Ned B. Williams

A Study of the Simultaneous Occurrence of Enterococci, Lactobacilli, and Yeasts in Saliva from Human Beings

THE MICROORGANISMS that may occur in the mouth have been studied almost continuously in a variety of ways and for a number of reasons ever since the original observations by Leeuwenhoek in 1683. Most of the investigations were undertaken in order to (1) obtain information on the etiologic agents of specific infections in the mouth or oral manifestations of infections in some other part of the body, and (2) determine the relative occurrence of some organism hitherto not described as being found in the mouth. While these studies have contributed toward a better understanding of the type of microbial flora that may exist in the oral cavity, few attempts have been made to determine whether there are ecologic relationships between the organisms of particular interest and other forms in the same flora. The recent report of Hemmens, Blayney, Bradel, and Harrison,5 on the microbic flora of the dental plaque is a good example of such a study. The endodontia clinic of this school requested identification of cultures of microorganisms obtained from several cases which did not respond to treatment with antibiotics. The cultures were obtained from the root canals of teeth being treated by topical application (within the root canal) of a combination of penicillin and streptomycin in high concentration.2 Cultural and biochemic study indicated that the organisms belonged to the enterococcus group of streptococci, the principal species being Streptococcus faecalis. Since the saliva was the probable source of the organisms, a study was made to determine how frequently enterococci could be recovered from the salivas of apparently healthy persons. Inasmuch as facilities were available for making lactobacillus counts on pH 5.0 tomato juice agar, a quantitative determination of lactobacilli and yeasts was made simultaneously on the same saliva samples.

Collection and Sterilization of Submaxillary-Sublingual Saliva

A METHOD was desired for obtaining sterile submaxillary-sublingual saliva in order to .carry out bacteriologic experiments. Regardless of variation in collection method, viable microbes, which contaminated the secretion outside Whartons duct, could not be eliminated. Attention was therefore centered on inactivating these microbes without significantly altering the enzyme systems. Ultraviolet irradiation of thin saliva films was selected after several experiments.

Factors in Immunity and Susceptibility to Dental Caries

Immunity may be defined as a state of resistance to the development of a disease. If the disease is caused by an infectious agent then the immunity may be due to substances in the blood or in the tissues which assist in destroying the organisms. These substances are called antibodies, and the degree of immunity to an infectious disease is somewhat dependent upon the concentration of these antibodies in the blood and in the tissues. Dental caries is unique in this respect since it cannot strictly be described as an infectious disease, even though bacteria play a role in the process, and thus one would not expect to find antibodies participating directly in immunity to it. An infectious disease is usually initiated after invasion of the tissues, but in dental caries the tooth is usually invaded after the enamel tissue has been damaged. The protective substances or antibodies would have direct access to the invading organisms of the infectious disease, but in dental caries access of any such substances to the causative organisms would be very indirect. On the other hand, human beings who are immune to caries demonstrate a resistance which we have not been able to explain, and many authors have suggested that an immunological principle, protective or inhibitory substance, or antibody is active either through the blood or saliva. Most of us are agreed that bacteria have an important role in caries, but just which bacteria are most important is not yet entirely clear, although available evidence points heavily toward the lactobacilli. But then there are all kinds of lactobacilli, just as there are all types of pneumococci, and we have not yet determined just which specific lactobacilli are involved. In spite of this uncertainty much knowledge has been gained by studying these microorganisms, and I would like to present for your consideration the various reports that have appeared in study of protective or inhibitory substances in the blood. Several years ago the group here at the University of Michigan were interested in determining tests for susceptibility to dental caries. They made a filtrate from a collection of cultures of lactobacilli and used that filtrate in a skin test in individuals to see what the reaction would indicate insofar as susceptibility to dental caries was concerned. They found that those persons who reacted to the filtrate, following intradermal injection, did not have lactobacillus antibodies in their blood sera, while those whose skin tests were negative did have lactobacillus antibodies in their sera. The determinations for presence or absence of antibodies in the sera of these persons were made by using the agglutination test, a widely used test for detection of specific antibodies in blood sera. Parenthetically, the principle of the agglutination test is that an even sus-