Chapter 15 Microbial Mech Of Pathogenicity Flashcards
What is Pathogenicity?
The Ability to cause disease
What is virulence?
What is Avirulent?
The extent of degree of Pathogenicity
Not pathogen
What are Koch’s Postulates?
Microorganisms are isolated form a diseased or dead animal
The microorganisms are grown in pure culture
The grown microorganisms are injected into a health animal
When the animal dies the identified microorganism should be present
What are the portals of entry?
Pathogens should gain access to the host to cause disease
Mucous membranes
Skin
Parenteral route
What is the most common route for infection and what do they include?
Mucous membranes
Respiratory tract
Gastrointestinal tract
Genitourinary tract
Conjunctiva -membrane covering the eyelid and eyeballs
What results from entry to the respiratory tract?
Common cold, Influenzam Pneumonia, measles
What is the outcome of bacteria ingested in the Gastrointestinal tract?
Usually they are destroyed by stomach pH. BUT
Some will survive and cause: Hep A Typhoid Fever Amoebic dysentery Shigellosis
The diseases that ado survive the Gastrointestinal tract are transmitted how?
Excreted in feces which can be transmitted via oral fecal transmission
How are diseases transmitted via the Genitourinary tract?
Give examples
STD
HIV/AIDS Genital Warts Chlamydia Gonorrhea Syphilis Herpes
How is the Skin a portal of entry?
Unbroken skin is a tough barrier to most microorganisms but they can enter through hair follicles and sweat glands
What is the Parenteral Route as a Portal of Entry?
A situation where microbes are introduced directly into the tissue beneath skin, or mucous membrane when these barriers are injured
Example: puncture, injections, bites, cuts, wounds
What is the preferred portal of entry?
Each specific microbe has a preferred portal of entry
Salmonella typhi = swallowed
Streptococcus is inhaled and causes pneumonia
How are the degrees of virulence and lethal dose of a microbe expressed as?
ID50: Infectious dose for 50% of the test population
LD50: Lethal dose (of a toxin) for 50% of the test population
What is the portal of entry and ID50 of Bacillus anthracis?
Skin = 10-50 endospores
Inhalation = 10,000 - 20,000 endospores
Ingestion = 250,000 - 1,000,000
Toxins
What is the portal of entry and ID50 for:
Botulinum
Shiga toxin
Staphylococcal enterotoxin
Botulinum = .03 ng/kg
Shiva toxin = 250 ng/kg
Staphylococcal enterotoxin = 1350 ng/kg
What is adherence? How and where does this take place on a pathogen
Attachment is a necessary step in infection
This attachment is between surface molecules on the pathogen and surface receptors on the host cells
What is the attachment called?
What else can communities form?
This attachment is called Adhesions or adherence
Some form biofilms: come together in masses, cling to surfaces and share nutrients
What are the surface molecules on the pathogen called?
Adhesins or ligands
Most adhesions are made of?
Where are these adhesions located?
Glycoproteins
Lipoproteins
Pili
Fimbriae
Flagella
Glycocalyx
What are the receptors on host cells typically made of?
Sugars like mannose
Can surface olecules on a pathogen bind to and surface of the host cell?
No, they bind specifically to complementary surface receptors of the host cell
What does Streptococcus mutans cause?
Causes tooth decay
What does Shigella cause?
Cause gastrointestinal diseases
What does Listeria monocytogenes cause?
Causes septicemia, CNS infections
What does Staphylococcus aureus cause?
Causes skin infections
What does Neisseria gonorrhoeae cause?
Gonorrhea
What are the three ways pathogens penetrate host defense?
- Capsules
- Components of cell wall
- Enzymes
What does capsules do for the pathogen when invading a host?
Prevent phagocytosis of
Streptococcus pneumonia
Haemophilus influenza
Klebsiella pneumonia
How does the cell wall contribute to a pathogens virulence?
Components of the cell wall contribute to virulence:
M protein resists phagocytosis
-Streptococcus pyogenes
Opa protein use to attach to the host (forms opaque colonies)
-Neisseria gonorrhoeae
Mycolic acid (waxy lipid) resists digestion
-Mycobaterium tuberculosis
How do enzymes help pathogens penetrate the host defense?
