Growth, cellular differentiation and virulence factor expression by Proteus mirabilis in vitro and in vivo.
(17/1592)
A uropathogenic strain of Proteus mirabilis was grown in vitro in human and mouse urine and brain-heart infusion broth (BHIB) and in vivo in subcutaneous open chambers (SOC) in mice, intraperitoneal diffusion chambers (IPC) in rats and by ascending urinary tract infection in mice in order to compare growth pattern, cellular differentiation and expression of virulence factors. Although the growth rate was slower in vivo than in vitro, the extent of growth was similar after 24 h. PR mirabilis differentiated into filamentous swarmer cells in all in-vitro culture conditions, but no filamentous cells were observed in either of the in-vivo chamber models. Transurethrally infected mice showed a rapid release or loss of filamentous cells and these could not be seen in kidney or bladder homogenates 7 days after infection. Bacteria showed increasing haemagglutination titres for fresh and tanned red blood cells after subculturing in BHIB, but bacteria grown in vivo did not show haemagglutination. An increasing resistance to normal serum was found when bacteria were grown in vivo. Significant haemolytic activity was detected with bacteria grown in BHIB and IPC, but almost no activity was found when bacteria had grown in urine. These findings improve the understanding of the role of P. mirabilis uropathogenic virulence factors in vivo. (+info)
K-1 antigen of Escherichia coli: epidemiology and serum sensitivity of pathogenic strains.
(18/1592)
K-1 Escherichia coli are far more frequent in neonatal sepsis (36% of E. coli sepsis) and meningitis (80% of E. coli meningitis) than would be expected by the frequency of K-1 E. coli colonization in neonates (11 to 25%). There is no apparent parallel in cases of sepsis in adults. To study further this apparent age-related difference in virulence, E. coli K-1 clinical isolates were tested for their sensitivity to sera. Strains isolated from cases of neonatal meningitis were more sensitive to serum bactericidal activity than those from cases of neonatal or adult sepsis or adult meningitis (P < 0.01). Serum sensitivity did not appear to be determined by K or O antigens. Four isolates sensitive to serum bactericidal activity obtained from neonatal cerebrospinal fluid were killed by adult serum chelated with 0.05 M Mg(2+) ethyleneglycol-bis (beta-aminoethyl ether)-N,N-tetraacetic acid (EGTA), suggesting that the alternative pathway was activated. Although untreated neonatal sera killed these strains as well as adult sera did, EGTA-treated neonatal sera were less effective than EGTA-treated adult sera. This suggests that the alternative pathway function was not activated in neonatal sera. The bactericidal defect of neonatal EGTA-treated serum was partially corrected by addition of either A or B hyperimmune equine meningococcal antiserum. (+info)
Plaque assay for measuring serum bactericidal activity against gonococci.
(19/1592)
A new semiquantitative plaque assay was developed to measure killing of gonococci by serum. Results compare well with an established quantitative method, but the plaque assay is faster, simpler, and less expensive. (+info)
Increased susceptibility of TNF-alpha lymphotoxin-alpha double knockout mice to systemic candidiasis through impaired recruitment of neutrophils and phagocytosis of Candida albicans.
(20/1592)
TNF-alpha and lymphotoxin-alpha (LT) are members of the TNF family, and these cytokines play crucial roles in the defense against infection with Candida albicans. The aim of the present study was to investigate the role of endogenous TNF and LT during disseminated candidiasis in TNF-/-LT-/- knockout mice. The TNF- and LT-deficient animals had a significantly increased mortality following C. albicans infection compared with control mice, and this was due to a 10- to 1000-fold increased outgrowth of the yeast in their organs. No differences between TNF-/-LT-/- mice and TNF+/+LT+/+ were observed when mice were rendered neutropenic, suggesting that activation of neutrophils mediates the beneficial effects of endogenous TNF and LT. Histopathology of the organs, combined with neutrophil recruitment experiments, showed a dramatic delay in the neutrophil recruitment at the sites of Candida infection in the TNF-/-LT-/- mice. Moreover, the neutrophils of deficient animals were less potent to phagocytize Candida blastospores than control neutrophils. In contrast, the killing of Candida and the oxygen radical production did not differ between neutrophils of TNF-/-LT-/- and TNF+/+LT+/+ mice. Peak circulating IL-6 was significantly higher in TNF-/-LT-/- mice during infection. Peritoneal macrophages of TNF-/-LT-/- mice did not produce TNF, and synthesized significantly lower amounts of IL-1alpha, IL-1beta, IL-6, and macrophage-inflammatory protein-1alpha than macrophages of TNF+/+LT+/+ animals did. In conclusion, endogenous TNF and/or LT contribute to host resistance to disseminated candidiasis, and their absence in TNF-/-LT-/- mice renders the animals susceptible through impaired recruitment of neutrophils and impaired phagocytosis of C. albicans. (+info)
The human antibacterial cathelicidin, hCAP-18, is bound to lipoproteins in plasma.
