TITLE:
Antagonistic Effect of Bacteria Isolated from the Digestive Tract of Lutzomyia evansi against Promastigotes of Leishmania infantum, Antimicrobial Activities and Susceptibility to Antibiotics
AUTHORS:
Rafael J. Vivero Gómez, Gloria E. Cadavid Restrepo, Claudia X. Moreno Herrera, Victoria Ospina, Sandra I. Uribe, Sara M. Robledo
KEYWORDS:
Intestinal Microbiota, Leishmanicidal Activity, Antimicrobial Activity, Antibiotic Susceptibility
JOURNAL NAME:
Advances in Microbiology,
Vol.6 No.10,
September
2,
2016
ABSTRACT: Lutzomyia evansi is
a phlebotomine insect endemic to Colombia’s Caribbean coast and is considered the
main vector of visceral and cutaneous leishmaniasis in the region. Specific studies
of the direct effects generated by bacteria in the digestive tract of the insect
vectors, under Leishmania infantum using in vitro models, represent
a novel alternative as a control strategy for the transmission of leishmaniasis
and also provide the opportunity to detect natural products or antimicrobial peptides
with different biological activities. In this study, we evaluate the leishmanicidal
and antimicrobial activities of Pantoea ananatis, Ochrobactrum anthropi and Enterobacter cloacae, isolated from the digestive tract of Lutzomyia evansi and the susceptibility
of these bacteria to commonly used antibiotics. The antagonistic effect of Pantoea ananatis, Ochrobactrum anthropi and Enterobacter cloacae was evaluated
against six species of human pathogenic bacteria and against stationary (Metacyclic-like)
and exponential promastigotes (Procyclic-like) of Leishmania infantum (BCN-GFP
strain) by co-culture assays for 24 hours. The activity of the bacterial isolates
on Leishmania infantum promastigotes was quantified by flow cytometry. The susceptibility
of the bacterial strains to clinically used antibiotics was analyzed by antibiogram.
The highest percentage of inhibition was observed against exponential promastigotes
with bacterial concentrations of 108 CFU/ml of Enterobacter cloacae (77.29%
± 0.6%) and Pantoea ananatis (70.17% ± 1.1%). The extracts produced
by three bacterial isolates showed similar biological activity
(13 mm - 22 mm inhibition halos) against all tested bacteria; however, significant
differences were observed with respect to gram-positive bacteria (P Bacillus cereus. Ochrobactrum anthropi was the isolate with the highest
number of antibiotic resistance patterns while Pantoea ananatis and Enterobacter cloacae showed greater susceptibility to the evaluated antibiotics.
The growth inhibitory activity of exponential Leishmania infantum promastigotes
shown by extracts of Enterobacter cloacae and Pantoea ananantis suggests
that the presence of these bacteria in the vector intestine may affect the parasite
development to metacyclic stages, infective to human hosts. This in turn confers
said bacteria, a potential in controlling the transmission of Leishmania spp. that deserves to be studied
in depth.