Molecular characterization of Staphylococcus aureus isolates from nasal samples of broiler chickens intended for slaughter in Algeria

Staphylococcus aureus (S. aureus) is a versatile pathogen which colonizes food-producing animals and causes infections in humans. This study aims to determine the prevalence of 1. S. aureus in broiler chickens destined for slaughter and evaluate their antibiotic resistance profiles and virulence characteristics. A total of 521 nasal samples were collected from broiler chickens in three slaughterhouses located in the Tizi Ouzou area (Algeria) and were analyzed for the presence of S. aureus. Multiplex PCRs were used to detect enterotoxin genes, the disc diffusion method determined antibiotic resistance phenotypes, and biofilm formation ability was assessed through Congo-red agar (CRA) and microtiter plate assays. The methicillin-resistant S. aureus (MRSA) isolates were characterized by spa-typing. Our findings revealed that 7.9% of analyzed samples were positive for S. aureus, with identification of 73 isolates through these positive samples. One or more genes encoding staphylococcal enterotoxins (SEs) were present in 34 (46.6%) of these isolates. The majority of the S. aureus isolates showed resistance to penicillin (75.3%), erythromycin (60.3%), and tetracycline (56.2%), with nearly half (47.9%) exhibiting multidrug resistance. Seven MRSA isolates were identified and ascribed to two spa-types: t688 and t003. One of them carried the gene lukF/S-PV encoding the Panton Valentine leukocidine. Fifty-three (72.6%) of the isolates were slime producers, and all of them could form biofilm in a microtiter. This study provided important insights into the phenotypic and genotypic characteristics of S. aureus isolates associated with the nasal carriage of healthy broiler chickens intended for slaughter in Algeria. The presence of multidrug-resistant (MDR) isolates, as well as strains carrying enterotoxin genes and forming biofilm highlight the need for establishing hygienic practices and biosecurity measures throughout the production chain.