Frequency of four different mutacin genes in Streptococcus mutans genotypes isolated from caries-free and caries-active individuals

Abstract

The ability of Streptococcus mutans to produce mutacins, combined with the production of other virulence factors such as lactic acid, may contribute to the pathogenesis of this bacterium. In the present study, the detection of genes encoding mutacin types I/III, II and IV was performed by PCR with specific primers to each type in a total of 63 S. mutans genotypes isolated from caries-active and caries-free individuals. In the caries-free group, PCR screening for mutacin IV revealed that 31 . 8 % of strains were positive for this mutacin. PCR for the other three mutacins tested (I/III and II) did not yield amplicons in any S. mutans strains in this group. The PCR with primers of mutacin IV showed 68 . 3 % positive genotypes in the caries-active group, on the other hand, the amplicons of mutacins I/III revealed 41 . 5 % positive strains that carried these genes. The chi square test showed significant differences in the number of positive strains to mutacin IV when comparing the caries-free and caries-active genotypes of S. mutans (P ¼ 0 . 01). All tested S. mutans strains were negative by PCR for mutacin II. The low frequencies of detection of some mutacin genes suggest the existence of high diversity and polymorphism in the production of genetic determinants of mutacin-like substances. In addition, the production of a wide spectrum of mutacins can play an important biological role in colonization by S. mutans strains, mainly in the niche of high-complexity microbial communities. INTRODUCTIONMutans streptococci are generally accepted as one of the principal aetiological agents of dental caries (Loesche, 1986;Becker et al., 2002). The dental biofilm consists of a complex bacterial community, and the ability of specific strains of Streptococcus mutans to compete with other strains may be essential for colonization. Alaluusua et al. (1996) suggested that some strains of S. mutans might be able to colonize the host and induce dental caries better than other strains. Alternatively, dietary patterns of the host may be an important factor, since a high salivary mutans streptococci count does not necessarily exert a cariogenic challenge (van Palenstein Helderman et al., 1996).Numerous factors affect the equilibrium among oral populations of micro-organisms, and several inhibitory substances have been identified, including mutacins (Fukushima et al., 1985;Caufield et al., 1985;Delisle, 1976). Mutacins are peptide or protein antibiotics that are mainly bactericidal for other bacteria of the same or closely related species, as well as for other Gram-positive micro-organisms, and are likely to confer an ecological advantage in diverse bacterial communities such as the dental biofilm (Parrot et al., 1990; Balakrishnan et al., 2002). Some studies have demonstrated that the mutacin activity of S. mutans could be related to the prevalence of this species in the dental biofilm, saliva and dental caries (Berkowitz and Jordan, 1975;Hillman et al., 1987).Classification of mutacin-producer strains based on their bactericidal activity...

Population Structure of Plasmid-Containing Strains of Streptococcus mutans , a Member of the Human Indigenous Biota

“…This proclivity for vertical transmission along maternal lines could make the population structure of S. mutans relevant to the evolutionary history of its human host, not unlike the mitochrondrial-DNA model (6). At present, however, the population structure of S. mutans remains fragmented, and only hints of phylogenetically informative patterns in S. mutans populations exist (5,8,14,31).Genetic diversity is well documented within S. mutans. For example, variability among strains of S. mutans has been demonstrated for the presence of plasmids (8, 11, 23); mutacin I, II, III, and IV operons (5, 14, 33, 34, 46); serotype antigens (38, 46); competence (15,21,29); and the msm, bgl, cel, and gtfBC loci (46), among others.…”

“…This proclivity for vertical transmission along maternal lines could make the population structure of S. mutans relevant to the evolutionary history of its human host, not unlike the mitochrondrial-DNA model (6). At present, however, the population structure of S. mutans remains fragmented, and only hints of phylogenetically informative patterns in S. mutans populations exist (5,8,14,31).…”

“…For example, variability among strains of S. mutans has been demonstrated for the presence of plasmids (8,11,23); mutacin I, II, III, and IV operons (5,14,33,34,46); serotype antigens (38,46); competence (15,21,29); and the msm, bgl, cel, and gtfBC loci (46), among others. Indeed, the genome of S. mutans UA159 shows that nearly one-third of its open reading frames are of unknown function and 16% are unique to S. mutans.…”

Fatores de virulência de Streptococcus mutans e sua relação com a persistência e transmissão de genótipos entre membros de famílias brasileiras

“…Por outro lado, a literatura reporta diferentes frequências de detecção dos genes mutAI (29,1% a 53%), mutAII (<10% a 80%), mutAIII (12,7%) e mutAIV (18,7 a 70%) em S. mutans isolados a partir do biofilme dentário e/ou saliva humana (QI; CHEN; CAUFIELD, 2001; LONGO; MATTOS-GRANER; MAYER, 2003;KAMIYA et al, 2005b;KRETH et al, 2005b;GONÇALVES, 2008;RODRIGUES et al, 2008;VALARINI et al, 2009;BALLINI, 2011 SLADE, 1980;BALAKRISHNAN et al, 2002;KAMIYA et al, 2005aKAMIYA et al, , 2005bGONÇALVES, 2008), a produção de bacteriocinas por S. mutans varia amplamente, sendo que praticamente todas as cepas produzem ao menos um tipo de mutacina.…”

“…A constatação desses genótipos em 48% dos isolados de S. mutans analisados pode significar um importante papel biológico das proteínas por eles decodificadas, sobretudo no processo de formação do biofilme dentário. De acordo com Kamiya et al (2005a), os genótipos de S. mutans que produzem um amplo espectro de mutacinas tendem, com o passar do tempo, a se tornar predominante na maioria dos sítios da cavidade bucal.…”