Microbial Contamination of Toothbrushes MICHAEL B. DAYOUB, DAVID RuSILKO, and ARTHUR GROSS Department of Microbiology, Division of Basic Sciences, United States Army Institute of Dental Research, Walter Reed Army Medical Center, Washington, D.C. 20012, USA This investigation was undertaken to determine the degree of bacterial contamination of toothbrushes after contamination and storage in vented containers or in air. The capacity of containers to exclude microorganisms of the environment from the toothbrush was also studied. In the first experiment 50 ml Trypticase Soy Broth cultures of P aeruginosa, E coli, and S aureus were incubated for 24 hours at 37 C and added to 400 ml pooled saliva. This mixture was used to contaminate 103 sterile toothbrushes and simulate the protective effects of salivary glycoproteins on the viability of potentially pathogenic bacterial contaminants. After immersion and agitation for one minute in the inoculum, brushes were aseptically withdrawn and then stored for one, two, three, four or five days. Fifty of the contaminated brushes were exposed to room air and 50 were stored in conventional cylindrical, vented toothbrush containers. The remaining three toothbrushes were used for determination of bacterial counts immediately after contamination. In addition three uninoculated brushes were suspended in air for 72 hours to detect possible airborne contamination. To assess the degree of bacterial contamination brushes were placed into 12 X 200 mm test tubes containing 10 ml sterile tap water and agitated for 30 seconds. One ml aliquots of the washings were placed in duplicate pour plates of Trypticase Soy Agar and incubated aerobically at 37 C. Colony-forming units (CFU) were counted at 48 hours. Washings of sterile brushes which had been hung in air yielded no growth. The average bacterial count (CFU) on toothbrushes immediately after contamination was 5.3 X 106 CFU/ ml of washings or 5.3 X 107/brush. Daily samples of washings of 10 brushes stored by each method demonstrated the presence of viable organisms over the entire five-day test period. The greatest losses of viable organisms occurReceived for publication October 27, 1976. Accepted for publication November 10, 1976.

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red during the first 24 hours of storage. Fewer organisms were found in the brushes drying in air than on brushes stored in vented containers. In the second experiment two types of toothbrush containers were evaluated for their capacity to exclude environmental contaminants. Toothbrushes were placed in the standard cylindrical containers and in similar containers which had collars designed to provide minimum contact with environmental surfaces (Figure).

FIG. Diagram of vented toothbrush container designed with collars extended to provide protection from environmental surfaces.

After ethylene oxide sterilization, ten containers of each type, holding sterile brushes were placed directly onto a stainless steel tray filled to a depth of two mm with a Trypticase Soy Broth culture of approximately 1 X 108 P aeruginosal ml. After 24 hours the toothbrushes were aseptically removed and examined as previously described. Duplicate one ml samples of washings of ten brushes from standard containers, even when diluted ten fold, developed colonies too numerous to count after 24 hours incubation. Washings of brushes from collar protected containers showed a maximum of 32 CFU/ml, and of the 20 plates counted, five showed no evidence of growth. The results indicate that the numbers of bacteria on toothbrushes stored in room air after use decrease more quickly than on brushes in containers. For prevention of contamination of toothbrushes, storage in vented containers, preferably with protective collars for the purpose of reducing contact with contaminated surfaces, appears to be the preferred method.

J Dent Res June 1977 Vol. 56 No. 6 Downloaded from jdr.sagepub.com at Univ of Connecticut / Health Center / Library on May 27, 2015 For personal use only. No other uses without permission.