Insecticidal potential of Serratia sp. on larvae of Aedes aegypti.

RONDAN DUEÑAS, J.C.; MUÑOZ, A.; BELAUS, A.; VÉLEZ, P.; DOUCET, M.E.; LAX, P.

Congreso; XI Congreso Argentino de Microbiología General; 2015

Some arthropods are vectors or agents transmitting diseases for public health importance. At present, indiscriminate use of synthetic insecticides generates environmental pollution, insect resistance and human toxicity. An alternative for insect control consists of obtaining molecules of bacterial origin with insecticidal activity. Some species within the genus Serratia are pathogenic to insects. The present work evaluated the potential insecticidal effect of Serratia sp. LB-1 isolated from the external cuticle of an entomopathogenic nematode (Steinernema sp.) on larvae of Aedes aegypti (mosquito that transmits dengue and chikungunya viruses). Bacteria were multiplied on culture with brain-heart medium for 48 h. Concentration was determined by optical density; then the bacterial phase was separated from the supernatant by centrifugation. Bacteria were suspended in sterile water and a series of dilutions (1x105, 5x105, 1x106, 5x106, 1x107, 1.5x107, 2.5x107 UFC/ml) were performed. The supernatant fraction was diluted in the same proportion as each one of the mentioned concentrations. Ten III and IV-stage larvae were placed in tubes containing 4 ml of each dilution; mortality was evaluated at 24 and 48 h. The experiment was performed at 25ºC, with 8 replications per treatment. None of the bacterial suspensions had larvicidal effect. At 24 h, the highest mortality percentages were observed in the 1.5x107 and 2.5x107 supernatant dilutions, with values ranging between 65-99%. At 48 h, 1x107, 1.5x107, 2.5x107 dilutions produced between 88-100% mortality. The results show that secondary metabolites produced by the strain of Serratia sp. would have potential for control of mosquito larvae of sanitary importance.