Commercial DNA Probes for Mycobacteria Incorrectly Identify a Number of Less Frequently Encountered Species▿ †

Although commercially available DNA probes for identification of mycobacteria have been investigated with large numbers of strains, nothing is known about the ability of these probes to identify less frequently encountered species. We analyzed, with INNO LiPA MYCOBACTERIA (Innogenetics) and with GenoType Mycobacterium (Hein), 317 strains, belonging to 136 species, 61 of which had never been assayed before. INNO LiPA misidentified 20 taxa, the majority of which cross-reacted with the probes specific for Mycobacterium fortuitum and the Mycobacterium avium-Mycobacterium intracellulare-Mycobacterium scrofulaceum group. GenoType misidentified 28 taxa, most of which cross-reacted with M. intracellulare and M. fortuitum probes; furthermore, eight species were not recognized as members of the genus Mycobacterium. Among 54 strains investigated with AccuProbe (Gen-Probe), cross-reactions were detected for nine species, with the probes aiming at the M. avium complex being most involved in cross-reactions

Molecular investigations applied to nontuberculous mycobacteria identification

Objective. Aim of this study was molecular identification in clinical specimens of NonTuberculous Mycobacteria (NTM) with commercial methods and automated sequencing. Materials and methods. Three thousand clinical specimens were analyzed for the isolation of Mycobacteria. Forty strains of NTM were previously analyzed with GenoType Mycobacteria CM/AS kit and then with partial 16S rDNA sequencing. Results. 38/40 NMT strains were identified with GenoType Mycobacteria CM/AS kit as: M. gordonae (15), M. intracellulare (8), M. xenopi (8), M. mucogenicum (2), M. kansasii (2), M. chelonae (1), M. avium (1), M. lentiflavum (1). Two unidentified strains were subjected to 16S rDNA sequencing and were identified as M. kumamotonense. Conclusions. Partial 16SrDNA sequencing is a valid assay to study NTM strains unidentified with commercial assays. This new approach, applied to clinical diagnostic, also permits the recognition of unusual strains or new species

Interaction of pneumococcal surface structures with microglia

Interaction of pneumococcal surface structures with microgli

The encapsulated strain TIGR4 of Streptococcus pneumoniae is phagocytosed but is resistant to intracellular killing by mouse microglia

The polysaccharide capsule is a major virulence factor of Streptococcus pneumoniae as it confers resistance to phagocytosis. The encapsulated serotype 4 TIGR4 strain was shown to be efficiently phagocytosed by the mouse microglial cell line BV2, whereas the type 3 HB565 strain resisted phagocytosis. Comparing survival after uptake of TIGR4 or its unencapsulated derivative FP23 in gentamicin protection and phagolysosome maturation assays, it was shown that TIGR4 was protected from intracellular killing. Pneumococcal capsular genes were up-regulated in intracellular TIGR4 bacteria recovered from microglial cells. Actual presence of bacteria inside BV2 cells was confirmed by transmission electron microscopy (TEM) for both TIGR4 and FP23 strains, but typical phagosomes/phagolysosomes were detected only in cells infected with the unencapsulated strain. In a mouse model of meningitis based on intracranic inoculation of pneumococci, TIGR4 caused lethal meningitis with an LD(50) of 2 × 10(2) CFU, whereas the LD(50) for the unencapsulated FP23 was greater than 10(7) CFU. Phagocytosis of TIGR4 by microglia was also demonstrated by TEM and immunohistochemistry on brain samples from infected mice. The results indicate that encapsulation does not protect the TIGR4 strain from phagocytosis by microglia, while it affords resistance to intracellular killing

Mycobacterium europaeum sp. nov., a scotochromogenic species related to Mycobacterium simiae complex

Four strains isolated in the last 15 years were revealed to be identical, in the 16S rDNA, to MCRO19, a sequence deposited in GenBank since 1995. In a polyphasic analysis including phenotypic and genotypic features the five strains (including MCRO19), which had been isolated in four European countries, turned out to represent an unique taxonomic entity. They are scotochromogenic slow growers and are genetically related to the group including, along with Mycobacterium simiae, 15 other species. In addition to the description of the new species, for which the name Mycobacterium europaeum is proposed, a thorough revision of phenotypic and genotypic characters of the species related to M. simiae was conducted which leads us to suggest, for this group, the denomination of M. simiae complex. FI-95228 (DSM45397=CCUG58464) was chosen as type strain