温度对采用头孢西丁纸片扩散法在异感测试琼脂上检测金黄色葡萄球菌耐甲氧西林情况的影响。
Effects of temperature on the detection of methicillin resistance in Staphylococcus aureus using cefoxitin disc diffusion testing with Iso-Sensitest agar.
作者信息
Skov R, Smyth R, Yusof A, Karlsson A, Mills K, Frimodt-Moller N, Kahlmeter G
机构信息
National Center for Antimicrobials and Infection Control, Statens Serum Institut, Copenhagen, Denmark.
出版信息
J Antimicrob Chemother. 2009 Apr;63(4):699-703. doi: 10.1093/jac/dkp019. Epub 2009 Feb 18.
OBJECTIVES
Cefoxitin is today the substance of choice for the phenotypic detection of methicillin-resistant Staphylococcus aureus (MRSA). We investigated the influence of incubation temperature in the standard range, i.e. 35-37 degrees C, and time, i.e. 18-20 h, versus a full 24 h.
METHODS
Cefoxitin disc testing was examined at incubation temperatures of 35 and 36 degrees C and times of 18-20 and 24 h, respectively, for 94 mecA-negative and 49 mecA-positive S. aureus on Iso-Sensitest agar using a semi-confluent inoculum.
RESULTS
Cefoxitin inhibition zones on Iso-Sensitest agar were larger at temperatures above 35 degrees C; two isolates (4%, 95% confidence interval=0.5-14%) incubated at 36 degrees C were falsely categorized as susceptible to methicillin. Incubation time across 18-24 h did not impact results.
CONCLUSIONS
Detection of methicillin resistance in S. aureus using the cefoxitin disc method with a semi-confluent inoculum on Iso-Sensitest agar is influenced by incubation temperature, and the temperature should not exceed 35 degrees C for the reliable detection of MRSA.
目的
头孢西丁是目前用于耐甲氧西林金黄色葡萄球菌（MRSA）表型检测的首选药物。我们研究了标准范围内的孵育温度（即35 - 37摄氏度）和时间（即18 - 20小时）与完整24小时相比的影响。
方法
使用半融合接种物，分别在35和36摄氏度的孵育温度以及18 - 20和24小时的时间下，对94株mecA阴性和49株mecA阳性金黄色葡萄球菌在异感测试琼脂上进行头孢西丁纸片试验。
结果
在异感测试琼脂上，温度高于35摄氏度时头孢西丁抑菌圈更大；在36摄氏度孵育的两株菌株（4%，95%置信区间 = 0.5 - 14%）被错误分类为对甲氧西林敏感。18 - 24小时的孵育时间不影响结果。
结论
在异感测试琼脂上使用半融合接种物的头孢西丁纸片法检测金黄色葡萄球菌对甲氧西林的耐药性受孵育温度影响，为可靠检测MRSA，温度不应超过35摄氏度。
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