Evidence that the capsule around mycobacteria grown in axenic media contains mycobacterial antigens: implications at the level of cell envelope architecture

Rastogi, Nalin; Hellio, Raymond

doi:10.1111/j.1574-6968.1990.tb13971.x

Cited by 17 publications

(5 citation statements)

References 12 publications

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“…However, the rough variant can apparently synthesize a partially glycosylated lipopeptide that may be similar to the apolar GPL (3,48). The inhibitory nature of these drugs may also suggest a glycosylated component(s) that is shared by both the rough and smooth variants, perhaps as a part of the reported polysaccharide outer layer (37).…”

Section: Discussionmentioning

confidence: 99%

Activities of fluoroquinolone, macrolide, and aminoglycoside drugs combined with inhibitors of glycosylation and fatty acid and peptide biosynthesis against Mycobacterium avium

Barrow

Wright

Goh

et al. 1993

Antimicrob Agents Chemother

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Smooth-and rough-colony variants of Mycobacterium avium serovar 4 were treated with three classes of drugs. The drugs were chosen for their potential inhibitory effects on the biosynthesis of the cell envelopeassociated serovar-specific glycopeptidolipid antigens. Growth was monitored radiometrically with a BACTEC 460-TB instrument, and MICs were determined for each drug. Both variants were then treated with inhibitory drugs in combination with antimicrobial agents that have demonstrated effectiveness against M. avium. No growth inhibition was observed with 6-fluoro-6-deoxy-D-glucose or avidin. Inhibitors of glycosylation, i.e., 2-deoxy-D-glucose, bacitracin, and ethambutol, were inhibitory to smooth-and rough-colony variants, whereas drugs that inhibit peptide synthesis, i.e., N-carbamyl-L-isoleucine and m-fluoro-phenylalanine, were more inhibitory for the rough-colony variant. Cerulenin, which affects fatty acid synthesis, was inhibitory for both variants, but it appeared to be more effective at inhibiting the growth of the smooth-colony variant at equivalent concentrations. Generally, when inhibitors of glycosylation were used with sparfloxacin and amikacin, a synergistic effect was observed for only the smooth variant. When drugs that affect peptide synthesis were used in combination with amikacin, a synergistic effect was observed for the rough variant, and when cerulenin was used in combination with sparfloxacin or amikacin, a synergistic effect was observed for both variants. Lipid analysis revealed that although the rough variant lacks the serovar-specific glycopeptidolipid antigens, it does possess a group of phenylalanine-isoleucine-containing lipopeptides that may explain its different susceptibility patterns to m-fluoro-phenylalanine and N-carbamyl-L-isoleucine. The significance of these results is discussed with reference to various components in the cell envelope and their importance in cell wall permeability.The new emphasis of the National Institute of Allergy and Infectious Diseases is "to spark efforts" to better understand the opportunistic infections associated with AIDS so that new and effective treatments can be developed (45). A major obstacle preventing the development of better therapies for those opportunistic pathogens is a "basic lack of knowledge about the pathogens that cause such diseases" (45). The Mycobacterium avium complex represents one of the most important groups of opportunistic pathogens infecting patients with AIDS (23,45 Rastogi et al. (33) proposed that a polysaccharide outer layer may be responsible for the impermeability of smoothtransparent variants to various substrates and drugs and also increased pathogenicity. The presence of the fibrillar material described by Draper (13) and Kim et al. (21) and later referred to as the superficial L, layer (2) may also be important as a barrier because of the polar glycopeptidolipids (GPLs) that make up its superficial location (4, 6, 44). Crowle et al. (9) suggested that both the polysaccharide layer (32, 33) and the GPL layer...

