Leal Sixto M, Jones Melissa, Gilligan Peter H
Clinical Microbiology-Immunology Laboratories, University of North Carolina Hospitals, Chapel Hill, North Carolina, USA.
Clinical Microbiology-Immunology Laboratories, University of North Carolina Hospitals, Chapel Hill, North Carolina, USA
J Clin Microbiol. 2016 Dec;54(12):2928-2936. doi: 10.1128/JCM.01393-16. Epub 2016 Sep 14.
Commensal bacteria from the skin and mucosal surfaces are routinely isolated from patient samples and considered contaminants. The majority of these isolates are catalase-positive Gram-positive rods from multiple genera routinely classified as diphtheroids. These organisms can be seen upon Gram staining of clinical specimens or can be isolated as the predominant or pure species in culture, raising a priori suspicion of a possible involvement in infection. With the development and adoption of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), suspicious isolates are now routinely identified to the species level. In this study, we performed a retrospective data review (2012 to 2015) and utilized site-specific laboratory criteria and chart reviews to identify species within the diphtheroid classification representative of true infection versus contamination. Our data set included 762 isolates from 13 genera constituting 41 bacterial species. Only 18% represented true infection, and 82% were deemed contaminants. Clinically significant isolates were identified in anaerobic wounds (18%), aerobic wounds (30%), blood (5.5%), urine (22%), cerebrospinal fluid (24%), ophthalmologic cultures (8%), and sterile sites (20%). Organisms deemed clinically significant included multiple Actinomyces species in wounds, Propionibacterium species in joints and cerebrospinal fluid associated with central nervous system hardware, Corynebacterium kroppenstedtii (100%) in breast, and Corynebacterium striatum in multiple sites. Novel findings include clinically significant urinary tract infections by Actinomyces neuii (21%) and Corynebacterium aurimucosum (21%). Taken together, these findings indicate that species-level identification of diphtheroids isolated with a priori suspicion of infection is essential to accurately determine whether an isolate belongs to a species associated with specific types of infection.
从患者样本中经常分离出皮肤和粘膜表面的共生细菌，并被视为污染物。这些分离株大多数是过氧化氢酶阳性的革兰氏阳性杆菌，来自多个属，通常归类为类白喉杆菌。这些微生物可以在临床标本的革兰氏染色中看到，或者可以在培养物中作为主要或纯菌种分离出来，这就引发了对其可能参与感染的先验怀疑。随着基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）的发展和应用，现在可以常规地将可疑分离株鉴定到种水平。在本研究中，我们进行了一项回顾性数据审查（2012年至2015年），并利用特定部位的实验室标准和病历审查来确定类白喉杆菌分类中代表真正感染与污染的菌种。我们的数据集包括来自13个属的762株分离株，构成41种细菌。只有18%代表真正的感染，82%被视为污染物。在厌氧伤口（18%）、需氧伤口（30%）、血液（5.5%）、尿液（22%）、脑脊液（24%）、眼科培养物（8%）和无菌部位（20%）中鉴定出具有临床意义的分离株。被认为具有临床意义的微生物包括伤口中的多种放线菌属菌种、与中枢神经系统硬件相关的关节和脑脊液中的丙酸杆菌属菌种、乳腺中的克氏棒状杆菌（100%）以及多个部位的纹带棒状杆菌。新发现包括纽氏放线菌（21%）和粘膜金色棒状杆菌（21%）引起的具有临床意义的尿路感染。综上所述，这些发现表明，对先验怀疑感染而分离出的类白喉杆菌进行种水平鉴定对于准确确定分离株是否属于与特定类型感染相关的菌种至关重要。
