Antibiotic susceptibility and pathogenicity of Aeromonas hydrophila isolated from red hybrid tilapia (Oreochromis niloticus×Oreochromis mossambicus) in Malaysia

Abstract

Background and Aim: Aeromonas hydrophila is a major cause of bacterial infections affecting a wide range of warm water fishes worldwide. In Malaysia, A. hydrophila isolations from diseased fishes were previously reported; however, with limited information. The present study investigates the antibiotic susceptibility and pathogenicity of A. hydrophila isolated from farmed red hybrid tilapia (Oreochromis spp.) in Malaysia. Materials and Methods: A. hydrophila was biochemically identified and subjected to antibiotic susceptibility tests. The isolate was then intraperitoneally injected into red hybrid tilapia, and the mortality, clinicopathological changes, and LD50 were determined up to 240 h post-infection (hpi). Results: The isolate demonstrated multiple antibiotic resistances (MAR) toward amikacin, ampicillin, cefotaxime, amoxicillin, trimethoprim-sulfamethoxazole, erythromycin, and streptomycin, with a MAR index of 0.5. The experimental infection of A. hydrophila at 105 CFU/mL in the red hybrid tilapia resulted in 100% mortality at 240 hpi. The LD50 was determined at 1.1×104 CFU/mL. Infected fish demonstrated occasional erratic swimming patterns, localized hemorrhages and depigmentation on the body and operculum areas, fin erosion, enlargement of the gall bladder, and hemorrhage in internal organs. Microscopic observation of infected fish revealed brain congestion, tubular necrosis, and glomerular shrinkage in the kidneys, necrosis of hepatocytes, and congestion of blood vessels in the liver. Conclusion: The high virulence of A. hydrophila to the red hybrid tilapia emphasizes the importance of active, on-going monitoring of its prevalence in Malaysian tilapia farming.

Co-Infections of Tilapia Lake Virus, Aeromonas hydrophila and Streptococcus agalactiae in Farmed Red Hybrid Tilapia

“…The gross lesions and histopathological assessment of the affected fish in this study resembled common findings of TiLV-, Aeromonasand Streptococcus-infected fish [7,14,36,37]. Syncytial giant cells and multinucleated cells were observed in the liver and brain sections, that were previously described in the TiLV-infected and co-infected fish [7,38].…”

“…Aeromoniasis and streptococcosis are common bacterial diseases affecting tilapia culture, specifically involving Aeromonas hydrophila and Streptococcus agalactiae [ 11 , 12 , 13 , 14 ]. Apart from tilapia ( Oreochromis sp.)…”

“…and golden pompano ( Trachinotus blochii ), respectively [ 15 , 16 ]. Infections caused by both bacterial pathogens also lead to massive fish mortalities and economic losses around the world [ 13 , 14 ].…”

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

“…In contrast, the A. hydrophila isolates showed multiple resistance to erythromycin, cloxacillin (100%), streptomycin and cefotaxime (84%). These findings are consistent with a past study [57], which found A. hydrophila isolates from red hybrid tilapia in Malaysia were multidrug resistant to cefotaxime, sulfamethoxazole, erythromycin and streptomycin, with an MAR index of 0.5. Similarly, one study [58] found that the MAR index of A. hydrophila was between 0.12 to 0.59 and another study [59] found that the MAR index was between 0.243 and 0.457 for Aeromonads isolated from decorative fish farming systems.…”

Comparative Pathogenicity of Aeromonas spp. in Cultured Red Hybrid Tilapia (Oreochromis niloticus × O. mossambicus)

“…Previous reports revealed the LD 50 of A. dhakensis was between 10 2 and 10 5 CFU/mL when challenged in zebrafish (Danio rerio), rainbow trout (Oncorhynchus mykiss) and pacu (Piaractus mesopotamicus) [30,43,44]. Similarly, few studies reported LD 50 < 10 6 CFU/mL for A. hydrophila in zebrafish, rainbow trout and tilapia [45][46][47].…”