Isolation and identification of Lactic Acid Bacteria in the people's mouth and studying on their inhibitory effect on some entropathogenic bacteria

Subject Areas : Medical Microbiology

Jamileh Noroozi ¹ , Anita Khanafari ² , Shirin Beiglari ³

1 - Iran University of Medical Sceinces, Tehran, Iran
2 - Science Faculty, Azad University North Branch, Tehran, Iran
3 - Science Faculty, Azad University North Branch, Tehran, Iran

Received: 2008-11-15 Accepted : 2009-01-14 Published : 2009-01-01

Keywords: Lactobacillus, Streptococcus mutans, Mouth, Inhibitory effect,

Abstract :

Background and objectives: Predominant organisms in plaques are of the genus Streptococcus, with Streptococcus mutans being the species most important in the formation of dental caries. Another organism that is important in the development of caries is the lactobacillus. Lactobacillus species are not important in the initiation of caries but in the continuation. The aim of this study was to isolate and identify of lactic acid bacteria from the mouth in different ages, determination of pH and study the inhibitory effect of isolated Lactobacilli on some entropathogens bacteria (Salmonella, Shigella and Escherchia coli). Material and Methods: From 75 persons in different ages, the samples were collected from saliva and around dental and were cultured in MRS medium. Lactobacilli and Streptococci were isolated and identified by standard methods (morphology, microscopic shape and chemical characteristics and fermentation of carbohydrates). Growth pH of isolated Lactobacillus was determined. Inhibitory effects of isolated bacteria were evaluated by spot on the lawn, blank disk and well-diffusion methods on Salmonella, Shigella and Escherichia coli. Results: Isolated Lactobacillus were including L. fermentum, L. casei, L. gasseri, L. brevis, L. plantarum and L. acidophilus, and isolated Streptococci was Streptococcus mutans. Isolated Lactobacilli had inhibitory effect on Escherichia coli but they didn't have any inhibitory effect on Salmonella and Shigella. Conclusion: Our results showed that some Lactobacilli had inhibitory effect on some pathogenic in vitro. So, consumption of dairy (because of the presence of Lactobacilli) is recommended.