Tracheal aspirate Gram stain has limited sensitivity and specificity for detecting Staphylococcus aureus
Tracheal aspirate Gram stain has limited sensitivity and specificity for detecting Staphylococcus aureus
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DOI：
10.1111/j.1440-1843.2010.01855.x
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发表时间：
2011-01-01
期刊：
影响因子：
6.9
通讯作者：
Metersky, Mark L.
中科院分区：
文献类型：
--
作者：
Tetenta, Sodienye;Metersky, Mark L.
背景与目的：耐甲氧西林金黄色葡萄球菌所致呼吸道感染的发病率不断增加，导致抗菌药物的经验性使用增加。关于呼吸道分泌物的革兰氏染色是否能准确预测金黄色葡萄球菌的生长，现有的数据有限。我们推测，金黄色葡萄球菌独特的形态可以快速、准确地鉴定呼吸道分泌物中的微生物。方法：作者复习了2008年4月1日至2008年10月31日送入医院微生物学实验室的所有可用革兰氏染色标本，对培养结果视而不见，并记录了形态与金黄色葡萄球菌一致的微生物的存在或不存在。结果：在136例气管抽吸物中，50例(37%)培养出金黄色葡萄球菌。其中34例患者的革兰氏染色结果与金黄色葡萄球菌一致。在86个没有生长金黄色葡萄球菌的样本中，62个样本的革兰氏染色为阴性。因此，革兰氏染色对金黄色葡萄球菌培养的敏感性为68%，特异性为72%，阴性预测值为80%，阳性预测值为59%。结论：在本研究中，由非微生物学家、有经验的临床医生读取的气管吸入物革兰氏染色结果不足以可靠地预测金黄色葡萄球菌的生长。
Background and objective:The increasing incidence of respiratory infections due to methicillin resistant Staphylococcus aureus has resulted in increased empirical use of antibiotics active against this pathogen. There are limited data available as to whether the Gram stain of respiratory tract secretions accurately predicts growth of S. aureus. We theorized that the distinctive morphology of S. aureus would allow rapid, accurate identification of the organism in respiratory secretions.Methods:The authors reviewed all available Gram stains of tracheal aspirates sent to our hospital's microbiology laboratory between 1 April 2008 and 31 October 2008, while blinded to the culture result, and recorded the presence or absence of organisms with a morphology consistent with S. aureus. These results were correlated with the semiquantitative culture result.Results:Among 136 tracheal aspirates studied, 50 (37%) grew S. aureus. The Gram stain was read as positive for organisms consistent with S. aureus in 34 of these. Among 86 samples that did not grow S. aureus, the Gram stain was read as negative in 62. Therefore, the Gram stain had a sensitivity of 68%, a specificity of 72%, a negative predictive value of 80% and a positive predictive value of 59% for culture of S. aureus. False negative Gram stains were more likely when the culture revealed only rare or small growth of S. aureus (P = 0.01).Conclusions:In this study, the tracheal aspirate Gram stain read by an experienced clinician who was not a microbiologist, was not accurate enough to reliably predict the growth of S. aureus.