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Chapter 6 : Streptococci as Effector Organisms for Probiotic and Replacement Therapy
Category: Clinical Microbiology
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This chapter examines the involvement of members of the genus Streptococcus as probiotics or as candidates for replacement therapy. Some researchers have turned to the development of replacement therapy strategies using relatively harmless indigenous streptococci as oral and nasopharyngeal probiotics, since (it is reasoned) these should have greater colonization potential than lactobacilli and bifidobacteria for these target tissues. The emphasis of the chapter is largely on current knowledge of the contribution of dedicated interbacterial inhibitors, the bacteriocins and bacteriocin-like inhibitory substances (BLIS), to the efficacy of streptococci as potential probiotics. It lists some of the practical factors such as safety, stability, formulation, colonization efficacy, and health benefits that may need to be taken into consideration when evaluating oral streptococcal probiotics. Acid resistance and adhesion to intestinal mucosa are desirable characteristics for traditional probiotics. For streptococcal probiotics targeting the oral cavity, acid tolerance is not a critical factor. Chronic multispecies bacterial infections of the oral cavity (e.g., dental caries, periodontal disease, and halitosis) are endemic, expensive to treat, and recalcitrant to conventional preventative protocols. These infections appear typically to be caused by the collective actions of more than one organism—the microbial community producing damage that individual microorganisms are probably incapable of inflicting. Intestinal probiotics are widely accepted for microbial population replacement and recolonization of the gastrointestinal tract, and a variety of beneficial strains are now inexpensively provided for the consumer.
Illustration of the four classes of bacteriocins produced by gram-positive bacteria with examples currently known to be produced by streptococci. Footnotes: 1, Beukes et al., 2000 ; 2, Chikindas et al., 1995 ; 3, Georgalaki et al., 2002 ; 4, Hale et al., 2004 ; 5, Hale et al., 2005a , 2005b ; 6, Heng et al., 2004 ; 7, Heng et al., 2006a ; 8, Heng et al., 2007a ; 9, Hillman et al., 1998 ; Smith et al., 2003 ; 10, Hyink et al., 2005 ; 11, Hyink et al., 2007 ; 12, Jack et al., 1994a , 1994b ; 13, Mantovani et al., 2002 ; 14, Marciset et al., 1997 ; 15, Mota-Meira et al., 1997 ; 16, Qi et al., 2001 ; 17, Qi et al., 2000 ; 18, Qi et al., 1999 ; 19, Robson et al., 2007 ; 20, Simmonds et al., 1996 ; 21, Ward and Somkuti, 1995 ; 22, Wescombe and Tagg, 2003 ; 23, Wescombe et al., 2006b ; Ross et al., 1993 ; 24, Whitford et al., 2001 ; 25, R. E. Wirawan, N. C. K. Heng, R. W. Jack, and J. R. Tagg, abstr. B14, 7th ASM Conference on Streptococcal Genetics, St. Malo, France, 2006; 26, Wirawan et al., 2006 ; 27, Wirawan et al., 2007 ; 28, Xiao et al., 2004 ; 29, Yonezawa and Kuramitsu, 2005 ; 30, Wescombe et al., unpublished (GenBank accession no. DQ889747); 31, Heng et al., 2006b .
Overview of the proposed role of S. salivarius in regulating population dynamics in the oral cavity. 1, megaplasmid transfer to other S. salivarius; 2, complete loss of megaplasmid and related function(s); 3, mutation(s) in specific loci resulting in loss of certain function(s); 4, acquisition and/or transfer of ecologically relevant loci between S. salivarius K12 and other streptococci; 5, potential superinfecting microbes. Filled arrows indicate expression of ecologically relevant loci; complete arrows (filled and unfilled) indicate observed phenotypic changes; dashed, unfilled arrows (containing question marks) indicate hypothetical processes. (Courtesy of R.W. Jack.)
Characteristics of streptococci having potential relevance to their use as oral probiotics
Major considerations when developing a new probiotic