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At least 19 recordsLinked to original sources
PubMed1956

Fate of Mycobacterium tuberculosis in mouse tissues as determined by the microbial enumeration technique. I. The persistence of drug-susceptible tubercle bacilli in the tissues despite prolonged antimicrobial therapy.

Observations are presented on the behavior of populations of tubercle bacilli in the tissues of mice during the administration of antimicrobial drugs. The behavior of the populations during therapy with any particular drug was different depending upon whether the tubercle bacilli were subsisting in the lung or in the spleen. Moreover, the pattern of microbial behavior was distinctive and predictable for each drug studied. Changes in the size of the populations of tubercle bacilli in the tissues appeared to be a more sensitive reflection of drug influence than microscopic study of the number and character of the tuberculous lesions. Nevertheless, in untreated animals, pulmonary lesions evolved and progressed steadily to a fatal outcome despite the fact that the populations of tubercle bacilli had stabilized at a relatively high census early in the course of therapy. The uniform persistence of tubercle bacilli in the spleen throughout prolonged drug administration was demonstrated with every drug or multiple drug regimens except for pyrazinamide when accompanied by isoniazid. Cultures of the bacilli which survived in the tissues despite antimicrobial therapy were highly susceptible to the drugs employed when tested in vitro. Thus the survival of the tubercle bacilli in the tissues represented microbial persistence rather than drug resistance. When pyrazinamide and isoniazid were administered together, it was not possible to detect the microorganisms in the spleen or lungs of treated animals. A detailed investigation of this apparent abolition of microbial persistence forms the subject of an accompanying report.

Aminosalicylic Acid↗
PubMed1956

The fate of Mycobacterium tuberculosis in mouse tissues as determined by the microbial enumeration technique. II. The conversion of tuberculous infection to the latent state by the administration of pyrazinamide and a companion drug.

Populations of tubercle bacilli of human origin exposed in vivo to pyrazinamide and a companion drug, vanished from the tissues of the mouse in so far as could be determined by microscopy, culture, or guinea pig subinoculation. The vanishing did not represent a complete elimination of the tubercle bacilli from all the animals. 90 days after the completion of treatment, tubercle bacilli could be cultured from approximately one-third of the animals examined at that time. This complete disappearance of the tubercle bacilli thus meets the definition of a truly latent infection in that the infection is present but is hidden beyond the limits of diagnostic reach. All but one of the strains of tubercle bacilli which survived in the animals and were detectable in the posttreatment period, were susceptible to pyrazinamide when tested under appropriate conditions in vitro. Only two factors could be identified which were essential for the uniform occurrence of the disappearance of tubercle bacilli: the administration of the pyrazinamide in a high daily dosage for at least eight of a total of 12 weeks of antimicrobial therapy; and the concurrent or prior exposure of the microbial populations to isoniazid or in some cases to other antituberculous drugs. The observations suggest that the ability of pyrazinamide-containing chemotherapies to bring about the disappearance of a tubercle bacillus is closely related to the occurrence of some alteration in the bacillus, essential for maximal pyrazinamide action, in response to environmental influences, including other antituberculous drugs present in the environment.

Animals↗