(9) MICROBIAL MECHANISMS OF PATHOGENICITY Flashcards
Includes mucous membranes, respiratory tract, gastrointestinal tract, genitourinary tract, conjunctiva, skin, and parental routes
Portals of Entry
Mechanisms of pathogens that include capsules, cell wall components, enzymes, siderophores, antigenic variation, and cytoskeleton
Penetration or Envasion of Host Defenses
Mechanisms of pathogens that include direct damage, toxins, exotoxins, endotoxins, and lysogenic conversion
Damage to host cells/cytopathic effects
Are generally the same as the portals of entry for a given microbe
Portals of Exit
Factors that affect the capability of pathogens to cause disease
Virulence Factors
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
Most pathogens enter through the ________ of the GI and respiratory tract
mucous membrances
Microorganisms can gain access in the GIT in food & water via ________
contaminated fingers
The portal of entry for pathogens that are contracted sexually
Gut
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]
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
Mechanisms of Adhesion by Pathogens
(1) _________
(2) _________
(3) _________
(1) Fimbriae
(2) Capsules
(3) Spikes
• Attaches to teeth by means of its glycocalyx which is primarily made up of DEXTRAN
Streptococcus mutans
• Have fimbriae that adhere to the glycocalyx of S. mutans
Actinomyces
• Have adhesions on fimbriae that adhere only to specific kinds of cells in the small intestine
Shigella and E. coli
• Uses tapered end as a hook to attach to host cells
Treponema pallidum
• Produces an adhesion for a specific receptor on a host cell
Listeria monocytogenes
• Has a fimbriae with adhesions
Neisseria gonorrhoeae
• Has a mechanism of adherence that resembles viral attachment
Staphylococcus aureus
They are surface molecules on a pathogen that bind specifically to complimentary surface receptors on cells of certain host tissues
Adhesins or Ligands
- Process of altering surface antigens thus evading immune response
- e.g. Neisseria gonorrhooeae, Trypanosoma brucei gambiense, and Influenza virus
Antigentic Variation
- Surface proteins that rearrange nearby actin filaments of the cytoskeleton
- Salmonella and Escherichia coli
Invasins
- 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
- Proteins that exhibit a high affinity to iron
- e.g. Enterobactin (E. coli), Bacillibactin (B. subtilis, B. anthracis), and Vibriobactin (V. cholerae)
Siderophores
- 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 ______
- Released when bacteria ____, and cell walls ____
- Stimulates _______ to release cytokines in very high concentrations
- Produce the same _______ (chills, fever, weakness, generalized aches and in some cases, shock and death)
- Can induce ______
- Severe consequences include: _____
- 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 ______
- The LPS of the bacterial cell wall are released. These endotoxins cause macrophages to produce a cytokine called _______
- IL-1 is carried via the blood to the ______
- IL-1 induces the hypothalamus to release lipids called ______
- 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 ______
- Release of ______ of host cell
- Formation of _____
- Fusion of ______ (syncytium or giant cells)
- Changes in ______ w/o any visible changes
- Some virus-infected cells produce substances called _______
- Induction of ______ in the surface of the infected cells
- Induction of _______ in the host cell
- 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
