Antimicrobial resistance in Enterobacteriaceae from healthy broilers in Egypt: emergence of colistin-resistant and extended-spectrum β-lactamase-producing Escherichia coli

Background: Poultry remains one of the most important reservoir for zoonotic multidrug resistant pathogens. The global rise of antimicrobial resistance in Gram-negative bacteria is of reasonable concern and demands intensified surveillance. Methods: In 2016, 576 cloacal swabs were collected from 48 broiler farms located in five governorates in northern Egypt. Isolates of Enterobacteriaceae could be cultivated on different media and were identified by MALDI-TOF MS and PCR. Escherichia coil isolates were genotyped by DNA-microarray-based assays. The antimicrobial susceptibility to 14 antibiotics was determined and resistance-associated genes were detected. The VITEK-2 system was applied for phenotypical confirmation of extended-spectrum beta-lactamase-producing isolates. The determination of colistin resistance was carried out phenotypically using E-test and genotypically using PCR for detection of the mcr-1 gene. Results: Out of 576 samples, 72 representatives of Enterobacteriaceae were isolated and identified as 63 E. coil (87.5%), 5 Enterobacter cloacae (6.9%), 2 Klebsiella pneumoniae (2.8%) and 2 Citrobacter spp. (2.8%). Seven out of 56 cultivated E. coil (12.5%) were confirmed as ESBL-producing E. coil and one isolate (1.8%) as ESBL/carbapenemase-producing E. coll. Five out of 63 E. coil isolates (7.9%) recovered from different poultry flocks were phenotypically resistant to colistin and harboured mcr-1 gene. Conclusions: This is the first study reporting colistin resistance and emergence of multidrug resistance in Enterobacteriaceae isolated from healthy broilers in the Nile Delta region, Egypt. Colistin-resistant E. coil in poultry is of public health significance. The global rise of ESBL- and carbapenemase-producing Gram-negative bacteria demands intensified surveillance. ESBL-producing E. coil in poultry farms in Egypt are of major concern that emphasizes the possibility of spread of such strains to humans. The results also reinforce the need to develop strategies and to implement specific control procedures to reduce the use of antibiotics.