Identification of Mycobacterium and Mycobacterium tuberculosis

The identification results of 3530 Mycobacterium strains isolated from a clinical material from tuberculosis patients are presented. 3219 (91.17%) of the strains are classified AS M. tuberculosis and 331 (8.83%) as nontuberculous, containing, generally, M. fortuitum group. (96 or 2.71% of the cases). Most of the nontuberculous mycobacteria had no clinical value. Mycobacteriosis caused by these mycobacteria was diagnosed in 6 patients. Biochemical identification tests allowed one to specify the species of 19 Mycobacteria. Out of 738 environmental inoculations, mycobacteria were isolated in 43 (5.82%) cases, including 42 (97.68%) nontuberculous strains.     

Enzymatic profile of Mycobacterium avium and Mycobacterium intracellulare

The characterization of extracellular enzymatic activities of Mycobacterium avium and Mycobacterium intracellulare which were identified by DNA probe (Gen-Probe, Cal., USA) was carried out using the API ZYM system (API, La Balme Les Grottes, France). The enzymatic activities of M. avium were attributed to esterase (C4), esterase lipase (C8), leucin arylamidase, acid phosphatase and phosphoamidase. Enzymatic characterization of M. intracellulare was very similar to that of M. avium. However, M. intracellulare differed from M. avium in the following two points: (i) Alkaline phosphatase activity was demonstrated, (ii) Acid phosphatase activity was much stronger.     

Relationship between Mycobacterium simiae and Mycobacterium habana.

Strains of the species Mycobacterium simiae give a positive niacin test. On the basis of their cultural and biochemical characteristics and by seroagglutination they can be classified into 2 subspecies. (1) The strains of serotype M. simiae 1 hydrolyze urea regularly and nicotinamide and pyrazinamide irregularly. They are photochromogenic after prolonged exposure to light. (2) The strains of serotype M. simiae 2 hydrolyze urea only. Three of 4 strains are scotochromogenic; the fourth has a pale pink pigment. Two of these strains possess alpha- and beta-esterase activity. The other two are negative in this test. Strains of M. habana are culturally and biochemically identical with the serotype M. simiae 1 and show the same serologic specificity as M. simiae 1. M. habana sera, after having been absorbed by M. simiae 1, retain a small amount of agglutinins specific for M. habana. We believe that the M. habana strains belong to the species M. simiae and are closely related to the serotype M. simiae 1.     

Differentiation between Mycobacterium malmoense and Mycobacterium nonchromogenicum by ethambutol susceptibility

Mycobacterium malmoense strains are resistant to 1 microgram/ml ethambutol in Ogawa egg medium, whereas Mycobacterium nonchromogenicum strains are susceptible to this concentration. Therefore, these two Group III nonphotochromogens are differentiated clearly from each other by the susceptibility test for ethambutol 1 microgram/ml. Ninety-five % of Mycobacterium avium complex strains are resistant to this concentration, while M. nonchromogenicum strains are susceptible. Therefore, the test serves for differentiating M. nonchromogenicum from M. avium complex. Previously, Tsukamura (Kekkaku 45: 237, 1970) reported that pathogenic and nonpathogenic mycobacteria of Group II and Group III are differentiated by the susceptibility test to ethambutol, 5 micrograms/ml. However, the use of Ogawa egg medium containing 1 microgram/ml ethambutol is superior to that of 5 micrograms/ml ethambutol for differentiating pathogenic and nonpathogenic ones of the Group III.     

Clinical and radiological features of Mycobacterium kansasii infection and Mycobacterium simiae infection

This retrospective study sought to systematically identify clinical and radiological features of Mycobacterium kansasii and Mycobacterium simiae infections. The sample included consecutive patients with a culture-positive diagnosis of M. simiae infection (n=102) or M. kansasii infection (n=62) derived from the databases of the Laboratory of Microbiology of a tertiary medical centre and two outpatient tuberculosis centres. Data on patient background and clinical features were collected, and chest radiographs were analysed. Sixty percent of the M. kansasii group were native born compared to 18% of the M. simiae group (p=0.0001). M. simiae infection was associated with a higher rate of co-morbid disease, including diabetes mellitus, heart disease, and malignancy. A similar rate of lung disease was found in both groups. Clinical symptoms were significantly more common in patients with M. kansasii infection. On radiological study, M. kansasii infection was associated with more cavitations, and M. simiae infection with more pulmonary infiltrates. Patients with M. simiae infection had a higher likelihood of middle and lower lobe disease whereas patients with M. kansasii infection had more upper lobe disease (p=0.001). Pleural effusions and lymphadenopathy were found only in the presence of M. simiae infection. We concluded that there are major differences in the epidemiologic features of M. kansasii and M. simiae infection which have important diagnostic and therapeutic implications.