Investigation of the Bacterial Communities Associated with Females of Lutzomyia Sand Fly Species from South America

Mauricio R V Sant’Anna,Alistair C Darby,James Montoya-Lerma,Paul A Bates,Viv M Dillon,Reginaldo P Brazil,Rod J Dillon,Luciano A Moreira

doi:10.1371/journal.pone.0042531

Mauricio R V Sant’Anna, Alistair C Darby + Show 6 more

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https://doi.org/10.1371/journal.pone.0042531

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Abstract

Phlebotomine sand flies are vectors of Leishmania that are acquired by the female sand fly during blood feeding on an infected mammal. Leishmania parasites develop exclusively in the gut lumen during their residence in the insect before transmission to a suitable host during the next blood feed. Female phlebotomine sand flies are blood feeding insects but their life style of visiting plants as well as animals, and the propensity for larvae to feed on detritus including animal faeces means that the insect host and parasite are exposed to a range of microorganisms. Thus, the sand fly microbiota may interact with the developing Leishmania population in the gut. The aim of the study was to investigate and identify the bacterial diversity associated with wild adult female Lutzomyia sand flies from different geographical locations in the New World. The bacterial phylotypes recovered from 16S rRNA gene clone libraries obtained from wild caught adult female Lutzomyia sand flies were estimated from direct band sequencing after denaturing gradient gel electrophoresis of bacterial 16 rRNA gene fragments. These results confirm that the Lutzomyia sand flies contain a limited array of bacterial phylotypes across several divisions. Several potential plant-related bacterial sequences were detected including Erwinia sp. and putative Ralstonia sp. from two sand fly species sampled from 3 geographically separated regions in Brazil. Identification of putative human pathogens also demonstrated the potential for sand flies to act as vectors of bacterial pathogens of medical importance in addition to their role in Leishmania transmission.

Highlights

Phlebotomine sand flies are responsible for the spread of the medically important Leishmania parasites that populate the female sand fly gut
In Brazil Lutzomyia longipalpis is the main vector for Leishmania infantum, the causative agent of severe visceral leishmaniasis [1]
Characterization of bacteria associated with Lutzomyia by sequencing a portion of the bacterial 16S rRNA gene from clone libraries led to the identification of 38 bacterial sequences through BLAST searches, with 19 distinct bacterial phylotypes (Table 1)

Summary

Introduction

Phlebotomine sand flies are responsible for the spread of the medically important Leishmania parasites that populate the female sand fly gut. In Brazil Lutzomyia longipalpis is the main vector for Leishmania infantum, the causative agent of severe visceral leishmaniasis [1]. The macro-ecology of the infection cycle for Leishmania infantum is complex; in this case Lu. longipalpis is the vector, domestic dogs are the main reservoir hosts in urban environments with humans as the accidental hosts [3]. Commonly termed ‘blood feeding insects’, adult sand flies are plant-feeders; only the female requires occasional blood as a protein source for egg production. Both males and females visit plants to acquire carbohydrates where they will acquire plant phyllosphere microbiota [4] which may be ingested directly into the gut after piercing leaves and stems [5]. Many of the microorganisms ingested by the larvae will be killed during the pupal stage (when the larval gut is reabsorbed) but some may survive pupation to re-colonise the adult gut [6]

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