Vibrio parahaemolyticus and Aeromonas hydrophila are major public health problems and the main cause of bacterial disease in Nile tilapia (Oreochromis niloticus). This study was conducted to determine the prevalence, antibiotic resistance and some virulence genes of both V. parahaemolyticus and A. hydrophila isolates from Nile tilapia. From Manzala Farm at Dakahlia governorate, 250 freshwater fish samples were collected. The confirmed bacterial isolates from the examined Nile tilapia samples in the study were 24.8% (62/250) for V. parahaemolyticus and 19.2% (48/250) for A. hydrophila. multiplex PCR, revealing that the tlh gene was found in 46.7% (29/62) of V. parahaemolyticus isolates, while the tdh and trh virulence genes were found in 17.2% (5/29). Meanwhile, 39.5% (19/48) of A. hydrophila isolates had the 16s rRNA gene and 10.5% (2/19) had the aerA and ahh1 virulence genes. The Multiple Antibiotic Resistance indices of V. parahaemolyticus and A. hydrophila were 0.587 and 0.586, respectively. In conclusion, alternative non-antibiotic control strategies for bacterial infections in farmed fish should be promoted to avoid multidrug-resistant bacteria. Therefore, it is suggested that farmers should be skilled in basic fish health control and that molecular detection methods are more rapid and cost-effective than bacteriological methods.
Keywords: Aeromonas hydrophila; Oreochromis niloticus; Vibrio parahaemolyticus; molecular identification.