NSG 6001 WEEK 3 MIDTERM EXAM QUESTIONS AND ANSWERS COURSE GRADED A+ COMPLETE STUDY GUIDE Exam

WGU D311 OA Final Exam Version 2 /
WGU D311 Microbiology Objective
Assessment Final Exam Newest
2025/2026 Actual Exam Complete 150
Questions And Correct Detailed
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1. A patient presents with fever, hypotension, and disseminated intravascular
coagulation (DIC) following a urinary tract infection. The Gram-negative bacteria
isolated from the urine are likely triggering this response through which structure?

 A) Teichoic acid
 B) Peptidoglycan
 C) Lipopolysaccharide (LPS)
 D) Capsule

✅ Correct Answer: C) Lipopolysaccharide (LPS)
Rationale: LPS (endotoxin) in the outer membrane of Gram-negative bacteria triggers a
strong inflammatory response, activating macrophages and releasing cytokines that can
lead to fever, septic shock, and DIC.




2. A 45-year-old with HIV has a CD4 count of 120 cells/mm³ and develops a dry
cough and dyspnea. A silver stain of sputum shows cup-shaped organisms. What is
the most likely pathogen?

, A) Mycobacterium tuberculosis
 B) Streptococcus pneumoniae
 C) Pneumocystis jirovecii
 D) Histoplasma capsulatum

✅ Correct Answer: C) Pneumocystis jirovecii
*Rationale: Pneumocystis jirovecii pneumonia (PCP) occurs when CD4 count drops below
200. Silver stain reveals characteristic cup-shaped or cystic forms. It is a common AIDS-
defining illness.*




3. A microbiology student accidentally discards a bacterial culture before
completing a Gram stain. To salvage identification, which structural difference
would most reliably distinguish Gram-positive from Gram-negative bacteria?

 A) Presence of ribosomes
 B) Thickness of peptidoglycan layer
 C) Presence of a cell membrane
 D) Type of nitrogenous bases in DNA

✅ Correct Answer: B) Thickness of peptidoglycan layer
Rationale: Gram-positive bacteria have a thick, multilayered peptidoglycan wall that
retains crystal violet-iodine complex. Gram-negative bacteria have a thin peptidoglycan
layer and an outer membrane that does not retain the stain.




4. A 30-year-old nurse develops a fever, severe headache, and jaundice 10 days
after a trip to a tropical region where she went white-water rafting. Leptospirosis
is suspected. Which virulence factor is most important in the pathogenesis of this
spirochete?

 A) Exotoxin A
 B) Flagellar motility
 C) Lipid A endotoxin
 D) Biofilm formation

, ✅ Correct Answer: B) Flagellar motility
Rationale: Leptospira species are spirochetes with axial flagella (endoflagella) that allow
corkscrew-like movement, enabling penetration through mucous membranes and rapid
dissemination to organs like the liver and kidneys.




5. A 25-year-old sexually active woman reports dysuria and increased urinary
frequency. A urine culture grows Gram-negative, lactose-fermenting colonies on
MacConkey agar. Which bacterial structure is primarily responsible for
colonization of the urinary tract?

 A) Fimbriae (pili)
 B) Flagella
 C) Endospores
 D) Glycocalyx

✅ Correct Answer: A) Fimbriae (pili)
Rationale: Uropathogenic E. coli use type 1 fimbriae to adhere to uroepithelial cells,
preventing elimination during urination. Adhesion is the critical first step in UTI
pathogenesis.




6. A microbiologist observes that an antibiotic inhibits bacterial protein synthesis
by binding to the 50S ribosomal subunit. Which drug class is most consistent with
this mechanism?

 A) Aminoglycosides
 B) Macrolides
 C) Tetracyclines
 D) Fluoroquinolones

✅ Correct Answer: B) Macrolides
Rationale: Macrolides (e.g., erythromycin, azithromycin) bind reversibly to the 50S
ribosomal subunit, blocking translocation and inhibiting protein synthesis.
Aminoglycosides bind 30S, tetracyclines bind 30S, and fluoroquinolones inhibit DNA
gyrase.

, 7. Which statement best explains why vancomycin is effective against methicillin-
resistant Staphylococcus aureus (MRSA) but not against Gram-negative bacteria?

 A) Vancomycin targets peptidoglycan, but Gram-negative bacteria lack peptidoglycan
 B) Vancomycin is too large to penetrate the outer membrane of Gram-negative bacteria
 C) Gram-negative bacteria produce beta-lactamase that inactivates vancomycin
 D) Vancomycin requires a functional electron transport chain to enter cells

✅ Correct Answer: B) Vancomycin is too large to penetrate the outer membrane of
Gram-negative bacteria
Rationale: Vancomycin is a large glycopeptide that inhibits cell wall synthesis by binding
D-Ala-D-Ala. It cannot cross the outer membrane of Gram-negative bacteria, limiting its
use to Gram-positive organisms.




8. A 60-year-old with a history of recurrent C. difficile infection receives fecal
microbiota transplantation (FMT). What is the primary mechanism by which FMT
restores gut health?

 A) Direct killing of C. difficile spores by donor bacteria
 B) Restoration of normal microbial diversity and colonization resistance
 C) Neutralization of toxin A and toxin B by donor antibodies
 D) Activation of innate immune cells to phagocytose vegetative cells

✅ Correct Answer: B) Restoration of normal microbial diversity and colonization
resistance
Rationale: FMT re-establishes a diverse gut microbiome that competes with C. difficile for
nutrients and niches, restores bile acid metabolism, and strengthens colonization
resistance — breaking the cycle of recurrence.




9. Which bacterial enzyme allows survival in the presence of oxygen by breaking
down reactive oxygen species?

 A) Coagulase