BACKGROUND: Escherichia coli (E. coli) serotypes have been implicated as etiological agents in the pathogenesis of diarrhea in children. The aim of this study was to investigate the prevalence, virulence and antibiotic resistance profile of serotypes of E. coli in children between 0 and 5 years with diarrhea in Lagos, Nigeria, the most populous country in Africa.METHODS: Stool samples of 200 children with diarrhea and 50 apparently healthy controls attending public health facilities were collected for a duration of 5 months. E. coli strains were isolated using standard microbiological techniques and genoserotyped by microarray. Antimicrobial susceptibility testing was done using the disc diffusion method and virulence genes including stx], stx2 and eaeA were assayed by polymerase chain reaction (PCR).RESULTS: Fifty non-O157 E. coli serotypes were isolated from 250 stool samples collected. Forty two percent of these were obtained from children aged 11-20 months. A significant number (P<0.0173) of the isolates were recovered from the stool of children with diarrhea. Antimicro-bial susceptibility patterns revealed that there was 70%, 80% and 84% resistance to gentamicin, amoxicillin plus clavulanic acid and ampicillin, respectively. Ninety-eight percent of the isolates were sensitive to ceftazidime, ciprofioxacin and ofioxacin. The genes stx], stx2 and eaeA were detected in only 4 (8%) of the isolates. CONCLUSIONS: Our findings show a high frequency of non-O157 E. coli serotypes in the stool of children with diarrhea in Lagos, Nigeria.