Background and Aim: The increasing number of multidrug-resistant (MDR) Salmonella species on poultry farms in Indonesia has caused concern regarding human health. This study was conducted to determine the presence of the virulence gene invA in MDR Salmonella species isolated from the cloacal swab of broiler chickens in Blitar district, East Java Province, Indonesia.

Materials and Methods: Cloacal swab samples were collected by purposive sampling from 15 farms in four districts. Isolation and identification of bacteria were performed using standard microbiological techniques. Confirmation of MDR isolates was done using five different classes of antibiotics, including the beta-lactam, aminoglycoside, fluoroquinolone, phenicol, and monobactam groups. An antibiotic susceptibility test was conducted using the Kirby–Bauer disk diffusion method, and a polymerase chain reaction method was used to screen for the presence of invA.

Results: It was observed that 32.26% (50/155) of the samples were positive for Salmonella species. Of these 50 Salmonella isolates, 7 (14%) were identified as MDR strains. An important finding was the detection of invA in all the seven MDR Salmonella strains (100%) isolated from the cloacal swab of broiler chickens in Blitar district, East Java Province.

Conclusion: Veterinarians have an extremely important role in monitoring the use of antibiotics in farm animals to mitigate the rapid spread of MDR organisms in our environment, which can otherwise cause serious economic losses and also public health issues.

Keywords: broiler chicken, invA gene, multidrug-resistant, public health, Salmonella.