RESISTENCIA ANTIMICROBIANA EN BACTERIAS AISLADAS DE TILAPIAS, AGUA Y SEDIMENTO EN VENEZUELA Antimicrobial Resistance in Bacteria Isolated From Tilapia, Water and Sediment Samples In Venezuela

The indiscriminate use of antimicrobials exerts high selective pressure on bacteria, provoking the emergence and dissemination of genes resistance to them. Considering that in Lake Valencia great volumes of water drain as a consequence of intense anthropogenic activities, the bacterial resistance in feral and cultured tilapia was evaluated, and the inhibitory concentration of selected antimicrobials was determined. The sensitivity was evaluated by two methods: a semi quantitative one (Mueller-Hinton agar disk diffusion method) and a quantitative one, determining the minimal inhibitory concentration (MIC). Variations were registered for the different species, observing multiple resistance in all the bacteria, with a higher resistance in cultured conditions (8-12 compounds) than in feral ones, although the antimicrobial resistance in Lake Valencia was high too (6-12 compounds). Oxolinic acid, a compound widely used in aquaculture, that does not have any importance in human health, seems to be the most effective in inhibiting the development of these bacteria, with a MIC in the range of 0.5-10 µg/mL. The high resistance and the wide range of MIC values found, emphasises the fact that the use of antimicrobials should be carried out in a controlled manner and with a previous study of resistance in vitro, in order to prevent the selection of resistant bacterial strains.