Characterization of bacterial isolates from breeding water of Dengue vector mosquito, Aedes albopictus

Abstract

The microbial composition of mosquito breeding grounds, which varies according to microhabitat conditions, climatic factors, and geographical regions, plays a crucial role in larval development, fecundity, and host-pathogen interactions of mosquitoes. Considering the relatively high fitness and wider distribution of Aedes albopictus mosquitoes, we characterised the bacteria associated with their breeding grounds. Samplings were carried out from Kurunegala and Kandy districts in Sri Lanka (May to November 2023). Twenty-five water samples were collected and cultured on Luria Broth media (LB) and Nutrient agar plates (NA). Identified morphologies were sub-cultured, and 80% glycerol stocks were prepared for pure colonies. Molecular identification of the pure colonies was conducted by sequencing the 16s rRNA gene. Morphological identification, based on shape, size, colour, margin, opacity, and elevation, confirmed 20 different bacterial morphologies and molecular identification confirmed 17 different bacterial isolates. Aeromonas hydrophila was the most abundant bacteria observed in all breeding grounds (100%). The second most abundant was Acinetobacter proteolyticus (32%). The remaining bacterial composition was represented by three Staphylococcus spp. viz., S. cohnii (20%), S. pseudoxylous (12%), Staphylococcus sp. strain 20 (16%); Bacillus subtilis (20%); two Fictibacillus spp. viz., F. phosphorivorans (20%) and F. halophilus (12%); Pseudomonas mosselii (12%); Citrobacter braakii (28%); Chromobacterium haemolyticum (8%); Exiguobacterium indicum (28%); Arhrobacter sp. (8%); Luteimonas terrae (28%); Micrococcus luteus (24%) and Deinococcus sp. (12%). Two to eight different species were reported from each mosquito breeding site. A maximum of four to five distinct species were reported from the majority of Aedes mosquito breeding sites (64%). The findings identified the microbes that are commonly associated with Aedes albopictus mosquitoes, and further studies will be carried out using different culture media to assess the bacterial diversity in the breeding habitat water of Aedes albopictus.