Molla Bayleyegn, Miko Angelika, Pries Karin, Hildebrandt Goetz, Kleer Josef, Schroeter Andreas, Helmuth Reiner
Department of Microbiology and Veterinary Public Health, Faculty of Veterinary Medicine, Addis Ababa University, P.O. Box 34, Debre Zeit, Ethiopia.
Acta Trop. 2007 Aug;103(2):142-9. doi: 10.1016/j.actatropica.2007.05.018. Epub 2007 Jun 6.
The present study was undertaken to identify and characterize integrons and integrated resistance gene cassettes among multidrug resistant (MDR) Salmonella isolates from slaughter animals and food products of animal origin in Ethiopia. A total of 98 epidemiologically unrelated Salmonella isolates comprising 13 serovars were characterized using serotyping, phage typing, antimicrobial resistance testing and the pulsed-field gel electrophoresis (PFGE) method. Integron-PCR was used to detect the presence of class 1 and class 2 integrons in the MDR strains. The associated individual resistance gene cassettes were identified using specific PCRs and DNA sequencing. The location of the integrons was determined by Southern blot hybridization analysis. Among the Salmonella serovars, a high level of antimicrobial resistance was found to streptomycin (82.6%), tetracycline (75.5%), sulfamethoxazole (60.2%), spectinomycin (53.1%), ampicillin (42.8%), nalidixic acid (34.7%), nitrofurantoin (30.6%), trimethoprim (27.5%), gentamicin (20.4%) and ciprofloxacin (19.4%). Class 1 integrons were detected in 53.1% of the MDR isolates comprising serovars Anatum, Braenderup, Kentucky, Saintpaul and Typhimurium. Of the class 1 integron positive isolates 61.5% harboured the integron-associated gene cassettes: aadA2, aadA2+bla(PSE-1), dfrA1-aadA1 and dfrA12-orf-aadA2 (amplicon sizes 1000 bp, 1000+1200 bp, 1600 bp and 1900 bp, respectively). The chromosomally located aadA2 and aadA2+bla(PSE-1) resistance gene cassettes occurred exclusively in S. Typhimurium DT104 isolates, the other cassettes were found on large plasmids in several serovars. An aacCA5-aadA7 gene cassette array (amplicon size 1600 bp) was exclusively found in all MDR S. Kentucky strains of R type Str/SpeSmxGenNalAmpTetCipCef and this integron was shown to be chromosomally located. Results of the present study indicate that class 1 integrons carrying gene cassettes, which confer resistance to different classes of antimicrobials such as aminoglycosides, beta-lactams and trimethoprim are widespread among the MDR Salmonella serovars isolated from slaughter animals and food products of animal origin in Ethiopia indicating the important role of these genetic elements in the dissemination of multidrug resistance.
本研究旨在鉴定和表征来自埃塞俄比亚屠宰动物及动物源性食品的多重耐药（MDR）沙门氏菌分离株中的整合子及整合的耐药基因盒。使用血清分型、噬菌体分型、抗菌药物耐药性检测和脉冲场凝胶电泳（PFGE）方法对总共98株流行病学上不相关的沙门氏菌分离株（包括13个血清型）进行了表征。采用整合子PCR检测MDR菌株中1类和2类整合子的存在。使用特异性PCR和DNA测序鉴定相关的单个耐药基因盒。通过Southern印迹杂交分析确定整合子的位置。在沙门氏菌血清型中，发现对链霉素（82.6%）、四环素（75.5%）、磺胺甲恶唑（60.2%）、壮观霉素（53.1%）、氨苄西林（42.8%）、萘啶酸（34.7%）、呋喃妥因（30.6%）、甲氧苄啶（27.5%）、庆大霉素（20.4%）和环丙沙星（19.4%）具有高水平的抗菌药物耐药性。在包括阿纳托姆、布伦德鲁普、肯塔基、圣保罗和鼠伤寒等血清型的53.1%的MDR分离株中检测到1类整合子。在1类整合子阳性分离株中，61.5%携带与整合子相关的基因盒：aadA2、aadA2+bla(PSE-1)、dfrA1-aadA1和dfrA12-orf-aadA2（扩增子大小分别为1000 bp、1000+1200 bp、1600 bp和1900 bp）。染色体定位的aadA2和aadA2+bla(PSE-1)耐药基因盒仅在鼠伤寒沙门氏菌DT104分离株中出现，其他基因盒在多个血清型的大质粒上发现。aacCA5-aadA7基因盒阵列（扩增子大小1600 bp）仅在所有R型为Str/SpeSmxGenNalAmpTetCipCef的MDR肯塔基沙门氏菌菌株中发现，且该整合子显示位于染色体上。本研究结果表明，携带赋予对不同类抗菌药物（如氨基糖苷类、β-内酰胺类和甲氧苄啶）耐药性的基因盒的1类整合子在从埃塞俄比亚屠宰动物及动物源性食品分离的MDR沙门氏菌血清型中广泛存在，表明这些遗传元件在多重耐药性传播中起重要作用。
