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[Why there were few isolations of tubercle bacilli in young children with pulmonary tuberculosis?]
1Department of Pediatrics, Yokohama City University School of Medicine.
Insights
Young children with pulmonary tuberculosis showed fewer positive cultures for tubercle bacilli compared to older children. This is likely due to non-cavitary lesions and a lack of delayed-type hypersensitivity in younger patients.
Area of Science:
- Pediatric Infectious Diseases
- Microbiology
- Pulmonology
Context:
- Pulmonary tuberculosis diagnosis in children presents unique challenges.
- Bacterial isolation rates vary significantly with age and lesion type.
- Understanding factors influencing Mycobacterium tuberculosis isolation is crucial for effective diagnosis.
Purpose:
- To retrospectively evaluate factors influencing tubercle bacilli isolation in pediatric pulmonary tuberculosis.
- To compare isolation rates between young (0-6 years) and older (7-14 years) children.
- To correlate chest X-ray findings with microbiological positivity.
Summary:
- Young children (0-6 years) with pulmonary tuberculosis had significantly lower positive smear and culture results than older children (7-14 years).
- Culture positivity was highest in patients with cavitary lesions (Type II) compared to non-cavitary lesions (Type III + Type H).
- BCG vaccination status correlated with age and lesion type, with young children predominantly having non-cavitary disease.
Impact:
- Highlights the lower yield of microbiological confirmation in young children with pulmonary tuberculosis.
- Suggests non-cavitary lesions and lack of delayed-type hypersensitivity contribute to reduced bacillary isolation in younger populations.
- Informs diagnostic strategies for pediatric tuberculosis, emphasizing clinical and radiological assessments alongside microbiological tests.
Abstract:
We retrospectively evaluated the factors influencing the isolation of tubercle bacilli in 51 children under 14 years of age with pulmonary tuberculosis who were admitted to Yokohama City University Hospital from 1975 to 1998. Young children (0-6 years of age) with pulmonary tuberculosis were significantly less positive by smear and culture than elder children (7-14 years of age) with pulmonary tuberculosis. According to the Japanese Society for Tuberculosis classification of finding on chest X-ray film for pulmonary tuberculosis, the culture-positive patients with type II (cavitary lesions) were found in all, the culture-positive patients with type III (non-cavitary lesions) in 39.3%, and the culture-positive patients with type H (hilar and mediastinal lymphadenopathys) in 35.3%. Patients with cavitary lesions (type II) were significantly more positive by smear and culture than patients with non-cavitary lesions (type III + type H). Only 15.8% of the young children with pulmonary tuberculosis had received BCG vaccine and all had non-cavitary lesions (type III and type H). But, 84.6% out of the older children had received BCG vaccine and half had cavitary lesions. Taken together, the result was that there were few isolation of tubercle bacilli in young children with pulmonary tuberculosis because they had non-cavitary tuberculosis without delayed-type hypersensitivity to tubercle bacilli.