Molecular Epidemiology of Tuberculosis in the Bata and Malabo Districts of Equatorial Guinea

Setting: Bata and Malabo districts, Equatorial Guinea, 1 March 1999 to 28 February 2001.

Objective: To study the molecular epidemiology of tuberculosis (TB).

Results: During the study period, 429 patients were diagnosed with TB in the Bata and Malabo districts. A positive culture was obtained in 206 (48%) TB patients, with RFLP analysis being performed in 185 (89.8%). Ninety-two different patterns were identified. Single patterns were found in 71 strains (38.3%) and the remaining 114 strains (61.6%) were classified into 21 clusters (of 2 to 25 patients). In addition, 37 of the typing strains were resistant to one or more anti-tuberculosis drugs, and 30 were included in clusters (81%), with 21 low level isoniazid (MIC < or = 1 microg/ml) resistance strains in the same cluster. Statistical analysis showed that resistance to anti-tuberculosis drugs (OR 3.1; 95% CI 1.2-7.6; P = 0.014), and positive smear results (4+ grade smear) (OR 4.3; 95% CI 1.5-12; P = 0.005), were significantly more frequent among patients with clustered strains. No epidemiological links were related to clustering.

Conclusions: The level of clustering (61.6%) observed suggests a high degree of recent transmission and a predominance of determined patterns of Mycobacterium tuberculosis strains among the population of Equatorial Guinea.