What Is in the Salad? Escherichia coli and Antibiotic Resistance in Lettuce Irrigated with Various Water Sources in Ghana

Introduction: Safety of the environment in which vegetables are grown, marketed and consumed is paramount as most are eaten raw. Irrigation sources include open drains and streams, which are often contaminated with human and animal waste due to poor sanitation infrastructure. In irrigated vegetable farms using such sources in Ghana, we assessed Escherichia coli counts, antibiotic resistance patterns and resistant genes on irrigated lettuce. Methods: A cross-sectional study was conducted between January–May 2022, involving five major vegetable farms in Ghana. Results: Escherichia coli was found in all 25 composite lettuce samples analyzed. Counts expressed in CFU/g ranged from 186 to 3000, with the highest counts found in lettuce irrigated from open drains (1670) and tap water using hose pipes (3000). Among all bacterial isolates, resistance ranged between 49% and 70% for the Watch group of antibiotics, 59% for the Reserved group and 82% were multidrug-resistant. Of 125 isolates, 60 (48%) were extended-spectrum beta-lactamase-producing, of which five (8%) had the bla(TEM)-resistant gene. Conclusions: Lettuce was contaminated with Escherichia coli with high levels of antibiotic resistance. We call on the Ghana Ministry of Food and Agriculture, Food and Drugs Authority and other stakeholders to support farmers to implement measures for improving vegetable safety.