Aim: This study compared several traditional culture‐based media and chairside cultural assays for ability to recover mutans streptococci (MS) from pure cultures and from saliva samples.
Methods and Results: When pure cultures were used with traditional culture‐based media, mitis‐salivarius bacitracin (MSB) agar demonstrated less support for bacterial recovery than trypticase‐yeast extract‐cysteine sucrose‐bacitracin (TYCSB) agar and the modified medium of Ritz (HLR‐S). One species of MS, Streptococcus ferus (c), was not recovered on MSB medium. Chairside cultural tests displayed considerable disparity between tests in recovering bacteria from pure cultures. On the glass adherence assay (Mucount®), S. ferus was not detected and Streptococcus criceti was not detected on the dipslide assay (Cariescreen SM®) or on the plastic adherence assay (Dentocult SM Strip mutans®). The frequency of isolation of pure strains of bacteria other than MS was common. From saliva samples, the frequency of isolation of MS on HLR‐S and TYCSB media and the glass adherence assay was 91–97%. The frequency of isolation on MSB medium and on the dip‐slide and plastic adherence assays was significantly decreased (37, 47 and 69%, respectively). Recovery scores varied considerably among the culture methods studied and tended to be highest on the HLR‐S medium and on the glass adherence assay.
Conclusions: Growth and recovery profiles of pure bacterial cultures and of saliva samples for the MS varied according to different media.
Significance and Impact of the Study: Caution should be exercised in comparing results between studies that employ different cultural methods for MS enumeration.
This study evaluated the effect of an alternate delivery system for chlorhexidine on salivary levels of mutans streptococci (MS) and other selected oral bacteria. On the basis of salivary MS levels ≥104 CFU/ml, 22 subjects were enrolled. All caries lesions were restored prior to treatment. Two pretreatment paraffin-stimulated saliva samples were obtained for culturing at least 1 week apart. Complete-arch vacuum-adapted mouthguards were individually fabricated and coated internally with a 3% w/v chlorhexidine varnish. Mouthguards were worn for an average of 7 h/night for 7 nights. Saliva samples were obtained immediately after treatment and 1 and 3 months later. There was no significant change in levels of any of the monitored bacteria between the two pretreatment samples. A significant and specific reduction in salivary MS levels was observed in the three after-treatment samples as compared with baseline values (p < 0.001, p < 0.001, p < 0.05, respectively). The levels of Actinomyces viscosus were also measured, and there was a significant reduction immediately after treatment (p < 0.05), a return to baseline values at 1 month, and a significant increase above baseline values at 3 months, (p < 0.001). There was no significant change in saliva volume, in total numbers of facultatively anaerobic bacteria, or in levels of lactobacilli or Streptococcus sanguis. This treatment system is capable of significant and specific suppression of MS levels for up to 3 months without retreatment.
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