Drug-resistant tuberculosis in children

Abstract

The number of children globally who develop drug-resistant tuberculosis is unclear, in part due to diagnostic challenges and limited resistance testing, and in part because recording and reporting is not comprehensive. Large numbers of children, however, are exposed to drug resistant bacilli each year and it is clear that the very young and those immune-compromised are vulnerable to developing disease. Few studies have looked at the progression from exposure to infection or from infection to disease in the child contacts of adults with drug-resistant tuberculosis. It is uncertain which factors influence this progression and also whether any interventions can prevent it. Finally, few studies have analysed the presentation, treatment and outcome of children with disease. This thesis starts by reviewing what is published regarding drug-resistant tuberculosis in children. This includes systematic reviews of the management of children exposed to drug resistant tuberculosis as well as the management of those with multi drug-resistant tuberculosis disease. It reviews what is known regarding the second-line tuberculosis drugs in children and then clarifies the definitions that are used throughout the rest of the work. The thesis then systematically examines each of the stages from infection to disease with a series of inter-related studies. The first study attempts to quantify the burden of drug resistance in the context that the work is carried out. The following study investigates the risk factors for infection and prevalent disease in children exposed to a multi drug-resistant tuberculosis source case. This is followed by two studies which explore the transmission of drug-resistant bacilli from adults to children. The identification and referral patterns and obstacles to referral for exposed children are examined through operational studies that include qualitative and quantitative components. A descriptive cohort study assesses the toxicity and efficacy of a standardised preventive treatment regimen given to child contacts. The final part of the thesis includes a series of studies to investigate the treatment of drug resistant tuberculosis disease in children and the adverse effects of the second-line medications.