Doctoral Degrees (Paediatrics and Child Health)

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Browsing Doctoral Degrees (Paediatrics and Child Health) by Author "Bekker, Adrie"

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    Prevention and treatment of perinatal and infant tuberculosis in the HIV era
    (Stellenbosch : Stellenbosch University, 2016-11-18) Bekker, Adrie; Hesseling, Anneke Catharina; Schaaf, Hendrik Simon; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Paediatrics and Child Health
    ENGLISH ABSTRACT : Infants (<12 months) born to women with tuberculosis are at high risk of Mycobacterium tuberculosis (M. tuberculosis) exposure, infection and disease early in life. In settings with high prevalence of human immunodeficiency virus (HIV) and tuberculosis, tuberculosis disproportionately affects women of childbearing age. The aim of this dissertation was to comprehensively investigate prevention and treatment strategies for perinatal and infant tuberculosis in a high HIV-prevalence setting. Research objectives included: 1) defining clinical and epidemiological aspects of maternal-infant tuberculosis at a large referral hospital; 2) identifying barriers and solutions to isoniazid preventive therapy (IPT) delivery in tuberculosis-exposed newborns; and 3) obtaining rigorous pharmacokinetic data to guide the dosing of firstline antituberculosis drugs in newborns and infants for the prevention and treatment of tuberculosis. In the first retrospective study, 70 newborns (42 HIV-exposed) were investigated for tuberculosis at Tygerberg Hospital, a large provincial referral hospital in Cape Town. Newborns were mainly screened for tuberculosis because of maternal tuberculosis. Isoniazid preventive therapy (IPT) was initiated in 36/50 (72%) newborns, because of maternal tuberculosis infectious risk and exposure of infants. Few of the newborns who received IPT were traceable at one-year, and of those traced, less than half completed IPT. To generate more rigorous clinical and epidemiological data on maternal-infant tuberculosis, a prospective cohort study was conducted in pregnant and postpartum women receiving tuberculosis treatment at Tygerberg Hospital. Over a one-year period, 74 pregnant and postpartum women, 53 (72%) HIV-infected, were consecutively enrolled. Nearly half of the women, 35 (47%) were diagnosed with tuberculosis only at delivery or postpartum, and a third of women with tuberculosis reported prior tuberculosis treatment. Tuberculosis-exposed newborns were often premature and of low birth weight (LBW; <2500 grams). All deaths occurred in HIVinfected women (n=5) and all stillbirths (n=4) and newborn deaths (n=6) were from HIV-infected women. Favourable maternal tuberculosis treatment outcomes (cure and tuberculosis treatment completion) were documented only in 41/74 (55%) women, while 33 (45%) had unfavourable treatment outcomes (death, treatment failure and loss to follow-up). These poor observed outcomes highlight the need for earlier diagnosis and treatment of tuberculosis during pregnancy, and close follow-up to ensure maternal tuberculosis treatment completion. Improved care for pregnant women with tuberculosis, with and without HIV infection, will likely reduce morbidity and mortality in mothers and tuberculosis-exposed newborns. Delayed maternal tuberculosis diagnosis led to IPT initiation in a large number of newborns. Forty-four newborns on IPT were followed to 6 months. A hospital-based tuberculosis linkage to care intervention, led to 29/44 (66%) newborns completing IPT without a study team intervention. A further 8 infants completed IPT after studyteam intervention. Appropriate tuberculosis referral and linkage to care from hospital to local tuberculosis clinic substantially improved IPT completion among tuberculosis-exposed newborns. More pharmacokinetic data regarding the appropriate use of antituberculosis drugs are required in neonates and infants, who undergo considerable physiological changes in the first year of life. An intensive isoniazid (INH) pharmacokinetic study was therefore designed and implemented in premature and LBW infants (n=20). Relatively high median INH peak concentrations of 5.63 μg/ml were achieved in LBW infants (at an INH dose of 10 mg/kg), compared to the adult proposed target value of > 3 μg/ml. INH exposures were higher with longer half-lives in smaller infants, and among genotypically determined N-acetyltransferase-2 (NAT2) slow acetylators, suggesting reduced clearance of INH. This first study of isoniazid use in LBW and premature neonates showed that the INH dose in premature and LBW infants should probably not exceed 10 mg/kg/day. The final study evaluated whether the revised higher 2009 World Health Organization (WHO)-recommended paediatric doses for rifampicin (RMP), INH, pyrazinamide (PZA) and ethambutol (EMB) achieved adequate drug concentrations in infants, compared to current adult pharmacokinetic target concentrations. All 39 infants enrolled achieved the minimum proposed adult target peak concentrations of > 3 μg/ml for INH at a mean dose of 12.8 mg/kg (10.3 - 15.4 mg/kg), and the minimum adult target of > 20 μg/ml for PZA at a mean dose of 33.3 mg/kg (28.5 – 38.5 mg/kg). RMP administered at mean dose of 15.4 mg/kg (10.1 - 20.5 mg/kg) resulted in very low RMP peak concentrations for both RMP formulations used during the study. None of the infants achieved the minimum proposed adult RMP target concentration of > 8 μg/ml. Given the findings of this study, higher doses of RMP in infants should be considered especially given emerging data from adult RMP doseescalation studies showing better efficacy at higher doses with limited toxicity for short-term use. For EMB, only 1 of 16 infants achieved the recommended adult target concentration of > 2 μg/ml when given at a mean dose of 20.2 mg/kg (15.4-24.1 mg/kg). EMB dose-dependent ocular toxicity however poses a concern regarding the recommendation of higher EMB doses in infants where vision testing is challenging. This is the largest pharmacokinetic study of first-line antituberculosis drugs performed in infants to date, which has generated valuable pharmacokinetic data to inform the effective and safe dosing of first-line antituberculosis drugs in infants. Pregnant women in settings with a high burden of tuberculosis and HIV and their infants face a considerable burden of tuberculosis disease in HIV-endemic settings. Maternal-infant tuberculosis care can be improved by health systems strengthening interventions. Data generated from pharmacokinetic studies of antituberculosis drugs in tuberculosis-exposed infants will inform much needed dosing guidelines of firstline antituberculosis drugs for newborns and infants, who have a high risk of tuberculosis and are prone to develop severe forms of tuberculosis.