UAMS MICROBIOLOGY FINAL EXAM] – QUESTIONS AND ANSWERS |
VERIFIED AND WELL DETAILED ANSWERS PLUS RATIONALES |
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1. A patient presents with a persistent cough, night sweats, and weight loss. A sputum
sample is collected and stained with Ziehl-Neelsen stain, revealing bright red, acid-fast
bacilli. Which of the following is the most likely pathogen?
A. Streptococcus pneumoniae
B. Mycoplasma pneumoniae
C. Mycobacterium tuberculosis
D. Legionella pneumophila
Acid-fast staining (Ziehl-Neelsen) is the diagnostic standard for identifying Mycobacterium
species, which possess mycolic acids in their cell walls that resist decolorization by acid-
alcohol.
2. Which bacterial structure is primarily responsible for preventing phagocytosis by host
immune cells?
A. Pili
B. Capsule
C. Flagella
D. Cell wall
The capsule is a thick, organized polysaccharide layer that masks surface antigens and
prevents adherence of phagocytes, making it a critical virulence factor.
3. During the bacterial growth curve, in which phase are the bacteria most sensitive to
antibiotics that target cell wall synthesis?
A. Lag phase
B. Log phase
C. Stationary phase
D. Death phase
During the log (exponential) phase, bacteria are rapidly dividing and synthesizing new
peptidoglycan, making them highly susceptible to beta-lactam antibiotics.
4. A lab technician identifies a Gram-positive coccus that is catalase-positive and coagulase-
positive. Which organism is identified?
A. Staphylococcus epidermidis
B. Staphylococcus aureus
,C. Streptococcus pyogenes
D. Enterococcus faecalis
Staphylococcus aureus is differentiated from other staphylococci by its ability to produce
coagulase, which clots blood plasma.
5. Which mechanism of horizontal gene transfer involves the uptake of naked DNA from
the environment by a competent cell?
A. Conjugation
B. Transduction
C. Transformation
D. Transposition
Transformation is the process where bacteria take up exogenous genetic material from the
surrounding environment.
6. A patient develops watery diarrhea after a course of clindamycin. Which organism is the
most likely culprit due to overgrowth?
A. Escherichia coli
B. Clostridioides difficile
C. Salmonella enterica
D. Vibrio cholerae
Clostridioides difficile is an opportunistic pathogen that flourishes in the gut after broad-
spectrum antibiotics eliminate competing normal flora.
7. Which component of the Gram-negative cell wall is responsible for endotoxin activity
and triggers a severe inflammatory response?
A. Peptidoglycan
B. Teichoic acid
C. Lipid A (LPS)
D. Porins
Lipid A, found in the lipopolysaccharide layer of the outer membrane, acts as an endotoxin
that stimulates the release of cytokines leading to sepsis.
8. Which test is used to confirm the identification of Group A Streptococcus (Streptococcus
pyogenes)?
A. Optochin sensitivity
B. Bacitracin sensitivity
C. Bile esculin hydrolysis
D. Novobiocin sensitivity
, Group A Streptococcus is characteristically inhibited by bacitracin, providing a simple,
inexpensive diagnostic marker for identification.
9. Which of the following viruses is characterized by its ability to remain latent in the
dorsal root ganglia and reactivate as shingles?
A. Herpes Simplex Virus 1
B. Cytomegalovirus
C. Varicella-Zoster Virus
D. Epstein-Barr Virus
VZV establishes latency in sensory nerve ganglia following the primary infection
(chickenpox) and can reactivate years later as localized dermatomal shingles.
10. An antimicrobial drug that inhibits bacterial protein synthesis by binding to the 50S
ribosomal subunit is:
A. Tetracycline
B. Azithromycin
C. Ciprofloxacin
D. Trimethoprim
Macrolides like azithromycin target the 50S ribosomal subunit to prevent the translocation of
peptides during protein synthesis.
11. Which bacterial feature allows for the colonization of the human stomach by
Helicobacter pylori?
A. Acid-resistant spores
B. Urease production
C. High-affinity iron transporters
D. Biofilm formation
H. pylori produces urease, which converts urea into ammonia and CO2, neutralizing stomach
acid in the immediate microenvironment of the bacteria.
