Enzymatic, antimicrobial, and leishmanicidal bioactivity of gram-negative bacteria strains from the midgut of , an insect vector of leishmaniasis in Colombia.

Knowledge regarding new compounds, peptides, and/or secondary metabolites secreted by bacteria isolated from the intestine of phebotominae has the potential to control insect vectors and pathogens (viruses, bacteria, and parasites) transmitted by them. In this respect, twelve Gram-negative bacteria isolated from the intestine of were selected and screened for their enzymatic, antimicrobial, and leishmanicidal activity. , and exhibited enzymatic activity. 83.3% of the isolates displayed lipolytic and nitrate reductase activity and 58.3% of the isolates displayed protease activity. Hemolytic activity (17%) was identified only in , and , and showed cellulolytic activity. , , and showed amylolytic activity. In general, the totality of methanolic extracts exhibited antimicrobial activity, where , , and presented the highest activity against the evaluated reference bacteria strains. Cell-free supernatants (CFS) of the Gram-negative bacteria showed higher growth inhibitory activity against the reference Gram-positive bacteria. The CFS of was the most active antimicrobial in this study, against (AA = 95.12%) and (AA = 86.90%). The inhibition percentages of CFS against Gram-positive bacteria showed statistically significant differences (repeated measure ANOVA 2; 6.095; 0.007832). The methanolic extract showed leishmanicidal activity (CE-50 μg/ml = 47.7 + 3.8) against metacyclic promastigotes of (UA301). Based on this finding, we discuss the possible implications of these bacteria in digestion and physiological processes in the intestine. , and were considered the most promising bacteria in this study and they could potentially be used for biological control.