CLASSIFICATION AND IDENTIFICATION OF MYCOBACTERIA. I. TESTS EMPLOYING TWEEN 80 AS SUBSTRATE

Mycobacterium terramassiliense, Mycobacterium rhizamassiliense and Mycobacterium numidiamassiliense sp. nov., three new Mycobacterium simiae complex species cultured from plant roots

Three slowly growing mycobacteria named strain AB308, strain AB215 and strain AB57 were isolated from the tomato plant roots. The 16S rRNA and rpoB gene sequence analyses suggested that each strain was representative of one hitherto unidentified slowly-growing Mycobacterium species of the Mycobacterium simiae complex. Genome sequencing indicated that each strain contained one chromosome of 6.015-6.029 Mbp. A total of 1,197, 1,239 and 1,175 proteins were found to be associated with virulence and 107, 76 and 82 proteins were associated with toxin/antitoxin systems for strains AB308, AB215 and AB57, respectively. The three genomes encode for secondary metabolites, with 38, 33 and 46 genes found to be associated with polyketide synthases/non-ribosomal peptide synthases and nine, seven and ten genes encoding for bacteriocins, respectively. The genome of strain AB308 encodes for one questionable prophage and three incomplete prophages, while only incomplete prophages were predicted in AB215 and AB57 genomes. Genetic and genomic data indicate that strains AB308, AB215 and AB57 are each representative of a new Mycobacterium species that we respectively named Mycobacterium terramassiliense, Mycobacterium numidiamassiliense and Mycobacterium rhizamassiliense.

Mycobacterium interjectum, a new species isolated from a patient with chronic lymphadenitis

Mycobacterium-like organisms, isolates 2081/92 and 4185/92, were recovered from a lymph node of a child with chronic lymphadenitis. The growth characteristics, acid-fastness, and mycolic acids of the isolate were consistent with those for Mycobacterium species. The isolates were biochemically distinct from described Mycobacterium species, although they most closely resembled M. scrofulaceum. Comparative 16S rDNA sequencing showed that these isolates represent a new slow-growing Mycobacterium species which is named M. interjectum. Our results demonstrate the importance of 16S rDNA sequencing for recognizing the diversity of species within the genus Mycobacterium.

Mycobacterium marinum infections in man

Mycobacterium marinum, formerly known as ‘Mycobacterium balnei’, is a free-living organism which causes disease in fish and occasionally in man. When such infections occur in man they are usually associated with some aquatic activity, e.g. swimming, fishing, boating and keeping tropical fish. For this reason, the organism has been called a ‘leisure-time pathogen’ by Feldman, Long & David (1974) and the disease a ‘hobby hazard’ by Heineman, Spitzer & Pianphongsant (1972).

Diagnostic probability matrix for identification of slowly growing mycobacteria in clinical laboratories

A probability matrix is presented for identification of slowly growing mycobacteria that are likely to be encountered in clinical laboratories. The matrix includes 23 features that are useful for identifying members of 14 species or species complexes. The computer program identifies strains as a function of the ID (identification) score, which measures the discrimination among possible alternative identifications, and the R (ratio) score, which measures the degree of fit to the most likely taxa. It is not necessary to employ all 23 tests when initiating an identification; the program will suggest additional tests to perform when a partial data set fails to yield a definitive identification. Two independent sets of cultures comprising a total of 1,212 strains were used to test the matrix. Correct diagnoses were based on clustering behavior in numerical taxonomic analysis with larger numbers of features. The probable efficiencies with the two sets were 94.2 and 83.4%, respectively, and the accuracy of the definitive identifications for both sets exceeded 95%. A discussion is presented of situations when it may be appropriate to override an R score that has caused the rejection of an identification and to thereby enhance the efficiency.

Mycobacteriocins produced by rapidly growing mycobacteria are Tween-hydrolyzing esterases

Smegmatocin, a protein produced by Mycobacterium smegmatis ATCC 14468, was found to have an esterase activity, hydrolyzing Tween 80, polyoxyethylene sorbitan monooleate, added to the assay medium for various "bacteriocins" from mycobacteria. Because M. diernhoferi ATCC 19340 (indicator strain for smegmatocin) is highly susceptible to oleic acid and smegmatocin requires Tween 80 for manifestation of its anti-M. diernhoferi activity, it is likely that smegmatocin-mediated antimicrobial action is caused by oleic acid generated by hydrolysis of Tween 80 by the inherent esterase action of smegmatocin. Other mycobacteriocins from rapidly growing mycobacteria also have inherent esterase activity against Tween 80 and require Tween 80 for expression of antimycobacterial action. Smegmatocin was found to hydrolyze various polyoxyethylene (sorbitan) fatty acyl esters but not sorbitan monooleate and glyceryl esters.

Isolation of the Mycobacterium avium-M. intracellulare-M. scrofulaceum complex from tank water in Queensland, Australia

Disease-associated serotypes of Mycobacterium intracellulare and M. avium have been isolated from 32 of 141 rainwater tanks situated in the basin of the Fitzroy River and its tributaries in central Queensland, 7 of 32 tanks situated in the hinterland of the coastal city of Rockhampton, and 2 of 32 tanks sampled repetitively in the southeastern Queensland city of Toowoomba. M. gordonae was also isolated from 23 of the river basin tanks, from 9 in the Rockhampton hinterland, and from 5 in the city of Toowoomba. One half of these isolates came from tanks which also yielded M. intracellulare. Mycobacteria of the M. terrae-M. triviale-M. nonchromogenicum complex were found in 7 tanks, usually in conjunction with M. intracellulare. The humans who consume the contaminated tank water are free of symptoms but have not been medically examined. It is suggested that mycobacteria adhering to dust particles disturbed by mechanical cultivation may be the source of contamination.

Preparation of a stable mycobacterial tween hydrolysis test substrate

A Tween 80 hydrolysis test substrate was found to be stable at room temperature for at least 6 months.

Diagnostic key to mycobacteria encountered in clinical laboratories

A diagnostic key has been developed which will permit identification of most mycobacteria encountered in clinical laboratories. The key is based on performance of a few simple tests. The efficiency and accuracy of the key was evaluated in terms of correlation between identifications based on the few tests and those arrived at through application of the techniques of numerical taxonomy, which involves a large battery of tests. Of 679 cultures of mycobacteria other than Mycobacterium tuberculosis, 86.5% were correctly identified by use of the key, and only 1.8% of the cultures were erroneously identified. The remaining cultures required further examination.

Selection of characters for an Adansonian analysis of mycobacterial taxonomy

Tests which are most frequently employed to provide characters for numerical analysis of bacterial taxonomy provide little differentiation among the slow-growing members of the genus Mycobacterium. A special scheme was proposed to deal with this problem. Characters were based, to some extent, on quantitative reactions to tests, and were defined, for each test, in terms of natural clustering behavior of a large collection of assorted strains. Inter- and intrataxon analyses were based on comparisons of reaction patterns with tentative hypothetical median strain patterns. This permitted the analysis of larger numbers of cultures than can be practically studied in a conventional n x n table.