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Biomedical subjects

H L David

Publications and source records attributed to H L David.

At least 127 records · Page 7Linked to original sources
PubMedDate not supplied

Specificity of Mycobacterium tuberculosis phenolic glycolipid (PGL-Tb1) antiserum.

The specificity of Mycobacterium tuberculosis anti-PGL-Tb1 antiserum prepared in rabbits was evaluated by an enzyme-linked immunosorbent assay. It was found that the antiserum immunoreacted with its homologous antigen but not with purified phenolic glycolipids from M. bovis BCG (mycoside B), M. kansasii (mycoside A), M. leprae (PGL-I) or M. marinum (mycoside G). The analysis of chloroform/methanol extracts from 15 strains of M. tuberculosis showed that all formed the antigen except the type strain (strain H37Rv). Chloroform/methanol extracts of M. bovis BCG, M. xenopi, M. flavescens and M. fallax cross-reacted with the immune serum. However, chloroform/methanol extracts of representative strains of 18 other mycobacterial species did not react, therefore indicating that these did not contain the antigen.

Animals↗
PubMedDate not supplied

Drug susceptibility testing in tuberculosis: a comparison of the proportion methods using Lowenstein-Jensen, Middlebrook 7H10 and 7H11 agar media and a radiometric method.

In the present investigation, the conventional drug susceptibility testing procedures using the 1% proportion method on Löwenstein-Jensen (LJ) and Middlebrook 7H10/7H11 agar media were compared with a recent radiometric method. The latter using "Bactec 460-TB" apparatus and a special broth medium (Becton and Dickinson Diagnostic Instrument Systems, Towson, MD, USA) gave drug susceptibility results within a week as compared to 4-5 weeks with the LJ method, and 3-4 weeks using 7H10/7H11 agar media. This report describes the critical concentrations retained for each of the methods and the methodology used. Also, the compatibility of the results obtained with the radiometric method with those obtained with conventional 7H11 agar method was perfect. In this report, we justify the choice of the 7H11 agar method instead of the LJ method as our conventional drug susceptibility procedure, and suggest also that radiometric drug susceptibility determination by Bactec 460-TB apparatus may be the method of choice for routine, rapid drug susceptibility determinations.

Colony Count, Microbial↗
PubMedDate not supplied

Selective inhibition of the Mycobacterium tuberculosis complex by p-nitro-alpha-acetylamino-beta-hydroxypropio phenone (NAP) and p-nitrobenzoic acid (PNB) used in 7H11 agar medium.

The potential of p-nitrobenzoic acid (PNB) and p-nitro-alpha-acetylamino-beta-hydroxypropiophenone (NAP) for discriminating the Mycobacterium tuberculosis (M.tb) complex from other mycobacteria was evaluated in cases of clinical isolates. For this purpose, 500 micrograms/ml of PNB and 5 or 10 micrograms/ml of NAP were incorporated in 7H11 agar medium, and appropriate dilutions corresponding to about 10(6) viable units were then plated on PNB- or NAP-containing media. Results were reported as growth or no growth as compared to a parallel control. Our data reconfirmed the potential of PNB to discriminate M.tb complex bacteria. This study also showed for the first time that the NAP test (used until now in 7H12a broth only) can also be successfully applied using 7H11 agar. Also, preliminary data with 5 micrograms/ml of NAP on a limited number of strains suggested that it may discriminate the M.tb complex bacilli from M. xenopi and M. gastri better than PNB in 7H11 agar.

Antitubercular Agents↗
PubMedDate not supplied

Evaluation of a novel 2,3-diacyl-trehalose-2'-sulphate (SL-IV) antigen for case finding and diagnosis of leprosy and tuberculosis.

