• result of an undesirable relationship between the host and the pathogen, marked by interruption in the normal functioning of a body part or parts.

• invasion of the body by pathogenic microorganisms. • The term is not synonymous with disease.

• prolonged and close interaction between organisms of different species.

• a form of symbiosis in which both organisms benefit from the relationship.

• a form of symbiosis in which one organism benefits from another organism without causing harm to it.

• a form of symbiosis where one organism benefits from another organism and at the same time causes harm to the other.

• ability of an organism to produce disease • An organism that can produce disease in humans is said to be ___

• describes the degree of pathogenicity of an organism or the degree to which an organism can produce disease

• presence of unwanted materials (chemical, biological, or radiological) where they should not be or at concentrations above the normal • presence of these substances may not necessarily lead to harm.

• presence of bacteria in the blood.

• presence of actively multiplying bacteria in the blood, usually from a source of infection • condition is called sepsis.

presence of pus producing bacteria in the bloodstream.

• presence of viruses in the blood.

• presence of toxins in the blood

• directly damaging tissues or body surfaces • involves invasion of the epithelial surface and penetration into deeper tissues. • Invasiveness encompasses three important steps • Colonization - ability to evade host immune defenses production of extracellular substances that can promote invasion. • Colonization involves the ability of the invading organism to enter the susceptible host and establish itself in the portal of entry.

• facilitate adhesion of the organism to specific target cells

• Secretes the enzyme coagulase • promotes formation of a coagulum within which the organism may hide to escapedetection by the immune surveillance cells

• can survive and multiply inside macrophages by inhibiting phagosome lysosome fusion. • some microorganisms produce substances or have developed mechanisms that can promote invasion

•can enter and multiply within host cells •after multiplication is extruded from the host cell allowing it to infect other host cells. •The process of extrusion from the host cell causes direct destruction of the host cells.

• _________ is an enzyme produced • Clostridium perfringens that causes breakdown of collagen • a major component of connective tissue of muscles • contributing to the development of the disease called gas gangrene.

• Toxins are poisonous substances and are often the primary factors that contribute to disease production • two major types of toxins—exotoxins and endotoxins.

• integral components of the outer membrane of gram negative bacteria such as Salmonella, Shigella, and Escherichia coli • specific component responsible for the endotoxin activity of these bacteria is the lipopolysaccharide(LPS) • composed of a lipid Amoiety and a polysaccharide moiety • Lipid A component is associated with its toxic activity while the polysaccharide component is antigenic.

• are intracellular products of some bacteria as part of their growth and metabolism • released into the surrounding medium •mainly proteins and many of them are enzymes. •Most of them are produced by gram positive bacteria •may also be produced by some gram negative bacteria. •soluble in body fluids and are thus easily diffused into the blood and rapidly transported throughout the body

•three principal types of exotoxins: • ________ which kill host cells or affect their function;

three principal types of exotoxins: • ________ which interfere with normal nerve impulse transmission

three principal types of exotoxins: • _________ which affect the cells lining the gastrointestinal tract.

five stages of an infectious disease : • corresponds to the time from initial entry of the infectious agent until the time the patient first manifests signs and symptoms.

five stages of an infectious disease : • corresponds to the initial manifestations of the patient • These manifestations are usually non specific constitutional symptoms such as fever, body malaise, cough, and colds.

five stages of an infectious disease : • period where there is maximal invasion by the infecting agent is the • It is during this period where signs and symptoms characteristic of the disease are seen.

five stages of an infectious disease : • is the period when the manifestations of the patient begin to diminish • also known as the period of defervescence.

five stages of an infectious disease : • also known as the recovery period • patient already becomes asymptomatic • body returns to its normal, pre diseased state.

ACUTE, SUBACUTE, AND CHRONIC DISEASES • rapid onset, followed by a relatively rapid recovery • measles, mumps, and influenza

ACUTE, SUBACUTE, AND CHRONIC DISEASES • insidious (slow) onset and lasts a long time • tuberculosis, leprosy (Hansen disease), and syphilis

ACUTE, SUBACUTE, AND CHRONIC DISEASES • sudden onset • can develop into a long-lasting disease • bacterial endocarditis, come on more suddenly than a chronic disease, but less suddenly than an acute disease • subacute bacterial endocarditis

• are subjective • perceived by the patient • ache or pain, a ringing in the ears (tinnitus), blurred vision, nausea, dizziness, itching, and chills

• or clinical disease • is a disease in which the patient is experiencing symptoms

• or subclinical disease • is a disease that the patient is unaware of because he or she is not experiencing any symptoms.

• defined as some type of objective evidence of a disease • Enlarged liver (hepatomegaly) or spleen (splenomegaly) • abnormal heart or breath sounds, blood pressure, pulse rate, and laboratory results as well as abnormalities that appear on radiographs, ultrasound studies, or computed tomography scans

• A is a disease that is lying dormant, not currently manifesting itself. • Herpes virus infections, such as cold sores (fever blisters), genital herpes infections, and shingles, are examples of latent infections • Virus remains dormant within cells of the nervous system until some type of stress acts as a trigger • stressful trigger may be a fever, sunburn, extreme cold, or emotional stress.

STAGES OF SYPHILIS Hardened, painless chancre develops about 3 weeks after exposure

STAGES OF SYPHILIS Chance curls inward and a rash develops about 4 to 6 weeks after exposure; rash resolves within weeks to 12 months

STAGES OF SYPHILIS No symptoms; may last for weeks to years; sometimes continues throughout life

STAGES OF SYPHILIS CNS, cardiovascular, and other symptoms (sometimes death) occur 5 to 20 years after exposure

PRIMARY VERSUS SECONDARY INFECTIONS • One infectious disease may commonly follow another, in which case the first disease

PRIMARY VERSUS SECONDARY INFECTIONS • A primary infection caused by one pathogen can be followed by a secondary infection caused by a different pathogen.

STEPS IN PATHOGENESIS OF INFECTION

LOCALIZED VERSUS SYSTEMATIC INFECTIONS - pathogen may multiply in one location of the body

LOCALIZED VERSUS SYSTEMATIC INFECTIONS it may multiply throughout the body