Cultured skin microbiota attracts malaria mosquitoes

Abstract

BackgroundHost-seeking of the African malaria mosquito, Anopheles gambiae sensu stricto, is guided by human odours. The precise nature of the odours, and the composition of attractive blends of volatiles, remains largely unknown. Skin microbiota plays an important role in the production of human body odours. It is hypothesized that host attractiveness and selection of An. gambiae is affected by the species composition, density, and metabolic activity of the skin microbiota. A study is presented in which the production and constituency of volatile organic compounds (VOCs) by human skin microbiota is examined and the behavioural responses of An. gambiae to VOCs from skin microbiota are investigated.MethodsBlood agar plates incubated with skin microbiota from human feet or with a reference strain of Staphylococcus epidermidis were tested for their attractiveness to An. gambiae in olfactometer bioassays and indoor trapping experiments. Entrained air collected from blood agar plates incubated with natural skin microbiota or with S. epidermidis were analysed using GC-MS. A synthetic blend of the compounds identified was tested for its attractiveness to An. gambiae. Behavioural data were analysed by a χ2-test and GLM. GC-MS results were analysed by fitting an exponential regression line to test the effect of the concentration of bacteria.ResultsMore An. gambiae were caught with blood agar plates incubated with skin bacteria than with sterile blood agar plates, with a significant effect of incubation time and dilution of the skin microbiota. When bacteria from the feet of four other volunteers were tested, similar effects were found. Fourteen putative attractants were found in the headspace of the skin bacteria. A synthetic blend of 10 of these was attractive to An. gambiae.ConclusionsThe discovery that volatiles produced by human skin microorganisms in vitro mediate An. gambiae host-seeking behaviour creates new opportunities for the development of odour-baited trapping systems. Additionally, identification of bacterial volatiles provides a new method to develop synthetic blends, attractive to An. gambiae and possibly other anthropophilic disease vectors.

Behavioural responses to human skin extracts and antennal phenotypes of sylvatic first filial generation and long rearing laboratory colony Rhodnius prolixus

“…2). These results emphasised the idea that the biting behaviour of R. prolixus, similarly to Anopheles gambiae (Takken & Knols 1999, Enserink 2002, Verhulst et al 2009), is not a random process and is clearly influenced by the bacteria present on the skin. The importance of the Rhodnius-bacteriahuman face interaction was confirmed here for Chagas disease transmission (Figs 2, 3).…”

Diagnosis of Tuberculosis by Trained African Giant Pouched Rats and Confounding Impact of Pathogens and Microflora of the Respiratory Tract

“…A wide variety of compounds occurring in M. tuberculosis strains may serve as basis for the odor detection. We identified volatiles shared by M. tuberculosis, Nocardia spp., Streptomyces spp., and Rhodococcus sp., for example, 2-phenylethanol or 2-hydroxy-3-pentanone (Table 3), which are also produced by other microbial species (28,29,37,41) and hence cannot be regarded as specific markers for M. tuberculosis. For example, aciphyllene, which is a known sesquiterpene from the endophytic fungus Muscodor albus (3), is a typical volatile compound of Nocardia spp.…”

Olfaction in vector-host interactions

“…Moreover, MM-X traps baited with a blend of 10 compounds present in the headspace of human feet microbiota (1-butanol, 2,3-butanedione, 2-methyl-1-butanol, 2-methylbutanal, 2-methylbutanoic acid, 3-hydroxy-2-butanone, 3-methyl-1-butanol, 3-methylbutanal, 3-methylbutanoic acid, benzeneethanol) caught significantly more An. gambiae during indoor trapping experiments than unbaited traps (Verhulst et al 2009). …”

“…gambiae. Identifying volatile compounds produced by microorganisms present on human skin revealed 10 putative attractants for this mosquito species (Verhulst et al 2009). …”