Microbiology Ch 15 Review

The ability to cause disease

The extent of pathogenicity

• -Mucous membranes
• -skin
• -Parenteral route-direct deposit
• -Preferred portal of entry 

Infectious dose for 50% of the test population

Lethal dose (of a toxin) for 50% of the test population

• *Adhesins/ligands bind to receptors on host cells
• -Glycocalyx: streptococcus mutans
• -Fimbriae: Escherichia coli
• -M protein: streptococcus pyogenes

Form biofilms 

• Capsules
• Cell wall components
• Enzymes
• Penetration into the Host cell cytoskeleton 
• Antigenic variation

 

• Prevent phagocytosis
•   -streptococcus pneumoniae
•   -Haemophilus influenzae
•   -Bacillus anthracis 

• -M Protein resists phagocytosis
•     streptococcus pyogenes
• -Opa Protein inhibits T helper cells
•   Neisseria gonorrhoeae
• -Mycolic acid (waxy lipid) resists digestion
•    Mycobacterium tuberculosis 

Coagulase: coagulates fibrinogen

Kinases: digest fribrin clots

Hyaluronidase: Hydrolyzes hyaluronic acid

Collagenase: hydrolyzes collagen

IgA proteases: Destroy IgA antibodies 

-Invasins: salmonella alters hsost actin to enter a host cell

-Use actin to move from one cell to the next: Listeria

 

Alter surfce proteins

• -Using the host's nutrients:siderophores
• -Direct damage
• -The production of toxins
• -Exotoxins
• -Endotoxins
• -Membrane disrupting toxins
• -A-B exotoxin
• -Superantigens
• -Exotoxin-protein
• -Endotoxins and the Pyrogenic Response
• -LAL assay 

Use host's iron, compete with transferrin

• -Disrupt host cell function
• -Produce waste products
• -Toxins
• -Cell rupture
•  

Toxins: substance that contributes to pathogenicity 

Ability to produce a toxin

Presence of toxin in the host's blood

Inactivated toxin used in a vaccine

Antibodies against a specific toxin

• 1) AB
• 2)Membrane disrupting
• 3) Superantigens
•  

Made of A subunit and B subunit

A: active subunit

B: the binding subunit 

• Lyse host's cell by  ; making protein channels in the plasma membrane  
•      ex) of membrane disrupting toxins
•                      Leukocidins
•                      Hemolysins
•                      Streptolysins

-Disrupting phopholipid bilayer  

• -Cause an intense immune response due to release of cytokines from host cells
• -symptoms: fever, nausea, vomiting, diarrhea, shock and death

T-cells -->cytokins-->inflammation--->organ failure 

• -Gram Negative
•  Always "Lipid A"
•  

• -Limulus amoebocyte lysate assay
• -Amoebocyte produces a clot
• -Endotoxin causes lysis  

• -Fungal waste products may cause symptoms
• -chronic infections provoke an allergic response
• -Tichothecene toxins inhibit protein synthesis
• -Proteases
• -Capsule prevents phagocytosis  

• -Ergot Toxin  : Claviceps
• -Aflatoxin: Aspergillus
• -Mycotoxins: Neurotoxins: Phalloidin, amanitin,  

• -Presence of protozoa
• -Protozoan waste products may cause symptoms
• -Avoid host defenses by : growing in phagocytes, antigenic variation  

• -use host tissue
• -presence of parasite interferes with host function
• -parasites metabolic waste can cause sypmtoms 

• -Paralytic shellfish poisoning
•      *Dinoflagellates
•       *saxitoxin

 

• -Respirtatory tract: cougphing and sneezing
• -Gastrointestinal tract: Feces and saliva
• -Genitourinary tract: Urine and Vaginal secretions
• -Skin
• -Blood:biting arthropods and needles or syringes  

Ergot toxin: can cause gangrene if exposed

Aflatoxin: given off by peanuts. Very potent toxin

Mycotoxins: neurotoxins