Prevalence, Virulence Determinants and Antimicrobial-Resistant Profile of Edwardsiella tarda Isolated from Nile Tilapia (Oreochromis niloticus) in Egypt
Prevalence, Virulence Determinants and Antimicrobial-Resistant Profile of Edwardsiella tarda Isolated from Nile Tilapia (Oreochromis niloticus) in Egypt
Samah Samir, Amal Awad*, Gamal Younis
ABSTRACT
Edwardsiella tarda (E. tarda) is an enterobacterium that causes edwardsiellosis, a fatal disease of farmed fishes that causes severe economic losses in the aquaculture industry. Edwardsiella tarda was categorized as a serious food- and waterborne infection that causes a high rate of mortality in people with liver cirrhosis. The goal of this study was to explore the prevalence, virulence-related genes (edw1, cds1, qseC and pvsA), and antibiotic susceptibility profile of E. tarda in Nile tilapia collected from Egyptian fish farms. Between December 2019 and March 2020, 250 Nile tilapia were collected from five fish farms located at Dakahlia governorate. Organ tissue samples from liver, kidneys, gills, skin and spleen were examined bacteriologically for the presence of E. tarda; and confirmed by PCR targeting gyrB1 gene. Disk diffusion was used to test their antimicrobial susceptibility, and PCR was used to screen E. tarda isolates for the presence of four virulence-related genes (cds1, edwI, qseC, pvsA). In addition, the ability of E.tarda to form biofilm was tested by tube test. E.tarda was detected in 15 fish (6%) and a total of 40 isolates were recovered from organ tissue samples and confirmed based on phenotypic and molecular characterization. The frequency of edw1, cds1, qseC and pvsA genes were 75%, 70%, 42.5% and 2.5% respectively. E. tarda isolates displayed high resistance to ampicillin, amoxicillin, clindamycin, cefuroxime, penicillin, and amikacin, while, it is more sensitive to ciprofloxacin. Multi antimicrobial resistance (MAR) was observed in 100% of the tested isolates. In addition, 33 isolates (82.5%) were positive for biofilm production. In conclusion, the presence of virulent -MDR E.tarda strains in fish farms constitutes a hazard to aquaculture as well as a significant public health concern, therefore, appropriate sanitary management is required to improve water quality and reduce sickness incidence and economic losses.
Keywords | E. tarda, Fish farms, Virulence, Antimicrobial susceptibility, Biofilm.
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