Survival of Bacteria from Human Dental Plaque Under Various Transport Conditions

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Abstract
The effects of transport media, temperature and anaerobiosis on survival of bacteria from human supragingival dental plaque were studied. Individual samples were obtained by passing sterile, unwaxed dental floss through interproximal spaces. The plaque-bearing portion of floss was immediately placed in vials containing reduced transport fluid, viability-preserving microbistatic medium or reduced salt solution transport fluid. Plaque samples were dispersed by ultrasonic oscillation, serially diluted and plated in duplicate on MM10-sucrose-blood agar, mitis salivarius bacitracin agar and Rogosa tomato juice agar. Initial viable counts (time 0) were compared with viable count determination after 48- and 72-h storage. Quantitative recovery (> 30%) of various groups of oral bacteria was accomplished from reduced transport fluid and viability-preserving microbistatic medium after 48- and 72-h storage. Storage of dental plaque in reduced salt solution proved unsatisfactory for most bacteria (< 10% survival). Since growth of some bacteria may occur in viability-preserving microbistatic medium and the charcoal present interferes with colonly enumeration on low-dilution plates, reduced transport fluid was apparently the most suitable medium for transport and recovery of bacteria from supragingival dental plaque. Subzero storage (-196 and -40.degree. C) did not enhance the survival of bacteria from dental plaque; storage at moderate (5 and 20.degree. C) temperatures gave better recovery of viable bacteria. Survival after anaerobic or aerobic storage was comparable for total colony-forming units; anaerobic storage enhanced survival of Streptococcus mutans and Lactobacillus. Since these organisms are specifically associated with dental caries, anaerobic techniques are preferred for caries activity testing of plaque.