Antipathogenic and probiotic potential of enterococci found in the entrails of the palmetto bug.

Insects that live in a microbially rich environment have a distinct gut microbiota that gives various benefits to the host, including infection-resistant metabolites. The current study isolated and assessed putative probiotic enterococcal strains from the guts of Periplaneta americana found in household sewage systems, utilizing biochemical and molecular biological approaches. The enterococcal strains demonstrated intense antibacterial activity against many Gram-positive and Gram-negative human infections. The active compound responsible for antimicrobial activity was lactic acid in strains NPL1311 and NPL1312 and a proteinaceous moiety in strain NPL1314; both exhibited lytic activity against pathogens and demonstrated thermotolerance and stability during refrigerated storage conditions. In vitro testing revealed that the strains lacked deleterious enzyme activities, had no adverse effect on the gut mucosal barrier, and lacked potentially transferable antibiotic resistance genes. Select enterococcal strains were tested for probiotic properties and demonstrated good resistance to human oral, gastric, and intestinal stressors. The two strains also showed bile salt deconjugation, hypocholesterolemic and antioxidant potential, ability to break down lactose, and a suite of enzymes of industrial interest. The prospective probiotic strains were also metabolically versatile, allowing them to thrive on diverse carbohydrate substrates, enhancing their chances of competing and surviving in new gut environs. When tested under physiologically gut-relevant conditions mimicking shear flow, the putative probiotic strains could adhere to mucosal surfaces, implying better colonization potential. Due to their significant probiotic qualities, the E. faecium strains reported here should be researched further using genomic and in vivo techniques for clinical therapy and functional foods. [ABSTRACT FROM AUTHOR]