Molecular and Bacteriological Studies on Staphylococcus aureus Cause Dead in Shell Eggs

Staphylococcus aureus is a significant pathogenic bacterium commonly implicated in the contamination of poultry products, including eggs. This study was designed to examine the molecular and bacteriological properties of S. aureus isolated from dead-in-shell eggs and surrounding environments (nests and hatcheries). Approximately 350 samples were aseptically collected from the internal organs of deceased embryos, egg nests, and hatcheries. S. aureus was isolated with a percentage of 49.8% of the total samples. The phenotypic evaluation of biofilm formation, revealed that 50 of tested isolates demonstrated biofilm-forming capabilities with different degrees. Antimicrobial susceptibility assays revealed widespread resistance among (50) representative isolates were tested, including (100%) resistance to erythromycin and rifampin, substantial resistance to chloramphenicol (88%), sulfonamides (76%), doxycycline (62%), and cefoxitin (50%), thereby classifying these isolates as MRSA. Analysis of multidrug resistance (MDR) indicated elevated resistance indices, with 22 isolates designated as extensively drug-resistant (XDR) and 28 as MDR. The MDR index values > 0.2. Molecular characterization using PCR confirmed the presence of the 16s rRNA gene in all examined isolates. Virulence genes eno, spa, and clfB were identified in 100%, 71.4%, and 57.1% of isolates, respectively. The antimicrobial resistance genes blaZ, mecA, and tetK were identified in 85.7%, 100%, and 100% of isolates, respectively, while vanA was present in 42.8%, and vanB was absent. The findings underscore the considerable prevalence of highly resistant biofilm  producing S. aureus in poultry habitats, highlighting the Important role of S. aureus as a causative agent of dead in shell embryos and the role of hatcheries in the spreading of the infection all over the poultry production process.