A study of human and non-human samples for Escherichia coli O157:H7 and typhoid in Benin City, Nigeria

Abstract

Escherichia coli O157:H7 and Salmonella species have continued to cause gastrointestinal complaints in 
people in developing countries. 180 stool specimens from 80 undergraduates , 100 food vendors, and 86 
specimens from non-human sources were screened for the presence of the pathogens. Fresh stool 
specimens were inoculated onto Sorbitol MacConkey Agar (Oxoid CM813), Selenite F Broth (Oxoid CM 395), 
Deoxycholate Citrate Agar (Oxoid CM 0227), MacConkey Agar (Oxoid CM 7) and Blood Agar (Oxoid CM 55). 
Colonies growing on media after 24 hours incubation at 370C were identified biochemically. Latex 
agglutination test reagents (Oxoid DR 620) were used for serological identification of O157:H7 strains. One 
(5.6%) specimen from a food vendor yielded E.coli O157:H7. 9(5%) specimens yielded Salmonella spp. Of the 
86 non-human samples, 3 (3.5%) were contaminated with E. coli O157:H7. Thirty (35%) non- O157: H7 strains 
were also recovered; the highest proportion of 26 (30.2%) being from hawked food items. Proteus spp (8.1%) 
was the next commonly isolated pathogen. Only an isolate each of Salmonella and Shigella spp were 
recovered from hawked foods. The incidence of E.coli O157:H7 and Salmonella spp was low in non-human 
samples; a possible reason for the low incidence observed in humans in this locality