Abstract
BACKGROUND: Antimicrobial resistance in avian pathogenic Escherichia coli (APEC) represents a major concern in the avian industry worldwide and limited studies have investigated Colistin resistance among APEC in Algeria. AIMS: Investigate antibiotic resistance, in particular, Colistin, and mediated-Colistin resistance (mcr) genes, as well as the virulence genes in APEC. METHODS: One hundred E. coli were isolated from poultry suspected of colibacillosis. Antimicrobial susceptibility testing was done on 14 antibiotics by the disk diffusion method. Colistin minimum inhibitory concentration (MIC) was assessed by the broth microdilution method. Using multiplex PCR, mcr genes (mcr-1 to 5) and 7 virulence-related genes were investigated in Colistin-resistant isolates. RESULTS: Results showed high resistance to Tetracycline (99%), Nalidixic acid (92%), Doxycycline (90%), Ampicillin (89%), Ofloxacin (74%), Sulfamethoxazole-Trimethoprim (72%), and Amoxicillin-Clavulanic acid (57%); in addition, 92% of isolates were multidrug resistant. The rate of resistance to Colistin was 27% (27/100) of which 96.3% (26/27) of isolates carried the mcr-1 gene. Twenty-five of the Colistin-resistant isolates (92.59%) had at least three virulence genes. The most frequently isolated virulence genes were: fim H (96.3%) followed by hlyF, iroN, and iss (77.7%, each), iutA and ompT were found in 59.25% and 55.5% of isolates, respectively. The most prevalent combination of virulence factors was hlyF-iss-iroN-iutA-ompT-fimH. CONCLUSION: This is the first report which highlighted Colistin resistance with the detection of mcr-1 in APEC isolates in the area of study. Colistin resistance and carriage of mcr-1 in virulent and multidrug-resistant isolates of E. coli are alarming and a surveillance program to limit the spread of these pathogens is mandatory.