Measuring and reducing biofilm in mosquito rearing containers

Catherine M Hunt,Mark Q Benedict,C Matilda Collins

doi:10.1186/s13071-020-04315-8

Catherine M Hunt, Mark Q Benedict + Show 1 more

Open Access

https://doi.org/10.1186/s13071-020-04315-8

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Abstract

BackgroundMosquito rearing containers contain organic-rich water that nourishes numerous bacteria, some of which are capable of forming biofilms. Biofilm is broadly an extracellular polymeric matrix (EPS) in which living bacteria occur, and the accumulation of biofilm is possible during routine stock-keeping as most of these containers are re-used. Whether biofilm has an effect on the mosquito rearing is not a question that has been investigated, nor have measures to reduce biofilm in this context been systematically studied.MethodsWe measured biofilm accumulation in standard rearing containers by staining with crystal violet and determining the OD using a spectrophotometer. We also treated rearing containers with 0.1% sodium hypochlorite to determine its effectiveness in reducing biofilm abundance. Lastly, we performed an analysis of the relationship between the occurrence of biofilm and the likelihood of microbial blooms that were associated with larval death during trials of larval diets.ResultsWe observed that soaking rearing containers overnight in 0.1% sodium hypochlorite greatly reduced biofilm, but we observed no relationship between the use of containers that had not been treated with bleach and subsequent microbial blooms.ConclusionsLarva rearing leaves detectable biofilm. While we were unable to correlate microbial blooms with the presence of biofilm, as a precaution, we recommend that plastic containers that are re-used be treated with 0.1% sodium hypochlorite occasionally.

Highlights

Mosquito rearing containers contain organic-rich water that nourishes numerous bacteria, some of which are capable of forming biofilms
We report the results of a simple method to detect biofilm in mosquito rearing containers and the effect of bleaching on removing biofilm
Food type and quantity There was no evidence of interactions between the species of mosquito being reared, the quantity or the type of food found in these data (P > 0.01 in all cases) affecting the measured abundance of biofilm

Summary

Introduction

Mosquito rearing containers contain organic-rich water that nourishes numerous bacteria, some of which are capable of forming biofilms. Whether biofilm has an effect on the mosquito rearing is not a question that has been investigated, nor have measures to reduce biofilm in this context been systematically studied. By far the most common containers used for rearing mosquito larvae are plastic or metal trays. These are usually re-used and may be cleaned in a number of ways including with detergent or water alone, and they are sometimes treated with bleach or autoclaved after washing. Because mosquito rearing is not aseptic, introduction of pathogens is always a possibility.

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