These are exoenzymes
They break open cells
They dissolve blood clots
What does the enzyme coagulase do?
Coagulates fibrinogen in the blood
-staph aureus (coag +)
What are Kinases?
Which microorganisms make kinases and what are they and what do they do?
Dissolve blood clots
Streptococcus pyogenes produces fibrinolysin (streptokinase)
S. Aureus produces staphylokinase
What hydrolyzes hyaluronic acid?
What does it do?
Hyaluronidase
Dissolves connective tissue: blackening of infected wound
What does Collagenase do?
What does this?
Hydrolyzes collagen
-Clostridium: facilitate spread in gas gangrene
What is the function of IgA proteases?
Destroys IgA antibodies
What are Necrotizing factors?
Causes necrosis
What does Lecithinase do?
Destroys RBC plasma membrane
What is the function of Hemolysin?
Causes lysis of erythrocytes (RBC)
- Streptococcus: streptolysins
- Staphylococcus
- Clostridium perfingens: Gas gangrene
What are the different kinds of Streptolysins?
Streptolysin O (SLO)
Streptolysin S (SLS)
What is Antigenic Variation?
Some pathogens are capable of changing their surface Ag, thereby evading the body immune system
What does the body produce in response to pathogens?
How does this take place?
Body produces Antibodies (Ab) in response to Antigen (Ag)
Antibody destroys or inactivated the antigen
What are invasions?
They are proteins produced by microbes after attachment. They change the appearance of the plasma membrane meaning changes the actin filaments of the cytoskeleton
What disrupts the cytoskeleton of host cell by causing membrane ruffling?
Salmonella typhimurium
This allows the pathogen to sink into the ruffles of the host and eventually be taken in.
What is used by Shigella and Listeria to bridge the junction and to move form cell to cell?
Cadherin
What are the 4 different mechanisms that microorganisms can damage host cells by?
Using host’s nutrients: Siderophores
Direct Damage to host cells by invasion
Produce Toxins
Inducing hypersensitivity
What is obtained by bacteria by using Siderophores?
This is required for bacterial growth?
Iron
Iron is required for growth of bacteria
What does Siderophores do?
Binds unbound free iron in the host that is not bound to transferrin or hemoglobin
What are ways to cause direct damage to the host cell after attachment?
Disrupt host cell function
Produce Waste products
Pathogens multiply in cell and the cell ruptures
How are some organisms brought into the host cell that fools the host cell?
What are a few organisms that do this?
Some organisms induce the host cell to engulf them by a process resembling phagocytosis
Then after they cause damage and are released the infect other cells.
Ex. E.coli, Shigella, Salmonella, Neisseria gnorrhaeae
What causes the most damage to host cells?
Toxins
Exotoxins are divide into 3 types?
A-B-toxins
Membrane-disrupting toxins
Superantigens
What is the action of a A-B Exotoxin?
- Bacterium produces and releases exotoxins
- B(binding) component of exotoxin attaches to host cell receptor
- A-B exotoxin enters hot cell by endocytosis
- A-B exotoxins enclosed in pinched-off portion of plasma membrane during pinocytosis
- A-B components of exotoxins separate. The A component alters cell function by inhibiting protein synthesis. The B component is released from the host cell
Membrane disrupting toxins do what to the membrane of the host?
Lyse (kill) the host cells by:
- Making protein channels in the plasma membrane
- Disrupting phospholipid bilayer
Ex. Clostridium perfringens
Leukocidins, Hemolysins, Streptolusins all do what and to which cells?
Leukocidins: Kill phagocytic leukocytes
Hemolysins: kills RBC
Streptolysins: by streptococcus
All make protein channels that all for the contents of the host cell to come out causing lysis of the cell.
What are Superantigens?
They cause very intense immune response due to the release of cytokines from host cells
Basically an over kill or too many WBC released to the site of infection.
What are the symptoms of Superantigens?
Fever, nausea, vomiting, diarrhea, shock, and death
What are some examples of Superantigens and what does it cause?
Staphylococcus
Causes food poisoning and TSS
What is Toxigenicity?
