Residual Antimicrobial Activity of Camphorated Chlorphenol

Abstract

Grossman' has pointed out the need for inactivating penicillin by means of penicillinase when taking a sample for culturing from a root canal, in order to rule out the possibility of obtaining a false negative culture. It is conceivable that both microorganisms and the antibiotic could be transferred from the root canal to the culture medium and that the antibiotic could destroy the few microorganisms inoculating the culture medium.Grossman, Parris, and Cobe2 have reported on the possible antibacterial effect of residual bacitracin, a component of the polyantibiotic PBSC (penicillin, bacitracin, streptomycin, and caprylate sodium in a silicone fluid vehicle). While the other components of the polyantibiotic can be inactivated, there is no known inactivator for bacitracin. It has been found that, of the 88 cases studied, only 2 showed a residual antibacterial effect from bacitracin.In discussing the addition of an inactivating agent to the culture medium with the object of neutralizing any antimicrobial activity that might be carried over from the medicament, Grossman' has stated that "no neutralizing agent had been added to the culture medium in the control cases in which the older medicaments such as monochlorphenol, beechwood creosote, etc., had been used." It has been assumed for a number of years, and it has also been stated in dental literature,3 4 that the non-antibiotic root canal medicaments do not need to be inactivated either because they exert no antimicrobial effect after being sealed in the root canal for 2 or 3 days or because they are so diluted by the culture medium that they no longer exert an antimicrobial effect. On the basis of the present studv, we found that this is an erroneous assumption. MATERIALS AND METHODSStudy A.-Agar plates were inoculated with mouth organisms according to the procedure described by Grossman and Appleton,5 as follows: 25 ml. of tap water were put into a sterile Erlenmeyer flask, and 3 ml. of sterile nutrient broth were added to preserve the viability of the organisms. About 10 ml. of this solution were taken into the mouth and swished forcibly back and forth around the teeth. This was continued for 1 minute, and the resultant bacterial suspension was returned to the flask. The flask was shaken by hand to distribute the organisms evenly before each inoculation. Ten milliliters of nutrient agar (pH 7.6) were liquefied, cooled to 450 C., and 1 ml. of