Oral bacteria may offer probiotic potential against upper respiratory infections

They detail their findings in the June 2010 issue of the journal Applied and Environmental Microbiology.

Although internal communication between human hosts and their microbes is only minimally understood, probiotics are live microorganisms thought to promote health within their host. So far, the benefits of probiotics have been predominantly explored in the intestinal tract, however, other initial studies suggest probiotics may contribute to wellness in the stomach, vaginal tract, skin and mouth.

Upper respiratory tract infections are the leading cause of visits to the pediatrician, especially in children between the ages of 5 and 12. Streptococcus pyogenes is one of the main causes associated with such infections and antibiotics are the only treatment currently available with prescription rates running as high as 90%.

"A probiotic strategy effective in the prophylaxis of pharyngitis, therefore, could provide a significant social benefit," say the researchers.

Bacteria newly isolated from the mouths of healthy volunteers were analyzed and two potential probiotic bacterial strains, Streptococcus salivarius RS1 and ST3, were identified. Following comparison with a recently developed oral probiotic prototype, S. salivarius strain K12, all three bound to human pharyngeal cells and antagonized S. pyogenes adhesion and growth. Additionally, all were sensitive to antibiotics routinely used for treating upper respiratory tract infections.

"We suggest that the selected commensal streptococci represent potential pharyngeal probiotic candidates," say the researchers. "They could display a good degree of adaptation to the host and possess potential immunomodulatory and anti-inflammatory properties."