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.

Molecular typing of Legionella pneumophila serogroup 1 isolates from patients and the nosocomial environment by arbitrarily primed PCR and pulsed-field gel electrophoresis.

The ubiquity of Legionella pneumophila in aquatic habitats means that epidemiological evaluation is important for the investigation and control of nosocomial outbreaks of legionellosis. Pulsed-field gel electrophoresis (PFGE) of chromosomal DNA following digestion with SfiI is considered to be one of the most discriminative methods for detecting DNA polymorphisms amongst L. pneumophila serogroup 1 (Lp1) isolates. This paper describes an arbitrarily primed PCR (AP-PCR) method with three different primers (20-mers) for detecting DNA polymorphisms of Lp1 isolates. The AP-PCR assay was compared with PFGE analysis. Both experimental methods were found to have good discriminatory power (discrimination index of 98% and 94.3%, respectively) with 27 unrelated isolates from different geographical areas collected between 1987 and 1997. Furthermore, when the AP-PCR was used in the epidemiological investigation of nosocomial cases of infection, convergent results with the three primers allowed an epidemiological link to be established between isolates from patients and their environment. The AP-PCR method, which is rapid and easy to perform, gave results at least as discriminatory as those obtained with the PFGE method and is proposed for use in the molecular typing of Lp1 outbreaks.