE), and spa sequence typing. Discordant isolate pairs, belonging to different MLST clonal complexes, were excluded, leaving 81 pairs for analysis. The stabilities of these methods were examined using Kaplan-Meier survival analysis, and discriminatory power was measured by Simpson's index of diversity. The probability percentages that the type remained unchanged at 6 months for spa sequence typing, TGP, multilocus variable number of tandem repeats analysis (MLVA), SCCmec subtyping, PDORF typing, and PFGE were 95, 95, 88, 82, 71, and 58, respectively, while the Simpson's indices of diversity were 0.48, 0.47, 0.70, 0.72, 0.89, and 0.88, respectively. Survival analysis using sequential clinical isolates adds an important quantitative dimension to the measurement of stability of a microbial typing system. Of the methods compared here, PDORF typing provides high discriminatory power, comparable with that of PFGE, and a level of stability suitable for MRSA surveillance and outbreak investigations.
稳定性知识对于微生物分子分型系统的开发和评估很重要，对于解释其结果也至关重要。通常，通过对多个体内传代后发生表型改变的分离株比例来衡量分型系统的稳定性，但这并不一定反映体内稳定性。本研究旨在利用生存分析为体内稳定性提供一种信息丰富的定量衡量方法，并比较用于检测耐甲氧西林金黄色葡萄球菌（MRSA）的各种技术的稳定性。我们鉴定了 100 对 MRSA 分离株（相隔至少 1 个月从同一患者中分离），并使用多位点序列分型（MLST）、噬菌体衍生开放阅读框（PDORF）分型、毒素基因谱（TGP）、葡萄球菌盒染色体 mec（SCCmec）亚分型、脉冲场凝胶电泳（PFGE）和 spa 序列分型进行分型。排除了属于不同 MLST 克隆复合体的分离株不一致对，最终对 81 对分离株进行分析。采用 Kaplan-Meier 生存分析方法检验这些方法的稳定性，并通过 Simpson 多样性指数测量区分能力。spa 序列分型、TGP、多位点可变串联重复分析（MLVA）、SCCmec 亚分型、PDORF 分型和 PFGE 在 6 个月时保持不变的概率百分比分别为 95%、95%、88%、82%、71%和 58%，而 Simpson 多样性指数分别为 0.48、0.47、0.70、0.72、0.89 和 0.88。使用连续临床分离株进行生存分析为微生物分型系统稳定性的测量增加了一个重要的定量维度。在比较的方法中，PDORF 分型提供了高区分能力，与 PFGE 相当，并且具有适合 MRSA 监测和暴发调查的稳定性水平。
