Kullin B, Brock T, Rajabally N, Anwar F, Vedantam G, Reid S, Abratt V
Department of Molecular and Cell Biology, University of Cape Town, Rondebosch Cape Town, 7700, South Africa.
Department of Medicine, Division of Gastroenterology, University of Cape Town, Cape Town, South Africa.
Eur J Clin Microbiol Infect Dis. 2016 Oct;35(10):1709-18. doi: 10.1007/s10096-016-2717-6. Epub 2016 Jul 27.
The C. difficile infection rate in South Africa is concerning. Many strains previously isolated from diarrhetic patients at Groote Schuur Hospital were ribotype 017. This study further characterised these strains with respect to their clonal relationships, antibiotic susceptibility, toxin production and various attributes impacting on pathogen colonisation. Multilocus variable-number tandem-repeat analysis (MLVA) was used to characterise all C. difficile isolates. Antibiotic susceptibility was determined by E-test and PCR-based analysis of the ermB, gyrA and gyrB genes. Auto-aggregation of cells was measured in broth, and biofilm formation observed in 24-well plates. Toxins were measured using the Wampole C DIFF TOX A/B II kit. Most isolates belonged to the ribotype 017 group. Identical MLVA types occurred in different wards over time, and several patients were infected with identical strains. All isolates were susceptible to vancomycin and metronidazole, but some ribotype 017 isolates showed reduced metronidazole susceptibility (≥2 mg l(-1)). Sixty-nine percent of ribotype 017 isolates were resistant to moxifloxacin, and 94 % to erythromycin, compared to 0 % and 17 % resistance, respectively, in non-ribotype 017 isolates. The ermB gene and mutations in the gyrA and/or gyrB genes were linked to erythromycin and moxifloxacin resistance, respectively. Ribotype 017 isolates auto-aggregated more strongly than other isolates and produced lower levels of the TcdB toxin than a reference strain. Certain strains produced strong biofilms. Patient-to-patient transfer and unique infection events could cause the predominance of ribotype 017 strains in the cohort. Multi-drug resistant strains are a potential reservoir for future infections.
南非艰难梭菌感染率令人担忧。此前在格罗特舒尔医院从腹泻患者中分离出的许多菌株属于核糖体分型017。本研究进一步对这些菌株的克隆关系、抗生素敏感性、毒素产生以及影响病原体定植的各种特性进行了表征。采用多位点可变数目串联重复分析（MLVA）对所有艰难梭菌分离株进行表征。通过E试验以及基于PCR的ermB、gyrA和gyrB基因分析来确定抗生素敏感性。在肉汤中测量细胞的自动聚集情况，并在24孔板中观察生物膜形成。使用Wampole C DIFF TOX A/B II试剂盒测量毒素。大多数分离株属于核糖体分型017组。随着时间推移，不同病房出现了相同的MLVA类型，并且有几名患者感染了相同的菌株。所有分离株对万古霉素和甲硝唑敏感，但一些核糖体分型017分离株对甲硝唑的敏感性降低（≥2 mg l(-1)）。核糖体分型017分离株中69%对莫西沙星耐药，94%对红霉素耐药，相比之下，非核糖体分型017分离株的耐药率分别为0%和17%。ermB基因以及gyrA和/或gyrB基因的突变分别与红霉素和莫西沙星耐药相关。核糖体分型017分离株比其他分离株的自动聚集性更强，并且产生的TcdB毒素水平低于参考菌株。某些菌株能形成强大的生物膜。患者之间的传播以及独特的感染事件可能导致该队列中核糖体分型017菌株占主导地位。多重耐药菌株是未来感染的潜在储存库。
