Transmission of multidrug-resistant tuberculosis

To compare the Mycobacterium tuberculosis isolates of adult index cases with multidrug-resistant (MDR) tuberculosis to the isolates obtained from their child contacts.

A 4-year prospective study in the Western Cape Province of South Africa. We evaluated 149 child contacts of 80 adult MDR pulmonary tuberculosis cases. This report includes those cases where a culture for M. tuberculosis was obtained from both the adult source case and the child contact. Isolates were compared by drug susceptibility pattern and restriction fragment length polymorphism analysis.

Six adult-child pairs with cultures for M. tuberculosis were identified. Two children had contact with more than one adult tuberculosis case. One child received previous isoniazid prophylaxis. Drug susceptibility pattern and restriction fragment length polymorphism analysis were identical for five adult-child pairs. One child, with no other known source case, had a strain different from that of the identified source case, but the MDR M. tuberculosis strain with which he was infected was prevalent in the community in which he resided. All children responded well to treatment.

This study confirms that most of the childhood contacts of adults with MDR tuberculosis are likely to be infected by these MDR source cases despite their exposure to other drug-susceptible adults with tuberculosis in some instances. Child contacts of adults with MDR tuberculosis should be treated according to the drug susceptibility patterns of the likely source cases' M. tuberculosis strains unless their own strain's susceptibility testing indicates otherwise. Contact tracing remains of fundamental importance in identifying children at risk.