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Practice Lesson of the Week

Extensive transmission of Mycobacterium tuberculosis from 9 year old child with pulmonary tuberculosis and negative sputum smear

BMJ 2008; 337 doi: (Published 28 August 2008) Cite this as: BMJ 2008;337:a1184
  1. S Paranjothy, Walport clinical lecturer in public health medicine1,
  2. M Eisenhut, consultant paediatrician2,
  3. M Lilley, consultant in health protection3,
  4. S Bracebridge, regional epidemiologist4,
  5. I Abubakar, consultant epidemiologist5, head of tuberculosis section6,
  6. R Mulla, consultant microbiologist2,
  7. K Lack, senior health protection nurse (TB)3,
  8. D Chalkley, lead TB nurse7,
  9. J Howard, specialist registrar4,
  10. S Thomas, specialist registrar4,
  11. M McEvoy, unit director3
  1. 1Department of Primary Care and Public Health, Clinical Epidemiology Interdisciplinary Research Group, School of Medicine, Cardiff University, Cardiff CF14 4YS
  2. 2Luton and Dunstable Hospitals NHS Foundation Trust, Luton LU4 0DZ
  3. 3Bedfordshire and Hertfordshire Health Protection Unit, Letchworth, Hertfordshire SG6 1BE
  4. 4Health Protection Agency (East of England) Regional Epidemiology Unit, Institute of Public Health, University Forvie Site, Cambridge CB2 2SR
  5. 5Respiratory Diseases Department, Centre for Infections, Health Protection Agency, London NW9 5EQ
  6. 6School of Medicine, Health Policy and Practice, University of East Anglia, Norwich NR4 7TJ
  7. 7Luton Training PCT, Liverpool Chest Clinic, Luton LU1 1HH
  1. Correspondence to: S Paranjothy paranjothys{at}
  • Accepted 9 July 2008

A negative sputum smear does not exclude substantial risk of infection from patients with pulmonary tuberculosis

Patients with pulmonary tuberculosis and either a positive sputum smear or cavitating pulmonary lesions have been considered to be infectious1 as these indicate higher bacterial load accumulating with longer duration of infection. The source of infection in outbreaks among children is usually an adult with these features.2 Children have been considered less likely to transmit infection because they were unlikely to expectorate infective droplet nuclei. In the absence of a positive sputum smear, guidelines do not recommend screening of wider contacts in addition to household contacts,3 although in the United States, contact screening is recommended if resources are sufficient.4 Here, we report extensive transmission of tuberculosis in a junior school in Luton, England, from a child with pulmonary tuberculosis in whom a sputum smear was negative.

The index case

The index case was a 9 year old boy of Black African ethnicity born in the United Kingdom. He was investigated by his family doctor because of a six year history of recurrent cough evolving into a daily chronic cough with night sweats and weight loss for eight weeks before referral to a paediatrician. The cough was occasionally productive with one episode of haemoptysis. He continued to attend school while symptomatic. A chest x ray film showed a right upper lobe consolidation and multiple poorly defined opacities in the right lower lobe. (figure). Three sputum collections were smear negative, and culture showed Mycobacterium tuberculosis, fully sensitive to all drugs tested (isoniazid, rifampicin, pyrazinamide, ethambutol). He started chemotherapy with a two month course of pyrazinamide, rifampicin, and isoniazid, followed by four months of isoniazid and rifampicin. All household contacts of the child were screened for M tuberculosis infection.

Fig 1 First chest …

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