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Haemophilus influenzae and Streptococcus pneumoniae are common causes of respiratory tract infections. H. influenzae attach to receptor epitopes in mucins and in epithelial cell membranes. Attachment is followed by an epithelial cell cytokine response. Secreted cytokines then initiate inflammation, upset the integrity of the mucosal barrier, and lead to disease. S. pneumoniae do not bind to mucins
BACKGROUND: This study analyzed antibodies to pneumococcal polysaccharides in human milk and their effect on nasopharyngeal colonization and acute otitis media in breast-fed infants.METHODS: A total of 503 milk samples were collected from 310 mothers. Nasopharyngeal cultures were obtained from their children at 2, 6 and 10 months postpartum, and the capsular groups/types of the Streptococcus pneum
To the breast-fed infant, human milk is more than a source of nutrients; it furnishes a wide array of molecules that restrict microbes, such as antibodies, bactericidins, and inhibitors of bacterial adherence. However, it has rarely been considered that human milk may also contain substances bioactive toward host cells. While investigating the effect of human milk on bacterial adherence to a human
This study examined apoptotic cell death associated with Shiga-like toxin (Stx)-producing Escherichia coli. Renal cortices from three children with postenteropathic hemolytic-uremic syndrome (HUS) and from mice infected with E. coli O157:H7 and pediatric renal tubular epithelial cells stimulated with Stx and E. coli O157:H7 extracts were examined for apoptotic changes. Apoptotic cells were detecte
Viruses are thought to facilitate bacterial infections of the respiratory tract, but the mechanisms are poorly understood. The present study analyzed the effect of adenovirus on bacterial adherence to human respiratory tract epithelial cells. The human lung carcinoma cell line A549 was infected with adenovirus of types 1, 2, 3, 4, 5, and 9. At a multiplicity of infection of 75 particles per cell,
Mucins are high-molecular-weight glycoproteins and major constituents of the mucus layer which covers the airway surface. We have studied the interactions between bacteria, mucins, and epithelial cells from the human respiratory tract. Nontypeable strains of Haemophilus influenzae were found to bind to purified airway mucins in suspension and on solid phase. Mucins in suspension inhibited the atta
Pneumococcal surface protein A (PspA) is able to elicit antibodies in mice and humans that can protect mice against fatal infection with Streptococcus pneumoniae. It has been observed that immunization with a single family 1 PspA can protect mice against infections with capsular type 3 or 6B strains expressing PspA family 1 or 2. However, several studies have shown that immunity to PspA is less ef
Pneumococcal surface protein A (PspA) can elicit protection against Streptococcus pneumoniae in mouse infection models. PspA is classified by serology and amino acid sequence into two major families that are divided by sequence into five clades. The most variable portion of the molecule is the alpha-helical domain, which comprises the N-terminal half of PspA. Prior studies of a family 1 PspA prote
In the present study, we have characterized the dihydrolipoamide dehydrogenase (DLDH) of Strepto-coccus pneumoniae and its role during pneumococcal infection. We have also demonstrated that a lack of DLDH results in a deficiency in alpha-galactoside metabolism and galactose transport. DLDH is an enzyme that is classically involved in the three-step conversion of 2-oxo acids to their respective acy
Human lactoferrin is an iron-binding glycoprotein that is particularly prominent in exocrine secretions and leukocytes and is also found in serum, especially during inflammation. It is able to sequester iron from microbes and has immunomodulatory functions, including inhibition of both complement activation and cytokine production. This study used mutants lacking pneumococcal surface protein A (Ps
The peroxide response transcriptional regulator, PerR, is thought to contribute to virulence of group A Streptococcus (GAS); however, the specific mechanism through which it enhances adaptation for survival in the human host remains unknown. Here, we identify a critical role of PerR-regulated gene expression in GAS phagocytosis resistance and in virulence during pharyngeal infection. Deletion of p
Streptolysin O (SLO) is a cholesterol-dependent cytolysin produced by the important human pathogen, group A Streptococcus (Streptococcus pyogenes or GAS). In addition to its cytolytic activity, SLO mediates the translocation of GAS NAD-glycohydrolase (NADase) into human epithelial cells in vitro. Production of both NADase and SLO is associated with augmented host cell injury beyond that produced b
CsrRS (or CovRS) is a two-component system implicated in the control of multiple virulence determinants in the important human pathogen, group A Streptococcus (GAS). Earlier studies suggested that extracellular Mg(2+) signalled through the presumed sensor histidine kinase, CsrS. We now confirm those findings, as complementation of a csrS mutant restored Mg(2+)-dependent gene regulation. Moreover,
Group A Streptococcus (GAS) colonizes the oropharynx and damaged skin. To cause local infection or severe invasive syndromes the bacteria must gain access into deeper tissues. Host cell death may facilitate this process. GAS internalization has been identified to induce apoptosis. We now report an alternate mechanism of GAS-mediated apoptosis of primary human keratinocytes, initiated by extracellu
Local host defenses limit proliferation and systemic spread of pathogenic bacteria from sites of mucosal colonization. For pathogens such as streptococci that fail to grow intracellularly, internalization and killing by epithelial cells contribute to the control of bacterial growth and dissemination. Here, we show that group A Streptococcus (GAS), the agent of streptococcal sore throat and invasiv
The present study was initiated to gain insight into the interaction between splenic dendritic cells (DC) and Salmonella enterica serovar Typhimurium in vivo. Splenic phagocytic cell populations associated with green fluorescent protein (GFP)-expressing bacteria and the bacterium-specific T-cell response were evaluated in mice given S. enterica serovar Typhimurium expressing GFP and ovalbumin. Flo
1. In normal mice, the distribution of adrenergic, cholinergic, some peptidergic, and neuronal nitric oxide synthase (nNOS)-containing nerves were investigated. Functional in vitro correlates were obtained. An in vivo model was developed in which erectile haemodynamics in response to drugs or nerve-stimulation were studied. 2. Immunoreactivities for vesicular acetylcholine transporter protein (VAC
We have examined whether in vivo exposure to the glutamate analogue, kainic acid, induces cell loss through apoptosis and/or through necrosis. The vulnerability of rabbit retinal cells was evaluated by routine histopathology. The DNA fragmentation was examined using an in situ method (TUNEL: TdT-mediated biotin-dUTP nick-end labelling) and agarose gel electrophoresis of extracted retinal DNA. Reti
This study analyzed the effect of breast-feeding on the frequency of acute otitis media. The protocol was designed to examine each child at 2, 6 and 10 months of age. At each visit nasopharyngeal cultures were obtained, the feeding pattern was recorded and the acute otitis media (AOM) episodes were documented. The analysis was based on 400 children from whom complete information was obtained. They
