Comparative Assessment of Antibiotic Residues Using Liquid Chromatography Coupled with Tandem Mass Spectrometry (LC-MS/MS) and a Rapid Screening Test in Raw Milk Collected from the North-Central Algerian Dairies

Antibiotic residues in milk are a major health threat for the consumer and a hazard to the dairy industry, causing significant economic losses. This study aims to assess the presence of antibiotic residues in raw milk comparatively by a rapid screening test (BetaStar(R) Combo) and Liquid Chromatography coupled with Tandem Mass Spectrometry (LC-MS/MS). A total of 445 samples were collected from 3 dairy companies of north-central Algeria (Algiers, Blida, Boumerdes), and they were rapidly screened for beta-lactams and tetracyclines; 52 samples, comprising 34 positive tanker-truck milk and 18 negative bulk-tank milk were tested by LC-MS/MS, which revealed 90.4% were contaminated (n = 47) and 55.3% exceeded the Maximum Residue Limit (MRL). The beta-lactams as parent compounds and their metabolites were the most frequently detected with maximum value for cloxacillin (1231 mu g/kg) and penicillin G (2062 mu g/kg). Under field condition, the false-positive results, particularly for tetracyclines, seems to be related to milk samples displaying extreme acidity values (>= 19 degrees D) or fat-level fluctuations (2.7 g/100 mL and 5.6-6.2 g/100 mL). Despite a relatively low prevalence (7.64%) of residues using the rapid test, the detection by LC-MS/MS of flumequine (52 mu g/kg), cefaclor (maximum 220 mu g/kg) and metabolites of beta-lactams at high levels should lead to reflections on the control of their human and environmental toxicological effects.

Automated summary

This study assessed the presence of antibiotic residues in raw milk in Algeria using a rapid screening test and LC-MS/MS. The results showed that 90.4% of the samples were contaminated and 55.3% exceeded the maximum residue limit. Beta-lactams and their metabolites were the most frequently detected, with cloxacillin and penicillin G having the highest levels.