The antibiotic susceptibility of Aeromonas schubertii isolated from snakehead in An Giang province of the Mekong Delta

Abstract

Antibiotic resistance and the transmission of resistance genes among bacteria in aquaculture are attracting world attention. The investigation was conducted to evaluate the antibiotic susceptibility of Aeromonas schubertii, which causes intensively cultured internal white spot disease in snakehead from An Giang province of the Mekong Delta. The findings isolated 29 bacterial strains from the kidney, spleen, and liver of diseased snakehead fish. Based on the morphological, biochemical, and 16S rRNA gene sequencing results, two strains of As9 and As11 showed a similarity of 98.71 % and 97.07 % to A. schubertii strains ZL-1 and GZ210812, respectively. The disc diffusion method was used to conduct antibiograms of the strains for 12 antibiotics. The research indicated that the bacteria were susceptible to the antibiotics ceftazidime, cefalexin, and doxycycline at rates of 86 %, 59 %, and 55 %, respectively. Meanwhile, bacteria were highly resistant to amoxicillin (93 %), flumequine (83 %), ciprofloxacin (76 %), rifampicin (66 %), erythromycin (62 %), colistin (59 %), florfenicol (59 %), and novobiocin (41 %). Interestingly, 100 % of the bacterial strains in the study demonstrated a multidrug-resistant phenotype, resistant to at least two antibiotics or more.