Antimicrobial resistance of vibrios isolated from fish and marine shrimp in Venezuela

Abstract

A worldwide practice in aquaculture rearing facilities is the routine use of antimicrobials, including compounds of value in human medicine, but despite this, vibriosis, caused fundamentally by luminous Vibrio haweyi, still prevails. The antimicrobial resistance was determined, by the agar diffusion disk method for tweive antimicrobials and for the vibriostatic agent, for members of the genus Vibrio, isolated from wild silver mullets (Mugil curema) and from feral and cultured penaeid shrimp (Litopenaeus schrnitti, L. vannamei y L. stylrostris), as well as from water and sediment from their environment. Samples were taken from kidneys, hepatopancreas, intestines, and from shrimp larval homogenates. In general terms, the animals were apparently healthy, with the exception of the first three samplings in the shrimp farm in 1996, when the larvae had sanitary problems. 629 vibrios were isolated with the mayor group clearly identified formed by the species V. harveyi. 93% of the vibrio strains had multiple resistance. The vibrios showed a resistance of ≥50% to eryihromycin, streptomycin, kanamycin, novobiocin, penicillin G, polymyxin B, tetracycline and triple sulpha. No significant statisticai difference (P ≤ 0.05) was determined between the species V. harveyi and the rest of the Vibrio species iocated in a second group, wnsidering both feral and culture conditions. But the level of resistance for V. haweyi became significantly greater (P ≤ 0.05) when considering separately the strains of V. harveyi isolated from diseased larvae. Here the strains were 100% resistant to a range of 7 to 10 of the antimicrobials tested. The high level of resistance among bacteria recovered here from cultured animals, could reflect the widespread use of antimicrobial compounds. The situation regarding feral animals may involve resistance transfer of R factors by means of plasmids.