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Thesis (M.S.)—University of Nebraska—Lincoln, 1971. Department of Microbiology.


Copyright 1971, the author. Used by permission.


The purpose of this study was threefold: (1) to define a procedure where organisms could be cultured in a synthetic liquid medium in cuvettes so that the optical density could be read each day and rates of growth more accurately determined than can be done by the present methods of observing media for the appearance of recognizable colonies; (2) to procure a culture collection of “atypical” mycobacteria and to observe some of the well-known characteristics that have been used for classification (acid-fast stain, cording, catalase production, niacin production and Tween hydrolysis); and (3) to investigate the feasibility of using media ordinarily used for the classification of Enterobacteriaceae for classifying “atypical” mycobacteria. A limited number of cultural characteristics of “atypical” mycobacteria were studied in regard to their usefulness in the clinical laboratory for classification of these organisms. The culture collection of 84 organisms included 26 known strains of M. kansaii. six known strains of M. marinum, a representative of Group II, a representative of Group III, three known strains of M. gastri, a representative of Group IV and 46 unclassified “atypical” mycobacteria. Nitrate reduction by these organisms was studied by three methods. Results with the PathoTec Nitrate Strip test were in agreement with the other methods using nitrate broth but were in disagreement with the advertised statement, “the nitrate reduction test is also useful in the identification of Mycobacterium tuberculosis (positive); other acid-fast bacilli except some strains of atypical AFB Group III are negative.”

A simplified key was devised to separate these organisms into groups. This key utilized the following characteristics: (1) carotene crystal production, nitrate reduction Tween 80 hydrolysis, catalase production at 68°C and growth on MacConkey’s agar. The unclassified organisms were classified as the known organisms in their Group. One organism, previously classified as M. marinum is in the group with Group IV organisms. A strain of M. kansasii, which was non-pigmented and did not reduce nitrate is in the same group as the known strains of M. gastri.

Advisor: Warren E. Engelhard and Carl E. Georgi