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.
Abstract: 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
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.