Mycobacterium tuberculosis transmission among high school students in Greece.

BACKGROUND: The aim of this study was to investigate the requirements and practical steps for screening of Mycobacterium tuberculosis (MTB) transmission among high school student populations in two regional high schools of central Greece. Case-matched control populations from other regional schools were included. METHODS: Case study of two indexed cases, 61 close contacts, 212 casual contacts and 369 controls were investigated. Detailed questionnaires, tuberculin-skin test (PPD test), chest radiography, medical evaluation and DNA fingerprinting of sputum isolates were used. RESULTS: In case A, three (1.97%) of 152 close and casual contacts developed tuberculosis, and a further 25 (16.4%) were classified as infected. In contrast, none of the 121 close or casual contacts investigated for Case B developed tuberculosis or were classified as infected. None of the control populations contained infected individuals. Contacts of case A had a much higher risk (3.08 < RR = 22.29 < 161.69, P < 0.001) of being infected than contacts of case B. Two different strains of MTB were found responsible for these outbreaks. CONCLUSION: There was a considerable difference in the infectivity of the two cases presumably due to environmental and clinical factors, although two different MTB strains were responsible. It is proposed that the extent of case investigation should be individualized with particular emphasis placed among close contacts.

Molecular characterization of Mycobacterium tuberculosis isolates presenting various drug susceptibility from Greece using three DNA typing methods.

OBJECTIVES: The purpose of the present study was the molecular characterization of Mycobacterium tuberculosis clinical isolates using three DNA typing methods. METHODS: One hundred nineteen independent (77 susceptible to all antituberculous drugs, 17 rifampin-resistant and 25 isoniazid-resistant), and nine related Mycobacterium tuberculosis isolates obtained over a 3-years period (1997-1999) from Greece were typed with restriction fragment length polymorphism (RFLP), using the non-radioactive IS6110 probe (IS6110-RFLP), and two PCR-based molecular methods: random amplification of polymorphic domains (RAPD) using four different primers and double repetitive element-PCR (DRE-PCR). RESULTS: IS6110-RFLP and RAPD-PCR using IRIS primer were proved to be the most discriminatory methods, while DRE-PCR gave satisfactory results and RAPD-PCR methods using the other three primers (A1245, B1245 and Leg2) were not so effective. The related strains, isolated from affected members of four families, gave similar PCR and RFLP patterns, while the independent strains presented a high degree of polymorphism. In terms of cost effectiveness and technical simplicity, the PCR-based methods were found to be superior. CONCLUSIONS: So, they may serve as screening methods to classify a large number of isolates into clusters for further subtyping and recognition of well-defined genotype families.