(9) MICROBIAL MECHANISMS OF PATHOGENICITY Flashcards by Rayben William Sanchez

Includes mucous membranes, respiratory tract, gastrointestinal tract, genitourinary tract, conjunctiva, skin, and parental routes

Portals of Entry

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Mechanisms of pathogens that include capsules, cell wall components, enzymes, siderophores, antigenic variation, and cytoskeleton

Penetration or Envasion of Host Defenses

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Mechanisms of pathogens that include direct damage, toxins, exotoxins, endotoxins, and lysogenic conversion

Damage to host cells/cytopathic effects

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Are generally the same as the portals of entry for a given microbe

Portals of Exit

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Factors that affect the capability of pathogens to cause disease

Virulence Factors

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VIRULENCE FACTORS
● (1) ________
● (2) ________
● (3) ________
● (4) ________

(1) Infect the host
(2) Protect itself from the body’s defense
(3) Invade and multiply in tissues
(4) Cause damage to or destruction of tissues

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Most pathogens enter through the ________ of the GI and respiratory tract

mucous membrances

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Microorganisms can gain access in the GIT in food & water via ________

contaminated fingers

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The portal of entry for pathogens that are contracted sexually

Gut

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Preffered Portal of Entry
(1) Salmonella typhi - ________
(2) Streptococci - ________
(3) Yersinia pestis - _________

(1) Swallowed
(2) Inhaled
(3) More than one portal of entry [can cause plague]

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INFECTIOUS DOSE - BACILLUS ANTRHACIS
• (1) _______ anthrax – 10-50 endospores
• (2) _______ anthrax – 10,000-20,000 endospores
• (3) _______ anthrax – 250,000- 1,000,000 endospores

(1) Cutaneous
(2) Inhalation
(3) Gastrointestinal

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Mechanisms of Adhesion by Pathogens
(1) _________
(2) _________
(3) _________

(1) Fimbriae
(2) Capsules
(3) Spikes

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• Attaches to teeth by means of its glycocalyx which is primarily made up of DEXTRAN

Streptococcus mutans

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• Have fimbriae that adhere to the glycocalyx of S. mutans

Actinomyces

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• Have adhesions on fimbriae that adhere only to specific kinds of cells in the small intestine

Shigella and E. coli

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• Uses tapered end as a hook to attach to host cells

Treponema pallidum

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• Produces an adhesion for a specific receptor on a host cell

Listeria monocytogenes

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• Has a fimbriae with adhesions

Neisseria gonorrhoeae

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• Has a mechanism of adherence that resembles viral attachment

Staphylococcus aureus

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They are surface molecules on a pathogen that bind specifically to complimentary surface receptors on cells of certain host tissues

Adhesins or Ligands

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Process of altering surface antigens thus evading immune response
e.g. Neisseria gonorrhooeae, Trypanosoma brucei gambiense, and Influenza virus

Antigentic Variation

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Surface proteins that rearrange nearby actin filaments of the cytoskeleton
Salmonella and Escherichia coli

Invasins

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A glycoprotein that bridges the junctions between cells
Used by certain microbes to move from cell to cell
e.g. Shigella spp., and Listeria spp.

Cadherin

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Proteins that exhibit a high affinity to iron
e.g. Enterobactin (E. coli), Bacillibactin (B. subtilis, B. anthracis), and Vibriobactin (V. cholerae)

Siderophores

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- Poisonous substances that are produced by certain microorganisms

Toxins

- Capacity of microorganisms to produce toxins

Toxigenicity

- Refers to the presence of toxin in the blood

Toxemia

TYPE OF TOXIN - Are produced inside mostly gram-positive bacteria as part of their growth and metabolism - Are then secreted or released following lysis into the surrounding medium

Exotoxins

TYPE OF TOXIN - Are part of the outer portion of the cell well of gram-negative bacteria - They are liberated when the bacteria die and the cell wall breaks apart

Endotoxins

EXOTOXINS 1. Produced mostly by ______ bacterium 2. Chiefly made up of ______ 3. Part of _________ 4. Released following _____ of bacterial cell 5. Carried by ______ 6. _____ in fluids 7. Most _____ substances known 8. ________

(1) gram positive (2) protein (3) growth and metabolism (4) lysis (5) bacterial plasmids (6) Soluble (7) lethal (8) Disease specific

- Antibodies produced by the body that provide immunity to exotoxins

Antitoxins

- Inactivated toxin used in a vaccine

Toxoids

Can be prevented by toxoid vaccination

Diptheria and Tetanus

• Also called as type III toxins • First toxins to be studied • Consist of two parts designated A and B, both of which are poplypeptides • A common example is the Diphtheria toxin

A-B Toxins

PART OF A-B TOXINS • (1) ______ is the active (enzyme) component • (2) ______ is the binding component

