Korean isolates of the Mycobacterium chelonae-Mycobacterium abscessus group, which had been isolated from two different hospitals in South Korea, were identified by PCR restriction analysis (PRA) and comparative sequence analysis of 16S rRNA genes, rpoB, and hsp65 to evaluate the proportion of four closely related species (M. chelonae, M. abscessus, M. massiliense, and M. bolletii). Of the 144 rapidly growing mycobacterial strains tested, 127 strains (88.2%) belonged to the M. chelonae-M. abscessus group. In this group, M. chelonae, M. abscessus, M. massiliense, and M. bolletii accounted for 0.8% (n ‫؍‬ 1), 51.2% (n ‫؍‬ 65), 46.5% (n ‫؍‬ 59), and 1.6% (n ‫؍‬ 2), respectively. Two isolates which showed discordant results, M. massiliense by rpoB sequence analysis and M. abscessus by hsp65 sequence analysis, were finally identified as M. massiliense based on the additional analysis of sodA and the 16S-23S internal transcribed spacer. M. abscessus group I isolates previously identified by hsp65 PRA were all found to be M. abscessus, whereas group II isolates were further identified as M. massiliense or M. bolletii by sequencing of rpoB and hsp65. Smooth, rough, or mixed colonies of both M. abscessus and M. massiliense isolates were observed. M. massiliense strains that were highly resistant to clarithromycin had a point mutation at the adenine at position 2058 (A 2058 ) or 2059 (A 2059 ) in the peptidyltransferase region of the 23S rRNA gene.Rapidly growing mycobacteria (RGM), which include members of the Mycobacterium fortuitum complex, the M. chelonae complex, and the M. smegmatis complex, are defined as mycobacteria that grow and form visible colonies on solid agar media within 7 days. Because of their low virulence, they usually cause respiratory tract or disseminated infections in persons with predisposing factors or who are immunosuppressed (27,29,32). However, recently, infections in immunocompetent persons have been reported more frequently. These cases are soft-tissue infections associated with trauma and injection and epidemics or pseudoepidemics that have occurred in hospitals (6, 12). Ninety-five percent of soft-tissue RGM infections are caused by members of the M. chelonae complex (7), which comprises M. chelonae, M. abscessus, and M. immunogenum. However, the situation is complex for the clinical microbiologist who must rapidly and correctly identify isolates because there are reports of heterogeneity in M. abscessus isolates. Two M. abscessus groups (groups I and II) were reported on the basis of hsp65 PCR-restriction fragment length polymorphism (RFLP) (11) and sequence analysis (21) of hsp65. High heterogeneity of M. abscessus isolates was also shown by rpoB analysis (2). Meanwhile, new RGM species were reported: M. massiliense (4) and M. bolletii (1). These were very closely related to M. abscessus and M. chelonae but showed different susceptibility to clarithromycin, and their pathogenic potentials were shown by infections in immunocompetent and immunocompromised hosts (13,19).RGM infections are a...

The population structure of Korean (150 strains) and Japanese (92 strains) Legionella pneumophila isolates along with 18 reference strains were investigated using hsp60 sequence (1647 bp) analysis. Twelve clonal subgroups (hsP-I to hsP-X and hsF-I and hsF-II) were designated on the hsp60 tree, inferred from representative sequences using the neighbor-joining method. Some of the isolates showed unique subgroups depending on the source of isolates, including hsP-I, hsF-I, and hsF-II from cooling tower water, and subgroups hsP-VIII and hsP-X from circulating hot water bath. These subgroups may be useful for epidemiological studies to chase or specify sources of infection in Korea and Japan. Key words genotype analysis, hsp60, Legionella pnuemophila.More than 70 serogroups in 54 Legionella species have been characterized and at least 21 species are known to be pathogenic to humans (1). Among them Legionella pneumophila is the most important human pathogen as it is the causative agent of many epidemics (2-8). It is frequently isolated from various aquatic habitats including ponds, water from cooling towers, and evaporative condensers, which become the sources of infection. Because L. pneumophila occupies the largest portion of isolates from community-acquired infections and nosocomial infection, it continues to attract more public attention than any other Legionella species. Thus, it is important to take preventive measures against the spread of an epidemic through diagnosis and treatment based on quick and precise isolation/identification of the bacteria as well as deter- mining the source of the infection through translational research.A variety of gene analysis methods have been used in translational research (9) for L. pneumophila, such as target gene sequencing (10) as in other microbiological infections. Recently, rpoB and dotA were used (11) to determine the population structures of the Korean and Japanese isolates. Although unique subgroup populations were identified and predominant clonality was observed, other house-keeping gene analysis may be required depending on the source of the isolates. In this study, we sequenced the hsp60 gene in Korean and Japanese isolates and type strains of L. pneumophila, and analyzed the genetic population structures based on the results. From these results we were able to construct a useful database 572