Department of Pathology and Laboratory Medicine, University of Calgary, Calgary, Alberta, Canada.
Department of Medicine, University of Calgary, Calgary, Alberta, Canada.
J Clin Microbiol. 2021 Oct 19;59(11):e0097321. doi: 10.1128/JCM.00973-21. Epub 2021 Aug 11.
Staphylococcus pseudintermedius can easily be mistaken for Staphylococcus aureus using phenotypic and rapid biochemical methods. We began confirming the identification of all coagulase-positive staphylococci isolated from human wound cultures at our centralized laboratory, servicing both community and inpatients, with matrix-assisted laser desorption ionization-time of flight mass spectrometry instead of using phenotypic and rapid biochemical tests, and determined the prevalence of S. pseudintermedius since the change in identification procedure and at what cost. A retrospective review was performed on all wound swab cultures from which coagulase-positive staphylococci were isolated 7 months before and after the change in identification procedure. A total of 49 S. intermedius (SIP) isolates were identified, including 7 isolates from 14,401 wound cultures in the before period and 42 isolates from 14,147 wound cultures in the after period. The number of SIP isolates as a proportion of isolated coagulase-positive staphylococci increased significantly from the before, 7/6,351 (0.1%), to the after, 42/5,435 (0.7%), period (difference, 0.6% [95% confidence interval, 0.037 to 0.83%, < 0.0001]). Antibiotic susceptibility testing was performed in 42 isolates; none had an oxacillin MIC of 1.0 to 2.0 μg/ml, the range in which, if the isolate was misidentified as S. aureus, a very major error in susceptibility interpretation would occur. The increase in cost of the change in identification procedure was Can$17,558 per year in our laboratory, performing microbiology testing for community and acute-care patients in a zone servicing nearly 1.7 million people. While we will only continue to learn more about this emerging pathogen if we make attempts to properly identify it in clinical cultures, the additional time and cost involved may be unacceptably high in some laboratories. .
金黄色葡萄球菌（Staphylococcus aureus）和中间葡萄球菌（Staphylococcus pseudintermedius）在表型和快速生化方法上很容易混淆。我们开始用基质辅助激光解吸电离飞行时间质谱（matrix-assisted laser desorption ionization-time of flight mass spectrometry）代替表型和快速生化试验，对我们集中化实验室（为社区和住院患者服务）分离的所有凝固酶阳性葡萄球菌进行鉴定确认，以确定中间葡萄球菌的流行率，并确定在改变鉴定程序前后的成本。我们对改变鉴定程序前后 7 个月内所有从伤口拭子培养物中分离出凝固酶阳性葡萄球菌的标本进行了回顾性研究。共鉴定出 49 株中间葡萄球菌（SIP），其中 7 株来自前一时期的 14401 例伤口培养物，42 株来自后一时期的 14147 例伤口培养物。SIP 分离株占分离出的凝固酶阳性葡萄球菌的比例从前一时期的 7/6351（0.1%）显著增加到后一时期的 42/5435（0.7%）（差异，0.6%[95%置信区间，0.037 至 0.83%，<0.0001]）。对 42 株分离株进行了抗生素药敏试验；没有一株的苯唑西林 MIC 值为 1.0 至 2.0μg/ml，而如果将分离株错误鉴定为金黄色葡萄球菌，在药敏解释中会出现非常严重的错误。我们的实验室每年进行社区和急性护理患者的微生物学检测，服务于近 170 万人口，改变鉴定程序的成本增加了 17558 加元。如果我们试图在临床培养物中正确鉴定这种新出现的病原体，我们只会更多地了解这种病原体，但在某些实验室中，额外的时间和成本可能高得无法接受。