Serum IgG and IgM antibodies against a 2,3-diacyl-trehalose-2'-sulphate (SL-IV) antigen using ELISA were determined in controls (n = 288) and in leprosy (n = 210) and tuberculosis (n = 99) patients. In all assays, the amount of antigen per well was 100.0 ng and sera were diluted 1/250. In the case of leprosy, anti-SL-IV IgG and IgM antibody titres increased from the tuberculoid towards the lepromatous pole of the spectrum. In the tested population, the sensitivity of the assay was 93.2% in multibacillary leprosy and 33.3% in paucibacillary leprosy (specificity of 88.7%). Multibacillary patients with erythema nodosum leprosum (ENL) had lower titres than non-ENL. ELISA results were similar to those obtained using the Mycobacterium leprae phenolic glycolipid-I (PGL-I) antigen. In the case of tuberculosis (pulmonary and extrapulmonary), significant titres of anti SL-IV IgG and IgM antibodies were detected in about 75% of the patients using a cutoff point of 0.150, and in 51.6% using a cutoff of 0.300 (specificities were, respectively, 88% and 100%). We concluded that the determination of IgG and IgM antibodies against SL-IV was useful in leprosy and tuberculosis case finding program using a cutoff point of 0.150, and for serodiagnosis using a cutoff of 0.300.

Antigens, Bacterial↗
PubMedDate not supplied

DOT-ELISA for detection of phenolic glycolipid PGL-Tb1 and diacyl-trehalose antigens of Mycobacterium tuberculosis.

A DOT-ELISA method for detection of 2,3-diacyl-trehalose (DAT, previously referred to as SL-IV antigen) and triglycosyl phenol phthiocerol di-mycocerosate (PGL-Tb1) antigens from Mycobacterium tuberculosis is described. The method enabled the detection of both antigens in 14 clinical isolates of M. tuberculosis from different geographic origins; the presence of the glycolipids was confirmed by chemical analysis. It was therefore concluded that the synthesis of both of these compounds is characteristic of the species.

Antigens, Bacterial↗
PubMedDate not supplied

Restriction endonuclease mapping and cloning of Mycobacterium fortuitum var. fortuitum plasmid pAL5000.

A restriction map of Mycobacterium fortuitum var. fortuitum plasmid pAL5000 was established. The unique sites for ApaI, BamHI, BglII, BstEII, ClaI, EcoRI, EcoRV, HpaI, KpnI and NarI were located on the 5.0-Kb plasmid. The plasmid had no sites for AhaIII, BclI, HindIII, PstI, SphI and XbaI. pAL5000 was cloned into pBR322 and propagated in Escherichia coli. Three hybrid pAL5000-pBR322 plasmids carrying the complete pAL5000 sequence were constructed by joining the plasmids at their BamHI, EcoRI or EcoRV sites. We also cloned into these plasmids a 1489-bp DNA fragment conferring resistance to kanamycin and originating from the streptococcal plasmid pJH1. The construction of these plasmids will facilitate the analysis and manipulation of pAL5000, and may allow the development of a vector system for genetic analysis in mycobacteria.

Chromosome Mapping↗
PubMedDate not supplied

Antimycobacterial spectrum of colistin (polymixin E).

Minimal inhibitory concentrations and minimal bactericidal concentrations of colistin (polymyxin E) were determined for the type strains of fifteen mycobacterial species. Colistin was found to be active against pathogenic species Mycobacterium xenopi, M. intracellulare, M. tuberculosis, M. fortuitum and also against the rapidly growing, non-pathogenic species M. phlei and M. smegmatis. The discriminatory potential of susceptibility to colistin as a test was investigated on 25 strains of the M. fortuitum/M. chelonei complex, and also on 11 strains of the M. avium/M. intracellulare complex. The experimental data indicated the potential of colistin susceptibility testing for discriminating M. fortuitum from M. chelonei.

Colistin↗
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Biochemical and cultural analysis of mycobacterial recombinants obtained by spheroplast fusion.

