Abstract
Background: Salmonellosis, particularly infections caused by Salmonella enterica, remains a major concern in poultry production and food safety. The disease poses significant economic losses due to mortality, reduced growth rates, and treatment costs, highlighting the need to characterize virulence gene patterns of Philippine isolates. This study aimed to molecularly confirm S. enterica isolates recovered from poultry-derived samples, particularly eggs, giblets, and cloacal swabs, collected from selected regions of the Philippines using 16S rRNA-targeted PCR, and to determine the presence and distribution of the invA (SPI-1) and sseC (SPI-2) virulence genes among these isolates. Methods: A total of 865 samples, including eggs, giblets, and cloacal swabs, were collected from Philippine poultry farms and wet markets. Standard microbiological procedures were employed: pre-enrichment in buffered peptone water, enrichment in Rappaport Vassiliadis broth, plating on xylose lysine deoxycholate agar, and purification on nutrient agar. Putative isolates were further analyzed using morphological and selected biochemical tests, followed by PCR targeting of 16S rRNA, invA, and sseC genes. Amplicons were visualized by gel electrophoresis. Results: All 56 suspected isolates were confirmed as S. enterica. Among these, 69.6% carried both invA and sseC, 14.3% carried invA alone, 3.6% lacked both genes, and none harbored sseC alone. These genes are associated with pathogenicity islands SPI-1 (invA) and SPI-2 (sseC). Conclusions: The presence of virulence genes linked to SPI-1 and SPI-2 among Philippine S. enterica isolates highlights their role in pathogenesis. This provides baseline data on virulence gene prevalence in poultry-derived Salmonella and emphasizes the importance of continued surveillance to mitigate risks of salmonellosis from poultry-derived isolates.

Keywords
Salmonella enterica, Pathogenicity islands, Poultry, invA, sseC, virulence genes