Erm gene distribution among Norwegian Bacteroides isolates and evaluation of phenotypic tests to detect inducible clindamycin resistance in Bacteroides species. (October 2017)

• Record Type: Journal Article
• Authors: Johnsen, Bjørn Odd; Handal, Nina; Meisal, Roger; Bjørnholt, Jørgen Vildershøj; Gaustad, Peter; Leegaard, Truls Michael
• Is Part Of: Anaerobe. Volume 47(2017)
• Page Start: 226
• Page End: 232
• Publication Date: 2017-10
• Subjects: Bacteroides species -- Clindamycin resistance -- erm genes -- Inducible resistance -- Phenotypic detection; Anaerobic infections -- Periodicals; Anaerobic bacteria -- Periodicals; Bacterial diseases -- Periodicals; Computer network resources; Anaerobic protozoa -- Periodicals; 579.3
• DOI: 10.1016/j.anaerobe.2017.06.004
• Languages: English
• ISSNs: 1075-9964

Abstract

Abstract: 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. Highlights: 175 Bacteroides isolates were included, 148 were clindamycin (CM) susceptible. erm (B), erm (F) (28 isolates) and/or e rm (G) were detected in 30 isolates (17%). erm genes were detected in six CM susceptible isolates (4%). Clinical implications and prevalence of inducible CM resistance need documentation. Tests for such resistance lack documentation and precision. Would erm PCR be better?.