StreptococcusAdherence and Colonization

Abstract

SUMMARY Streptococci readily colonize mucosal tissues in the nasopharynx; the respiratory, gastrointestinal, and genitourinary tracts; and the skin. Each ecological niche presents a series of challenges to successful colonization with which streptococci have to contend. Some species exist in equilibrium with their host, neither stimulating nor submitting to immune defenses mounted against them. Most are either opportunistic or true pathogens responsible for diseases such as pharyngitis, tooth decay, necrotizing fasciitis, infective endocarditis, and meningitis. Part of the success of streptococci as colonizers is attributable to the spectrum of proteins expressed on their surfaces. Adhesins enable interactions with salivary, serum, and extracellular matrix components; host cells; and other microbes. This is the essential first step to colonization, the development of complex communities, and possible invasion of host tissues. The majority of streptococcal adhesins are anchored to the cell wall via a C-terminal LPxTz motif. Other proteins may be surface anchored through N-terminal lipid modifications, while the mechanism of cell wall associations for others remains unclear. Collectively, these surface-bound proteins provide Streptococcus species with a “coat of many colors,” enabling multiple intimate contacts and interplays between the bacterial cell and the host. In vitro and in vivo studies have demonstrated direct roles for many streptococcal adhesins as colonization or virulence factors, making them attractive targets for therapeutic and preventive strategies against streptococcal infections. There is, therefore, much focus on applying increasingly advanced molecular techniques to determine the precise structures and functions of these proteins, and their regulatory pathways, so that more targeted approaches can be developed.

Two-component signal transduction systems in oral bacteria

“…Although S. mitis and S. sanguinis are pioneer colonizers of teeth, S. sanguinis is mostly restricted to dental surfaces, while S. mitis is abundant in a large range of mucosal and tooth sites, and may persist in significant numbers in biofilms associated with caries [83,84], a consequence of the high level of genetic heterogeneity within the species [85,86]. On the other hand, Mutans species S. mutans and S. sobrinus show a low abundance in health-associated biofilms and are poor initiators of tooth colonization [82], but predominate in biofilm communities in the presence of sucrose and acidic environments promoting the growth of the acidogenic and aciduric microbiota associated with dental caries [14,87,88]. Sequence homology analyses reveal that different streptococcal species including S. gordonii , S. sanguinis , and S. mutans share several TCSs controlling functions for bacterial persistence in the oral cavity [87,89].…”

“…On the other hand, Mutans species S. mutans and S. sobrinus show a low abundance in health-associated biofilms and are poor initiators of tooth colonization [82], but predominate in biofilm communities in the presence of sucrose and acidic environments promoting the growth of the acidogenic and aciduric microbiota associated with dental caries [14,87,88]. Sequence homology analyses reveal that different streptococcal species including S. gordonii , S. sanguinis , and S. mutans share several TCSs controlling functions for bacterial persistence in the oral cavity [87,89]. However, molecular studies indicate that even highly conserved TCS, e.g.…”

Autoinducer-2 influences interactions amongst pioneer colonizing streptococci in oral biofilms

“…Such physical and chemical interactions are important when considering the development of dental-plaque biofilms because both Streptococcus gordonii and Streptococcus oralis are indigenous commensal species that are among the first to colonize clean tooth surfaces (Aas et al, 2005;Diaz et al, 2006;Nyvad & Kilian, 1987;Socransky et al, 1977). S. gordonii and S. oralis belong to a genus that has been referred to as containing 'pioneering colonizers' (Kolenbrander et al, 1990) and these species are consistently isolated from dental-plaque biofilm communities, albeit at different relative amounts (Nobbs et al, 2009;Paster et al, 2006;Whittaker et al, 1996). The two species coaggregate with each other and numerous other oral species through complex adhesin-receptor mechanisms (Kolenbrander et al, 2002;Nobbs et al, 2009) and both have also recently been demonstrated to produce AI-2 (Blehert et al, 2003;McNab et al, 2003;Rickard et al, 2006).…”

“…S. gordonii and S. oralis belong to a genus that has been referred to as containing 'pioneering colonizers' (Kolenbrander et al, 1990) and these species are consistently isolated from dental-plaque biofilm communities, albeit at different relative amounts (Nobbs et al, 2009;Paster et al, 2006;Whittaker et al, 1996). The two species coaggregate with each other and numerous other oral species through complex adhesin-receptor mechanisms (Kolenbrander et al, 2002;Nobbs et al, 2009) and both have also recently been demonstrated to produce AI-2 (Blehert et al, 2003;McNab et al, 2003;Rickard et al, 2006). Such pioneer colonizers may promote the sequential integration of other oral species, including oral pathogens, into the developing dental-plaque communities Whitmore & Lamont, 2011).…”

Novel Model for Multispecies Biofilms That Uses Rigid Gas-Permeable Lenses

“…Genetically distinct oral bacteria have been shown to adhere to tooth enamel and to one another by several specific adhesinreceptor interactions. Research from various groups demonstrated that members of the Streptococcus genus are the early colonizers that anchor the biofilms to saliva-coated substratum in vitro and reflect in vivo biofilm initiation (11,34,35), and, in particular, S. gordonii demonstrates this property (8,17). Intraspecies coaggregation of streptococci has been shown by extensive coaggregation analysis (23); however, in our study, unique sequential deposition of taxonomically related coaggregation partners such as S. gordonii, S. oralis, and S. sanguinis was also observed.…”