Microbiological contamination, antimicrobial residues, and antimicrobial resistance in raw bovine milk in Lebanon

Abstract

A total of 195 raw milk samples were collected over two consecutive years from 48 milk sources in Lebanon. Collected samples were examined for microbiological quality and antibiotic susceptibility. Results revealed non-conformity with local and international standards, in 96% of samples for total aerobic mesophilic bacteria (TAMB), 81% for total coliform (TC), 17% for Staphylococcus aureus (S. aureus), 35% for Salmonella spp., and 65% for Escherichia coli (E. coli). Antimicrobial residues of oxytetracycline, tetracycline, ciprofloxacin, sulfamethazine, and doxycycline were below the maximum residue limits (MRL). On the other hand, E. coli isolates showed resistance to tetracycline (41%), doxycycline (39%), nalidixic acid (20%), and ciprofloxacin (3%), while S. aureus isolates were found resistant to doxycycline (63%), and tetracycline (51%). For Salmonella spp., isolates were found to be resistant to doxycycline (12%), tetracycline (6%), and nalidixic acid (4%). In conclusion, sampled milk shows high levels of pathogenic bacteria and antimicrobial resistance.