Measuring and reducing biofilm in mosquito rearing containers
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(2020) 13:439 Hunt et al. Parasites Vectors https://doi.org/10.1186/s13071-020-04315-8
Open Access
SHORT REPORT
Measuring and reducing biofilm in mosquito rearing containers Catherine M. Hunt1* , C. Matilda Collins2 and Mark Q. Benedict1
Abstract Background: Mosquito 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. Methods: We 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. Results: We 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. Conclusions: Larva 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. Keywords: Mosquito rearing, Biofilm, Bacteria, Aquaculture, Pathogens
Background 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. In our experience, many insectary staff are reluctant to use detergents for fear of contaminating the containers with any residue that might harm larvae, but we are aware of no systematic efforts to determine how likely this is. Other effects of any change in larval rearing *Correspondence: [email protected] 1 Centers for Disease Control and Prevention (CDC), 1600 Clifton Road, NE, Atlanta, GA 30329‑4027, USA Full list of author information is available at the end of the article
methods are often of concern. For example, two reports have noted that larval exposure to detergents and hydrogen peroxide affected the level of insecticide resistance measured in resulting adults though intergenerational selection for this was not demonstrated [1, 2]. No comparison with the level of trace contamination of cleaners used in mosquito rearing was made. Because mosquito rearing is not aseptic, introduction of pathogens is always a possibi
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