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L Thibert

Publications and source records attributed to L Thibert.

14 recordsLinked to original sources
PubMed2004

Mycobacterium saskatchewanense sp. nov., a novel slowly growing scotochromogenic species from human clinical isolates related to Mycobacterium interjectum and Accuprobe-positive for Mycobacterium avium complex.

A pigmented, slowly growing Mycobacterium avium complex AccuProbe-positive organism was isolated from the sputum and pleural fluid of a 72-year-old female with bronchiectasis. The unusual morphology of the organism prompted further identification by 16S rRNA gene sequencing, revealing a perfect identity with previously uncharacterized strain Mycobacterium sp. MCRO 8 (GenBank accession no. X93034), with the closest established species by 16S rDNA analysis being Mycobacterium interjectum. HPLC of the organism corresponded to previously obtained patterns identified as M. interjectum-like and, upon sequence evaluation of a selection of strains with a similar profile, more were subsequently identified as MCRO 8. A total of 16 strains isolated from human respiratory samples were evaluated in the characterization of this novel species, for which the name Mycobacterium saskatchewanense sp. nov. is proposed. The type strain is strain 00-250(T) (=ATCC BAA-544(T)=DSM 44616(T)=CIP 108114(T)).

Bacterial Proteins↗
PubMed2004

Mycobacterium parascrofulaceum sp. nov., novel slowly growing, scotochromogenic clinical isolates related to Mycobacterium simiae.

A group of pigmented, slowly growing mycobacteria identified by 16S rRNA gene sequencing as 'MCRO 33' (GenBank accession no. AF152559) have been isolated from several clinical specimens in various laboratories across Canada. Genotypically, the organism is most closely related to Mycobacterium simiae. However, it presents with a similar phenotypic profile to Mycobacterium scrofulaceum. Several reference strains obtained from ATCC and TMC culture collections, previously identified as M. scrofulaceum or M. simiae, have also been found to possess the MCRO 33 16S rRNA gene sequence. Biochemical testing, susceptibility testing, HPLC, hsp65 gene and 16S-23S spacer (ITS1) sequencing were performed on clinical and reference strains to characterize further this unique species. Of the clinical strains, one was isolated from a cervix biopsy whereas all other clinical isolates were obtained from respiratory samples. In one patient, symptoms, imaging and repeat clinical specimens positive on culture for this organism were suggestive of active clinical disease. The description of this species, for which the name Mycobacterium parascrofulaceum sp. nov. is proposed, follows the present trend of a large number of novel Mycobacterium species identified due in great part to sequence-based methods. The type strain is HSC68T (= ATCC BAA-614T = DSM 44648T).

Adult↗
PubMed2000

pncA mutations as a major mechanism of pyrazinamide resistance in Mycobacterium tuberculosis: spread of a monoresistant strain in Quebec, Canada.

Pyrazinamide (PZA) is an important first-line tuberculosis drug that is part of the currently used short-course tuberculosis chemotherapy. PZA is a prodrug that has to be converted to the active form pyrazinoic acid by pyrazinamidase (PZase) activity, encoded by the pncA gene of Mycobacterium tuberculosis, and loss of PZase activity is associated with PZA resistance. To further define the genetic basis of PZA resistance and determine the frequency of PZA-resistant strains having pncA mutations, we sequenced the pncA gene from a panel of 59 PZA-resistant clinical isolates from Canada, the United States, and Korea. Two strains that did not contain pncA mutations and had positive PZase turned out to be falsely resistant. Three PZase-negative strains (MIC, >900 microgram of PZA per ml) and one PZase-positive strain (strain 9739) (MIC, >300 microgram of PZA per ml) did not have pncA mutations. The remaining 53 of the 57 PZA-resistant isolates had pncA mutations, confirming that pncA mutation is the major mechanism of PZA resistance. Various new and diverse mutations were found in the pncA gene. Interestingly, 20 PZA-monoresistant strains and 1 multidrug-resistant isolate from Quebec, Canada, all had the same pncA mutation profile, consisting of an 8-nucleotide deletion and an amino acid substitution of Arg140-->Ser. Strain typing indicated that these strains are highly related and share almost identical IS6110 patterns. These data strongly suggest the spread of a PZA-monoresistant strain, which has not previously been described.

Amidohydrolases↗
PubMed2000

Mycobacterium branderi from both a hand infection and a case of pulmonary disease.

Mycobacterium branderi, a potential human pathogen first characterized in 1995, has been isolated from respiratory tract specimens. We report here a case in which M. branderi was the only organism isolated upon culture from a hand infection. This isolate, along with a second isolate from a bronchial specimen, was subjected to conventional identification tests for mycobacterial species. Further analysis by high-performance liquid chromatography (HPLC) of mycolic acids and 16S rRNA gene sequencing was performed, and the antibiotic susceptibility profile was determined for both strains. Biochemical tests and the HPLC pattern were consistent with that of M. branderi and M. celatum, which are very similar. The 16S rRNA gene sequence of both strains corresponded to that of M. branderi and enabled us to confidently differentiate this organism from other closely related species such as M. celatum. This contributes to a further understanding of the status of this species as a potential human pathogen as well as illustrating the need for molecular diagnostics as a complementary method for the identification of rare mycobacterial species.

