Institut de Recherche en Sciences de La Santé (IRSS) / Centre Muraz, Bobo Dioulasso, Burkina Faso.
Université Nazi Boni / Centre Muraz, Bobo-Dioulasso, Burkina Faso.
Malar J. 2020 Oct 2;19(1):352. doi: 10.1186/s12936-020-03420-4.
This is now a concern that malaria eradication will not be achieved without the introduction of novel control tools. Microbiological control might be able to make a greater contribution to vector control in the future. The interactions between bacteria and mosquito make mosquito microbiota really promising from a disease control perspective. Here, the impact of Chromobacterium violaceum infections, isolated from both larvae and adult of wild-caught Anopheles gambiae sensu lato mosquitoes in Burkina Faso, was evaluated on mosquito survival, blood feeding and fecundity.
To assess entomopathogenic effects of C. violaceum infection on mosquitoes, three different types of bioassays were performed in laboratory. These bioassays aimed to evaluate the impact of C. violaceum infection on mosquito survival, blood feeding and fecundity, respectively. During bioassays mosquitoes were infected through the well-established system of cotton ball soaked with 6% glucose containing C. violaceum.
Chromobacterium violaceum kills pyrethroid resistant Anopheles coluzzii (LT80 of 8.78 days ± 0.18 at 10 bacteria cell/ml of sugar meal). Interestingly, this bacterium had other negative effects on mosquito lifespan by significantly reducing (~ 59%, P < 0.001) the mosquito feeding willingness from day 4-post infection (~ 81% would seek a host to blood feed) to 9- day post infection (22 ± 4.62% would seek a host to blood feed). Moreover, C. violaceum considerably jeopardized the egg laying (~ 16 eggs laid/mosquito with C. violaceum infected mosquitoes vs ~ 129 eggs laid/mosquito with control mosquitoes) and hatching of mosquitoes (a reduction of ~ 22% of hatching rate with C. violaceum infected mosquitoes). Compared to the bacterial uninfected mosquitoes, mosquitoes infected with C. violaceum showed significantly higher retention rates of immature eggs and follicles.
These data showed important properties of Burkina Faso C. violaceum strains, which are highly virulent against insecticide-resistant An. coluzzii, and reduce both mosquito blood feeding and fecundity propensities. However, additional studies as the sequencing of C. violaceum genome and the potential toxins secreted will provide useful information render it a potential candidate for the biological control strategies of malaria and other disease vectors.
人们越来越担心，如果不引入新的控制手段，疟疾根除工作将无法完成。微生物控制可能在未来对病媒控制做出更大的贡献。从疾病控制的角度来看，细菌与蚊子之间的相互作用使蚊子的微生物组具有很大的潜力。在这里，评估了从布基纳法索野生捕获的按蚊 sensu lato 的幼虫和成虫中分离出的紫罗兰色噬菌体能对蚊子的生存、吸血和繁殖能力产生怎样的影响。
为了评估 C. violaceum 感染对蚊子的昆虫病原效应，在实验室中进行了三种不同类型的生物测定。这些生物测定旨在分别评估 C. violaceum 感染对蚊子存活率、吸血和繁殖的影响。在生物测定过程中，通过用 6%葡萄糖浸泡的棉花球将 C. violaceum 感染到蚊子中。
紫罗兰色噬菌体能杀死对拟除虫菊酯有抗性的按蚊（LT80 为 10 个细菌细胞/ml 糖餐中的 8.78 天±0.18）。有趣的是，这种细菌通过显著降低（59%，P<0.001）感染后第 4 天（81%的蚊子会寻找宿主吸血）到第 9 天（22±4.62%的蚊子会寻找宿主吸血）的蚊子取食意愿，对蚊子的寿命产生了其他负面影响。此外，C. violaceum 极大地危及了蚊子的产卵能力（感染 C. violaceum 的蚊子产卵数约为 16 个/只，而对照蚊子产卵数约为 129 个/只）和孵化率（感染 C. violaceum 的蚊子孵化率降低了约 22%）。与未感染细菌的蚊子相比，感染 C. violaceum 的蚊子的不成熟卵和卵泡保留率明显更高。
这些数据显示了布基纳法索 C. violaceum 菌株的重要特性，这些菌株对杀虫剂抗性的 An. coluzzii 具有高度毒力，并降低了蚊子的吸血和繁殖倾向。然而，进一步的研究，如 C. violaceum 基因组的测序和潜在毒素的分泌，将提供有用的信息，使其成为疟疾和其他病媒生物控制策略的潜在候选者。