(1) A part (2) B part

- Also called Type II toxins - Include Leukocidins and Hemolysin

Membrane - Disrupting Toxins

- Membrane-disrupting toxins that kill phagocytic leukocytes - e.g. staphylococci, streptococci, and pneumococci

Leukocidins

- Membrane-disrupting toxins that destroy erythrocytes - Subtypes: SLO (streptolysin O and SLS) - e.g. Streptococci

Hemolysin

• Also called type I toxins • Bacterial proteins • Stimulate the proliferation of immune cells called T cells with release of enormous amounts of cytokines • Include the staphylococcal toxins that cause food poisoning and toxic shock syndrome

Superantigens

Superantigens stimulate the proliferation of immune cells called ______ with release of enormous amounts of cytokines

T cells

Superantigens include the ________ that cause food poisoning and toxic shock syndrome

staphylococcal toxins

ENDOTOXINS 1. Chiefly made up of ______ 2. Released when bacteria ____, and cell walls ____ 3. Stimulates _______ to release cytokines in very high concentrations 4. Produce the same _______ (chills, fever, weakness, generalized aches and in some cases, shock and death) 5. Can induce ______ 6. Severe consequences include: _____ 7. Microbes that produce such: _______

(1) LPS (lipopolysaccharides) (2) dies; lyse (3) macrophage (4) signs and symptoms (5) miscarriage (6) Disseminated Intravascular Coagulation (DIC) & Shock (7) S. typhi, Proteus, N. meningitidis

PATHOGENESIS OF SHOCK 1. Phagocytosis of ______ 2. Secretion of ______ 3. Binding to ______ 4. Alteration of ______ 5. Damage of ______ 6. Increase in ______ 7. _______ 8. Decrease in ____ 9. ______

(1) gram (-) bacteria (2) TNF 9 tumor necrosis factor / Cachectin (3) body tissues (4) metabolism (5) capillaries (6) permeability (7) Fluid loss (8) BP (9) Shock

PYROGENIC RESPONSE CAUSED BY ENDOTOXINS 1. Gram-negative bacteria are ingested by ______ and degraded in ______ 2. The LPS of the bacterial cell wall are released. These endotoxins cause macrophages to produce a cytokine called _______ 3. IL-1 is carried via the blood to the ______ 4. IL-1 induces the hypothalamus to release lipids called ______ 5. The result is a ______

(1) phagocytes; vacuoles (2) interleukin-1 (IL-1) (3) hypothalamus (4) prostaglandins (5) fever

• Small, circular, DNA molecules capable of independent replication • Resistance (R) factors

Plasmids

• Incorporation of VIRAL DNA into the bacterial chromosome • The newly integrated genetic material is now called a PROPHAGE

Lysogeny

• A bacterial cell containing a prophage

Lysogenic

• Exhibition of new properties coded by the prophage in the bacterial cell, both the host cell and its progeny

Lysogenic Conversion

• Depend on gaining access to host • Evading host’s defense • Damage or death of the host cell while reproducing themselves

Viruses

CYTOPATHIC EFFECTS OF VIRUSES 1. Stops ______ 2. Release of ______ of host cell 3. Formation of _____ 4. Fusion of ______ (syncytium or giant cells) 5. Changes in ______ w/o any visible changes 6. Some virus-infected cells produce substances called _______ 7. Induction of ______ in the surface of the infected cells 8. Induction of _______ in the host cell 9. Loss of ________

(1) mitosis (2) enzymes (3) inclusion bodies (4) adjacent infected cells (5) host cell’s function (6) interferons (7) antigenic changes (8) chromosomal changes (9) contact inhibition

- Doesn’t have a well-defined set of virulence factors - Produces capsules

Fungi

- Inhibit CHON synthesis - Causes headaches, chills, severe nausea, vomiting and visual disturbances - Produced by FUSARIUM (grains and rice)

Trichothecenes (Toxin)

• An alkaloid • Produced by Claviceps purpurea • Found in sclerotia • Causes hallucinations and limb gangrene

Toxin Ergot

• Produced by Aspergillus flavus • Found in nuts which is carcinogenic

Aflatoxin

• Examples: phalloidin and amanitin • Produced by Amanita phalloides (death angel) • Amanita mushrooms may result in death

Mycotoxins

• Invade host cells and reproduce within them, causing their rupture

Plasmodium

• Attaches to macrophages and gains entry by phagocytosis

Toxoplasma

• Attach to host cells and digest the cells and tissue fluids

Giardia lamblia

• Produces neurotoxins • e.g. Saxitoxin

Algae

- Produced by some genera of dinoflagellates such as Alexandrium - Causes Paralytic Shellfish Poisoning

Saxitoxin

• Use host tissues for growth and metabolism • Waste products can lead to disease symptoms

Helminths