Primary drug-resistant tuberculosis in children. Correlation of drug-susceptibility patterns of matched patient and source case strains of Mycobacterium tuberculosis.

The purpose of this study is to compare the drug-susceptibility patterns of Mycobacterium tuberculosis isolated from patients (children) and from their corresponding adult contacts. We wished to ascertain if the susceptibility pattern of the isolate from the adult contact could be used as a guide in the initial selection of the antituberculous drug regimen in the child. Strains resistant to one or more antituberculous drugs were emphasized in our study. For 120 children with positive cultures, adults were identified who had positive cultures and who were the source of the children's infections. All strains had susceptibility tests for isoniazid, streptomycin, aminosalicylic acid, ethionamide, and, when they became available, ethambutol and rifampin. There were 29 instances in which either the adult's and/or the child's strain were resistant to one or more antituberculous drugs. In 111 (92.5%) instances the organism isolated from the child and that from the adult contact had identical drug-susceptibility patterns. Fourteen (93%) of 15 of the adult/child pairs were both resistant to isoniazid. The drug-susceptibility pattern of isolates obtained from the source of a child's illness is useful as a guide in planning initial drug therapy. In addition, knowledge of isoniazid-resistant strains in adult contacts may alert the physician to the potential failure of isoniazid prophylaxis.