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Section: Discussionmentioning

confidence: 99%

Activities of fluoroquinolone, macrolide, and aminoglycoside drugs combined with inhibitors of glycosylation and fatty acid and peptide biosynthesis against Mycobacterium avium

Barrow

Wright

Goh

et al. 1993

Antimicrob Agents Chemother

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“…Adequate chemotherapy of these organisms is hampered, first, because of the multiple drug resistance, which has been attributed to an exclusion barrier localized in the cell wall (2,22), and, second, because of their particular mode of intracellular parasitism (20,21), implying that actively growing M. avium is not only surrounded by a capsule-like structure (28) but is also further protected inside the usually hostile phagosomal or phagolysosomal environment by its ability to inhibit normal macrophage functions (5,20,31).…”

Section: Discussionmentioning

confidence: 99%

Antimycobacterial spectrum of sparfloxacin and its activities alone and in association with other drugs against Mycobacterium avium complex growing extracellularly and intracellularly in murine and human macrophages

Rastogi

Labrousse

Goh

et al. 1991

Antimicrob Agents Chemother

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The MICs and MBCs of the new difluorinated quinolone drug sparfloxacin against type strains belonging to 21 species of mycobacteria were screened. The MICs and MBCs were within the range of 0.1 to 2.0 and 0.1 to 4.0 ,ug/ml, respectively (with an MBC/MIC ratio of 1 to 2), and against 18 of the 21 species tested, the drug showed significant bactericidal activity (at least 99% killing or more of the initial inoculum added) at concentrations well within the reported peak concentrations in serum (Cm.) in humans. MICs of sparfloxacin for 7 of 10 Mycobacterium avium complex strains were below the Cm,,, with MBC/IMIC ratios within the range of 2 to 4. Enhancement of its activity by ethambutol, rifampin, amikacin, and clarithromycin (which were used at sublethal concentrations) assessed by using BACTEC radiometry revealed that its activity was further enhanced in 2 of 10 strains by rifampin and in 7 of 10 strains by ethambutol. The bactericidal effects of various drugs used alone as well as two-drug combinations used at Cm.. levels were also screened against four strains of M. avium complex growing intracellularly in two different macrophage systems, namely, mouse bone marrow-derived macrophages and peripheral blood monocyte-derived human macrophages. Our results showed a satisfactory correlation between the extracellular and intracellular drug activity data.Recently, newer fluoroquinolones have been reported to have broad antimicrobial spectra, including mycobacteria (3,14,25). Both the N-cyclopropyl analog ciprofloxacin and the tricyclic compound ofloxacin were found to penetrate actively and concentrate inside mammalian cells (6,13,35), and were found to be capable of killing intracellularly growing tubercle bacilli (19). A newly synthesized difluorinated quinolone, sparfloxacin [5 amino-1-cyclopropyl-6,8-difluoro-1,4-dihydro-(7 cis-3,5-dimethyl-1-piperazinyl)-4-oxoquinolone-3-carboxylic acid], was retained for this study because it is a broad-spectrum drug with in vitro and in vivo efficacies equal to or better than those of ofloxacin and ciprofloxacin (17), and compared with other fluoroquinolones, it has lower MICs against both tubercle bacilli (24) and the multiple-drug-resistant opportunistic pathogens belonging to the Mycobacterium avium complex (MAC) (37). Considering the intracellular parasitism of MAC organisms as well as that of other difficult-to-treat atypical mycobacteria, it was interesting that sparfloxacin attained levels in mouse and rat tissues which were 1 to 11 times higher than its concentrations in plasma (maximum concentration in serum [Cmax], 1.4 ,ug/ml) (16).After we made the observations described above, we decided to perform the present four-point study on sparfloxacin activity (i) to assess its antimycobacterial spectrum against 21 species of mycobacteria by MIC and MBC determinations with 7H9 broth; (ii) by radiometric determination of its MICs and MBCs against 10 MAC strains; (iii) to investigate the enhancement of its action (used at a sublethal concentration of 0.25 ,ug/ml) against 10 M...

