[Molecular epidemiology of tuberculosis in Almeria (Spain). Factors associated with recent transmission]. / Epidemiología molecular de la tuberculosis en Almería. Factores asociados a transmisión reciente.

BACKGROUND: Molecular epidemiology is used in tuberculosis (TB) to identify clusters in which the cases are assumed to belong to the same recent transmission chain. An endogenous reactivation of latent TB is considered when the Mycobacterium tuberculosis isolates have a unique genotype. OBJECTIVE: To describe factors associated with recent transmission of TB in Almeria, from 2003-2007. METHODS: We conducted an observational prospective study that included patients with Mycobacterium tuberculosis positive culture. The strains were genotyped by Restriction Fragment Length Polymorphism and spoligotyping. Adjusted odds ratio and 95% confidence intervals were calculated to study factors associated with cluster groups, using a multivariate logistic regression model. RESULTS: We analysed 427 isolates, of which 71% were from males and 56.2% of them belonged to foreign residents. Furthermore, 44% were classified as a cluster. The resistance to isoniazid was 8.4%. The factors associated with clusters were age, principally the group under 10 years (adjusted OR=12.75; 95% CI, 2.52-64.58) and the group aged between 50-59 years (adjusted OR=13.85; 95% CI, 3.04-63.17), and born in Spain (adjusted OR=2.17; 95% CI, 1.41-3.36). CONCLUSIONS: In Almeria, native population, children under 10 years old and patients aged between 50-59 years have more probability to belong to the same recent transmission chain. The molecular epidemiology can be used to find out which population groups need more control and this information must be used in tuberculosis prevention programs.

Epidemiología molecular de la tuberculosis en Almería. Factores asociados a transmisión reciente / Molecular epidemiology of tuberculosis in Almeria (Spain). Factors associated with recent transmission

Introducción La epidemiología molecular aplicada a la tuberculosis (TB) permite identificar clusters, cuyos miembros se asume que pertenecen a la misma cadena de transmisión reciente. Se considera reactivación endógena cuando el aislado presenta un genotipo único. Objetivo describir los factores asociados a la transmisión reciente de la TB en Almería, en el período 2003-2007. Métodos Se realizó un estudio observacional prospectivo de pacientes con tuberculosis, cuyos aislados fueron caracterizados genotípicamente mediante Restriction Fragment Length Polymorphism y spoligotyping. Se calcularon odds ratio y sus intervalos de confianza del 95% y mediante regresión logística se analizaron los factores asociados a pertenecer a un cluster. Resultados Se analizaron 427 aislados, de los cuales el 71% procedía de varones y 56,2% de ellos pertenecían a extranjeros. Un 44% de los pacientes participaba en algún cluster. La resistencia a isoniazida fue del 8,4%. Los factores relacionados con cluster fueron la edad, fundamentalmente los menores de 10 años (OR ajustada=12,75; IC del 95%, 2,52-64,58) y el grupo entre 50 y 59 años (OR ajustada=13,85; IC del 95%, 3,04-63,17), así como los nacidos en España (OR ajustada=2,17; IC del 95%, 1,41-3,36).Conclusiones En Almería, los autóctonos presentan más posibilidades de estar implicados en una cadena de transmisión reciente, así como los pacientes de ciertos tramos de edad como los niños menores de 10 años, y los de 50-59 años. La epidemiología molecular permite conocer qué grupos de población requieren mayor control, y reorientar hacia ellos los programas de prevención de la tuberculosis (AU)

Background: Molecular epidemiology is used in tuberculosis (TB) to identify clusters in which the cases are assumed to belong to the same recent transmission chain. An endogenous reactivation of latent TB is considered when the Mycobacterium tuberculosis isolates have a unique genotype. Objective: To describe factors associated with recent transmission of TB in Almeria, from 2003-2007.Methods: We conducted an observational prospective study that included patients with Mycobacterium tuberculosis positive culture. The strains were genotyped by Restriction Fragment Length Polymorphismand spoligotyping. Adjusted odds ratio and 95% confidence intervals were calculated to study factors associated with cluster groups, using a multivariate logistic regression model. Results: We analysed 427 isolates, of which 71% were from males and 56.2% of them belonged to foreign residents. Furthermore, 44% were classified as a cluster. The resistance to isoniazid was 8.4%. The factors associated with clusters were age, principally the group under 10 years (adjusted OR= 12.75; 95% CI, 2.52-64.58) and the group aged between 50-59 years (adjusted OR= 13.85; 95% CI, 3.04-63.17), and born in Spain (adjusted OR= 2.17; 95% CI, 1.41-3.36).Conclusions: In Almeria, native population, children under 10 years old and patients aged between 50-59years have more probability to belong to the same recent transmission chain. The molecular epidemiology can be used to find out which population groups need more control and this information must be used intuberculosis prevention programs (AU)

Evaluation of the new advanced 15-loci MIRU-VNTR genotyping tool in Mycobacterium tuberculosis molecular epidemiology studies.

BACKGROUND: During the last few years, PCR-based methods have been developed to simplify and reduce the time required for genotyping Mycobacterium tuberculosis (MTB) by standard approaches based on IS6110-Restriction Fragment Length Polymorphism (RFLP). Of these, MIRU-12-VNTR (Mycobacterial interspersed repetitive units- variable number of tandem repeats) (MIRU-12) has been considered a good alternative. Nevertheless, some limitations and discrepancies with RFLP, which are minimized if the technique is complemented with spoligotyping, have been found. Recently, a new version of MIRU-VNTR targeting 15 loci (MIRU-15) has been proposed to improve the MIRU-12 format. RESULTS: We evaluated the new MIRU-15 tool in two different samples. First, we analyzed the same convenience sample that had been used to evaluate MIRU-12 in a previous study, and the new 15-loci version offered higher discriminatory power (Hunter-Gaston discriminatory index [HGDI]: 0.995 vs 0.978; 34.4% of clustered cases vs 57.5%) and better correlation (full or high correlation with RFLP for 82% of the clusters vs 47%). Second, we evaluated MIRU-15 on a population-based sample and, once again, good correlation with the RFLP clustering data was observed (for 83% of the RFLP clusters). To understand the meaning of the discrepancies still found between MIRU-15 and RFLP, we analyzed the epidemiological data for the clustered patients. In most cases, splitting of RFLP-clustered patients by MIRU-15 occurred for those without epidemiological links, and RFLP-clustered patients with epidemiological links were also clustered by MIRU-15, suggesting a good epidemiological background for clustering defined by MIRU-15. CONCLUSION: The data obtained by MIRU-15 suggest that the new design is very efficient at assigning clusters confirmed by epidemiological data. If we add this to the speed with which it provides results, MIRU-15 could be considered a suitable tool for real-time genotyping.

Impact of laboratory cross-contamination on molecular epidemiology studies of tuberculosis.

Laboratory cross-contamination by Mycobacterium tuberculosis is known to be responsible for the misdiagnosis of tuberculosis, but its impact on other contexts has not been analyzed. We present the findings of a molecular epidemiology analysis in which the recent transmission events identified by a genotyping reference center were overestimated as a result of unnoticed laboratory cross-contamination in the original diagnostic laboratories.