Objective: To collect intestinal lactobacilli in healthy infants and to characterize them biochemically for further studies.
Methods: Lactobacilli were isolated from the fecal samples collected from total 41 of 1-4 month old healthy infants with culture method by selective medium. After morphological observation and oxygen test, the isolates were tested for their abilities to use 50 carbohydrate and identified with API 50 CHL system and 16 S RNA sequencing. The isolates were also detected for their 19 enzyme activities with API ZYM system.
Results: A total of 71 Lactobacillus strains were successfully isolated and well identified, including L. paracasei( 42. 3%), L. gasseri( 18. 3%), L. salivarius( 14. 1%), L. brevis( 5. 6%), L. rhamnosus( 4. 2%), L. fermentum( 1. 4%), L. plantarum( 1. 4%) and other species( 12. 7%). The seven species of Lactobacillus had strong ability of utilizing carbohydrate. Except for 14 carbohydrates that could not be fermentable, 4 kinds of carbohydrates could be metabolized by all lactobacilli from the seven species, and the other 31 kinds of carbohydrates were metabolized differently among species. Most lactobacilli were active on Leucine arylamidase, Galactosidase and Glucosidase, while other enzyme activities were species-specific and strains-specific.
Conclusion: L. paracasei, L. gasseri and L. salivarius could be considered as dominant species of 1-4 months healthy infants. However, the carbohydrate utilization and enzyme activities of the fecal lactobacilli might be species and strain dependent.
Keywords: carbohydrate; enzyme activity; infant; lactobacilli.