Deciphering mucin degrading ability and safety aspects of enterococcus strain from human feces

Mucus is an integral polydisperse molecule around the epithelium layer throughout the gastrointestinal tract and acts as a nutrition source for gut microbiota. In the present study, three Enterococcus strains, i.e., Enterococcus faecium KS2, Enterococcus faecium KS3, and Enterococcus gallinarum KS4, having mucin degrading ability, were isolated from human feces and identified by metagenomic technique. The cultures exhibited halos when grown in a mucin-containing medium, whereas quantitative data indicated a decrease in oligosaccharide concentration ranging between 28.74 and 73.05%, further confirming its degradation behavior. The physiological properties revealed that E. gallinarum KS4 lacks virulence, whereas E. faecium KS2 and E. faecium KS3 had the virulence factors. All identified isolates could tolerate pH 2.0 for up to three hours and exhibited survivability ranging between 75 and 111%. They also exhibited more than 70% survivability after eight hours against 0.5% (w/v) bile concentration. Antibiotic susceptibility data revealed that the KS2 strain showed susceptibility against 12 out of 26 antibiotics, including tetracycline, chloramphenicol, gentamicin, and kanamycin. At the same time, KS3 did not show susceptibility against ceftazidime, cefixime, and nalidixic, while E. gallinarum KS4 strain was susceptible to all tested antibiotics except cefixime and nalidixic. The study highlights mucin degrading behavior of human-derived Enterococcus strains and physiological traits specifically depicted E. faecium KS2 and KS3 as opportunistic pathogens. However, E. gallinarum KS4 showed promising functional attributes and required to be corroborated using a suitable in-vivo model.