Characterization of drug resistant <i>Enterobacter species</i> isolated from poultry and rats in Ibadan, Nigeria

Abstract

Enterobacter species are emerging clinical pathogens and they play important roles in the dissemination of drug resistant traits within the food chain due to their intrinsic abilities for resistance to commonly used antibiotics such as cephalosporins. Two Enterobacter cloacae and one Enterobacter hormaechei characterized in this study were isolated from cloaca of poultry and a rat captured from a poultry house in Ibadan, Nigeria. The isolates were identified based on conventional bacteriological procedure and confirmed by PCR based 16S RNA identification. The three isolates were screened for their antibiotic susceptibilities to ten commonly used antibiotics including: ceftazidime, ceftriaxone, amikacin, cefepime, levofloxacin, sulfametoxazole, kanamycin, ampicillin, streptomycin and chloramphenicol using the standard method by CLSI. Based on the isolates, antibiotics profiles, they were further characterized by PCR screening for plasmid and chromosomalbased drug resistant mechanisms such as: integron gene from the Salmonella genomic Island, bla NDM-1 gene, and the presence of point mutation at the gyrA of the quinolone resistant determining region among the fluoroquinolone resistant isolates. Two of the isolates 2/3(66.67%) carried the integron gene, none of the three isolates carried the bla NDM-1 gene despite their phenotypic resistance to three of or all the indicator antibiotics. Two of the isolates 2/3(66.67%), despite their high MICs of 64μg/mL and >128 μg/mL for levofloxacin did not present any point mutation at the quinolone resistant determining region, suggesting other quinolone/fluoroquinolone resistance mechanism apart from chromosomal based. The findings from this work suggest that Enterobacter species from poultry and rat could serve as sources of drug resistant traits dissemination to the public through the food chain.

Keywords: Enterobacter cloacae, Enterobacter hormaechei, drug resistant poultry