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Recent studies have shown that Nocardia asteroides isolates have five major antibiotic resistance patterns; one of these patterns identifies isolates of Nocardia farcinica. In the current study, we investigated a second pattern characterized by susceptibility to ampicillin and erythromycin. This pattern was seen in 17% of 223 clinical isolates identified by standard techniques as N. asteroides and associated with diseases typical for nocardiae. Biochemically, isolates with this drug pattern were relatively homogeneous and identical to the type strain and previous descriptions of Nocardia nova. The strains studied were unique among nocardiae in having both alpha- and beta-esterase activity (85 and 95%, respectively). However, the arylsulfatase activity at 14 days (75%) and antimicrobial susceptibility patterns, including susceptibility to erythromycin (100%), were the only routinely available methods that would separate N. nova strains from other members of N. asteroides. N. asteroides should be considered a complex because current clinical identification schemes include isolates of N. farcinica and N. nova and may well include additional species. This is the first detailed description of N. nova as a pathogen in humans.

Mycobacterium chelonae-like organisms are nonpigmented rapidly growing mycobacteria whose clinical significance is unknown. We evaluated 87 sporadic isolates encountered in a clinical laboratory. Most isolates (62%) were respiratory; only 2 of 54 (4%) (both from patients with AIDS) were clinically significant. Among 33 nonrespiratory isolates, 20 of 33 (or 61%) were clinically significant. Clinical diseases included posttraumatic wound infections and catheter-related sepsis. Routine biochemical features included growth inhibition by 5% NaCl (100%), a smooth colony morphology (94%), positive 3-day arylsulfatase reaction (84%), no color or a light tan color on iron uptake (100%), and variable nitrate reduction (45%). Additional characteristics that helped to separate this group from M. chelonae and Mycobacterium abscessus were susceptibility to cephalothin (90%) and ciprofloxacin (100%), utilization of mannitol (94%) and citrate (83%) as carbon sources, and unique patterns of mycolic acid esters by high-performance liquid chromatography. This group was quite drug susceptible, with 100% of isolates inhibited by amikacin, imipenem, cefoxitin, cefmetazole, and the newer quinolones ciprofloxacin and ofloxacin. Three examples of this group, including a proposed type strain, have been deposited in the American Type Culture Collection.

A recent study of Nocardia asteroides revealed that 95% of clinical strains had one of five antibiotic resistance patterns. We found the pattern of resistance to cefotaxime and cefamandole in 19% of 200 clinical N. asteroides isolates. Isolates with this drug resistance pattern were from numerous geographic sources and were associated with significant clinical disease (56% of patients had disseminated infections). Phenotypic studies revealed that these isolates were relatively homogeneous and matched previous descriptions and reference strains of the controversial species N. farcinica. Growth at 45 degrees C, acid production from rhamnose, ability to utilize acetamide as a nitrogen and carbon source, and resistance to tobramycin and cefamandole were features of N. farcinica that could be tested in the clinical laboratory and allowed their distinction from N. asteroides. The serious nature of disease due to N. farcinica and its resistance to the newer cephalosporins suggest a clinical need for laboratory identification of this species. (Current tests used in clinical laboratories do not distinguish N. farcinica from N. asteroides.) This is the first recognition that N. farcinica has a specific drug resistance pattern and confirms the previously described concept that drug resistance patterns of N. asteroides may be associated with specific taxonomic groups.

A case of severe progressive subcutaneous abscesses and necrotizing tenosynovitis of the right arm of a 30-year-old woman caused by Rhodococcus aurantiacus is reported.

We attempted to identify the Mycobacterium avium complex (MAC) isolated in Japan by using DNA probes specific for M. avium or Mycobacterium intracellulare (Gen-Probe Rapid Diagnostic System for MAC; Gen-Probe, Inc., San Diego, Calif.). The source and drug susceptibility distributions were examined. This assay system proved to be rapid, sensitive, specific, and reliable for identification of MAC and of the species as either M. avium or M. intracellulare. The DNA probe test showed that of the generally accepted MAC serovars, serovars 1 to 6, 8 to 11, and 21 belonged to M. avium and 7 and 12 to 20 belonged to M. intracellulare. Moreover, with the DNA probe test we found that the distribution patterns of M. avium and M. intracellulare isolates in Japan differed depending on the district in which MAC was isolated. The ratio of M. avium was much higher in eastern Japan. In Tokai and Shimane districts, the ratio of M. avium and M. intracellulare isolates significant in human disease was related to that of isolates from soil and house dust (natural sources). In M. avium, human disease-associated isolates were more resistant to rifampin, streptomycin, and kanamycin than were isolates from natural sources. However, this source dependence was not evident for M. intracellulare. In human disease-associated MAC, M. avium isolates were more resistant to most agents, except for quinolones, than were M. intracellulare isolates.

Rhodococcus sputi caused tuberculosislike lymphadenitis of mesenteric lymph nodes in swine. This is the first study reporting that R. sputi can be a pathogen in swine.

Although it has been recommended that photochromogenicity of mycobacteria should be tested after incubation at 25 to 30 degrees C for 2 weeks (Wayne et al., Int. J. Syst. Bacteriol. 24:412-419, 1974), our results indicate that photochromogenicity should be determined at 37 degrees C in the dark and under continuous exposure to light for 2 weeks. The test at 37 degrees C gives more stable results for Mycobacterium kansasii, Mycobacterium marinum and Mycobacterium szulgai.