Under laboratory conditions, the mosquitoes were reared in hygienic and controlled conditions whereas, reverse is true for the field conditions. Hence, the larvae in field are more exposed to the microbial flora of the open water than their counterparts in the laboratory. Larvae being filter feeders ingest the water in immediate vicinity irrespective of their preference. Similarly, adult mosquitoes feed on uncontrolled natural diet, while laboratory-reared mosquitoes were fed with sterile glucose solution and resins. Even the blood offered to female mosquitoes in laboratory is from infection-free rabbit; on the other hand, the blood meal in field is good

source of various infections. Thus, field-collected mosquitoes have more chances of having diverse gut flora as was observed. Mosquitoes are known to elicit specific immune responses against parasites [3, 4, click here 42]. Some of these immune responsive genes are expressed in response to bacteria and this raises the possibility that the presence of specific bacteria in the gut may have an effect on the efficacy at which a pathogen is transmitted by a vector mosquito [9]. In previous studies CSF-1R inhibitor of lab-reared A. stephensi adults, it was demonstrated that great number of S. marcescens were found in the midgut of the insects, but was not found in larvae and pupae [10]. In another study, it was observed that Plasmodium vivax load in A. albimanus

mosquitoes co-infected with E. cloacae and S. marcensces were lower (17 and 210 times respectively) than control aseptic A. albimanus mosquitoes with Plasmodium vivax infection (without E. cloacae and

S. marcensce). In our study, we also observed that a relatively high number of S. marcescens (35 isolates from lab-reared male/female and 48 clones from field-collected female/larvae) were identified from lab and field- populations of A. stephensi. However, none S. marcescens species were identified from field- collected male A. stephensi. At this point it is premature to draw correlation between the occurrences Methocarbamol of S. marcensce and pathogeneCity or vector load. However, previous reports suggest that mortality in S. marcensces-infected A. albimanus mosquitoes was 13 times higher compared with the controls [12]. The present study assumes importance in the light of earlier studies which suggested that the composition of midgut microbiota has a significant effect on the survival of dengue (DEN) viruses in the gut lumen [43]. The overall susceptibility of Aedes aegypti mosquitoes to dengue viruses increased more than two-folds, with the incorporation of bacterium Aeromonas culicicola. However, the increase in susceptibility was not observed when the BEZ235 antibiotic-treated A. aegypti mosquitoes were used, indicating that A. aegypti mosquito midgut bacterial flora plays a role in determining their capaCity to carry viral load to the virus [43].