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“…Early reports suggested that the outer surface of mycobacteria was composed of mycosides (10,11). Later studies indicated the presence of an outer polysaccharide-rich layer (45, 50), which could explain the presence of the so-called electron-transparent zone often seen in electron micrographs of mycobacteria inside M (13, 18) and more recently in axenically grown bacteria (17,42,43,51). Support for this contention has come from studies describing the presence of an outer surface capsule on M. tuberculosis (12).…”

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confidence: 98%

Mycobacterium tuberculosisCpn60.2 and DnaK Are Located on the Bacterial Surface, Where Cpn60.2 Facilitates Efficient Bacterial Association with Macrophages

Hickey¹,

Thorson

Speert

et al. 2009

Infect Immun

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Mycobacterium tuberculosis, the causative agent of tuberculosis, initially contacts host cells with elements of its outer cell wall, or capsule. We have shown that capsular material from the surface of M. tuberculosis competitively inhibits the nonopsonic binding of whole M. tuberculosis bacilli to macrophages in a dosedependent manner that is not acting through a global inhibition of macrophage binding. We have further demonstrated that isolated M. tuberculosis capsular proteins mediate a major part of this inhibition. Twodimensional polyacrylamide gel electrophoresis analysis of the capsular proteins showed the presence of a wide variety of protein species, including proportionately high levels of the Cpn60.2 (Hsp65, GroEL2) and DnaK (Hsp70) molecular chaperones. Both of these proteins were subsequently detected on the bacterial surface. To determine whether these molecular chaperones play a role in bacterial binding, recombinant Cpn60.2 and DnaK were tested for their ability to inhibit the association of M. tuberculosis bacilli with macrophages. We found that recombinant Cpn60.2 can inhibit ϳ57% of bacterial association with macrophages, while DnaK was not inhibitory at comparable concentrations. Additionally, when polyclonal F(ab) 2 fragments of anti-Cpn60.2 and anti-DnaK were used to mask the surface presentation of these molecular chaperones, a binding reduction of ϳ34% was seen for anti-Cpn60.2 F(ab) 2 , while anti-DnaK F(ab) 2 did not significantly reduce bacterial association with macrophages. Thus, our findings suggest that while M. tuberculosis displays both surfaceassociated Cpn60.2 and DnaK, only Cpn60.2 demonstrates adhesin functionality with regard to macrophage interaction.The initiation of a tuberculous infection involves the adherence and phagocytosis of Mycobacterium tuberculosis bacilli by host cells. It is generally thought that the primary host niche of M. tuberculosis is the alveolar macrophage (M). To access this cell, ligands on the outer surface of the M. tuberculosis bacillus must come in contact with surface receptors of the M. Although a significant amount of information concerning the M receptors involved in this interaction is available (15, 71), the identities of the mycobacterial cell surface components that mediate this binding are less well understood. However, evidence for the involvement of mycobacterial lipoarabinomannans (57), capsular polysaccharides (8), glycopeptidolipids (72), 19-kDa antigen (9), mycotin (21), and Apa glycoprotein (47) has been reported previously.For any of the aforementioned moieties to be involved in the binding of mycobacteria to host cells, they would have to be located on the surface of the bacterium. Early reports suggested that the outer surface of mycobacteria was composed of mycosides (10,11). Later studies indicated the presence of an outer polysaccharide-rich layer (45, 50), which could explain the presence of the so-called electron-transparent zone often seen in electron micrographs of mycobacteria inside M (13, 18) and more recently in axe...

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Evidence that the capsule around mycobacteria grown in axenic media contains mycobacterial antigens: implications at the level of cell envelope architecture

Cited by 17 publications

References 12 publications

Activities of fluoroquinolone, macrolide, and aminoglycoside drugs combined with inhibitors of glycosylation and fatty acid and peptide biosynthesis against Mycobacterium avium

Activities of fluoroquinolone, macrolide, and aminoglycoside drugs combined with inhibitors of glycosylation and fatty acid and peptide biosynthesis against Mycobacterium avium

Antimycobacterial spectrum of sparfloxacin and its activities alone and in association with other drugs against Mycobacterium avium complex growing extracellularly and intracellularly in murine and human macrophages

Mycobacterium tuberculosisCpn60.2 and DnaK Are Located on the Bacterial Surface, Where Cpn60.2 Facilitates Efficient Bacterial Association with Macrophages

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