Bacteriocin-like inhibitory substance (BLIS) production by the normal flora of the nasopharynx: potential to protect against otitis media?

Abstract

The normal bacterial flora of the upper airways provides an important barrier to invading pathogens. This study investigated the production of bacteriocin-like inhibitory substances (BLIS) by streptococci isolated from the nasopharyngeal flora of children who either do or do not experience recurrent acute otitis media (AOM). Twenty children with recurrent AOM and 15 controls were tested. Swabs from the nasopharynx were evaluated for streptococci having BLIS activity against two representative strains of each of the AOM pathogens Streptococcus pneumoniae, Streptococcus pyogenes, Haemophilus influenzae and Moraxella catarrhalis. Streptococci displaying strong BLIS activity were characterized further and tested for known streptococcal bacteriocin structural genes. Sixty-five per cent of children had nasopharyngeal streptococcal isolates that were inhibitory to strains of one or more of the AOM pathogens. Six children (17 %) had streptococci that demonstrated strong BLIS activity against strains of at least three of the pathogenic species. Three of these inhibitory isolates were Streptococcus salivarius, two were S. pneumoniae and one was S. pyogenes. The inhibitory S. salivarius and S. pyogenes were shown to have structural genes for known streptococcal bacteriocins. No statistically significant difference was found between the two groups of children with respect to the presence of inhibitory streptococci in their nasopharyngeal floras. The finding of S. salivarius with strong inhibitory activity against several AOM pathogens in the nasopharyngeal flora of children is unique. Although there is no clear evidence from the present study that these organisms protect against AOM, their low pathogenicity and strong in-vitro BLIS production capability indicate that they should be incorporated in future trials of bacteriotherapy for recurrent AOM.

Effect of Streptococcus salivarius K12 on the In Vitro Growth of Candida albicans and Its Protective Effect in an Oral Candidiasis Model

“…While there are various reports on the antibacterial activities of S. salivarius K12 and other strains with bacteriocin action in the literature (28,30,31), Candida albicans was not directly inhibited by bacteriocin action, and it appears that yeast cell-to-bacterial cell contact may be required. In this study, S. salivarius K12 directly interacted with Candida, as demonstrated by in vitro assays, and also showed a protective effect in a murine model of Candida infection.…”

Protective Mechanisms of Respiratory Tract Streptococci against Streptococcus pyogenes Biofilm Formation and Epithelial Cell Infection

“…Beneficial roles of probiotic bacteria have already been reported for treatments in the oral cavity (14). Thus far, only a few products became commercially available, e.g., the Streptococcus salivarius strain K-12, which is sold as BLIS lozenges in New Zealand (15), and freeze-dried powders of Lactobacillus rhamnosus plus Bifidobacterium casei and Enterococcus faecalis, which are sold as Symbiolact compositum and Symbioflor, respectively (16,17). Like other probiotics these have three major activity routes.…”

Probiotics in addition to antibiotics for the treatment of acute tonsillitis: a randomized, placebo-controlled study

“…The colonization of indigenous S. salivarius inhibits colonization and overgrowth of competing and pathogenic microorganisms [17]. S. salivarius, isolated from the nasopharynx of children who rarely suffered from throat infections, were found to produce bacteriocins with anti-S. pyogenes activity [18]. Bacteriocin or bacteriocin-like inhibitory substances (BLIS) are peptide molecules produced by Gram-positive bacteria and some genera of Gram-negative bacteria.…”