Prevalence and Antibiogram of Vibrio parahaemolyticus and Aeromonas hydrophila in the Flesh of Nile Tilapia, with Special Reference to Their Virulence Genes Detected Using Multiplex PCR Technique

Abstract

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.

Bacterial diseases of tilapia, their zoonotic potential and risk of antimicrobial resistance

“…Tilapia may be infected with various bacteria, including species of the genera Vibrio , Aeromonas , Pseudomonas and Streptococcus , 5 whereas some genera may be present also on healthy fish, like species of the genera Pseudomonas Aeromonas , and Plesiomonas 6 . In general, most fish diseases are induced by a stress factor, like a suboptimal environment, for instance, bad water quality, and this allows opportunistic bacteria including Aeromonas hydrophila to infect tilapia and cause disease 7–9 . Moreover, many bacterial diseases are multifactorial 10 .…”

“…Nile tilapia juveniles, after being exposed to transport‐induced stress, appeared to have 19 responsible isolates of A . hydrophila in their body, as identified by 16S rRNA testing 9 . The A .…”

Assessment of animal diseases caused by bacteria resistant to antimicrobials: kept fish species

“…The third study from Egypt (Zaher et al, 2021 ) was also based on disk diffusion but provided a reference with a non‐standard method for the medium and temperature (30°C), and then classified isolates as sensitive, intermediate and resistant according to a breakpoint designed for a different media and temperature (35°C). Hence, results should also be interpreted with care, as highlighted by the surprisingly low levels of resistance found for ampicillin among the 19 isolates tested (52.6%, with 32% of the remaining isolates classified as intermediate).…”

“…As described above, three references (Lukkana et al, 2012 ; Scarano et al, 2018 ; Zaher et al, 2021 ) reported different proportions of susceptible isolates to amoxicillin and/or ampicillin in their bacterial panels, even though mesophilic Aeromonads are considered intrinsically resistant to aminopenicillins (CLSI, 2016 ), thus highlighting the difficulties associated with the evaluation of the resistance phenotype in A . hydrophila isolates (and in bacteria from aquatic animals in general), a process in which small variations may lead to significant variations in the results.…”

Efficacy of combination of slightly acidic electrolyzed water and ultrasound for inactivation of Vibrio parahaemolyticus in vitro and in sliced tilapia

“…Although V. parahaemolyticus infection has been commonly associated with seafood consumption, its existence in non‐seafood products such as freshwater fish and infections caused by contaminated non‐seafood products have also been reported (Chao et al, 2009; Liu et al, 2015). Zaher et al reported a prevalence rate of 24.8% (62/250) for Nile tilapia samples (Zaher et al, 2021) and Li et al found that 3.67% of 300 miscellaneous ready‐to‐eat food samples were positive for V. parahaemolyticus (Li et al, 2020). Dong et al isolated and characterized V. parahaemolyticus strains from crayfish raised in freshwater (Dong et al, 2016) and a V. parahaemolyticus outbreak with 375 infections were attributed to undercooked frozen crayfish in Jiangxi province, China in 2011 (Sun et al, 2012).…”