Food safety risk posed to consumers of table eggs from layer farms in Gauteng Province, South Africa: Prevalence of Salmonella species and Escherichia coli, antimicrobial residues, and antimicrobial resistant bacteria

Abstract

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.

Risk factors associated with Salmonella prevalence, its antibiotic resistance, and egg antibiotic residues in the layer farming environment

“…This study found only aminoglycoside and tetracycline residues in the eggs (in both albumen and yolk). The prevalence of tetracycline residues found in this study was higher than that in the study performed by Adesiyun et al [11]. In contrast, our finding was lower than that in the report by Adesiyun et al [28].…”

“…The prevalence of Salmonella in the eggs in the present study was lower than that found in the results of Camba et al [10]. The Salmonella prevalence in the ESM eggshells in our study was higher than that found in the report of Adesiyun et al [11] (7.7%) and Camba et al [10] (0.06 %). Contaminated eggshells can cause human salmonellosis by consuming raw or undercooked eggs that lack shell-cleaning or are stored at temperatures above room temperature (30 o C) for more than 3 weeks.…”

Genomic Characterization of Listeria innocua Isolates Recovered from Cattle Farms, Beef Abattoirs, and Retail Outlets in Gauteng Province, South Africa

“…The resistance of bacteria to tetracycline in South Africa has been attributed to the unregulated use of veterinary drugs, including tetracycline, in the country. This is attributed to the existing Fertilizers, Farm, and Agricultural and Stock Remedy Act (Act 36, 1947), which legalizes the use of certain antimicrobial agents, such as sulphonamides and trimethoprim, to be purchased over-the-counter, and they are used for treatment and as growth promoters [ 70 ]. Interestingly, the phenotypic resistance exhibited to tetracycline (36.8%) determined by Gana [ 37 ] correlates well with the putative resistance to tetracycline due to both tet ( M ) and tet(S ) genes based on WGS on the same isolates, suggesting that the genes may have been partly responsible for the resistance detected.…”

Staphylococcus aureus as a foodborne pathogen in eggs and egg products in Indonesia: A review

“…Numerous studies have been conducted on related contamination of eggs caused by Salmonella spp. and E. coli [15,16]; however, S. aureus infection in eggs in Indonesia has yet to be studied intact and is only limited in prevalence. This review aimed to describe the incidence of S. aureus and methicillin-resistant Staphylococcus aureus (MRSA) in Indonesia compared with that in several other countries, as well as One Health approach to the prevention and control of S. aureus contamination of eggs in Indonesia.…”