Prevalence and Antibiotic Resistance of Staphylococcus aureus and Escherichia coli Isolated from Bovine Raw Milk in Lebanon: A study on Antibiotic Usage, Antibiotic Residues, and Assessment of Human Health Risk Using the One Health Approach

Abstract

The emergence, persistence, and spread of antibiotic-resistant microbes is a tremendous public health threat that is considered nowadays a critical One Health issue. In Lebanon, the consumption of raw bovine milk has been recently reported as a result of the financial crisis. The objectives of the current study were (1) to evaluate raw bovine milk samples in a comprehensive manner for the types of antibiotics used and their residues, (2) to determine the presence of mesophilic bacteria, extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA), and (3) to determine the associated human health risk caused by drinking raw milk with antibiotic residues among all age categories. LC-MS-MS was used to carry out the analysis. From 200 milk samples, 30 (15%) were found contaminated with four major antibiotics. The highest average concentration detected was for oxytetracyline 31.51 ± 13.23 μg/kg, followed by 5.5 ± 0.55 μg/kg for gentamicin, 4.56 ± 0.73 μg/kg for colistin, and 4.44 ± 0.89 μg/kg for tylosin. The mean contamination among most samples was below the maximum residue limits (MRLs). Upon comparison with the acceptable daily intake (ADI), the estimated daily intake (EDI) across all age groups was acceptable. The hazard quotient (HQ) was also below 1 across all age groups, signifying the absence of associated health risks for the Lebanese consumers. On the other hand, all milk samples were found exceeding the maximum tolerable value of mesophilic flora. Antibiotic-resistant bacteria (ARB) were detected and represented by ESBL-producing E. coli and MRSA isolates. Thus, the greatest threat of antibiotic use in Lebanon does not fall under antibiotic residues but rather the proliferation of antibiotic resistance in potentially pathogenic bacteria. In this study, the virulence profile of detected bacteria was not investigated; thus their pathogenicity remains unknown. Therefore, to mitigate this health threat in Lebanon, a "One Health" action plan against ABR is required. It will provide a framework for continued, more extensive action to reduce the emergence and spread of ABR in Lebanon.

Keywords: Escherichia coli; Lebanon; Staphylococcus aureus; antibiotic residues; antibiotic-resistant bacteria; raw milk; risk characterization.

Figure 1

Sampling points of raw milk across Lebanon.