Phenotypic and molecular characterization of enteropathogenic Escherichia coli and Salmonella spp. causing childhood diarrhoea in Awka, South-Eastern Nigeria

Background Diarrhoea is a major cause of childhood disease in the developing countries. This experimental study investigated the prevalence of ESBL and MBL genes in enteropathogenic strains of Escherichia coli and Salmonella spp. isolated from diarrheagenic children in Awka, Nigeria. Methods Two hundred stool samples were collected from diarrhea patients in three paediatric hospitals within Awka metropolis, Nigeria. All E. coli and Salmonella spp. isolated through standard bacteriological methods were subjected to antibiotic-susceptibility testing. Double disc synergy and imipenem-EDTA combined disc tests were used to phenotypically confirm the presence of ESBL and MBL respectively. PCR amplification of β -lactamase genes was done. Results The prevalence of E. coli and Salmonella species in this study were 54% and 24.5% respectively. The organisms were highly resistant to metronidazole, cefuroxime and ceftazidime, and also showed a high sensitivity to nitrofurantoin and gentamicin. ESBL production was recorded in E. coli (49%) and Salmonella spp. (51.1%) while 27 isolates of E. coli (25%) and 7 isolates of Salmonella spp. were confirmed MBL positive by the combined disk diffusion technique. Eleven E . coli and 4 Salmonella spp. co-harbored both ESBL and MBL production. The most prevalent MBL gene in this study is the bla VIM gene (18.8%) which mediate MBL production in Gram negative bacteria; and this was followed by bla SHV (12.5%), bla TEM and bla CTX-M (6.3% each) for E. coli isolates. Salmonella spp. was recorded to have bla VIM (28.8%), bla SHV (28.8%), bla TEM (14.3%) and bla CTX-M (14.3%) genes. Conclusions This study reveals the prevalence of enteropathogenic E. coli and Salmonella strains bacteriologically recovered from diarrheic children in Awka, Nigeria, and which were found to be multiple resistant to clinically-relevant antibiotics because they co-express ESBL and MBL genes which mediate multidrug resistance in Gram negative bacteria.