Transcript Bacterial Classification

Nonspecific Host Defenses
Introduction
Skin & Mucous Membranes
Phagocytosis
Inflammation
Fever
Antimicrobial Substances
Defenses - Introduction
Ability to ward off disease is resistance
 Lack of resistance is susceptibility
 Resistance is of two types
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– Nonspecific – body defenses that ward off
disease without respect to organism
– Specific – attack a specific type of
organism; usually associated with
immune system
Defenses – Skin & Mucus
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Physical Factors
– Intact skin & keritin resist microbes
– Lacrimal apparatus (tears & blinking
protect eyes
– Saliva washes teeth & gums
– Mucus traps microorganisms & ciliary
escalator moves mucus up & out
– Urine and vaginal secretions keep
organisms out of genitourinary tract
Defenses – Skin & Mucus
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Chemical Factors
– Sebum – unsaturated fats which inhibit
microogansisms on skin (some bacteria can
metabolize – acne)
– Perspiration –washes bacteria – high salt
– Lysozyme digest cell wall; found in saliva,
nasal secretions, tears and perspiration
– Acid (pH 1-3) prevents bacterial growth in
stomach
– Normal bacteria inhibit pathogens
Defenses - Phagocytocis
Ingestion of microorganisms or
particles by a cell - phagocytosis
 Usually accomplished by white blood
cells
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Defenses - Phagocytocis
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Blood composition
– Fluid (plasma) – water, ions, proteins
– Formed elements (cells)
» Erythrocytes (red blood cells)
» Platlets
» Leukocytes (white blood cells)
Granulocytes (neutrophils, basophils,
eosinophils)
 Lymphocytes
 Monocytes
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Defenses - Phagocytocis
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Actions of Phagocytic cells
– Neutrophils & Monocytes
– Monocytes are “fixed” or “wandering”
– Fixed phagocytes are located in selected
tissue, i.e. spleen
– Granulocytes predominate in early
infection; monocytes are present later in
infection
– Phagocytes are activated by bacterial
components (lipid A) or cytokines
(chemical messengers)
Defenses - Inflammation
Inflammation is a bodily response to
cell damage
 Characterized by
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Redness
Pain
Heat
Swelling
Loss of function
Defenses - Inflammation
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Inflammatory Response Release of chemical signals
– Histamine-a biogenic amine involved in local immune responses
as well as regulating physiological function in the gut and acting
as a neurotransmitter. Evidence indicates that histamine plays an
important role in chemotaxis of white blood cells. Derived from
histidine.
– Kinins-any of various structurally related polypeptides, such as
bradykinin and kallikrein. They act locally to induce vasodilation
and contraction of smooth muscles.
– Prostaglandins-One of a number of hormone-like substances that
participate in a wide range of body functions such as the
contraction and relaxation of smooth muscle, the dilation and
constriction of blood vessels, control of blood pressure, and
modulation of inflammation. Prostaglandins are derived from a
chemical called arachidonic acid.
Defenses - Inflammation
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Phagocytes move to site of
inflammation
– Can stick to lining of blood vessels
(margination)
– Can squeeze through blood vessels
(emigration)
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Pus is the accumulation of damaged
tissue and dead microbes, granulocytes
and macrophages
Defenses - Inflammation
Defenses - Fever
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Fever is high body temperature (>100.5°F)
produced in response to infection
Fever is induced by
– Endotoxins
– Interleukin-1 (a cytokinin)
– LPS endotoxins (exogenous)
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Stages
– Chill – rising body temperature
– Crisis – sweating; falling body temperature
Defenses – Antimicrobials
Substances
The Complement System – a system of
proteins which inactivate cells
 Interferons – antiviral proteins
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Defenses - Complement
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A group of 8-25 serum proteins that activate
one another to destroy cells
Two pathways classical and alternative
Both pathways activate protein C3 of system
which binds to cell surface
– Opsonization (coating bacteria –promotes
phagocytosis)
– Cell lysis (through further activation)
– Inflammation
Defenses - Complement
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Streptococcus especially provokes inflamation
People tend to produce antibodies to cell wall rather
than capsule
Peptidoglycan & teichoic acid ellicit production of IL1 & TNFa
Opsonization would occur at cell surface but
prevented by capsule
Results in escalating inflamatory response because
bacteria are not cleared
Fluid accumulates in lungs disrupting gas exchange
and essentially suffocating patient
Defenses - Complement
Defenses - Complement
Defenses - Complement
Defenses - Interferons
Antiviral proteins
 3 types alpha, beta & gamma
 Produced by virus infected cell and
migrate to uninfected cells that then
produce antiviral proteins
 Host cell specific but not virus specific
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