Isolation and evaluation of antagonistic activity against pathogenic bacteria by Lactobacillus and Enterococcus spp. from the saliva of Speothos venaticus and Chrysocyon brachyurus

Saliva plays a crucial role in oral defense across mammals by combining host-derived antimicrobial factors with antagonistic indigenous microbiota. Understanding the composition of the oral lactic microbiota in wild canids may provide valuable insights into microbial ecology and animal health. In this study, Lactobacillus and Enterococcus spp. isolated from the saliva of South American bush dogs (Speothos venaticus) and maned wolves (Chrysocyon brachyurus) were enumerated, identified, and evaluated for their antagonistic activity against pathogenic bacteria. For bacterial isolation, MRS agar and BHI agar supplemented with sodium azide (BHI-SA) were used for Lactobacillus and Enterococcus, respectively. Identification of the bacterial isolates was performed using PCR-ARDRA and multiplex PCR. Antagonistic activity was assessed using a double-layer agar diffusion assay, which detects diffusible inhibitory effects without identifying the compounds involved. A total of 23 bacterial isolates were obtained from BHI-SA and 24 from MRS for bush dogs, while 15 were recovered from BHI-SA and 23 from MRS for maned wolves. Salivary bacterial counts ranged from 4.0 to 5.0 log10 CFU/mL. In bush dogs, Enterococcus faecalis and Enterococcus faecium were identified, while E. faecalis and Enterococcus hirae were found in maned wolves. Limosilactobacillus reuteri, Lactiplantibacillus paraplantarum, Lactiplantibacillus plantarum and Lactobacillus johnsonii were isolated from bush dogs, while Ligilactobacillus salivarius and Latilactobacillus curvatus were identified in maned wolves. Antagonistic activity against indicator pathogens was more frequent among Lactobacillus isolates. These results suggest that the antibacterial properties observed in the saliva of these wild canids may be partly attributed to indigenous Lactobacillus and Enterococcus species.