What does it contribute to?
Toxingenicy: Ability to produce toxin
Toxins are substances that contributes to Pathogenicity
What do Toxins cause?
Fever
Diarrhea
Affect the nervous system
Destroy RBC
What is Toxemia?
Presence of toxin in the host’s blood
What is Toxoid?
Inactivated toxin used in a vaccine
What is Antitoxin?
Antibodies against a specific toxin
What are exotoxins?
Are produced inside bacterial cell and release into the surroundings
What are the characteristics of exotoxins?
Mostly made by G+
Their genes are carried on plasmids or phages
What are the 3 groups of Exptoxins and what do they do?
Cytotoxins - kills host cells
Neurotoxins - affects nervous system
Enterotoxins - affects the gastrointestinal tract
Diphtheria toxin is produced by what pathogen? What does this toxin cause?
Produced by Corynebacterium diphtheria
The toxin is produced by the gene (Tox) in a phage
It inhibits protein syntheses in host cell
Diphtheria toxin is an example of what type of toxin?
A-B toxin
What Erythrogenic toxin is deactivated by O2?
Streptolysin O (SLO)
What Erythrogenic toxin has an affinity for albumin found in serum?
Streptolysin S (SLS)
Toxins that damage blood capillaries and produce red skin rash is called?
Scarlet Fever
Clostridium botulinum forms what toxin?
What type of toxin is this and what does it cause?
Botulinum toxin.
Neurotoxin that inhibits release of neurotransmitter ACh that prevents muscle contraction resulting in flaccid paralysis (diaphragm can’t contract and patient can’t inhale)
A-B neurotoxin
What are the characteristics of Tetanus toxin?
Neurotoxin by C.tetani
Causes muscle contraction or Lockjaw
A-B neurotoxin
What are Vibrio enterotoxin?
How are these toxins brought into the host?
What does it cause?
By V.cholerae
They are ingested
Causes sever diarrhea with vomiting because epithelial cells release large large amount of fluid and electrolytes
A-B enterotoxin called Cholera toxin
What produces TSS?
S.aureus
It’s superantigen enterotoxin
How does Endotoxins differ from exotoxins?
Located within bacterial cells and are part of the outer portion of the cell wall of Gram negative bacteria.
The lipid portion of the Lipopolysaccharides lipid A is the endotoxin.
When are endotoxins released?
During Multiplication and when bacterial cells die lysis
What do endotoxins cause?
Fever (pyrogens response)
Septic shock or endotoxic shock - which is a drop in blood pressure
Can also cause blood clotting and death
What is a example of a pathogen that could cause blood to clott
Salmonella typhi, Proteus (urinary tract infections), Neisseria meningitis
Phagocytosis of gram negative bacteria endures the release of TNF, what does TNF cause?
Damages blood capillaries which causes los of large amounts of fluid which leads to shock due to a drop in Blood pressure
What is the Pyrogenic response?
Macrophages ingest G- bacteria
LPS released toxin
Release of cytokines IL-1 and TNF-alpha that travel to the hypothalamus
Releases prostaglandins that resets the norm temp higher this is fever
What does Asprin do to fevers?
Reduces fever by inhibiting synthesis of Prostaglandins
What do Macrophages release?
TNF or Cachectin from ingesting G- bacteria
Damages blood capillaries - fluid loss
Drops blood pressure which causes shock
What does Salmonella cause?
What does Proteus cause?
Neisseria meningitis?
Typhoid fever
Urinary tract infection
Meningitis
What are the characteristics of Exotoxins?
Mostly G+
Relation to microbe: BY-products of growing cell Chemistry: Protein Doesn't cause fever It is neutralized by antitoxin It's LD50 is small
What is Lysogenic conversion?
DNA of a virus is incorporated in to the DNA of a host cell becoming a prophage that sits latent not causing lysis of a cell.
The host bacterial cell and its progeny can exhibit new characteristics encoded by the bacteriophages DNA this change is Lysogenic conversion.
Lysogenic conversion enables what to take place?
Prophage will enable bacteria to produce toxins:
Diphtheria toxin
Botulinum neurotoxins
Capsule produced by Streptococcus pneumoniae
What are the characteristics of Endotoxins?
