MOLECULAR DETECTION OF INVA AND HILA VIRULENT GENES IN SALMONELLA SEROVARS ISOLATED FROM FRESH WATER FISH

Abstract

The present study was conducted to monitor the prevalence of salmonellae in fresh water fish in Gharbia governorate, Egypt. A total of 120 random samples of fresh water fish (Tilapia niloticus, Mugil cephalous and Clarias lazera, 40 of each) were analyzed bacteriologically for the presence of salmonella pathogens and were further identified using biochemical and serological tests. Positive samples were confirmed by polymerase chain reaction (PCR) through detection of common virulent genes invasion A (invA) and hyper-invasive locus (hilA). The obtained biochemical and serological results revealed presence of seven different serotypes including S. typhimurium which was the most frequent one followed by S. enteriditis, S. infantis , S. virchow, S. heidelberg, S. wingrove and S. tsevie with a prevalence of 33.3%, 23%, 12.8%, 12.8%, 10.25%, 5% and 2.5%, respectively. The obtained molecular results revealed presence of the two virulent genes in all the detected serovars with a total prevalence rate of 100% for invA gene and 66.6% for hila gene. These results reflected a high prevalence of salmonella species in fresh water fish which act as a potential source of food borne infection and constitutes a major concern for public health. Key words: fresh water fish; salmonella; serotypes; invA; hilA; PCR