Lec 6 - Virulence & Pathogenecity

Disease

Any deviation from the normal functioning of the body

Infectious disease

caused by a microorganism; mere presence does not constitute an infection unless organisms multiply in the body, produce symptoms of the disease and pathological changes in tissues

Non-infectious disease

physical; caused by injury, vegetable or mineral poison, , heat or cold, faulty nutrition, abnormal physiology or abnormal tissue growth

Contagious disease

caused by microorganism that is readily transferrable from one individual to another by direct or indirect contact

True

TRUE OR FALSE. Contagious diseases are all infectious but not all infectious are contagious

False

TRUE OR FALSE. Infectious diseases are all contagious but not all contagious are infectious

Saprophytic

live on dead matter; putrefaction of retained placenta; sapremia

Parasitic

live at the expense of host to which they cause injury

Pathogens

organisms that are capable of producing disease

Pathogenicity

ability to cause disease

Virulence

degree of pathogenicity

Streptolysin O

labile protein containing sulfur and oxidized by atmospheric oxygen

Streptolysin O

Neutralized by specific immune serum and by cholesterol

Streptolysin S

• Stable in the presence of atmospheric oxygen

• Lipoprotein and not neutralized by cholesterol

Serum (S)

Streptolysin S is extractable from streptococcal cells by means of ____; preserved by lyophilization

beta hemolysis, aerobic

Streptolysin forms ______ around streptococci colonies under _____ conditions

Streptolysin S

Toxic to leukocytes, platelets and other cells

Leucocidin

Staphylococci, cause destruction of leukocytes; reacts to WBC

Leucocidin

Identical to hemolysin O

Leucocidin

Destruction of phagocytes, protective mechanism

Fibrinolysin

streptokinase

Fibrinolysin

Dissolution of fibrin clots

proteolytic, inactive

fibrinolysin activates _____ enzymes normally present in plasma in _____form

Coagulase

Staphylococcus aureus

Coagulase

Enzyme-like substance which causes coagulation of blood plasma from rabbits and humans

penetration of leukocytes and lytic agents

Coagulation of plasma around colonies prevents _______ and _______

Lecithinase

toxin which brings about hydrolysis of lecithin when acted upon by calcium ions; effect on blood-vascular system

Collagenase

proteolytic enzyme which causes disintegration of muscle tissue by decomposing reticular scaffolding; lowers resistance

Hyaluronidase

enzyme which hydrolyzes hyaluronic acid

Hyaluronic acid

A viscous, polysaccharide acid of high molecular weight present in intercellular ground substance of tissues

Hyaluronidase

Increases permeability and allows rapid spread of infection (spreading factor)

• Growth on ordinary artificial media

• High temperature

• Contact with chemicals

Enumerate loss of virulence

anthrax bacillus

it maintains virulence on artificial media but losses virulence at 42’C

Attenuation

decrease in virulence

blood or serum

Avirulent strains can be made virulent when grown on media containing

phenomenon of dissociation

Loss or acquisition of virulence associated with

S

is more virulent than R form

Capsulated

is more virulent than non-capsulated

polysaccharide, immunity

Organisms more virulent when they contain a specific _____ which has an important role in _______

Gram negative bacteria

possess endotoxic substance known as O or somatic Ag composed of carbohydrate, protein and phospholipid located near cell-surface and liberated upon lysis of cells; highly toxic and pyrogenic

Pyrogens

substances that increase body temperature

Specificity for certain tissue respiratory vs digestive

Extent to which bacteria are able to multiply in tissue and response of defense mechanism of the host

Malnutrition, temperature, fatigue and genetic constitution

Factors that alter resistance of host

Direct contact, indirect contact, vertical transmission

Transmission of Infectious Agents

direct contact

Licking in diarrhea in calves & Rabies thru bites

indirect contact

mastitius thu milker’s hand

pullorum disease

example of vertical transmission

Salmonella pullorum

causative agent of pullorum disease in chickens

convalescent, asymptomatic, inapparent, vectors, soil (tetanus), aerosol or dust, sexual contact (venereal disease)

types of carriers

convalescent carrier

pullorum disease is what kind of carrier

inapparent carrier

pseudorabies in swine is what type of carrier

Convalescent carrier

have experienced illness because of an infectious agent and are still able to transmit it to others

Asymptomatic carrier

infected with a disease (or develops a disease; diagnosed) but fails to display any noticeable symptoms

Inapparent carrier

able to transmit an infection to others, without ever developing the infection themselves

Vectors

ticks, fleas, lice and mosquitoes

Atria of Infection

Avenue thru which organism gains entrance to the body; portal of entry

Cryptogenic infection

impossible to determine portal of entry

Bacteremia

presence of bacteria in blood vascular system

Septicemia

accompanied by fever, rapid pulse rate, marked prostration

Sapremia

absorption of end products of tissue disintegration

Pyemia

pus

Toxemia

generation and accumulation of metabolic wastes and exogenous toxins within the body

Exanthematous disease

skin eruptions

Primary infection

one cause only (usually virus)

Mixed infection

more than one cause

Secondary infection

may naunang cause, may pangalawang dumating (usually bacteria)

Focal infection

pagpasok ni organism tsaka sha mag multiply (localized infection)

Hyaluronic acid

cementing substance

Coagulated plasma

acts as a shell that protects the organism

Fibrin clots

network for clotting

Fibrinogen

converts into fibrin

Hemolysins

ruptures or lyses RBC

Tetanus and anthrax

example of bacteria that varies in ability to cause disease (pathogenicity)

Tetanus

takes days before it’s fatal

Anthrax

death will be fast

Tetanus and botulism

example in contagious disease are all infectious, but not all infectious are contagious

Clostridium tetani

causes tetanus

Clostridium botulinum

causes botulism