Low antimicrobial resistance rates of Mycobacterium tuberculosis complex between 2000 and 2015 in Gipuzkoa, northern Spain

Abstract

Objective: Although the incidence of tuberculosis (TB) has declined, TB drug resistance remains a major problem. The TB rate in Gipuzkoa (northern Spain) is higher than the European average. The objective of this study was to determine the antimicrobial susceptibility of 1855 Mycobacterium tuberculosis complex isolates (94.5% of confirmed cases between 2000 and 2015).

Methods: Susceptibility testing was performed using the agar proportion method and a commercial broth system (MGIT 960). In isoniazid- or rifampicin-resistant strains, we studied genetic determinants of drug resistance and genotype (MIRU-VNTR).

Results: The annual mean incidence of TB was 24.5 cases per 100,000 population on average, and tended to decrease. The multidrug-resistant TB rate was 0.5% (9/1855), and no extensively drug-resistant TB strains were detected. Rates of resistance to isoniazid and rifampicin were 3.9% (range, 3.4-4.3%) and 0.6% (range, 0.4-1.4%), respectively. TB resistance was more common among foreign-born individuals and those who had received previous TB treatment. Genotyping of 102 resistant strains showed predominance of the Euro-American lineage, although 4/9 multidrug-resistant strains had Eastern lineages (2 East African-Indian, and 2 East Asian [Beijing]).

Conclusions: In Gipuzkoa, with a moderate incidence of TB, resistance was very low, mostly being detected among individuals who were born abroad or who had a history of TB treatment.

Keywords: Drug-resistant tuberculosis; Epidemiology; Epidemiología; Microbial sensitivity test; Multidrug-resistant tuberculosis; Susceptibilidad antibiótica; Tuberculosis multirresistente; Tuberculosis resistente.