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Increasing outbreaks of pulmonary infections and surgical nosocomial infections caused by Mycobacterium fortuitum-chelonei complex (referred to MFCC) suggested that species identification is epidemiologically important. Differentiation of M. fortuitum from M. chelonei is usually based on two biochemical properties, i.e., nitrate reduction and uptake of iron. However, by means of numerical analysis, M.fortuitum could be further divided into biovar fortuitum and biovar peregrinum, and M. chelonei was also divided into subsp. chelonei and subsp. abscessus. In this study, 26 strains of rapidly growing mycobacteria isolated from sputa patients with tuberculosis-like diseases were identified by arylsulfatase, iron uptake, nitrate reduction, growth on Lo¨wenstein-Jensen media containing 5% NaCl and MacConkey agar and violet pigmentation of colonies on L-J media containing crocin (referred to crocin reaction) . In addition, rapid and reliable clinical bacteriological procedure distinguishing species and subspecies of the MFCC from nonpathogenic rapidly growing mycobacteria encountered with clinical bacteriology is described. The results are summarized as follows: 1. By means of biochemical properties of arylsulfatase and iron uptake, rapidly growing mycobacteria isolated from sputa of patients with tuberculosis-like pulmonary diseases were divided into 3 of large clusters, 1) arylsulfatase and iron uptake positive group belonging to the MFCC, (referred to tentatively groupⅠ), 2) arylsulfatase negative but iron uptake positive group (referred to tentatively group Ⅱ) and 3) arylsulfatase and iron uptake negative group (referred to tentatively group Ⅲ). 2. Out of 26 strains, 9 strains (34.6%) were arylsulfatase 3-day positive and iron uptake 17-day positive and identified as M. fortuitum, but none of the strain was identified as M. chelonei. Species identification of M. fortuitum was confirmed by nitrate reduction test (88.8%) and growth ability on both MacConkey agar (100%) and 5% NaCl medium (100%). 3. Nine strains of M. fortuitum were further divided into 3 types by crocin reaction, i.e., crocin reaction 7-day positive group belonging to biovar fortuitum (referred to type 1) were 6 strains (66.6%), crocin reaction 7-day negative but 21-day positive belonging ti biovar peregrinum(referred to type 2) were 2 strains (22.2%) and all negative group (referred to type 3) was one strain (11.1%), respectively.
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