Assessment of antibiotic residues and microbiological safety in Lebanese dairy products: Akkawi cheese, yogurt, and labneh, collected across Lebanese dairy industries.
Joubrane Karine K, Daher Zeina Z, Jammoul Adla A, Chahrour Jamil Atef JA et al.
Antibiotic residues in dairy products and the resulting antibiotic-resistant bacteria represent a major global public health concern. This study evaluated the microbiological safety of 400 dairy samples collected over two consecutive years (2022 and 2023) from 16 dairy residue industries across four governorates in Lebanon. In addition, antibiotic residues were screened from 126 dairy product samples randomly chosen out of the 400. An optimized multi-class method for the identification and quantification of 30 antibiotics was developed using liquid chromatography-mass spectrometry. Results revealed that 48% of the analyzed samples were contaminated with at least one antibiotic residue, among which 33% showed co-occurrence of multiple antibiotic classes. Meanwhile, microbiological assessment of 400 dairy samples collected over 2 years from the same dairies revealed higher levels of contamination with total coliforms, Escherichia coli, and Staphylococcus aureus in Akkawi cheese samples collected during the first year (44%, 32%, and 15%, respectively) compared to those collected the second year (38.8%, 31%, and 0%). Moderate contamination levels were observed in Labneh (strained yogurt) samples collected during both seasons, with yeast (12%; 11%), molds (1.2%; 11%), total coliforms (6%; 11%), and Escherichia coli (3.7%; 11%). On the other hand, comparable levels of non-conformity were observed in yogurt samples across the two years, with contamination by yeast (7.5%; 6.2%), molds (3.75%; 6.2%), total coliforms (26%; 31.2%), E. coli (20%; 21%), and Staphylococcus aureus (1.25%; 0%). Escherichia coli isolates exhibited resistance to tetracycline while being 100% sensitive to ciprofloxacin and nalidixic acid. As for S. aureus isolates, they presented a high sensitivity to tetracyclines, doxycycline, and ciprofloxacin. These findings highlight the importance of implementing and maintaining good hygienic practices within dairy industries. Antimicrobial residues of oxytetracycline, tetracycline, ciprofloxacin, sulfamethazine, and doxycycline were detected at levels below the maximum residue limits.