Structure of Human Astrovirus Human astrovirus falls under Astroviridae and genus Mamastrovirus. The particles are round in shape, 28 nm in diameter with a smooth margin and display a five or six pointed star motif on their surface.The term astrovirus (Greek: astron- star) was coined to refer this feature. They are non-enveloped, spherical, capsid of about … Read more Human Astrovirus
Virulence factors of Legionella pneumophila Heat shock protein 60: enhances invasion and cytokine expression in macrophages. Outer membrane protein: binding with and delivery of packaged materials into the eukaryotic cells. inhibit the fusion of phagosomes with lysosomes. Macrophage infectivity potentiator (Mip) protein: promotes adherence and phagocytosis. Genes encoding for the type II secretion systems required for … Read more Virulence factors, Pathogenesis and Clinical manifestations of Legionella pneumophila
Pathogenesis of Coxiella burnetii Human infection usually follows inhalation of aerosols containing C. burnetii. It is estimated that only between 1 and 10 bacteria are necessary to cause infection. C. burnetii has also been known to enter the body via other mucous membranes, abrasions, and the gastrointestinal tract through consumption of milk from infected animals. C. burnetii … Read more Pathogenesis and Clinical Manifestations of Coxiella burnetii
Pathogenesis of Chlamydia trachomatis Chlamydia are acquired by direct contact with mucous membranes or abraded skin, that is, by sexual contact or by direct inoculation into the eye in the case of trachoma or neonatal conjunctivitis. Two forms of the organism are needed for infection and disease to occur: the infectious, extracellular form called an … Read more Pathogenesis and Clinical Manifestations of Chlamydia trachomatis
Pathogenesis of Leptospira interrogans Leptospires usually enter the body through the mucous membranes of the upper respiratory tract or the conjunctivae, or through abraded skin, following exposure to contaminated water, infected urine or animal tissues. Ingestion is considered to be less important. The severity of the leptospirosis depends on (a) host immunity, (b) virulence of … Read more Pathogenesis and Clinical Manifestations of Leptospira interrogans
Pathogenesis of Lyme disease caused by Borrelia burgdorferi Lyme disease is caused by the spirochete B. burgdorferi, which is transmitted by the bite of a small tick of the genus Ixodes. Humans are “accidental” hosts for B. burgdorferi because spirochetes from infected people are not transmitted to other hosts. While in the midgut of the Ixodes tick … Read more Pathogenesis and Clinical Manifestations of Borrelia burgdorferi
Virulence factors of Streptococcus pneumoniae Polysaccharide capsule The capsule is antiphagocytic, inhibiting complement deposition and phagocytosis. 2. Cell wall associated polymers and proteins Teichoic acid – binds to epithelial cells and activates alternative complement pathway Protein adhesion – binds to epithelial cells Peptidogylcan – activates alternative complement pathway Phosphorylcholine – mediates invasion of host cell … Read more Virulence factors, Pathogenesis and Clinical manifestations of Streptococcus pneumoniae
Pathogenesis of Francisella tularensis Francisella tularensis is carried by many species of wild rodents, rabbits, beavers. Humans become infected by handling the carcasses or skin of infected animals, by inhaling infective aerosols or ingesting contaminated water, through insect vectors and by being bitten by carnivores that have themselves eaten infected animals. Humans are infected by … Read more Pathogenesis and Clinical manifestations of Francisella tularensis
Pathogenesis of Corynebacterium diphtheriae In nature, C diphtheriae occurs in the respiratory tract, in wounds, or on the skin of infected persons or normal carriers. It is spread by droplets or by contact to susceptible individuals; the bacilli then grow on mucous membranes or in skin abrasions, and those that are toxigenic start producing toxin. … Read more Pathogenesis and Clinical manifestations of Corynebacterium diphtheriae
Virulence factors of Listeria monocytogenes 1. Adhesion proteins (Ami, Fbp A, flagellin) Mediate bacterial binding to host cell that contribute to virulence. 2. Listeriolysin O A hemolytic and cytotoxic toxin that allows for survival within phagocytes. 3. Internalin Cell surface protein that induces phagocytosis. 4. Act A Induces actin polymerization on the surface of host cells, … Read more Virulence factors, Pathogenesis and Clinical manifestations of Listeria monocytogenes
Pathogenesis of Treponema pallidum The two major routes of transmission of Treponema pallidum are sexual and transplacental. Sexual exposure to a person who has an active syphilitic chancre carries a high probability of acquiring syphilis. The organisms enter a susceptible host by penetration of intact mucous membranes or the minute abrasions in the skin surface … Read more Pathogenesis and Clinical manifestations of Treponema pallidum
Pathogenesis of Gardenerella vaginalis A. Adherence of G. vaginalis to Host Epithelium: Initial Steps in Invasion The initial steps of establishing infection include adherence to host receptor sites, production of cytotoxic substances specific for host cells, and biofilm formation. vaginais produces vaginolysin, a cholesterol-dependent cytolysin, for human cells and encodes a pore-forming toxin that binds … Read more Pathogenesis and Clinical manifestation of Gardenerella vaginalis
Virulence factors of Mycobacterium tuberculosis A. Mycolic acid and Lipoarabinomannan (LAM) Waxy layer that protects the bacteria from many host factors and also to many antibiotics including beta lactamases. Muramyl dipeptide (from peptidoglycan) complexed with mycolic acids can cause granuloma formation, phospholipids induce caseous necrosis. LAM is structurally and functionally related to the O antigenic … Read more Pathogenesis and Clinical manifestation of Mycobacterium tuberculosis
Virulence factors or antigenic structures of Neisseria gonorrhoeae A. Pili Pili are the hair like appendages that extend up to several micrometers from the gonococcal surface. It mediates the exchange of genetic material between strains and attachment to human mucosal cell surface, invasion of host cells, and survival through the inhibition of phagocytosis. Two types: … Read more Pathogenesis and Clinical Manifestation of Neisseria gonorrhoeae
Virulence factors of Staphylococcus aureus A. Cell wall components Polysaccharide Capsule: inhibits phagocytosis Peptidoglycan: activates complement, IL-1, chemotactic to PMNs Teichoic acid: species specific, mediate binding to fibronectin Protein A: It binds to the Fc region of IgG and complement ,exerting an anti-opsonin effect. Fibronectin binding protein(FnBP): promote binding to ,mucosal cells and tissue matrices. … Read more Virulence factors and Clinical manifestation of Staphylococcus aureus
