Streptococcus mutans strains recovered from caries‐active or caries‐free individuals differ in sensitivity to host antimicrobial peptides

Abstract

SUMMARY Antimicrobial peptides (AMPs) are among the repertoire of host innate immune defenses. In the oral cavity, several AMPs are present in saliva and have antimicrobial activities against oral bacteria, including Streptococcus mutans, a primary etiologic agent of dental caries. In this study, we hypothesized that unique S. mutans strains as determined by DNA fingerprinting from sixty 13 year-old subjects with or without caries experience would have different susceptibilities to α-defensins-1-3 (HNP-1-3), β-defensins-2-3 (HBD-2-3) and LL-37. The salivary levels of these peptides in subjects also were measured by enzyme-linked immunosorbent assays (ELISA). We found that S. mutans strains from caries-active subjects showed greater resistance to salivary HNP-1-2, HBD-2-3 and LL-37 at varying concentrations than those from caries-free subjects. In addition, combinations of these peptides increased their antimicrobial activity against S. mutans either additively or synergistically. The salivary levels of these peptides were highly variable among subjects with no correlation to host caries experience. However, the levels of a number of these peptides in saliva appeared to be positively correlated within an individual. Our findings suggest that the relative ability of S. mutans to resist host salivary AMPs may be considered a potential virulence factor for this species such that S. mutans strains that are more resistant to these peptides may have an ecological advantage to preferentially colonize within dental plaque and increase the risk of dental caries.

Antimicrobial peptides in saliva of children with severe early childhood caries

“…Except for hBD-1, all peptides demonstrated nearly 100% bactericidal activity with concentrations less than 10 mg/l. Some authors have suggested that the reduced concentration of certain peptides could be associated with dental caries in children (Tao et al, 2005;Davidopoulou, Diza, Menexes, & Kalfas, 2012;Phattarataratip et al, 2011). The levels of a-defensin (hNP1-3) (Tao et al, 2005) and LL-37 (Davidopoulou et al, 2012) were lower in saliva from caries-active children compared to caries-free children.…”

Antimicrobial peptide LL‐37 and its pro‐form, hCAP18, in desquamated epithelial cells of human whole saliva

“…LL‐37 has been demonstrated in human whole saliva from both adults and children , and can also be found in saliva isolated from human parotid and submandibular/sublingual glands, showing that hCAP18/LL‐37 is indeed produced by cells of the major salivary glands . It has been reported that LL‐37 possesses antibacterial effects against many strains of oral bacteria, including Streptococcus mutans and Porphyromonas gingivalis which are associated with caries and periodontitis . Patients with the congenital disease Kostmann's syndrome, characterized by neutropenia and frequent and severe infections, have either no or extremely low levels of LL‐37 in plasma and saliva .…”

The host defense peptide LL‐37 is detected in human parotid and submandibular/sublingual saliva and expressed in glandular neutrophils

“…Interestingly, LL‐37 shows antimicrobial activity against many oral bacteria, such as Porphyromonas gingivalis , Streptococcus mutans , Treponema denticola , Fusobacterium nucleatum , and Prevotella intermedia . With respect to S. mutans , LL‐37 seems to have a more pronounced cytotoxic effect on S. mutans strains isolated from caries‐free individuals than on S. mutans strains isolated from caries‐active individuals, suggesting that S. mutans strains recovered from caries‐active subjects have become less sensitive to LL‐37‐evoked cytotoxicity .…”