Oxygen sensitivity of indigenous gingival crevice organisms
Eskow, Robert N.
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Many strict anaerobes are known to be indigenous to the oral cavity of man. In as much as the oral and dental tissues are repeatedly exposed to atmospheric oxygen levels, it was of some interest to determine just how toxic oxygen is for certain anaerobic strains. Representative strains of Bacteroids melaninogenious, Fusobacterium nucleatum, Bacteroids oralis were employed and compared to the micro- aerophilic Vibrios: Vibrio sputorum, Vibrio fetus and Vibrio bubulus. Each organism was streaked on blood agar plates in an an aerobic chamber and incubated in duplicate at oxygen tensions ranging from 0 to 12%. When these studies revealed that many of the apparently anaerobic organisms could grow at relatively high oxygen tensions, the experiments were repeated with all streaking manipulations performed at room atmosphere followed by incubation at the oxygen concentrations utilized above. In order to more definitively delineate the oxygen kill level of the various organisms, high dilution plating was performed within the chamber with incubation at various oxygen levels. B. melaninogenicus and B. oralis, when streaked in an anaerobic environment, were seen to grow in the presence of as much as 8% O2. Similarly F. nucleatum grew with 10% O2. All of these organisms however demonstrated a diminished tolerance for oxygen when manipulated in room atmosphere prior to incubation. B. melaninogenicus and B. oralis did not grow in the presence of more than 6% O2. F. nucleatum, most affected, grew only up to 4% O2. The Vibrio strains were observed to grow at all oxygen tensions tested, regardless of the conditions under which they were streaked. An oxygen analyzer was utilized to measure the oxygen concentrations in four areas of the oral cavity: the maxiallary and mandibular buccal folds and the anterior and posterior aspects of the tongue. The findings respectively were: 0.4%; 0.3%, 16.4% and 12.4%. This information, as well as taking into consideration the oxygen sensitivity patterns of organisms studies, augments the ecological explanation of why certain bacteria are found in specific niches and are not ubiquitous throughout the mouth.
PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact firstname.lastname@example.org.Thesis (M.Sc.D.)--Boston University School of Graduate Dentistry, 1969.Bibliography, charts, photographs included.
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