(21/1592)
Cathelicidins are a family of antibacterial and lipopolysaccharide-binding proteins. hCAP-18, the only human cathelicidin, is a major protein of the specific granules of human neutrophils. The plasma level of hCAP-18 is >20-fold higher than that of other specific granule proteins relative to their levels within circulating neutrophils. The aim of this study was to elucidate the background for this high plasma level of hCAP-18. Plasma was subjected to molecular sieve chromatography, and hCAP-18 was found in distinct high molecular mass fractions that coeluted with apolipoproteins A-I and B, respectively. The association of hCAP-18 with lipoproteins was validated by the cofractionation of hCAP-18 with lipoproteins using two different methods for isolation of lipoproteins from plasma. Furthermore, the level of hCAP-18 in delipidated plasma was <1% of that in normal plasma. Immunoprecipitation of very low, low, and high density lipoprotein particles with anti-apolipoprotein antibodies resulted in coprecipitation of hCAP-18. The binding of hCAP-18 to lipoproteins was mediated by the antibacterial C-terminal part of the protein. The binding of hCAP-18 to lipoproteins suggests that lipoproteins may play an important role as a reservoir of this antimicrobial protein. (+info)
Tumor necrosis factor receptor p55 controls the severity of arthritis in experimental Yersinia enterocolitica infection.
(22/1592)
OBJECTIVE: To dissect the host defense mechanisms in relation to the development of Yersinia-associated arthritis by evaluating the impact of tumor necrosis factor receptor p55 (TNFRp55) deficiency on Yersinia enterocolitica infection. METHODS: TNFRp55-/- and C57BL/6 mice were inoculated intravenously with arthritogenic strain 8081 of Yenterocolitica serotype 0:8. Mice were observed daily for generating survival curves and monitoring arthritis. In subsequent sets of experiments, mice were sacrificed at day 14 after infection for examination of histopathology of joints, bacterial clearance, macrophage microbicidal activity, nitric oxide (NO) production, oxidative burst generation, and cytokine production. RESULTS: There was an 80% mortality rate in TNFRp55-/- mice compared with 25% in the controls at 8 weeks after inoculation with 70 colony-forming units of Y. enterocolitica 0:8. Histologic examination of joint tissues revealed that TNFRp55-/- mice developed more severe arthritis, including cartilage degradation and bony destruction, than controls at day 14 after infection. The more extensive joint pathology in TNFRp55-/- mice was correlated with the higher bacterial load in liver, spleen, and lungs, and with the increased levels of interleukin-10. TNFRp55-/- mice displayed impaired intracellular killing of bacteria by macrophages. This was associated with decreased NO production and impaired oxidative burst activity. CONCLUSION: This study demonstrates that TNF signaling through TNFRp55 controls the severity of Yersinia-induced arthritis and implicates TNF-mediated macrophage microbicidal activity as a central event in this process. (+info)
Immunization with Treponema pallidum outer membrane vesicles induces high-titer complement-dependent treponemicidal activity and aggregation of T. pallidum rare outer membrane proteins (TROMPs).
(23/1592)
The purpose of this study was to determine whether immunization with purified outer membrane vesicles (OMV) from Treponema pallidum (T.p. ) could elicit Abs capable of killing this organism. It is well established that the immunization of rabbits or mice with killed T.p. or with recombinant T.p. Ags has failed to generate serum killing activity comparable with that of infection-derived immunity. Because of the small amount of T.p. OMV obtainable, a single mouse was immunized with purified OMV. The mouse anti-OMV serum and infection-derived immune rabbit serum (IRS) were compared by reactivities on two-dimensional T.p. immunoblots and by the T.p. immobilization test, a complement-dependent killing assay. Whereas IRS detected >40 Ags, the anti-OMV serum identified only 6 Ags corresponding to proteins identified previously in the outer membrane. T.p. immobilization testing showed that IRS had a 100% killing titer of 1:44 and a 50% killing titer of 1:662. By comparison, the mouse anti-OMV serum had a significantly greater 100% killing titer of 1:1,408 and a 50% killing titer of 1:16,896. Absorption of the anti-OMV serum to remove Ab against outer membrane-associated lipoproteins did not change the 100% killing titer. Freeze-fracture analysis of T.p. incubated in IRS or anti-OMV serum showed that T.p. rare membrane-spanning outer membrane proteins were aggregated. This is the first demonstration of high-titer killing Abs resulting from immunization with defined T.p. molecules; our study indicates that the targets for these Abs are T. p. rare outer membrane proteins. (+info)
Neutropenia restores virulence to an attenuated Cu,Zn superoxide dismutase-deficient Haemophilus ducreyi strain in the swine model of chancroid.
(24/1592)
Haemophilus ducreyi causes chancroid, a sexually transmitted cutaneous genital ulcer disease associated with increased heterosexual transmission of human immunodeficiency virus. H. ducreyi expresses a periplasmic copper-zinc superoxide dismutase (Cu, Zn SOD) that protects the bacterium from killing by exogenous superoxide in vitro. We hypothesized that the Cu,Zn SOD would protect H. ducreyi from immune cell killing, enhance survival, and affect ulcer development in vivo. In order to test this hypothesis and study the role of the Cu,Zn SOD in H. ducreyi pathogenesis, we compared a Cu,Zn SOD-deficient H. ducreyi strain to its isogenic wild-type parent with respect to survival and ulcer development in immunocompetent and immunosuppressed pigs. The Cu,Zn SOD-deficient strain was recovered from significantly fewer inoculated sites and in significantly lower numbers than the wild-type parent strain or a merodiploid (sodC+ sodC) strain after infection of immunocompetent pigs. In contrast, survival of the wild-type and Cu,Zn SOD-deficient strains was not significantly different in pigs that were rendered neutropenic by treatment with cyclophosphamide. Ulcer severity in pigs was not significantly different between sites inoculated with wild type and sites inoculated with Cu,Zn SOD-deficient H. ducreyi. Our data suggest that the periplasmic Cu,Zn SOD is an important virulence determinant in H. ducreyi, protecting the bacterium from host immune cell killing and contributing to survival and persistence in the host. (+info)