Screening of mcr-1 gene being mediated colistin resistance in Escherichia coli isolates from clinical and poultry specimens.

Thesis Report.

ABSTRACT: The emergence of coexistence of colistin and carbapenem resistance within E. coli isolates in poultry and human being narrow down the effectiveness of antibiotics alarming a big threat to human being in disease management worldwide. The problem is more severe in the developing countries like Nepal where colistin is highly in poultry feed and drinks. However, there is still no any report of emergence of colistin resistance in human being and comparative report of mcr-1 in poultry and human being. Hence a laboratory and field based cross sectional study was conducted from august 2018 to march 2019 so as to determine the trends of colistin resistance among E. coli isolates from poultry and human origin. A total of 240 rectal swabs were collected from five different poultry farm of Kathmandu, Bhaktapur and Kavrepalanchok and processed. Similarly, 705 urine samples collected from patients attending Kantipur Hospital Pvt. Ltd were further analyzed for microbial growth. All isolates were subjected to antibiotic susceptibility testing using Kirby Bauer disc diffusion methods and minimum inhibitory concentration of colistin was determined by agar dilution method using 0.5 µg/ml to 32 µg/ml. The resistant strains were screened for mcr-1 gene and OXA-48 gene by using conventional PCR assays. Colistin resistant poultry isolates were highly resistant to tetracycline (67.1%) followed by Amoxyclav (55.3%), ciprofloxacin (50%), while human isolates were most resistant to cefixime (71.4%) followed by ceftazidime (66.1%) and ciprofloxacin (53.6%). The phenotypic prevalence of colistin resistance in poultry and human were 31.57% (24/76) and 21.42% (12/56) respectively but genotypically, colistin resistant mcr-1 gene was detected as 27.6% (21/76) in poultry and 19.64% (11/56) in human being. The prevalence of carbapenem resistance gene among colistin resistant mcr-1 positive isolates was found to be 38% (8/21) in poultry and 18.2% (2/11) in human being. The study also had reported the presence of colistin resistance among human E. coli isolates and carbapenem resistance among colistin resistant isolates from both poultry and human being. Moreover, the resistant genes in plasmid DNA suggests the possible spread of resistance to other human pathogens in environment causing problem in diseases management. Keywords: mcr-1, OXA-48, colistin resistant E. coli, CRE.