Epidemiology and Pathogenesis of Infectious Diseases

Question 1

• Found in Gram-negative bacteria.
• The lipid A component of LPS triggers fever, inflammation, and septic shock when released
  during bacterial lysis.

Answer 1

Endotoxin in Lipopolysaccharide (LPS) Layer:

Question 2

Prevents the bacterium from being engulfed and destroyed by phagocytic immune cells like
macrophages and neutrophils.

Answer 2

Anti-Phagocytic Proteins Induced by oxyR:

Question 3

• A component of the LPS that inhibits killing by phagocytes.
• Plays a role in immune evasion by altering antigenic properties.

Answer 3

O Antigen:

Question 4

• Provides motility, allowing the bacterium to move toward favorable environments.
• Aids in immune evasion by inhibiting phagocytic killing.

Answer 4

Flagellum (H Antigen):

Question 5

• Helps the bacterium adhere to host tissues, a critical first step in colonization and
  infection.

Answer 5

Type 1 Fimbriae (Adherence):

Question 6

• Facilitates bacterial adhesion to and invasion of host cells

Answer 6

inv Encoded Surface Appendage (Adherence):

Question 7

Molecules secreted by the bacteria to scavenge iron from the host, which is essential for
bacterial growth and survival

Answer 7

Siderophores:

Question 8

A circular DNA element carrying genes for virulence factors, such as toxins and enzymes
that contribute to pathogenicity.

Answer 8

Virulence Plasmid:

Question 9

inhibits complement binding, protecting the bacterium from complement
mediated lysis and promoting survival in the host

Answer 9

*Vi Capsule Antigen:

Question 10

Two types of Exotoxins

Answer 10

Cytotoxin
Enterotoxin (Diarrhea):

Question 11

Disrupts host cell protein synthesis and induces calcium influx into the host cells, facilitating bacterial adherence
and causing host cell death.

Answer 11

Cytotoxin

Question 12

Causes the host’s intestinal cells to secrete water and electrolytes, leading to diarrhea. This helps the pathogen
spread to new hosts.

Answer 12

Enterotoxin (Diarrhea):

Question 13

Corynebacterium diphtheriae
* Causes cell death, leading to the formation of a
pseudomembrane in the throat and systemic
complications.

Answer 13

Diphtheria Toxin

Question 14

Shigella dysenteriae and some Escherichia coli
strains (e.g., E. coli O157:H7)
* Causes bloody diarrhea (dysentery) and hemolytic
uremic syndrome (HUS)

Answer 14

Shiga Toxin

Question 15

Bordetella pertussis
* Weakens the immune response and damages
respiratory epithelial cells, leading to whooping
cough.

Answer 15

Pertussis Toxin

Question 16

• Bacillus anthracis
• Causes tissue necrosis and systemic effects in
  inhalational anthrax.

Answer 16

Anthrax Toxin (Lethal Factor)

Question 17

• Streptococcus pyogenes
• Contributes to diseases like necrotizing
  fasciitis and strep throat.

Answer 17

Streptolysin S and Streptolysin O

Question 18

• Clostridium perfringens
• Causes gas gangrene and massive tissue
  destruction.

Answer 18

Alpha-Toxin

Question 19

• Pseudomonas aeruginosa
• Contributes to tissue damage in infections,
  particularly in burn patients.

Answer 19

Pseudomonas Exotoxin A

Question 20

• Helicobacter pylori
• Contributes to peptic ulcers and gastric
  cancer.

Answer 20

VacA (Vacuolating Cytotoxin A

Question 21

Neutralizes stomach acid, enabling survival in the gastric
environment.

Answer 21

Urease

Question 22

Lyse red blood cells, releasing iron for bacterial growth.

Answer 22

Hemolysins

Question 23

Degrades DNA to reduce pus viscosity and enhance
bacterial motility.

Answer 23

DNase

Question 24

Breaks down lipids for nutrient acquisition in sebaceous
glands.

Answer 24

Lipase

Question 25

Dissolves clots, allowing bacteria to spread from trapped sites.

Answer 25

Streptokinase

Question 26

Promotes clot formation to shield bacteria from immune cells.

Answer 26

Coagulase

Question 27

Breaks down collagen to allow deeper penetration into tissues.

Answer 27

Collagenase

Question 28

Degrades hyaluronic acid to facilitate tissue invasion.

Answer 28

Hyaluronidase