part 3( bacte 2nd qz) Flashcards
STAGES OF INFECTIOUS DISEASE
Incubation stage
Prodromal stage
Clinical stage
Stage of Decline
Convalescent stage
No signs or symptoms (s/s)
Time interval between the initial infection and the first appearance of any signs and symptoms.
Incubation stage
Full recovery of surviving host OR
Chronic infection develops or death
Convalescent stage
First signs and symptoms appear
Early, mild symptoms of disease such as general aches and malaise
Pathogen may be highly communicable
Prodromal stage
Peak of characteristic signs and symptoms
Person exhibits overt signs and symptoms
Clinical stage
Condition of host deteriorates possibly to death OR
Signs and symptoms begin to subside as host condition improves
Patient is vulnerable to secondary infections
Stage of Decline
First Line of Defense
Skin
Mucous membranes
Normal microbiota
Second Line of Defense
Phagocytosis
Inflammation
Host properties that confer RESISTANCE of the host to foreign substances
immunity
Sum of all mechanisms used by the body as protection against environmental agents that are not normally present in the body
immunity
Customized protection against invading microorganisms
Adaptive/Acquired/Specific Immunity
Adaptive/Acquired/Specific Immunity
Defense once microorganisms breached innate immunity
Involves the 3rd line of defense against invading microorganisms
Customized protection against invading microorganisms
Has a memory (can recall previous contact w/ a foreign molecule)
Innate/Natural/Nonspecific Immunity
Defenses that are present at birth
Involves the 1st and 2nd lines of defense against invading microorganisms
Occurs regardless of the type of invading organism (no specific recognition); acts against all microbes in the same way
Does not have a memory (cannot recall previous contact w/ a foreign molecule
Intact Skin function
mechanical barrier
Low pH (pH 3-5) due to fatty acids also has antimicrobial effect
skin
skin
The stratified and cornified epithelium serve as mechanical barriers
Fatty acids secreted by sebaceous glands have antibacterial and antifungal properties
Low pH (pH 3-5) due to fatty acids also has antimicrobial effect
Desquamation of the skin surfaces – keratinized squamous epithelium
Those capable of penetrating a normal, healthy skin are few like: leptospires, Francisella tularensis, treponemes, and some fungi
Mucous Membranes
Mucous membrane of the RT is lined with cilia and covered w/ mucus w/c trap bacteria
The RT has also lysozymes that lyse bacterial cell walls
The GIT has hydrolytic enzymes in saliva and stomach acids that can break down bacteria
The stomach’s low pH and presence of gastric enzymes limit the number of microbes.
Lysozyme
Lyse bacterial cell walls
Immunoglobulin A (IgA
Serve as opsonins, thereby enhancing phagocytosis
Beta-lysins
Destroy gram positive bacteria
Interferon
Inhibits viral replication
Interferon - gamma
Inhibits cell proliferation
Inhibits tumor growth
Enhances phagocytosis
They compete w/ pathogens for nutrients and space. This competition limit the growth of pathogens, thereby, lessening the chance for colonization – COLONIZATION RESISTANCE
Normal Microbiota
Cells that ingest bacteria and other foreign particles by endocytosis and engulf them through their phagosome
PHAGOCYTES
is the primary mechanism in the host defense against extracellular bacteria, viruses and fungi
Phagocytosis
Origin
Location
Life span
Predominates in NUETROPHILS
Bone marrow
Circulating blood and tissues
2 – 7 hrs (blood)
Less than 1 week (tissues)
Pyogenic infections
Origin
Location
Life span
Predominates in MACROPHAGES
Bone marrow
Blood ( monocytes) Tissue (macrophages)
Longer life span
Granulomatous infections
Function OF neutrophils
Phagocytic (first cells present during bacterial invasion)
MACROPHAGES function
Phagocytic
Plays both an impt role in nonspecific phagocytosis and specific immunity
Histamine
Dilates blood vessels
Kinins
Increase vascular permeability; initiate/enhance release of other wbc mediators; derived from the clotting cascade kininogen
Leukotrienes
Affect wbcs’ mobility and metabolism
C-reactive protein, serum amyloid A, antitrypsin,
Liver proteins playing a role in the acute response
Interleukin-1
Stimulates immune response; increases fever by interaction w/ prostaglandins; increases adhesion of neutrophils to endothelium; promotes T cell proliferation
Interleukin-2
Causes proliferation of activated T and B cells
Cytokines
Stimulate wbcs, promoting their growth and differentiation
Gamma interferon
Promotes growth of T and B cells
Reinforcement mechanism against microbial survival and proliferation; activated by trauma / tissue injury
INFLAMMATORY RESPONSE
Ingest and destroy microorganisms
Phagocytes
Attracts phagocytes to infection site
Helps phagocytes recognize and bind to bacteria
Directly kills Gram(-) bacteria
Complement system
Attracts phagocytes to infection site
Increases blood and fluid flow to infection site
Walls off infection site to physically inhibit spread of microorganisms
Coagulation system
Multiple effects that enhance the activities of many different cells to non-specific and specific responses
cytokines
Swelling/Edema
– caused by increased flow of fluid and cells to the infection site
Pus formation
continued accumulation of phagocytes
Redness
results from vasodilation at the infection site
Heat
results from increased temperature of affected tissue
Pain
due to tissue damage and pressure from increased flow of fluid and cells
involves the host’s immune system/ immune response
3rd line of defense-
3rd line of defense-
ADAPTIVE
SPECIFIC
ACQUIRED
adaptive
Immunity is induced; that is, it adapts to a microbial invader
specific
Acts only to a specific type of invader (antigen)
Customized defense against invading microorganisms
acquired
Immunity is developed only after exposure to a suitable antigen; or after transfer of antibodies
“nonself” or foreign substances made up proteins, nucleoproteins, polysaccharides and some glycolipids to which antibodies respond
antigens
“self” substances or immunoglobulins that are made up of glycoproteins present in serum and tissue fluids; produced by B cells
Antibodies
Central molecule of the immune response
ANTIBODIES OR IMMUNOGLOBULINS
Specific proteins produced by B cells in response to antigens
ANTIBODIES OR IMMUNOGLOBULINS
5 classes of immunoglobulins
IgG, IgA, IgM, IgE, IgD
Responds to protein Ags
IgG
IgM
First Ab produced during infection (primary immune response)
Responds best to polysaccharide Ags
Bacterial agglutination
Neutralization of of endotoxins
Most active at 20-25 deg C
IgD
Found on external membranes of B cells; initiates B cell differentiation
May play a role in autoallergic diseases
IgA
Secreted in body fluids (tears, milk, saliva, resp and GI secretions)
Primarily protects body surfaces lined w/ mucous membranes
IgG
Mainly involved in secondary (anamnestic) immune response
Most active at 37deg C
Neutralization of viruses and exotoxins
Major Ig in normal serum; Passive immunity for newborns (can cross the placenta)
IgE
Stimulates release of histamine and other chemicals to cause allergic rxns
Increased during parasitic infections
Two Arms of the Immune System
HUMORAL IMMUNITY
CELL-MEDIATED IMMUNITY
Temporary resistance to infectious agents by administration of preformed ANTIBODIES
PASSIVELY ACQUIRED IMMUNITY
PASSIVELY ACQUIRED IMMUNITY
The host DOES NOT PRODUCE ANTIBODIES since preformed Abs are already given
Resistance to infectious agents by contact/administration of an ANTIGEN
The host PRODUCES ANTIBODY in reaction to antigens
ACTIVELY ACQUIRED IMMUNITY
