Experimental pneumococcal meningitis in mice: a model of intranasal infection.
ABSTRACT Effective laboratory animal models of bacterial meningitis are needed to unravel the pathophysiology of this disease. Previous models have failed to simulate human meningitis by using a directly intracerebral route of infection. Hyaluronidase is a virulence factor of Streptococcus pneumoniae. In this study, a novel model of murine meningitis is described. Intranasal administration of S. pneumoniae with hyaluronidase induced meningitis in 50% of inoculated mice, as defined by a positive cerebrospinal fluid (CSF) culture and an inflammatory infiltrate in the meninges. None of the mice inoculated without hyaluronidase developed meningitis. Hyaluronidase was found to facilitate pneumococcal invasion of the bloodstream after colonization of the upper respiratory tract. Meningitis was characterized by pleocytosis of CSF and the induction of proinflammatory cytokines and CXC chemokines in brain tissue. These results indicate that this murine model mimics important features of human disease and allow for the use of this model for studying issues related to the pathophysiology and the treatment of pneumococcal meningitis.
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ABSTRACT: Bacterial cell-surface proteins play integral roles in host-pathogen interactions. These proteins are often architecturally and functionally sophisticated and yet few studies of such proteins involved in host-pathogen interactions have defined the domains or modules required for specific functions. Streptococcus pneumoniae (pneumococcus), an opportunistic pathogen that is a leading cause of community acquired pneumonia, otitis media and bacteremia, is decorated with many complex surface proteins. These include β-galactosidase BgaA, which is specific for terminal galactose residues β-1-4 linked to glucose or N-acetylglucosamine and known to play a role in pneumococcal growth, resistance to opsonophagocytic killing, and adherence. This study defines the domains and modules of BgaA that are required for these distinct contributions to pneumococcal pathogenesis. Inhibitors of β-galactosidase activity reduced pneumococcal growth and increased opsonophagocytic killing in a BgaA dependent manner, indicating these functions require BgaA enzymatic activity. In contrast, inhibitors increased pneumococcal adherence suggesting that BgaA bound a substrate of the enzyme through a distinct module or domain. Extensive biochemical, structural and cell based studies revealed two newly identified non-enzymatic carbohydrate-binding modules (CBMs) mediate adherence to the host cell surface displayed lactose or N-acetyllactosamine. This finding is important to pneumococcal biology as it is the first adhesin-carbohydrate receptor pair identified, supporting the widely held belief that initial pneumococcal attachment is to a glycoconjugate. Perhaps more importantly, this is the first demonstration that a CBM within a carbohydrate-active enzyme can mediate adherence to host cells and thus this study identifies a new class of carbohydrate-binding adhesins and extends the paradigm of CBM function. As other bacterial species express surface-associated carbohydrate-active enzymes containing CBMs these findings have broad implications for bacterial adherence. Together, these data illustrate that comprehending the architectural sophistication of surface-attached proteins can increase our understanding of the different mechanisms by which these proteins can contribute to bacterial pathogenesis.PLoS Pathogens 09/2014; 10(9):e1004364. · 8.14 Impact Factor
Article: Streptococcus penumoniae meningitis01/2007;
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ABSTRACT: Streptococcus agalactiae is the causative agent of septicemia and meningitis in fish. Previous studies have shown that hyaluronidase (Hyl) is an important virulence factor in many Gram-positive bacteria. To investigate the role of S. agalactiae Hyl during interaction with macrophages, we inactivated the gene encoding extracellular hyaluronidase, hylB, in a clinical Hyl(+) isolate. The isogenic hylb mutant (Δhylb) displayed reduced survival in macrophages compared to the wild-type, and stimulated a significantly higher release of pro-inflammatory cytokines, such as IL-1β, IL-6 and TNF-α, than the wild-type in macrophages as well as in mice. Furthermore, only Hyl(+) strains could grow utilizing hyaluronic acid (HA) as the sole carbon source, suggesting that Hyl permits the organism to utilize host HA as an energy source. LD50 determinations in zebrafish demonstrated that the hylb mutant was highly attenuated relative to the wild-type strain. Experimental infection of BALB/c mice revealed that bacterial loads in the blood, spleen and brain at 16 h post-infection were significantly reduced in the ΔhylB mutant compared to wild-type infected mice. In conclusion, hyaluronidase has a strong influence on the intracellular survival of S. agalactiae and pro-inflammatory cytokine expression, suggesting that it plays a key role in S. agalactiae pathogenicity.Infection and immunity 04/2014; · 4.16 Impact Factor