A Study of the Antimicrobial Resistance and Transfer of Resistance Among Organisms Isolated From Lettuce (Lactuca sativa) Leaves in Three Localities in Southwest Nigeria

The bacterial flora of lettuce from western Nigeria were investigated for their identity, antimicrobial resistance, and ability to transfer such resistance to other organisms. The isolated contaminants were mostly Gram-negative organisms of the Enterobacteriaceae family, which included Enterobacter species and E. coli. The organisms were resistant to a wide range of antimicrobials and they exhibited multiple antimicrobial resistance phenotypes. Common resistance phenotypes observed included those to beta lactam antibiotics, trimethoprim, and streptomycin. A majority of the isolates had minimum inhibitory concentration of trimethoprim over 1,000 mg/L and they were shown to possess the ability to transfer their resistance to a plasmidless E. coli strain. The results of the authors’ study underscore the contributory role of lettuce in the dissemination of antimicrobial resistance in the Nigerian community.