Introduction. The use of partially or untreated wastewater in the irrigation of vegetable crops constitutes a risk of microbiological contamination that can cause diarrhea in the consumer. Aim. This study mainly aimed to assess the level of contamination of irrigation water and lettuce as well as to determine the antibiotic resistance profile of isolated bacteria. Methods. A total of eighty samples of lettuce and ten irrigation waters were collected from the market gardening sites of Boulmiougou, Bissigin, the National School of Public Health and Tanghin. The research of thermotolerant coliforms, Escherichia coli and Salmonella was done following ISO standard methods. Isolated Escherichia coli and Salmonella strains were tested for their resistance profile by using the Kirby-Bauer method with a panel of twenty different antibiotics. Results. Out of the eighty lettuce samples, 68.75% (55) contained thermotolerant coliforms with an average load of 8.75 ×105 CFU g-1. The prevalence of Escherichia coli was 57.5% (46) and Salmonella prevalence was 11.25% (9) including eight strains of Salmonella enterica spp. and one strain of Salmonella enterica arizonea. All irrigation waters were contaminated by thermotolerant coliforms at an average
concentration of 3.11×104 CFU/100mL. The prevalence of Escherichia coli in the irrigation waters was 40% (4/10) while Salmonella enterica spp. was 20% (2/10). The highest antibiotic resistance was found in Escherichia coli strains with ampicillin 28.26%, amoxicillin + clavulanic acid 26.09% and tetracycline 19.57%. Conclusion. The water used to irrigate vegetable crops in Ouagadougou could be a major source of contamination of vegetables by microorganisms. In addition, the consumption of lettuce would constitute a risk of propagation of salmonellosis among the population.

Lettuce, Irrigation water, Salmonella, Escherichia coli, Sensitivity to antibiotics, Ouagadougou.