Abstract
We conducted a case–control study to examine risk factors for isoniazid-monoresistant Mycobacterium tuberculosis in an ongoing outbreak in London. Cases were defined as individuals with an isoniazid-monoresistant strain diagnosed from 1995 to the third quarter of 2006 with an indistinguishable restriction fragment length polymorphism (RFLP) or mycobacterial interspersed repetitive unit (MIRU)-variable number tandem repeats (VNTR) pattern who were resident in or had epidemiological links with London. Controls were all other individuals reported with tuberculosis to the Health Protection Agency London regional epidemiology unit or the HPA London TB Register during 2000 to 2005. Of 293 cases, 153 (52%) were sputum smear-positive compared with 3,266 (18%) of controls. Cases were more likely to be young adults (aged between 15 and 34 years), born in the United Kingdom (OR: 2.4; 95% CI: 1.7–3.4) and of white (OR: 2.9; 95% CI: 1.8–4.8) or black Caribbean (OR: 12.5; 95% CI: 7.7–20.4) ethnicity, a prisoner at the time of diagnosis (OR: 20.2; 95% CI: 6.7–60.6), unemployed (OR: 4.1; 95% CI: 3.0–5.6), or a drug dealer or sex worker (OR: 187.1; 95% CI: 28.4–1,232.3). A total of 113 (39%) of cases used drugs and 54 (18%) were homeless. Completion of treatment gradually improved in cases from 55% among those diagnosed up to the end of 2002 compared with 65% by the end of 2006. Treatment completion increased from 79% to 83% in controls from 2000 to 2005. There are complex social challenges facing many cases in this outbreak that need to be addressed if medical interventions are to be successful.
Highlights
The incidence of active tuberculosis (TB) increased in London from 20 per 100,000 population in 1987 to www.eurosurveillance.org44 per 100,000 in 2006 [1]
During 2000 to 2006, TB rates were consistently higher in north London, among people born outside the United Kingdom (UK) and in those aged 20–29 years [2,3]
The proportion of Mycobacterium tuberculosis strains in London that were isoniazid resistant was relatively stable at 8–9% during 2000 to 2006 [2]
Summary
The incidence of active tuberculosis (TB) increased in London from 20 per 100,000 population in 1987 to www.eurosurveillance.org. As a result of this, a London-wide Incident Control Committee was established. It was agreed that the HPA Mycobacterium Reference Unit would type isoniazid-monoresistant M. tuberculosis strains from across London prospectively and retrospectively to 1999 (the most recent strains that were available). Since 2002 all TB clinics have been using the HPA London TB Register, a web-based electronic case management and surveillance system. It was developed and has been maintained by the HPA, in collaboration with clinical staff in the city. We report on treatment outcome of the cases and describe the particular challenges encountered in implementing the recommended control measures
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