Microbiological quality of raw vegetables in Ouagadougou: enumeration of Escherichia coli and detection of Salmonella spp. and antibiotic resistance profiles

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Résumé

This study explores the microbiological quality of raw vegetables and salads in Ouagadougou, Burkina Faso, by assessing contamination levels and antimicrobial resistance of isolated bacteria across the supply chain. A total of 300 samples were collected from production fields, urban markets, and mass catering sites, and analyzed for Escherichia coli and Salmonella spp. using ISO standard methods. Susceptibility testing was performed on isolates. The results show that contamination levels vary significantly (p<0.05), with E. coli concentrations reaching up to 4.08 ± 0.04 log CFU/g. The prevalence of Salmonella spp. remains low (0 to 3%), with contamination detected only in ready-to-eat salads. In terms of antimicrobial resistance, E. coli isolates showed high resistance to amoxicillin (62.12%), and the Multi-Antibiotic Resistance (MAR) index exceeded 0.2 for 45.5% of isolates. Among Salmonella spp. isolates, 42.11% were resistant to amoxicillin, but notable sensitivity to fluoroquinolones and carbapenems (84.21%) was observed. These findings highlight that agricultural practices and final preparation hygiene are critical control points and confirm the vegetable supply chain as a reservoir for antimicrobial resistance, providing essential data to guide public health policies in Ouagadougou.

Mots-clés

Salmonella, Contamination, Antibiotic resistance, Antimicrobial, Hygiene, Escherichia coli, Enumeration