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

<p><em>Staphylococcus aureus</em> 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 <em>S. aureus</em> 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. <em>S. aureus</em> 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 <em>16s</em> rRNA gene in all examined isolates. Virulence genes <em>eno</em>, <em>spa</em>, and <em>clf</em>B were identified in 100%, 71.4%, and 57.1% of isolates, respectively. The antimicrobial resistance genes <em>bla</em>Z, <em>mec</em>A, and <em>tet</em>K were identified in 85.7%, 100%, and 100% of isolates, respectively, while <em>van</em>A was present in 42.8%, and <em>van</em>B was absent. The findings underscore the considerable prevalence of highly resistant biofilm  producing <em>S. aureus</em> in poultry habitats, highlighting the Important role of <em>S. aureus</em> 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.</p>