The Enterococcus secretome inhibits the growth of Mycobacterium tuberculosis complex mycobacteria.

Enterococcus mundtii ( E. mundtii ), a commensal intestinal bacterium, was demonstrated to inhibit the growth of some Mycobacterium tuberculosis ( M. tuberculosis ) complex (MTC) species that cause tuberculosis in humans and mammals. To further expand this preliminary observation, we cross-investigated five E. mundtii strains and seven MTC strains representative of four MTC species using a standardized quantitative agar well diffusion assay. All five E. mundtii strains, calibrated at 3.10 9 colony forming units/mL, inhibited the growth of all M. tuberculosis strains with various susceptibility profiles, but no inhibition was observed with lower inoculums. Further, 9 Enterococcus species freeze-dried cell-free culture supernatants (CFCS) including Enterococcus avium, Enterococcus devriesei , Enterococcus durans , Enterococcus dispar , Enterococcus hirae , Enterococcus casseliflavus , Enterococcus faecalis , Enterococcus faecium , and E. mundtii, inhibited the growth of M. tuberculosis , Mycobacterium africanum ( M. africanum ), Mycobacterium bovis ( M. bovis ) and Mycobacterium canettii ( M. canettii ), the most susceptible MTC species (inhibition diameter 25 ±1 mm), proportionally to CFCS protein concentrations. Data reported here indicated that the Enterococcus secretome inhibits growth of main MTC species of medical interest, which broadens previously reported data. In the gut, the Enterococcus secretome may modulate the expression of tuberculosis, exhibiting an anti-tuberculosis effect, with some protective roles in human and animal health.