Abstract
Background:
Campylobacter jejuni is a major zoonotic pathogen that causes gastroenteritis in humans, with broiler chickens as its primary reservoir. The pathogenicity of this bacterium is highly dependent on virulence factors encoded by specific genes, such as the cytolethal distending toxin (CDT) operon (cdtA, cdtB, and cdtC), the motility gene (flaA), and the invasion-related gene (virB).

Aim:
This study aimed to identify and determine the prevalence of the virulence genes cdtA, cdtB, cdtC, flaA, and virB in C. jejuni isolates from the small intestine of broiler chickens in Indonesia.

Methods:
This study used a cross-sectional design on 200 small intestine jejunum samples randomly collected from 200 Cobb broiler chickens in Pasuruan Regency, East Java, between October and December 2023. Bacterial isolation was performed through an enrichment stage using Bolton Broth, followed by cultivation on mCCDA under microaerophilic conditions at 42°C. Confirmation of the C. jejuni species was performed using conventional PCR targeting the hipO gene. Isolates that had been confirmed positive were then further analyzed to detect the presence of five virulence genes (cdtA, cdtB, cdtC, flaA, and virB) using polymerase chain reaction.

Results:
Isolation and identification results showed that 40 (20%) isolates of C. jejuni were found out of 200 small intestine samples from Cobb broiler chickens at several farms and poultry slaughterhouses in Pasuruan Regency, East Java, Indonesia. Specifically, 100% of the tested isolates carried the three genes that make up the CDT operon: cdtA, cdtB, and cdtC. Furthermore, the flaA gene was almost universal in the isolates studied, with 38 (95%) of the 40 isolates identified as positive. All isolates (100%) tested negative for the virB gene.

Conclusion:
Campylobacter jejuni isolates from the intestines of broiler chickens in Indonesia contained the cdtA, cdtB, cdtC, and flaA virulence genes, indicating a public health risk. An integrated approach of surveillance, biosecurity, antibiotic management, and research and development of natural therapies is a priority strategy to protect public health and the Indonesian poultry industry’s sustainability.

Key words: Campylobacter; Gene; Virulence; Chicken; Public health.