Azam Mudsser, Jan Arif Tasleem, Kumar Ashutosh, Siddiqui Kehkashan, Mondal Aftab Hossain, Haq Qazi Mohd Rizwanul
Department of Biosciences, Jamia Millia Islamia, New Delhi, India.
School of Biosciences and Biotechnology, Baba Ghulam Shah Badshah University, Rajouri, India.
Braz J Microbiol. 2018 Jul-Sep;49(3):471-480. doi: 10.1016/j.bjm.2017.11.001. Epub 2018 Feb 12.
Escalating burden of antibiotic resistance that has reached new heights present a grave concern to mankind. As the problem is no longer confined to clinics, we hereby report identification of a pandrug resistant Escherichia coli isolate from heavily polluted Delhi stretch of river Yamuna, India. E. coli MRC11 was found sensitive only to tobramycin against 21 antibiotics tested, with minimum inhibitory concentration values >256μg/mL for amoxicillin, carbenicillin, aztreonam, ceftazidime and cefotaxime. Addition of certain heavy metals at higher concentrations were ineffective in increasing susceptibility of E. coli MRC11 to antibiotics. Withstanding sub-optimal concentration of cefotaxime (10μg/mL) and mercuric chloride (2μg/mL), and also resistance to their combinatorial use, indicates better adaptability in heavily polluted environment through clustering and expression of resistance genes. Interestingly, E. coli MRC11 harbours two different variants of blaTEM (blaTEM-116 and blaTEM-1 with and without extended-spectrum activity, respectively), in addition to mer operon (merB, merP and merT) genes. Studies employing conjugation, confirmed localization of blaTEM-116, merP and merT genes on the conjugative plasmid. Understanding potentialities of such isolates will help in determining risk factors attributing pandrug resistance and strengthening strategic development of new and effective antimicrobial agents.
抗生素耐药性负担不断加剧，已达到新的高度，这引起了人类的严重关切。由于这个问题不再局限于诊所，我们在此报告从印度亚穆纳河德里段污染严重的区域分离出一株对多种药物耐药的大肠杆菌。在测试的21种抗生素中，大肠杆菌MRC11仅对妥布霉素敏感，对阿莫西林、羧苄青霉素、氨曲南、头孢他啶和头孢噻肟的最低抑菌浓度值>256μg/mL。添加较高浓度的某些重金属并不能提高大肠杆菌MRC11对抗生素的敏感性。能够耐受次优浓度的头孢噻肟（10μg/mL）和氯化汞（2μg/mL），以及对它们联合使用的耐药性，表明通过抗性基因的聚类和表达，其在污染严重的环境中具有更好的适应性。有趣的是，大肠杆菌MRC11除了含有mer操纵子（merB、merP和merT）基因外，还含有两种不同变体的blaTEM（分别为blaTEM-116和blaTEM-1，前者具有、后者不具有超广谱活性）。采用接合试验的研究证实了blaTEM-116、merP和merT基因定位于接合质粒上。了解此类分离株的潜在特性将有助于确定导致对多种药物耐药的风险因素，并加强新型有效抗菌药物的战略开发。
