Pintomyia evansi is recognized by its vectorial competence in the transmission of parasites that cause fatal visceral leishmaniasis in rural and urban environments of the Caribbean coast of Colombia. The effect on and the variation of the gut microbiota in female
P. evansi infected with
Leishmania infantum were evaluated under experimental conditions using 16S rRNA Illumina MiSeq sequencing. In the coinfection assay with
L. infantum, 96.8% of the midgut microbial population was composed mainly of Proteobacteria (71.0%), followed by Cyanobacteria (20.4%), Actinobacteria (2.7%), and Firmicutes (2.7%). In insect controls (uninfected with
L. infantum) that were treated or not with antibiotics,
Ralstonia was reported to have high relative abundance (55.1–64.8%), in contrast to guts with a high load of infection from
L. infantum (23.4–35.9%). ASVs that moderately increased in guts infected with
Leishmania were
Bacillus and
Aeromonas. Kruskal–Wallis nonparametric variance statistical inference showed statistically significant intergroup differences in the guts of
P. evansi infected and uninfected with
L. infantum (
p < 0.05), suggesting that some individuals of the microbiota could induce or restrict
Leishmania infection. This assay also showed a negative effect of the antibiotic treatment and
L. infantum infection on the gut microbiota diversity. Endosymbionts, such as Microsporidia infections (<2%), were more often associated with guts without
Leishmania infection, whereas
Arsenophonus was only found in guts with a high load of
Leishmania infection and treated with antibiotics. Finally, this is the first report that showed the potential role of intestinal microbiota in natural populations of
P. evansi in susceptibility to
L. infantum infection.
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