Pathogenesis of infectious disease

Path means disease Pathogens refer to microorganism capable to cause a disease. Pathology : the study of structural and functional manifestation of disease. Pathologist : a physician who has specialized in pathology. Pathogenicity : the ability to cause a disease Pathogenesis : is the step or mechanisms involved in development of a disease

Phs in the corse of an infectious disease: Incubation period: is the time that elapses between arrival of the pathogens and the onset of symptoms. And it is varies by many factor as health state-virulence of the pathogens- number of pathogens that enter the body. Prodormal period: is the time during which patient feels out of sorts but not yet experiencing actual symptoms of the disease. Period of illness: is the time during which the patient experiences the typical symptoms associated with that particular disease .(headache – sore throat-sinus congestion)

The convalescent period: is the time during which the patient recover. Localized infection Systemic infection Acute infection : rapid infection followed out by rapid recovery (measles-mumps-influenza) Chronic infection : slow insidious and last for long time Symptoms of a disease: define as some evidence of a disease that is experienced by the patients. ( headache-fever-pain-itching) Asymptomatic disease Sign of a disease: define as some objective evidence of a disease that is experienced by the patients. (skin rash-enlargment of the spleen)

Latent infection : an old infection that was contained by the body but may re-activate at any time as ( ?) Primary infection: is the infection that the body get exposed to for the first time . Secondary infection : is an infection that follows a primary infection.

Step in the pathogenesis of infections disease: Entry: of the pathogen into the body by: (Penetration, inhalation, ingestion and introduction of the pathogens directly into the blood. [shades needles] Attachment: of the pathogen to some tissues within the body. Multiplication: with local or system Invasive / spread of the pathogens Evasion of a host defenses. Damage to host tissue (s). extensive or death.

Virulence: is measure or degree of pathogenecitiy. different organism vary in their ability to cause disease some strain virulence some is a virulence. Virulence factor: are the phenotypic characteristics of a microorganism that enable it to cause disease.

Structural features as pili ,capsule, flagella Structural features as pili ,capsule, flagella. It help adhesion: which is molecule on the surface of the pathogens that able to recognize the reception on the host cell: that is glycoprotein molecule on the surface of the host cell that the adhesion on the pathogen attach to it. Obligate intracellular pathogens. Facultative intracellular pathogens. Capsules: antiphagocytic by WBC. (No receptor). Flagella: move and invade the aqueous area in the body it avoid phagocytosis.

Exoenzymes : is the two major virulence factors by which bacteria cause disease the exoenzyme as (a) coagulase as in staphaurus: clot plasma → sticky coat → protect it from phagocytes. (b) kinases: → streptococcus & stophausus: body produce fibricolt → kinases → lysis. (c) hyaluronidase: enable organism to spread through connective tissue by breaking down hyaluronic acid. (d) collagenase: Break down the collagen to invade tissue. (e) hemolysins: damage RBC. (f) lecithinase: damage extensive area of tissue.

Toxins: there are endotoxins that is integral part of the cell wall of the gram-negative bacteria can cause a number of adverse physiologic effect. Exotoxins are the toxins that produced within the cells and then releases from the cell example: Neurotoxins= that cause paralysis. Enterotoxins = gastro intestinal disease.

Mechanisms by which pathogens escape immune responses: The pathogens change their surface antigens example: influenze virus, HIV and nisseria. The pathogen's surface antigens closely resemble host antigens and therefore not recognized by immune system = molecular mimicry. Destruction of the host antibodies by producing enzyme as (IgA protease) that destroy IgA.