Rapid Detection and Control of Gram-negative Bacterial Pathogens Isolated from Summer Mortality Outbreak Affecting Tilapia Farms

The present work aimed to investigate the causes of summer mortality syndrome affecting cultured European seabass (Dicentrarchus labrax) by examining physiochemical farm water characteristics, isolation, and identification of recovered bacterial pathogens from diseased fish studying the effect of water temperature on stress biomarkers and disease severity. Studied water parameters were normal except ammonia and dissolved oxygen was higher and lower than the standard value. Sixty-two bacterial isolates were recovered from moribund fish and identified as 31 Vibrio fluvialis, 23 Pseudomonas aeruginosa and 8 Staphylococcus aureus isolates. The calculated LD50 of V. fluvialis, P. aeruginosa and S. aureus for D. labrax fingerlings were 4.67 × 107, 2.37 × 106 and 1.38 × 107, respectively. There was a direct correlation between water temperature and mortality rate of fish challenged with V. fluvialis as the mortality rate was 44.44, 50, 66.66, and 83.33% for fish maintained at 27, 30, 33, and 36°C. Plasma cortisol, superoxide dismutase, catalase and malondialdehyde significantly increased when the water temperature exceeded 30°C. The experimentally infected fish showed similar clinical signs and postmortem lesions of naturally diseased fish with no boundary between different pathogens. Antibiogram test indicated that florfenicol was the most effective antibiotic against all the recovered bacterial isolates while all isolates resisted sulfamethoxazole-trimethoprim. Massive degenerative changes observed in the hepatopancreas, posterior kidney and gill tissues of experimentally infected fish.

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“…The recovered bacterial isolates were identified by VITEK 2 system as described by Ali et al (2018) with few modifications.…”

Section: Automated Biochemical Identification Of the Recovered Bacterial Isolates By Vitek 2 Systemmentioning

confidence: 99%

Summer Mortality Syndrome Affecting Cultured European Seabass at Kafrelsheikh Province, Egypt

Ali

El-Nokrashy

Gouda³

et al. 2021

Front. Mar. Sci.

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“…Bacterial infections are the most abundant diseases affecting cultured fish [5]. Globally, fish diseases are estimated to contribute to more than 30% of the overall production loss, and bacterial diseases represent a serious challenge for tilapia culture worldwide [6].…”

Section: Introductionmentioning

confidence: 99%

Enrofloxacin, Effective Treatment of Pseudomonas aeruginosa and Enterococcus faecalis Infection in Oreochromis niloticus

Aboyadak,

Ali

2024

Microorganisms

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Enrofloxacin is a broad-spectrum synthetic antimicrobial drug widely used in veterinary medicine. The present study aimed to determine the effective enrofloxacin dose for treating Pseudomonas aeruginosa and Enterococcus faecalis infection in Oreochromis niloticus. P. aeruginosa and E. faecalis isolates were verified using selective differential media and biochemically using the Vitek 2 test. Bacterial isolates were virulent for O. niloticus with LD50 equal to 2.03 × 106 and 2.22 × 107 CFU fish−1 for P. aeruginosa and E. faecalis, respectively. Infected fish suffered from decreased feed intake followed by off-food, tail erosion, darkening of the external body surface, exophthalmia, ascites, and loss of escape reflex. Internally, congested hemorrhagic hepatopancreas with engorged distended gall bladder were dominant. The posterior kidney was congested with enlarged spleen, and empty elementary tract. Pathologically, severe degenerative changes were dominant in the hepatopancreas, posterior kidney, spleen, stomach, and gills of infected fish. Antimicrobial sensitivity test indicated the high susceptibility of P. aeruginosa and E. faecalis to enrofloxacin with MIC estimated at 1 and 0.0625 µg/mL, respectively. Enrofloxacin effectively protected O. niloticus against E. faecalis and P. aeruginosa infection when used with medicated feed at doses of 10 and 20 mg kg−1 body weight.

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Virulence genes contributing to Aeromonas hydrophila pathogenicity in Oreochromis niloticus

et al. 2019

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Rapid Detection and Control of Gram-negative Bacterial Pathogens Isolated from Summer Mortality Outbreak Affecting Tilapia Farms

Cited by 4 publications

References 17 publications

Summer Mortality Syndrome Affecting Cultured European Seabass at Kafrelsheikh Province, Egypt

Summer Mortality Syndrome Affecting Cultured European Seabass at Kafrelsheikh Province, Egypt

Enrofloxacin, Effective Treatment of Pseudomonas aeruginosa and Enterococcus faecalis Infection in Oreochromis niloticus

Virulence genes contributing to Aeromonas hydrophila pathogenicity in Oreochromis niloticus

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