Article

Genetic basis for Mycobacterium avium hominissuis resistance to host antimicrobial peptides.

Journal of medical microbiology 05/2014; DOI: 10.1099/jmm.0.072744-0
Source: PubMed

ABSTRACT Antimicrobial peptides are an important component of the innate immune defense. Mycobacterium avium subsp hominissuis (M. avium) is an organism that establishes contact with the respiratory and gastrointestinal mucosa as a necessary step for infection. M. avium is resistant to high concentrations of polymyxin B, a surrogate for antimicrobial peptides. To determine gene-encoding proteins that are associated with this resistance, we screened a transposon library of M. avium strain 104 for susceptibility to polymyxin B. Ten susceptible mutants were identified and the inactivated genes sequenced. The greatest majority of the genes were related to cell wall synthesis and permeability. The mutants were then examined for their ability to enter macrophages and to survive macrophage killing. Three clones among the mutants had impaired uptake by macrophages compared to the wild-type strain, and all ten clones were attenuated in macrophages. The mutants were shown also to be suceptible to cathelicidin (LL-37), in contrast to the wild-type bacterium. All but one of the mutants were significantly attenuated in mice. In conclusion, this study indicated that the M. avium envelope is the primary defense against host antimicrobial peptides.

0 Bookmarks
 · 
32 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Vitamin D3 (D3) has been shown to activate several macrophage functions. To determine whether D3 could activate macrophages to kill or inhibit intracellular growth of Mycobacterium avium complex (MAC), human monocyte-derived macrophages were treated with D3 (10(-7), 10(-8), and 10(-9) M) 24 hr before or for 48 hr after MAC infection. All three concentrations were associated with inhibition of growth or killing of MAC in a dose-dependent fashion (28 +/- 4% and 22 +/- 3% of killing and inhibition of growth, respectively, at pharmacological concentrations) when added to the monolayer before injection or 60.4 +/- 6%, 50.4 +/- 3%, and 41.4 +/- 6%, respectively, when added to the monolayers after infection. We found that D3-treated macrophages produced increased concentrations of tumor necrosis factor (TNF) and granulocyte-monocyte colony stimulating factor (GM-CSF). Subsequently, macrophages were activated by D3 in the presence of anti-TNF or anti-GM-CSF antibody: At 10(-9) M of D3 there was no inhibition of D3-dependent macrophage activation by anti-TNF antibody, whereas anti-GM-CSF antibody was associated with 100% inhibition. At 10(-8) M of D3, anti-TNF antibody inhibited 35 +/- 6% of killing, and anti-GM-CSF antibody was associated with 100% inhibition. At 10(-7) M of D3, anti-TNF antibody inhibited 58 +/- 4% and anti-GM-CSF antibody 89 +/- 3% of killing. D3 treatment is associated with anti-MAC activity in human macrophages, and this activity appears to be mediated by both TNF and GM-CSF.
    Cellular Immunology 06/1990; 127(2):432-41. · 1.87 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Mycobacterium avium subsp. paratuberculosis adapts to the environment via the regulation of genes affecting its envelope's composition. Bacteria grown in milk (in vivo conditions) presented differences in the cell wall-associated lipids and in the expression of genes involved in lipid metabolism (FadE8, FadE6 and MAP1420) and host cell invasion (MAP1203, LprL). A different lipid profile was also observed in the envelope of intracellular bacteria after 1 h of infection. Intracellular bacteria showed up-regulation of a LuxR regulator which controls the envelope's composition by up-regulation of FadE8, MAP1420, MAP1203 and LprL and by down-regulation of pks12, mmpL2 and MAP2594. A LuxR-overexpressing strain with a lipid-deficient envelope phenotype, infected epithelial cells more efficiently than the wild-type bacteria; however, it was not more resistant than the wild-type strain to the action of bactericidal proteins. Here we show that LuxR regulates virulence determinants and is involved in mycobacteria adaptation to the host.
    Innate Immunity 09/2009; 16(4):235-47. · 2.46 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We have examined the activity of defensins from human neutrophilic granulocytes against Mycobacterium avium-Mycobacterium intracellulare. M. avium-M. intracellulare at 2.5 x 10(6)/ml or 2.5 x 10(8)/ml was cultured in the presence of defensins at 37 degrees C from 4 to 48 h. After incubation, CFU were enumerated. Human neutrophil peptide 1 (HNP-1) at 5 micrograms/ml had the ability to kill M. avium-M. intracellulare. Treatment with HNP-1 resulted in significant (96.3 to 97.7%) killing of M. avium-M. intracellulare, even after taking clumping into consideration. This activity was not affected by the presence of calcium (0.5 and 1.0 mM), magnesium (0.5 and 1.0 mM), or sodium chloride (25, 50, and 100 mM). The optimal pH for bactericidal activity was higher than 5. We tested numerous M. avium-M. intracellulare strains, and HNP-1 was successful in killing every strain, although the degree of killing varied among them (34.2 to 87.2%). Additionally, this activity was independent of colonial morphology. We also examined the activity of HNP-2 and HNP-3 against M. avium-M. intracellulare and found that they were as effective in killing M. avium-M. intracellulare as HNP-1 was. These observations suggest that defensins may play an important role in the host defense against M. avium-M. intracellulare.
    Infection and Immunity 12/1992; 60(11):4720-5. · 4.16 Impact Factor