[Evaluation of rapidly growing Mycobacteria isolates in a general hospital: reports from the hospital microbiology laboratory].

Forty isolates of rapidly growing Mycobacteria, Mycobacterium fortuitum group including M. fortuitum and M. peregrinum and M. chelonae group including M. chelonae subsp. chelonae and M. chelonae subsp. abscessus at Showa University Fujigaoka Hospital collected between February 1981 and December 1997 were investigated in this study. These isolates were from the patients who were not infected with HIV. The average age of fourteen patients, from whom M. fortuitum group was isolated, was 58 years, ranging from 17 to 80 years old. One patient (71-year-old) with chronic myelogenous leukemia and another (64-year-old) with chronic diabetes mellitus were diagnosed with skin abscesses of M. fortuitum group, which were located on the right site of the neck and in the scar after injecting insulin (injection abscess), respectively. The average age of twenty-six patients, from whom M. chelonae group was isolated, was 57 years, ranging from 32 to 84 years old. One patient (75-year-old) with articular rheumatism was diagnosed with a lung infection of mixed M. chelonae group and Pseudomonas aeruginosa, and another (74-year-old) with diabetes mellitus and kidney failure was strongly suspected of a lung infection. The isolates of the two mycobacteria from the remaining patients were due to colonization, while these patients had the following underlying diseases contributing to infections: pulmonary emphysema; diabetes mellitus; leukemia; collagen diseases; lung cancer; chronic kidney diseases; systemic lupus erythematosus; carcinomatous pleurisy; bronchiectasis; post-tuberculosis. Most isolates of the two mycobacteria were separated from the specimens of patients' respiratory tracts, but since M. chelonae group was a contaminant in the tap-water for diluting concentrated chlorhexidine, the organism happened to be isolated with the mucous membranes of the 6 patients' colons that were picked up while using the washed fiber-scope. These findings suggest that M. fortuitum and M. chelonae groups, in spite of the fact that they rarely cause infection, have a significant risk of infecting aged patients in general hospitals with various underlying diseases attributable to infections. As only a few colonies were isolated from patients' specimens in the majority of cases, it took time to carry out these clinical examinations, and to improve this "laboratory's delay", it is needed to make faster report to clinicians.