Bacterial Pathogenesis and Host Defences - Sheet1-1

Question 1

hypersensitivity

Answer 1

refers to undesirable reactions produced by the normal immune system, including allergies and autoimmunity.

Question 2

endotoxin is only produced by _______

Answer 2

gram neg bacteria

Question 3

Pathogen

Answer 3

bacteria capable of causing disease

Question 4

Virulence

Answer 4

quantitative measure of pathogenicities measured by the number of bacteria required to cause disease

Question 5

LD50

Answer 5

number of bacteria necessary to kill half the host

Question 6

ID50

Answer 6

number of bacteria necessary to cause infection in half the hosts

Question 7

Virulence Factors

Answer 7

properties of a bacteria which assist in causing disease ex: pili, capsules,

Question 8

Bacterial Structure virulance factors

Answer 8

Pili, Capsules
Glycocalyx
Endotoxin
Biofilms
Bacterial Secretion Systems

Question 9

Coagulase

Answer 9

eg. Helps coat Staph. aureus with fibrin to help protect from phagocytosis

Question 10

Immunoglobulin A protease

Answer 10

Degrades IgA allowing Strep. Pneumonia to adhere to mucous membranes

Question 11

Leukocidins

Answer 11

a type of cytotoxin created by some types of bacteria. It is a type of pore forming toxin. Leukocidins get their names by killing (“-cide”) leukocytes

Question 12

Other Bacterial Factors

Answer 12

M protein - antiphagocytic protein produced by Strep. pyogenes

Protein A - binds to IgG and prevents activation of complement

Invasins - bacterial molecules which promote bacterial entry or contact with host cells - eg. Heliobacter pylori

Outer membrane proteins - produced by Yersinia species to inhibit phagocytosis and cytokine production
**Pathogenicity Islands (PAIs) – code for groups of virulence factors particularly in **Gram negatives

Question 13

Pathogenicity Islands (PAIs)

Answer 13

code for groups of virulence factors particularly in **Gram negatives. Some are located on chromosomes and some are not.

Question 14

Exotoxins

Answer 14

Polypeptides secreted by bacteria

Become toxoids when treated with formaldehyde, and/or heat and used for protective vaccines

Frequently have an A-B subunit structure (A portion has toxic activity and B portion is involved in binding to cells)

Are genetically coded on the bacterial chromosome, plasmid or phage

Have one of five biological effects:

• -Alter cellular components
• -Are superantigens
• -Inhibit protein synthesis
• -Increase synthesis of cAMP
• -Alter nerve impulse transmissions

Question 16

Endotoxins

Answer 16

Are integral parts of the cell wall of Gram negative rods and cocci

Involve the Lipid A component of lipopolysaccharide

Only weakly antigenic; no toxoids made

Induced biological effects focus on fever and shock

Question 17

two types of immunity

Answer 17

1. Innate Immunity
Macrophages
---Phagocytize and digest bacteria
Complement
----Assist host immune cells and antibody in lysis of bacteria and virus-infected cells

2. Acquired Immunity
Antibodies
---Cytolytic
---Neutralizing: body synthesizes ***antibody to viral receptor protein. Ability of virus to infect is lost
---Opsonins

Cytotoxic T Cells: recognize antibody binding and kill bacteria
—Kill antibody-coated bacteria and virus-infected cells

Question 18

Passive vs. Active Immunity

Answer 18

Passive Immunity

• –Administration of preformed antigen-specific antibodies to help protect from disease ex. Human rabies immune globulin Active Immunity
• –Administration of specific antigens to stimulate an individual to develop immunity to help protect from a disease ex. Influenza vaccine

Question 19

Avoiding the Innate Immune Response–avoid their killing by macrophage

Answer 19

There are essentially three categories of bacterial strategies to deal with phagocytic cells:

• Avoiding contact with phagocytes
• Inhibition of engulfment
• Survival within the phagocyte

Question 20

Stapholoccocal virulance factor:

Answer 20

*Protein A: binds immunoglobulin (IgA)–which disguises itself from immune response.

Question 21

Pseudomonas aeruginosa

Answer 21

An opportunistic pathogen that infects humans with compromised natural defences. The propensity of P. aeruginosa to form biofilms further protects it from antibiotics and from the host immune system.

Question 22

influenza

Answer 22

Orthomyxoviruses. Enveloped, negative single­ stranded RNA viruses with 8-segment genome. Contain hemagglutinin (promotes viral
entry) and neuraminidase (promotes progeny virion release) antigens. Patients at risk for
fatal bacterial superinfection. Rapid genetic changes.

Question 23

Corynebaderium

diphtheriae

Answer 23

Causes diphtheria via exotoxin encoded by beta-prophage. Potent exotoxin inhibits protein synthesis via ADP-ribosylation ofEF-2.
Symptoms include pseudomembranous pharyngitis (grayish-white membrane) with lymphadenopathy, myocarditis, and arrhythmias.
Lab diagnosis based on gram-positive rods with metachromatic (blue and reel) granules and Elek’s test for toxin.
Toxoid vaccine prevents diphtheria.