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Compromised Host
- 1. damaged physical barriers: broken skin and
- mucous membranes. (use of intravenous devices)
2. suppressed immune system.
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Chain of Transmission
- 1. Direct contact: From hospital staff to patient and from patient to patient.
- 2. Indirect contact- through fomites
- 3. Hospital ventilation systems (air borne transmission)
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First Line of Defense
- Intact skin
- Mucous membranes and their secretions
- normal microbiota
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Second line of defense
- phagocytic WBCs
- Infalmmation
- Fever
- Antimicrobial substances
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Non-Specific Defense (Innate/ inborn immune response)
- Same immune response against any type of pathogen.
- Faster response time
- No memory of previous exposure
-
Non-specific immune responses consists of
First and second lines of defense
-
Skin as a first line of defense
- 1. Sebum/oil- rich in fatty acid --> acidic pH on skin
- 2. Keratinized epidermis keeps the skin dry
- 3. Closely packed cells
- 4. Periodic shedding of skin cells
- 5. Sweat, high salt concentration
- 6. Lysoszyme (in sweat) (damages peptidoglycan) and hurts GM+ bacteria
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Mucous membrane protective membrane
- 1. In conjunctiva of eyes: tears (rich in salt and lysozyme) tears flush eyes out
- 2. Respiratory: ciliary living (ciliary escalator), Lysoszyme
- 3. In GI tract: Acidic pH (gastric juice) preistalsis (movement through GI Tract)
- 4. Gastroferritin- Reduces iron for pathogen
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Genitourinary tract as a protective factor of mucous membrane
- Urine- Flushes the urinary tract
- Vaginal pH and normal flora is acidic (prevents pathogen growth)
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MIcrobial antagonism
Competition among microbes (observed b/w normal microbiota and pathogens) for common growth factors
-
Normal microbiota protect host by
- -Occupying niches that pathogens might occupy (habitats, receptors on host tissue)
- - Producing acids
- - Producing bacteriocins
- -Changing oxygen availability
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Second Line of Defense
- 1. Complement System
- 2. Inflammation
- 3. Phagocytosis
- 4. Fever
- 5. Antimicrobial compounds (Interferons, Transferrin, Antimicrobial peptides)
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Components of Blood
Plasma and Formed elements
- RBC- Erythrocytes (transport gases)
- WBC- Leukocytes (defense)
- Platelets- Thrombocytes (blood clotting)
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Types of White Blood Cells
- 1. Granulocytes
- 2. Agranulocytes
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Types of Granulocytes
- 1. Neutrophils
- 2. Basophils
- 3. Eosinophils
Cells have granules that are stained easily
-
Neutrophils
- Perform Phagocytosis
- Usually the first to reach the site
-
Basophils
Produce histamine
-
Eosinophil
- Allergic response
- Destroy parasitic worms (helminths)
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Type of Agranulocytes
- Monocytes (macrophages)
- Lymphocytes (Natural killer cells, T cells, B Cells)
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Monocytes
Large nucleus, mature to macrophages (phagocytosis)
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2 categories of macrophages
Wandering-(Can leave blood vessels and reach infection)
Fixed- (non motile), localized to specific tissue Ex- Microglia cells (nervous tissue) Kupffer cells (liver)
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Dendritic Cells
Underneath skin; use phagocytosis
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3 Types of Lymphocytes
- Natural Killer (NK) cell
- T Cells
- B Cells
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Natural Killer Cells (NK cells)
Destroy infected cells of the body and tumor cells (non-specifically)
-
B Cells
Antibody production
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T Cells
Helper T Cells (Th)- Secrete cytokine (Chemical messenger) and activates other cells (B cells, T cytotoxic cells)
Cytotoxic T Cells (Tc)- Destroys infected cells and tumor cells, specific response
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Cells of specific immune response
B cells, T cells (lymphocytes)
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High esinophil count during
Allergies and helminth infections
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High neutrophil count during
Bacterial infection
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High lymphocyte count during
viral infections, chronic infections
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Blood Plasma
Fluid, still has blood clotting factor; then centrifuge to separate blood cells from serum
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Blood serum
- No clotting factor present
- Rich in antibodies, used to diagnose an infection by detecting presence of specific antibodies against pathogens
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