The component peptides of lacticin 3147 were degraded by ␣-chymotrypsin in vitro with a resultant loss of antimicrobial activity. Activity was also lost in ileum digesta. Following oral ingestion, neither of the lacticin 3147 peptides was detected in the gastric, jejunum, or ileum digesta of pigs, and no lacticin 3147 activity was found in the feces. These observations suggest that lacticin 3147 ingestion is unlikely to have adverse effects, since it is probably inactivated during intestinal transit.Lacticin 3147 is a lantibiotic produced by Lactococcus lactis (16,23). Its antimicrobial activity is mediated by the combined action of its component peptides, LtnA1 and LtnA2 (29). Like other bacteriocins, lacticin 3147 has a number of potential applications for both food and biomedicine (8). In particular, it offers advantages for use in foods, and previous studies have demonstrated its efficacy, both as a food biopreservative and in improving food quality (9, 27). While its broad spectrum offers certain advantages, it may also be a cause for concern, given that it has inhibited all gram-positive bacteria tested to date, including prominent members of the resident gut microbiota such as Lactobacillus, Enterococcus, and Streptococcus spp. (23). Indeed, the direct addition of lacticin 3147 to a human fecal fermentation gut model causes a dramatic reduction in gram-positive populations after only 30 min (22). Consequently, the ingestion of lacticin 3147 or other broad-spectrum bacteriocins in foods has the potential to perturb the commensal gut microbiota. Therefore, as part of a risk assessment for bacteriocins with potential applications in foods, it is important to determine their fate in the gastrointestinal tract (GIT) in vivo. This type of information is also important when considering potential therapeutic applications of orally delivered bacteriocins. This study evaluates the fate of lacticin 3147 in the digestive tract, initially by means of in vitro/ex vivo simulation studies and subsequently in vivo using the pig as a model. A food-grade lacticin 3147 ingredient developed in our laboratory to facilitate food applications was employed (17,18). This spray-dried lacticin 3147 skim milk powder was manufactured as described previously (22) and reconstituted (10%, wt/vol) in sterile distilled water to prepare the reconstituted lacticin 3147 skim milk (RLSM) used in experiments.To test lacticin 3147's sensitivity to a range of proteolytic enzymes representative of those found in the mammalian GIT, RLSM was incubated at 37°C for 3 h with 25 mg/ml trypsin,

Aims:  To isolate and characterise Streptococcus mutans from Irish saliva samples and to assess their sensitivity to a food‐grade preparation of the lantibiotic, lacticin 3147, produced by Lactococcus lactis DPC3147. Methods and Results:  Saliva samples collected from children with varying oral health status were screened on Mitis Salivarius agar for the presence of pathogenic streptococci. Following selective plating, 16S rDNA sequencing and Pulsed Field Gel Electrophoresis (PFGE), 15 distinct strains of Strep. mutans were identified. These were grouped according to their relative sensitivity to lacticin 3147 which ranged from 0·78 to 6·25%; relative to a sensitive indicator strain, Lactococcus lactis ssp. lactis HP. Inhibition of indicator Strep. mutans strains from sensitive, intermediate and tolerant groupings were assessed in microtitre plate assays with increasing concentrations of lacticin 3147. The concentration of lacticin 3147 required to give 50% growth inhibition correlated with their relative sensitivities (as assayed by well diffusion methodology) and ranged from 1280 to 5120 AU ml−1. Concentrated preparations of lacticin 3147 caused a rapid killing of Strep. mutans strains in broth. Moreover, in human saliva deliberately spiked with Strep. mutans, the pathogen was eliminated (initial inoculum of 105) in the presence of 40 000 AU ml−1 of lacticin 3147. Furthermore, a food‐grade lacticin 3147 spray dried powder ingredient was assessed for the inhibition of Strep. mutans in human saliva, spiked with a strain of intermediate sensitivity, resulting in up to a 4‐log reduction in counts after 20 min. Conclusion:  A food grade preparation of lacticin 3147 was effective in the inhibition of oral Strep. mutans. Significance and Impact of the Study:  The inhibition of oral streptococci by food grade preparations of lacticin 3147 may offer novel opportunities for the development of lacticin 3147 as an anti‐cariogenic agent particularly in the area of functional foods for the improvement of oral health.