Background: The presence of plasmid mediated mcr-1 gene in multidrug resistant Gram-negative bacteria poses a serious public health concern in today’s world.

Objective: The present study was aimed to detect the presence of plasmid mediated mcr-1 encoding resistance to colistin in multiple drug resistant (MDR) E. coli and K. pneumoniae isolates.

Methods: A total of 180 clinical isolates of E. coli (n=120) and K. pneumoniae (n=60) were isolated from different clinical specimens, i.e., urine, blood, stool and pus, from diagnostic labs of two major public sector tertiary care hospitals in Peshawar, Pakistan. MDR profile of these isolates was assessed through Kirby-Baur disc diffusion method. All isolates were screened for colistin resistance by dilution methods. Colistin resistant isolates were subjected to PCR for mcr-1 detection and confirmation was done by Sanger sequencing method.

Results: Overall, 83.3% (100/120) E. coli and 93.3% (56/60) K. pneumoniae were detected as MDR. Colistin resistance was found in 23.3% (28/120) E. coli and 40% (24/60) K. pneumoniae isolates, whereas mcr-1 gene was detected in 10 out of 52 colistin resistant isolates, including six E. coli and four K. pneumoniae isolates. Minimum inhibitory concentrations (MICs) of colistin in these ten mcr-1 positive isolates ranged from 4μg/ml to 16μg/ml. All mcr-1 positive isolates showed 99% sequence similarity when compared with other present sequences in GenBank.

Conclusion: Hence, our study confirms the presence of mcr-1 mediated colistin resistance in the studied area. Therefore, urgently larger scale surveillance studies are recommended to investigate prevalence of mcr-1 mediated colistin resistance and to prevent its further spread in the area.

背景：多药耐药革兰氏阴性菌中质粒介导的 mcr-1 基因的存在在当今世界引起了严重的公共卫生问题。

目的：本研究旨在检测质粒介导的 mcr-1 编码对多药耐药 (MDR) 大肠杆菌和肺炎克雷伯菌分离株中的粘菌素耐药性的存在。

方法：从两个主要公共医疗机构的诊断实验室中，从尿液、血液、粪便和脓液等不同临床标本中分离出180株大肠杆菌（n=120）和肺炎克雷伯菌（n=60）临床分离株。巴基斯坦白沙瓦的三级医院。这些分离株的 MDR 谱通过 Kirby-Baur 圆盘扩散法进行评估。通过稀释方法筛选所有分离株的粘菌素抗性。对粘菌素抗性分离株进行 PCR 检测 mcr-1，并通过 Sanger 测序方法进行确认。

结果：总体而言，83.3% (100/120) 大肠杆菌和 93.3% (56/60) 肺炎克雷伯菌被检测为 MDR。在 23.3% (28/120) 大肠杆菌和 40% (24/60) 肺炎克雷伯菌分离株中发现了粘菌素耐药性，而在 52 株粘菌素耐药株中的 10 株中检测到了 mcr-1 基因，其中包括 6 株大肠杆菌和四个肺炎克雷伯菌分离株。在这十个 mcr-1 阳性分离株中，粘菌素的最低抑菌浓度 (MIC) 范围为 4μg/ml 至 16μg/ml。与 GenBank 中的其他现有序列相比，所有 mcr-1 阳性分离株均显示出 99% 的序列相似性。

结论：因此，我们的研究证实了研究区域中存在 mcr-1 介导的粘菌素耐药性。因此，建议紧急进行更大规模的监测研究，以调查 mcr-1 介导的粘菌素耐药性的流行情况，并防止其在该地区进一步传播。