Johnsen Bjørn Odd, Handal Nina, Meisal Roger, Bjørnholt Jørgen Vildershøj, Gaustad Peter, Leegaard Truls Michael
Department of Microbiology and Infection Control, Akershus University Hospital, PO Box 1000, 1478 Lørenskog, Norway.
Department of Microbiology, Oslo University Hospital, PO Box 4950 Nydalen, 0424 Oslo, Norway; Institute of Clinical Medicine, University of Oslo, PO Box 1171 Blindern, 0318 Oslo, Norway.
Anaerobe. 2017 Oct;47:226-232. doi: 10.1016/j.anaerobe.2017.06.004. Epub 2017 Jun 8.
The aims of this study were to describe the distribution of the most common erm genes in a collection of Norwegian Bacteroides isolates and to investigate whether the phenotypic tests for determining inducible clindamycin resistance among Bacteroides species recommended by EUCAST, NordicAST and the manufacturer of E-test, are effective. We investigated 175 unique Bacteroides isolates for the presence of erm(B), erm(F) and erm(G) genes, determined their minimum inhibitory concentrations (MICs) to clindamycin and categorised their susceptibility according to EUCAST breakpoints. 27 isolates were resistant to clindamycin. Furthermore, we investigated whether these recommended methods could detect inducible resistance in the Bacteroides isolates: 1) EUCAST recommendation: Dissociated resistance to erythromycin (clindamycin susceptible with erythromycin MIC > 32 mg/L), 2) NordicAST recommendation: Double disk diffusion test (DDD) or 3) Manufacturer of E-test's recommendation: prolonged incubation of clindamycin E-test for 48 h. erm genes were detected in 30 (17%, 95% CI 12%-23%) of 175 Bacteroides isolates with erm(F) as the dominating gene. There were six (4%, 95% CI 1%-7%) of 148 clindamycin susceptible isolates harbouring erm genes, they were considered inducibly resistant to clindamycin. None of the methods for phenotypic detection of inducible clindamycin resistance performed satisfactory with sensitivities of 33%, 17% and 0% and specificities of 90%, 99% and 97% for dissociated resistance, DDD and prolonged incubation of clindamycin E-test, respectively. In our view, the scientific basis for investigating every Bacteroides isolate for inducible resistance to clindamycin is weak. Molecular detection of erm genes may prove a better option than the phenotypic methods we evaluated.
本研究的目的是描述挪威拟杆菌属分离株中最常见的erm基因分布情况，并调查欧盟CAST、北欧抗菌药物敏感性试验委员会（NordicAST）以及E-test制造商推荐的用于确定拟杆菌属物种中诱导性克林霉素耐药性的表型试验是否有效。我们调查了175株独特的拟杆菌属分离株中erm(B)、erm(F)和erm(G)基因的存在情况，确定了它们对克林霉素的最低抑菌浓度（MIC），并根据欧盟CAST的断点对其敏感性进行分类。27株分离株对克林霉素耐药。此外，我们调查了这些推荐方法是否能检测拟杆菌属分离株中的诱导性耐药性：1）欧盟CAST推荐方法：对红霉素的解离耐药性（克林霉素敏感，红霉素MIC＞32mg/L）；2）北欧抗菌药物敏感性试验委员会推荐方法：双纸片扩散试验（DDD）；3）E-test制造商推荐方法：将克林霉素E-test延长孵育48小时。在175株拟杆菌属分离株中，有30株（17%，95%可信区间12%-23%）检测到erm基因，其中erm(F)是主要基因。在148株克林霉素敏感分离株中，有6株（4%，95%可信区间1%-7%）携带erm基因，它们被认为对克林霉素有诱导性耐药。对于诱导性克林霉素耐药性的表型检测方法，没有一种表现令人满意，解离耐药性、DDD和克林霉素E-test延长孵育的敏感性分别为33%、17%和0%，特异性分别为90%、99%和97%。我们认为，对每一株拟杆菌属分离株进行诱导性克林霉素耐药性调查的科学依据不足。erm基因的分子检测可能比我们评估的表型方法是更好的选择。