Source: Gram negative
Relation to Microbe: Outer membrane
Chemistry: Lipid A
Fever? Yes
Not neutralized by antitoxin
Has a relatively large LD50
What is The LAL Assay and what is it used for?
Limulus amoebocyte lysate assay is a test to detect endotoxins
What are amoebocytes?
What do these cells do?
They are WBC’s of horseshoe crab
These cells contain proteins that clot blood
It’s endotoxin causes lysis of cells and release protein and clots blood
The visible effects of a viral infraction are know as?
Cytophathic Effects (CPE) of viruses
What are the characteristics of CPE’s?
Intercellular parasites
Need to attach to host cells
How do CPE’s kill?
Multiplication and producing large number of particles
Change permeability of host cell membrane
Stop protein, DNA or RNA synthesis
If CPE causes the death of the cell it is called?
Cytocidal effect
What are some examples of CPE’s?
Herpes Simplex Virus stops Mitosis
Viruses causes lysosomes to release their enzyme and destroy Intracellular contents of the cell
What are inclusion bodies and what are they used for?
Granules in the cells and they are used for the identification of:
Rabies virus
Measles Virus
Small Pox Virus
What is a Syncytium?
Several adjacent infected cells fuse to form a very large multinucleated cell called a Syncytium
What can CPE’s cause to the surface of infected cells?
They can induce antigenic changes of the surface of infected cells
If CPE’s cause chromosomal changes what are these changes called?
Oncogenes (cancer causing genes)
What is lost when Oncogenes transform cells into a tumor?
Cells loss their contact inhibition which causes the over production of cells and they now touch forming a tumor.
Even though Fungi can cause disease what is unique about it virulence factors?
Do not have a well defined set of virulence factors
What are the toxins that fungi produce?
The products of fungi is what is toxic to fungi, however the toxin is only an indirect cause of disease because fungus is already growing in or on the host.
What of the fungus cause the disease?
Fungal waste products may cause symptoms
What can happen with chronic fungal infections?
Give an example?
Chronic infections provoke an allergic response
Example: athletes foot.
What is Trichothecene toxin?
What do they cause?
They are fungal toxins that inhibit protein synthesis in eukaryotic cells
Ingestion of these toxins cause headaches, chills, severe nausea, vomiting and visual disturbances
What pathogens cause Trichothecene?
Fusarium and Stachybotrys
Which fungi cause skin infections that secrete proteases?
Candida albicans and Trichophyton
What do these enzymes of these proteases do to the host cell membranes?
What pathogen causes this and what does it produce?
They modify the host cell membranes to allow attachment of the fungi. Produces a capsule that helps it resist phagocytosis.
Cryptococcus neoformans (meningitis)
What is the disease Ergot toxin? What does it cause?
Common during the Middle Ages
It’s an alkaloid that causes hallucination like LSD
It constricts capillaries and can cause gangrene of the limbs by preventing proper blood circulation in the body.
What pathogen grows on grains that’s an Ergot toxin?
Claviceps purpurea
What is the toxin that usually gets peanut butter recalled?
Aflatoxin, which has carcinogenic properties.
Aspergillus flavus (mold) : could be mutagenic once its ingested into the human body.
What are Mycotoxins?
Some mushrooms produce these.
Examples are phalloidin and amanitin
What mushrooms are referred to as the death cap mushroom?
What type of toxins are these?
Phalloidin, and amanitin
Amanita
Neurotoxins
What of the Protozoa cause diseases?
Plasmodium reproduces how?
Protozoan waste products may cause symptoms
Some reproduce inside the cell and causes it to rupture
How do Protozoa avoid the host defenses?
They grow with in phagocytes and they alter their Antigenic Variation
What is antigenic Variation?
Microbes can make many different antigens or alter their surface proteins to evade the host immune system
What are the Portals of Exit and method of exit?
Respiratory tract- coughing and sneezing
Gastrointestinal tract- feces and saliva
Genitourinary tract- urine and vaginal secretions
Skin
Blood- biting Arthropods and needles or syringes can transfer blood-Bourne pathogens
