Characterization of a bacteriocin produced by Enterococcus faecium GM‐1 isolated from an infant

Aim:  To partially characterize the bacteriocin produced by the GM‐1 strain of Enterococcus faecium , isolated from the faeces of a newborn human infant. Methods and Results:  The bacteriocin produced by E. faecium GM‐1 showed a broad spectrum of activity against indicator strains of Escherichia coli , Staphylococcus aureus , Vibrio spp., Salmonella typhimurium , Listeria monocytogenes , Lactobacillus acidophilus , and Streptococcus thermophilus . Treatment of the GM‐1 bacteriocin with proteolytic enzymes reduced its inhibitory activities. The bacteriocin was stable at 100°C for 20 min and displayed inhibitory activity at neutral pH. The optimal production of bacteriocin from E. faecium GM‐1 was obtained when the culture conditions were pH 6·0–6·5 and 35–40°C. The inhibitory activity of the bacteriocin was not substantially changed by the use of different carbon sources in the media, except when galactose was substituted for glucose. The use of a sole nitrogen source caused a decrease in inhibitory activity. A bacteriocin gene similar to enterocin P was identified from the total DNA of E. faecium GM‐1 by PCR and direct sequencing methods. Conclusion:  E. faecium GM‐1, which was isolated from the faeces of a newborn baby, produces an enterocin P‐like bacteriocin with inhibitory activity against Gram‐positive and Gram‐negative bacteria, including food‐borne pathogens. Significance and Impact of the Study: E. faecium GM‐1, isolated from infant faeces, produces a new bacteriocin that is similar to enterocin P. This bacteriocin is heat stable and has a broad antibacterial spectrum that includes both Gram‐positive and Gram‐negative bacteria.