The optimisation of laboratory cultivation in childhood mycobacterial disease in South Africa

Abstract

The role of the mycobacteriology laboratory in the diagnosis of childhood tuberculosis has become increasingly important in the human-immunodeficiency virus era. Due to the paucibacillary nature of childhood mycobacterial disease, laboratory optimisation of mycobacterial cultivation is necessary for paediatric clinical management and epidemiological surveillance. Previous studies have shown that growth supplements markedly improve the recovery rate and time-to-detection in mycobacterial cultures. In this study, we hypothesised that specialised culture media and meat-based growth supplements would improve the recovery rate and time-to-detection in clinical samples from paediatric patients. Pulmonary sputa and gastric aspirates and extra pulmonary fine needle aspiration biopsies were processed from children less than 15 years of age routinely investigated for mycobacterial disease. The processed clinical samples were split into a control aliquot that was cultured in liquid and solid media without growth supplement, and an intervention aliquot cultured on supplemented media. The effect of enrichment of the culture media was then calculated by comparison to the control. These results indicated a significant reduction in the time-to-detection, 18.5 to 12.4 days, and an improved primary recovery rate of 14% in paediatric samples when cultured in liquid media enriched with a nutrient meat broth growth supplement. The findings of this study confirm the value of optimising mycobacterial cultivation with the use of growth supplements to enhance the detection of childhood mycobacterial disease.