Chromatography, High Pressure Liquid↗
PubMed1996

Growth inhibition of Mycobacterium tuberculosis by polyoxyethylene stearate present in the BACTEC pyrazinamide susceptibility test.

We have previously found that approximately 3.5% of 428 clinical isolates of Mycobacterium tuberculosis yield uninterpretable results in the BACTEC pyrazinamide (PZA) susceptibility test system, because of inadequate growth. We tested the hypothesis that polyoxyethylene stearate (POES), the ingredient of the reconstituting fluid for the test, was the cause of this growth inhibition. A total of 15 isolates known for their previously uninterpretable results and 100 randomly chosen clinical isolates were tested in parallel both with and without POES. Repeat testing of the isolates with previously uninterpretable results yielded results in the presence of POES in only seven (47%). In the absence of POES, all gave interpretable results but one such result showed false resistance. For the other 100 clinical isolates, interpretable results were obtained with and without POES, but growth was enhanced in the absence of POES, especially in the PZA-susceptible strains. This was evidenced by a decreased time to attain a growth index of 200 in the control vial (4.9 days without POES versus 5.8 days with POES; P < 0.001) and a higher mean growth index ratio on the day of interpretation of the test (7.4% without POES versus 2.2% with POES; P < 0.001). However, the enhanced growth without POES led to 20 susceptible strains being misinterpreted as either resistant or borderline. We suggest that isolates of M. tuberculosis which yield uninterpretable results in the BACTEC PZA test system should be retested both with and without POES. If interpretable results indicating PZA resistance are obtained only in the absence of POES, the result should be confirmed by a pyrazinamidase assay or by the conventional proportion method. Routine omission of POES from the BACTEC test for all clinical strains is discouraged because of the unacceptably high false-resistance rates.

Antitubercular Agents↗
PubMed1995

Testing of susceptibility of Mycobacterium tuberculosis to pyrazinamide: comparison of Bactec method with pyrazinamidase assay.

The susceptibility of 428 clinical isolates of Mycobacterium tuberculosis to pyrazinamide was assessed by the Bactec method and the Wayne pyrazinamidase assay. The correlation between the two tests was 98.2 and 100% for susceptible and resistant strains, respectively. False resistance was seen in four (0.8%) strains with the Bactec test, and false-susceptible results occurred in two (0.5%) pyrazinamidase assays. The Bactec test is rapid and reliable, and the Bactec results correlate well with the pyrazinamidase test results, although some strains did not grow well in the test medium.

Antitubercular Agents↗
PubMed1993

Routine application of high-performance liquid chromatography for identification of mycobacteria.

Mycolic acid analysis by high-performance liquid chromatography (HPLC) was introduced in our laboratory as the routine technique for identifying all clinical isolates of mycobacteria referred to us. HPLC identified 96.1% of the 1,103 strains analyzed, whereas the biochemical procedures and/or the commercial DNA probes identified 98.3% of strains, for an overall agreement of 94.4%. Compared with the probes, there was 100% specificity and 98.9% sensitivity for Mycobacterium tuberculosis identification. HPLC allowed early detection and identification of the rare mycobacterial species M. haemophilum, M. malmoense, M. shimoidei, and M. fallax as well as uncharacteristic strains of M. simiae. After 18 months of routine use, HPLC proved to be reliable, easy to perform, rapid, and less costly than other identification methods.

Bacterial Typing Techniques↗
PubMed1992

Identification of Mycobacterium avium complex strains and some similar species by high-performance liquid chromatography.

Strains of Mycobacterium avium, Mycobacterium intracellulare, Mycobacterium scrofulaceum, Mycobacterium xenopi, and Mycobacterium gordonae were identified by high-performance liquid chromatography (HPLC) analysis of mycolic acids as bromophenacyl esters. HPLC criteria were used to develop a flow chart identification scheme, which was evaluated in our laboratory with a set of 234 strains representing five species and a hitherto undescribed species. Correct identifications of M. gordonae and M. xenopi were easily made. Flow chart differentiation of M. avium, M. intracellulare, and M. scrofulaceum was done with 97.9, 97.5, and 89.2% accuracies, respectively. Independent evaluation of the flow chart at a separate laboratory demonstrated an overall identification accuracy of 97% for M. avium complex. Strains that have been described biochemically as being intermediate between M. avium-M. intracellulare and M. scrofulaceum were identified as one or the other of these known species. Strains which were negative with the species-specific radioactive probe for M. avium complex but which were positive with the nonradioactive SNAP X probe were usually identified as M. intracellulare and M. scrofulaceum but rarely as M. avium.

Chromatography, High Pressure Liquid↗
PubMed1990

Two cases of Mycobacterium haemophilum infection in Canada.

In 1987, Mycobacterium haemophilum was isolated from cutaneous lesions, a lymph node, and the right eye of a male patient with acquired immunodeficiency syndrome and also from a cervical lymph node in a 3-year-old girl. These two cases are the first M. haemophilum infections to be reported in Canada.

Acquired Immunodeficiency Syndrome↗