INFECTIOUS DISEASE EXAM 2 UPDATED ACTUAL QUESTIONS AND CORRECT ANSWERS

INFECTIOUS DISEASE EXAM 2 UPDATED ACTUAL
QUESTIONS AND CORRECT ANSWERS

Question:
1. ETEC - Enterotoxigenic E. coli
Answer:
"Traveler's diarrhea" (developing countries).
Spread by fecally contaminated food/water. High infectious dose (no person-to-person spread).
Symptoms: watery diarrhea (no blood), cramps, nausea, vomiting.
Virulence factors: Heat-labile toxin (LT): ‘ cAMP ’ chloride + water secretion. Heat-stable toxin (ST): ‘
cGMP ’ fluid secretion.
Colonization factors (fimbriae CFA/I-III) for gut adherence.

Question:
2. EPEC - Enteropathogenic E. coli
Answer:
Infant diarrhea (developing world; daycare/nurseries in developed).
Low infectious dose ’ person-to-person spread.
Symptoms: severe watery diarrhea, vomiting, fever.
Pathology: Attachment and effacement (A/E) ’ destruction of microvilli.
Virulence factors: Bundle-forming pili (BFP) for microcolony formation.
Type III secretion system injects proteins (e.g., Tir ’ binds bacterial intimin, disrupts cytoskeleton, cell
death).

Question:
3. EAEC - Enteroaggregative E. coli
Answer:
Chronic watery diarrhea in infants & travelers. Can stunt growth in children.
Symptoms: persistent diarrhea. Pathology: "Stacked-brick" adhesion ’ biofilm formation.
Virulence factors: Aggregative adherence fimbriae (AAF-1). Biofilm protects from phagocytosis &
antibiotics.
Toxins: enteroaggregative heat-stable toxin + plasmid-encoded toxin.

Question:
4. EHEC - Enterohemorrhagic E. coli
Answer:
Most common pathogenic strain in the developed world (O157:H7 classic).
Source: undercooked meat, contaminated water, produce, cattle feces.
Very low infectious dose (person-to-person spread possible).
Symptoms: bloody diarrhea, abdominal pain, sometimes Hemolytic Uremic Syndrome (HUS: renal failure,
thrombocytopenia, anemia).
Virulence factors: Shiga toxins (Stx-1, Stx-2) ’ block protein synthesis. Attaching/effacing lesions (like
EPEC).

Question:
5. EIEC - Enteroinvasive E. coli

,Answer:
Rare (O124, O143, O164).
Symptoms: watery diarrhea ’ dysentery (bloody diarrhea, fever, cramps).
Pathology: Invade epithelial cells via endocytosis, escape vacuole, multiply in cytoplasm ’ cell death +
ulceration. Similar to Shigella.

Question:
6. O antigen
Answer:
Polysaccharide portion of LPS. Strain-specific.

Question:
7. K antigen
Answer:
Capsule polysaccharide. Protects against phagocytosis, complement, antibody binding.

Question:
8. H antigen
Answer:
Flagellar proteins. Variable between strains.

Question:
9. Endotoxic shock
Answer:
systemic reaction to LPS ’ clotting, vascular leakage, shock, organ failure.

Question:
10. Type III secretion system
Answer:
"Molecular syringe" to inject toxins into host cells.

Question:
11. Siderophore
Answer:
iron-scavenging compound bacteria use to steal iron.

Question:
12. Antigenic phase variation
Answer:
switching expression of O, H, or K antigens on/off to evade immunity.

Question:
13. Nosocomial infection
Answer:
hospital-acquired infection.

, Question:
14. Iatrogenic infection
Answer:
infection caused by a medical procedure.

Question:
15. Cystitis
Answer:
bladder infection.

Question:
16. Pyelonephritis
Answer:
kidney infection.

Question:
17. Sequelae
Answer:
disease conditions that appear after the infection resolves (e.g., renal impairment after EHEC)

Question:
18. Pathology of Salmonella Typhi
Answer:
Transmission: contaminated food/water, person-to-person possible (low infectious dose). No animal
reservoir (human-only).
Disease states caused by S. Typhi: Typhoid (Enteric) Fever
Pathogenesis: Bacteria cross intestinal lining ’ taken up by macrophages. Survive inside macrophages ’
spread to liver, spleen, bone marrow. Bacteremic phase: fever, headache, malaise, myalgia, anorexia. Later
colonize gallbladder ’ reinfect intestine ’ GI symptoms worsen. Chronic carriage: ~1% of cases ’ bacteria
persist in gallbladder (e.g., Typhoid Mary).

Question:
19. Other Salmonella disease syndromes
Answer:
Gastroenteritis - most common; nausea, vomiting, watery diarrhea, fever (self-limiting).
Septicemia - bloodstream infection (more common in Typhi, Paratyphi, Choleraesuis). Can lead to
endocarditis, osteomyelitis, suppurative arthritis.
Asymptomatic colonization - chronic gallbladder carrier state after infection resolution.

Question:
20. Endemic
Answer:
Disease always present at stable levels in humans

Question:
21. Enzootic