Optimizing the recovery rate of Mycobacterium species from gastric lavages in children at an urban Zambian Hospital

Abstract

Tuberculosis (TB) has re-emerged as a major worldwide public health hazard with increasing incidence among adults and children, with children representing a small percentage of all TB cases and possible reservoir from which many adult cases will arise.
Objectives: To determine whether the BACTEC MGIT 960 culture system will optimize the isolation of Mycobacterium species and also whether different Mycobacterium species are the etiological agents of TB in children.
Design: Gastric lavage specimens were received from a total of 408 TB suspects from different wards of the Department of Paediatrics and Child Health wing of the University Teaching Hospital (UTH) and examined by microscopy, Lowenstein-Jensen (L-J) culture and MGIT960 culture.
Main outcomes and results: This study analyzed gastric lavages from 408 children suspected of having TB. Recovery of Mycobacterium spp was optimized by the use of the relatively new nonradiometric fully automated BACTEC MGIT 960 which produced a positivity rate of 27.2% against 17.2% that of L-J media. Direct microscopy yielded a 5.6% positive rate. BACTEC MGIT960 had also a very high isolate detection rate of 98.2% compared to that of L-J media of 61.9%, and only 20.4% were detected with the direct microscopy. On time taken isolates, the BACTEC MGIT 960 technique had a shorter mean time to detection, 12.5 days as compared to 34.3 days shown by the L-J media technique. The study showed that children normally get tuberculosis from adult members of the household. A positive TB case was found in the households of 55.4% of the suspects. The study has found that 46.4% of the children below the age of 4 years developed the disease, compared to 10.5% of the older children in the age group 10 to 14 years.
Conclusion: The study found that tuberculosis in children is mainly caused by Mycobacterium tuberculosis. Out of the 113 isolates detected, 110 (97.3%) were M. tuberculosis. The remaining 2.7% were the non-tuberculous M. avium complex and M. kansasii. It was inconclusive whether the 2.7% of other species were causing tuberculosis and this need to be studied further. 

Keywords: Mycobacterium, gastric lavage, children