Spheroplast fusion using polyethylene glycol 6000 resulted in mycobacterial recombinants with a frequency of about 10(-3). The parental strains were two carotenoid pigment mutants of Mycobacterium aurum which were obtained by chemical mutagenesis of the wild-type strain with N-methyl-N'-nitro-N-nitrosoguanidine. Isolation of recombinant clones was based on their pigmentation on Löwenstein-Jensen medium, and genetically stable recombinants were analysed for their carotenoid pigments and their alpha- and beta-mycolic acids. They were then submitted to 14 biochemical tests as well as determination of their susceptibility to 13 drugs and their ability to grow at 30 and 42 degrees C. Recombinants were found to be positive for nitrate reductase (100%), gamma-glutamyl transferase (94%), urease (53%) and arylsulphatase (21%). Out of 34 recombinants tested, 5 grew both at 30 degrees and 42 degrees C, whereas 1 grew only at 37 degrees C. The results of drug susceptibility testing were inconclusive.

Anti-Bacterial Agents↗
PubMedDate not supplied

Differentiation of Mycobacterium thermoresistibile from Mycobacterium phlei and other rapidly growing mycobacteria.

Mycobacterium thermoresistibile is the only chromogenic rapidly growing mycobacterial species reported to cause infections in humans and animals. DNA-DNA hybridization (S1 nuclease method) showed that M. thermoresistibile formed a DNA relatedness group which was only 24 to 30% related to M. phlei. Alkaline phosphatase and beta-galactosidase differentiated M. thermoresistibile from M. phlei. Among the rapidly growing mycobacteria, the mycolic acid pattern of M. thermoresistibile was unique (alpha-, alpha'-, methoxy-and keto-mycolates). Fourteen other species of chromogenic rapidly growing mycobacteria, including M. phlei, produced different mycolic acid patterns which always included dicarboxylic mycolate. Nine species of non-chromogenic rapidly growing mycobacteria produced mycolic acid patterns devoid of ketomycolate.

Alkaline Phosphatase↗
PubMedDate not supplied

Basis for lack of drug susceptibility of atypical mycobacteria.

The patterns of multiple-drug resistance of the nontuberculous mycobacteria as judged from population analysis of recent isolates are described. In this article the various possible mechanisms of drug resistance in these mycobacteria (high frequencies of spontaneous mutation, drug-resistance factors, permeability, and exclusion) are analysed in light of current evidence. Epidemiologic and bacteriologic arguments are presented that appear to refute the hypothesis that high frequency of spontaneous mutation and drug-resistance factors explain multiple-drug resistance. Preliminary work suggesting that resistance in nontuberculous mycobacteria may be caused by the failure of antibiotics to reach the cytoplasmic membrane is discussed.

Drug Resistance, Microbial↗
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Interaction of Mycobacterium leprae and mycobacteriophage D29.

This study of the interaction between Mycobacterium leprae and the mycobacteriophage D29 showed that the viruses caused a patchy damage of cell wall structure and the accumulation in the host of internal crystalline structures. Whether the observed ultrastructural alterations were caused by the replication of D29 was not clear. Mitomycin C also caused the accumulation of crystalline structures in M. leprae.

Cell Wall↗
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Taxonomy of mycobacterial strains isolated from the tissues of leprosy patients.

Thirty-six slowly growing mycobacteria isolated from the tissues of leprosy patients were studied using 40 characteristics as well as susceptibility to 27 distinct mycobacteriophages. The composition in mycolic acids of selected strains was also studied. According to the data, the strains formed 5 clusters. Some of the clusters were possibly as yet undescribed species; however, comparison of the data with the known properties of Mycobacterium leprae leads to the conclusion that none of the strains were identical to the leprosy bacillus.

Anti-Bacterial Agents↗
PubMedDate not supplied

Lipids as taxonomic markers for bacteria derived from leprosy infections.

Lipid analysis allows the specific detection of M. leprae among various other bacteria isolated from leprosy lesions. In this report mycolates and glycolipid compositions were used for such a discrimination. Comparative studies of the lipid composition of tissue fragments from different organs of experimentally infected armadillos, and of cultivable strains isolated from these tissues showed that the last ones did not multiply extensively in the tissues of the animals.

Animals↗