Increase in detection of Corynebacterium diphtheriae in Canada: 2006-2019.

K. Bernard, A. L. Pacheco, T. Burdz, D. Wiebe
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引用次数: 20

Abstract

Background Increasingly, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) has been used to provide rapid, inexpensive and precise identification of bacteria, including Corynebacterium species. Only three Corynebacterium species are able to produce diphtheria toxin (DT), and strains recovered may be either toxin-producing or non-toxin-producing. It appears the more precise bacterial identification provided by MALDI-TOF systems has led to an increase in requests submitted to the National Microbiology Laboratory (NML) for toxin testing. Objective To describe the number of isolates identified as C. diphtheriae, C. ulcerans and C. pseudotuberculosis, submitted to the NML between January 2006 and July 30, 2019, including their geographic area, source, and whether they produce DT. Methods Referrals to the NML of human or animal isolates that were identified as any of those three Corynebacterium species were studied with respect to province, source and toxigenicity. Species identification was confirmed and then specimens were tested by polymerase chain reaction for the presence of tox genes and, if positive, for expression of DT by the modified Elek method. Analysis was descriptive. Results Over the study period, 639 isolates were identified as C. diphtheriae, 22 isolates as C. ulcerans; no isolates were identified as C. pseudotuberculosis. There was an increase in C. diphtheriae referrals for DT testing: from eight per year in 2006 to an average of 15 per month in 2019, or a 1,200% increase over the 13.6-year period. The referrals were primarily from western Canada (n=609/639; 95%). Most (638/639, 99%) were human isolates and most were obtained from cutaneous sites. Of those isolates, 87/639 (13.6%) were found to be toxigenic and 552/639 (86.4%) non-toxigenic. Among C. ulcerans referrals, 17/22 (77%) were from humans and five (23%) were from animals, with 10/22 (45%) being toxigenic. Conclusion There has been a marked increase in referrals to the NML for DT testing of Corynebacterium species. This could be due to the enhanced ability to identify these bacteria using MALDI-TOF systems. Ongoing monitoring will help to assess whether the increase is due solely to increased precision of diagnosis or whether these are emerging cutaneous pathogens.
2006-2019年加拿大白喉棒状杆菌检出率的增加
越来越多的基质辅助激光解吸/电离飞行时间质谱(MALDI-TOF)被用于提供快速、廉价和精确的细菌鉴定,包括棒状杆菌种类。只有三种棒状杆菌能够产生白喉毒素(DT),并且恢复的菌株可能产生毒素或不产生毒素。MALDI-TOF系统提供的更精确的细菌鉴定似乎导致了向国家微生物实验室(NML)提交毒素检测请求的增加。目的了解2006年1月至2019年7月30日期间提交给NML的白喉、溃疡和假结核三种分离株的数量,包括其地理区域、来源和是否产生DT。方法对经鉴定为这3种棒状杆菌的人、动物分离株的NML进行省份、来源和毒力分析。确认物种鉴定,然后用聚合酶链反应检测标本是否存在tox基因,如果呈阳性,则用改进的Elek法检测DT的表达。分析是描述性的。结果在研究期间,鉴定出白喉支原体639株,溃疡支原体22株;未发现假结核杆菌分离株。转介进行白喉滴虫检测的病例有所增加:从2006年的每年8例增加到2019年的平均每月15例,在13.6年的时间里增加了1200%。转介者主要来自加拿大西部(n=609/639;95%)。大多数(638/639,99%)为人类分离株,多数来自皮肤部位。其中87/639株(13.6%)为产毒株,552/639株(86.4%)为非产毒株。其中17/22例(77%)来自人类,5例(23%)来自动物,10/22例(45%)为产毒菌。结论转到NML进行棒状杆菌种类DT检测的病例明显增加。这可能是由于使用MALDI-TOF系统识别这些细菌的能力增强。持续监测将有助于评估增加是否仅仅是由于诊断精度的提高,还是这些是新出现的皮肤病原体。
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