Leonard R B, Mayer J, Sasser M, Woods M L, Mooney B R, Brinton B G, Newcomb-Gayman P L, Carroll K C
Associated Regional and University Pathologists, Inc., Salt Lake City, Utah 84108, USA.
J Clin Microbiol. 1995 Oct;33(10):2723-7. doi: 10.1128/jcm.33.10.2723-2727.1995.
An outbreak of methicillin-resistant Staphylococcus aureus infections at the University of Utah Health Sciences Center occurred over a 7-month period. While the isolates phenotypically appeared to be similar in gross morphology and have similar Vitek antibiotic susceptibility patterns, two additional methods of strain characterization were evaluated to enhance the epidemiological investigation: pulsed-field gel electrophoresis and gas chromatography with the MIDI Sherlock system. Sherlock uses gas chromatography to qualitatively and quantitatively analyze the cellular fatty acid composition of organisms and creates two-dimensional plots based on principal-component analysis to define groups of closely related organisms. All isolates were also evaluated by digesting their chromosomal DNAs with the low-frequency-cutting enzyme SmaI and separating the restriction fragments by contour-clamped homogeneous electric field gel electrophoresis. Sample preparation for this pulsed-field gel electrophoresis included a novel cell lysis procedure involving achromopeptidase, greatly reducing the turnaround time. Isolates tested were recovered from the following: 45 suspected outbreak patients, 6 hospitalized patients believed to be unrelated to the outbreak, 6 patients from outside the hospital, and one health care practitioner implicated in the outbreak. Of 45 phenotypically similar suspect strains, 43 clustered tightly on the Sherlock two-dimensional plot. All outbreak patient isolates were also identical by pulsed-field gel electrophoresis with the exception of the same two outliers identified by Sherlock. In this epidemiologic investigation, we found an excellent correlation between the Sherlock and pulsed-field gel electrophoresis results for strain characterization of methicillin-resistant S. aureus.
犹他大学健康科学中心在7个月的时间里爆发了耐甲氧西林金黄色葡萄球菌感染。虽然这些分离株在总体形态上表型相似，且具有相似的Vitek抗生素敏感性模式，但为加强流行病学调查，评估了另外两种菌株鉴定方法：脉冲场凝胶电泳和使用MIDI Sherlock系统的气相色谱法。Sherlock利用气相色谱法定性和定量分析生物体的细胞脂肪酸组成，并基于主成分分析创建二维图来定义密切相关的生物体组。还通过用低频切割酶SmaI消化其染色体DNA并用轮廓钳制均匀电场凝胶电泳分离限制性片段，对所有分离株进行了评估。这种脉冲场凝胶电泳的样品制备包括一种涉及无色肽酶的新型细胞裂解程序，大大缩短了周转时间。检测的分离株来自以下方面：45名疑似爆发患者、6名据信与爆发无关的住院患者、6名院外患者以及一名与爆发有关的医护人员。在45个表型相似的可疑菌株中，43个在Sherlock二维图上紧密聚集。除了Sherlock鉴定出的相同两个异常值外，所有爆发患者的分离株通过脉冲场凝胶电泳也完全相同。在这项流行病学调查中，我们发现Sherlock和脉冲场凝胶电泳结果在耐甲氧西林金黄色葡萄球菌菌株鉴定方面具有极好的相关性。
