Strains of a new type of group 111 nonphotochromogenic mycobacteria have been repeatedly isolated from four patients with clinical and roentgenological signs of lung mycobacteriosis. These strains split nicotinamide and pyrazinamide as do those of Mycobacterium avium, but they show no esterase activity. Furthermore, the strains produce thermolabile catalase and hydrolyze Tween 80. They also have a unique lipid pattern and special sensitins and agglutinins. These strains, therefore, are considered as belonging to a new species of pathogenic, nonphotochromogenic mycobacteria, for which we propose the name Mycobacterium malmoense. Strain M-o 816 is the type strain, and it has been deposited in the American Type Culture Collection under the number 29571.During the years 1968 through 1970, seven unusual mycobacterial strains were isolated from four patients from Malmo and Lund, Sweden. All of the strains grew extremely slowly and poorly as tiny colonies. Their properties, as determined at laboratories in Malmo, Sweden, and in Borstel, Germany, indicated that they belonged to a new species. This paper reports the results of a taxonomic study of these strains. MATERIALS AND METHODSBacterial strains. The seven strains of atypical mycobacteria studied (referred to herein as the Malmo strains) and their sources are cited below. Strain M-6 648 was isolated from a needle aspiration of a process in the right lung, and strains M-6 649 and M-o 650 were isolated from gastric lavage and bronchial secretion, respectively, of the patient. Strains M-o 709 and M-o 710 were isolated from gastric lavage and sputum, respectively, from the second patient, who had two more sputum samples which were culture positive. Strain M-o 716 was isolated from the sputum of the third patient, who had four more positive samples. Strain M-o 816 was isolated from resected lung tissue in the fourth patient, who also had positive sputum cultures.The results of earlier studies (11) of strains of Mycobacterium avium, Mycobacteriurn intrace&-lare, and Mycobacterium xenopi were compared with the properties of these new strains.Strain characteristics. Colony morphology and the ability of the strains to grow at various temperatures (22, 31, 37, 39, 43, and 45°C) were observed during 6 weeks of incubation of cultures on Lowenstein-Jensen medium inoculated with mg of mycobacteria per tube.Drug susceptibility testing was performed with Lowenstein-Jensen medium in tubes closed with stoppers which allowed exchange of air. Chemotherapeutic agents were added before inspissation. Tubes containing isoniazid, streptomycin, ethambutol, rifampin, p-aminosalicylic acid, or thiosemicarbazone were inoculated with mg of mycobacteria per tube; those with ethionamide, capreomycin, viomycin, kanamycin, or cycloserine were inoculated with mg per tube. Two control tubes were included in each test series, as were two additional controls, with an inoculum of lo+ mg of bacteria per tube. Cultures were incubated for 4 weeks at 37°C. Strains were reported as resistant if they grew in ...

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Mycobacterium malmoense was first described in 1977 and today is second only to the Mycobacterium avium complex as a cause of atypical mycobacterial infection in Sweden. We retrospectively studied the records of 221 patients from whom M. malmoense was isolated during 1968-1989. M. malmoense was recovered from the respiratory tract of 171 patients (170 adults and one child) and from cervical lymph nodes of 36 patients (35 children and one adult). In addition, the organism was isolated from the urine of six patients, one of whom had disseminated disease and two of whom had abscesses caused by M. malmoense. A majority of the patients with pulmonary infection as well as the patient with disseminated disease had other underlying diseases.