The study conducted on 39‐layer farms in Gauteng Province, South Africa determined the prevalence and resistance of enteropathogens, and antimicrobial residues in table eggs collected from the farms. Eggs were tested for the presence of bacteria using standard methods. The resistance of bacteria to eight antimicrobial agents was determined using the disc diffusion method. Antimicrobial residues were detected in table eggs using the microbial inhibition test, enzyme‐linked immunosorbent assay (ELISA), and high performance liquid chromatography (HPLC). Risk factors for egg contamination by bacteria and antimicrobial residues were determined through a questionnaire survey of farmers. The farm prevalence of Salmonella spp. and Escherichia coli in table eggs was 7.7 and 48.7%, respectively. Nineteen (48.7%) and 2 (5.1%) of eggshells and egg contents, respectively, were positive for E. coli but only eggshells yielded Salmonella species, 2.0% (4 of 196). Overall, 71.4% of 49 E. coli isolates exhibited resistance to one or more antimicrobial agents. The farm prevalence and egg content prevalence of antimicrobial residues was 2.6 and 0.5%, respectively, with the detection of sulfonamide (79 ppb) and oxytetracycline (106 ppb). The prevalence of resistant E. coli and Salmonella spp. and the occurrence of antimicrobial residues in egg content may pose food safety and therapeutic threats to consumers.
The occurrence, concentrations and variables associated with tetracycline, polyether ionophore and anthelmintic residues in the livers of chickens sold in the informal market in South Africa were determined. An ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS) was used to simultaneously analyze for four tetracyclines, five polyether ionophores and six anthelmintic residues. The study determined the presence of residues in liver samples at both the limit of quantifications (LoQ) and concentrations over the maximum residue limit (MRLs), i.e. non-compliant. Doxycycline (tetracycline group) was detected in 24.5% (24/98) of chicken livers and 15.3% (15/98) were non-compliant. The mean±SD concentration of 919.04±1081.30 (LoQ) and 1410.57±108.89 ppb (MRL) were obtained. Maduramycin was detected in 27.6% (27/98) of chicken livers and 19.4% (19/98) were non-compliant. The mean±SD for LoQ was 117.96±84.56 and MRL was 153.21±76.29 ppb. The concentrations of residues of doxycycline and maduramycin in chicken livers varied significantly across townships. Lasalocid was quantified in 31.6% (31/98) of the samples, of which 5.1% (5/98) contained concentrations above the MRL. The mean±SD concentrations of Lasalocid was 62.90±170.84 for samples in which Lasalocid was quantified and 310.16±356.68 ppb for non-compliant samples. The frequencies of chicken livers that contained detectable concentrations of the three anthelmintic residues were 3.1% (3/98), 1.0% (1/48) and 2.0% (2/98) for praziquantel, closantel and rafoxanide, respectively. The presence of three classes of veterinary drugs residues in chicken liver poses food safety implications to consumers and indicates a need for enhanced regulatory enforcement in controlling these drugs in South Africa.
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