Abstract

Background

Diphtheria is mainly caused by diphtheria-toxin-producing strains of Corynebacterium diphtheriae and Corynebacterium ulcerans. The recommended first-line antibiotic is penicillin or erythromycin, but reliable susceptibility data are scarce.

Objectives

To define WT MIC distributions of 12 antimicrobial agents and provide data for the determination of tentative epidemiological cut-off values (TECOFFs) for potentially toxigenic corynebacteria and to evaluate the potential usefulness of a gradient test (Etest) for susceptibility testing of penicillin, erythromycin and clindamycin.

Methods

For the 421 human or veterinary isolates from the period 2011–17, MICs of 12 antimicrobial agents were determined. Etest performance was evaluated for penicillin, erythromycin and clindamycin.

Results

MIC distributions were characterized and TECOFFs could be set for 11 out of 24 antibiotic/species combinations. The current EUCAST clinical breakpoints, predominantly determined for Corynebacterium species other than C. diphtheriae and C. ulcerans, divide the WT MIC distributions of penicillin and clindamycin, thereby making reproducible susceptibility testing of C. diphtheriae and C. ulcerans difficult. For erythromycin, 4% of C. diphtheriae and 2% of C. ulcerans had MICs higher than those for WT isolates. Phenotypically detectable resistance to other antibiotics was rare. Etest underestimated MICs of penicillin and lower concentrations needed to be included for erythromycin, while for clindamycin the Etest was not a good surrogate method.

Conclusions

MIC distributions based on reference broth microdilution for potentially toxigenic Corynebacterium spp. were developed. For five and six agents, TECOFFs were suggested for C. diphtheriae and C. ulcerans, respectively, but for Corynebacterium pseudotuberculosis the number of isolates was too low.

中文翻译：

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德国白喉棒状杆菌和溃疡性棒状杆菌的抗菌药敏性2011-17。

摘要

背景

白喉主要是由白喉棒状杆菌和溃疡性棒状杆菌产生白喉毒素的菌株引起的。推荐的一线抗生素是青霉素或红霉素，但缺乏可靠的药敏数据。

目标

定义12种抗菌药物的WT MIC分布，并提供数据来确定潜在的产毒棒状杆菌的暂定流行病学临界值（TECOFFs），并评估梯度试验（Etest）对青霉素，红霉素和克林霉素。

方法

对于2011–17年期间的421种人类或兽医分离株，确定了12种抗菌药物的MIC。对青霉素，红霉素和克林霉素的测试性能进行了评估。

结果

对MIC分布进行了表征，可以为24种抗生素/物种组合中的11种设置TECOFF。当前主要针对除白喉衣原体和溃疡病菌之外的棒杆菌属物种确定的EUCAST临床断点将青霉素和克林霉素的WT MIC分布进行了划分，因此很难对白喉衣原体和溃疡菌进行可重复的药敏试验。对于红霉素，白喉衣原体的4％和溃疡性念珠菌的2％MIC高于WT分离株。表型上可检测到的对其他抗生素的耐药性很少见。Etest低估了青霉素的MIC，而红霉素需要包括较低的MIC，而对于克林霉素，Etest并不是一种好的替代方法。

结论

基于潜在肉毒杆菌棒状杆菌参考肉汤微量稀释的MIC分布。被开发。对于五种和六种病原体，建议分别对白喉衣原体和溃疡病原菌使用TECOFFs ，但对于假结核杆菌，分离株的数量太少。