12. What is the primary mode of action of beta-lactam antibiotics?
A. Inhibition of DNA gyrase
B. Disruption of the cell membrane
C. Inhibition of transpeptidase (peptidoglycan cross-linking)
D. Inhibition of folic acid synthesis
Beta-lactams bind to penicillin-binding proteins (PBPs), which are transpeptidase enzymes
responsible for cross-linking the peptidoglycan chains.
VERIFIED AND WELL DETAILED ANSWERS PLUS RATIONALES |
GUARANTEED PASS | LATEST EXAM UPDATE | EXAM PREP | STUDY
GUIDE | PRACTICE TEST| DOWNLOAD INSTANT PDF
1. A patient presents with a persistent cough, night sweats, and weight loss. A sputum
sample is collected and stained with Ziehl-Neelsen stain, revealing bright red, acid-fast
bacilli. Which of the following is the most likely pathogen?
A. Streptococcus pneumoniae
B. Mycoplasma pneumoniae
C. Mycobacterium tuberculosis
D. Legionella pneumophila
Acid-fast staining (Ziehl-Neelsen) is the diagnostic standard for identifying Mycobacterium
species, which possess mycolic acids in their cell walls that resist decolorization by acid-
alcohol.
2. Which bacterial structure is primarily responsible for preventing phagocytosis by host
immune cells?
A. Pili
B. Capsule
C. Flagella
D. Cell wall
The capsule is a thick, organized polysaccharide layer that masks surface antigens and
prevents adherence of phagocytes, making it a critical virulence factor.
3. During the bacterial growth curve, in which phase are the bacteria most sensitive to
antibiotics that target cell wall synthesis?
A. Lag phase
B. Log phase
C. Stationary phase
D. Death phase
During the log (exponential) phase, bacteria are rapidly dividing and synthesizing new
peptidoglycan, making them highly susceptible to beta-lactam antibiotics.
4. A lab technician identifies a Gram-positive coccus that is catalase-positive and coagulase-
positive. Which organism is identified?
A. Staphylococcus epidermidis
B. Staphylococcus aureus
,C. Streptococcus pyogenes
D. Enterococcus faecalis
Staphylococcus aureus is differentiated from other staphylococci by its ability to produce
coagulase, which clots blood plasma.
5. Which mechanism of horizontal gene transfer involves the uptake of naked DNA from
the environment by a competent cell?
A. Conjugation
B. Transduction
C. Transformation
D. Transposition
Transformation is the process where bacteria take up exogenous genetic material from the
surrounding environment.
6. A patient develops watery diarrhea after a course of clindamycin. Which organism is the
most likely culprit due to overgrowth?
A. Escherichia coli
B. Clostridioides difficile
C. Salmonella enterica
D. Vibrio cholerae
Clostridioides difficile is an opportunistic pathogen that flourishes in the gut after broad-
spectrum antibiotics eliminate competing normal flora.
7. Which component of the Gram-negative cell wall is responsible for endotoxin activity
and triggers a severe inflammatory response?
A. Peptidoglycan
B. Teichoic acid
C. Lipid A (LPS)
D. Porins
Lipid A, found in the lipopolysaccharide layer of the outer membrane, acts as an endotoxin
that stimulates the release of cytokines leading to sepsis.
8. Which test is used to confirm the identification of Group A Streptococcus (Streptococcus
pyogenes)?
A. Optochin sensitivity
B. Bacitracin sensitivity
C. Bile esculin hydrolysis
D. Novobiocin sensitivity
, Group A Streptococcus is characteristically inhibited by bacitracin, providing a simple,
inexpensive diagnostic marker for identification.
9. Which of the following viruses is characterized by its ability to remain latent in the
dorsal root ganglia and reactivate as shingles?
A. Herpes Simplex Virus 1
B. Cytomegalovirus
C. Varicella-Zoster Virus
D. Epstein-Barr Virus
VZV establishes latency in sensory nerve ganglia following the primary infection
(chickenpox) and can reactivate years later as localized dermatomal shingles.
10. An antimicrobial drug that inhibits bacterial protein synthesis by binding to the 50S
ribosomal subunit is:
A. Tetracycline
B. Azithromycin
C. Ciprofloxacin
D. Trimethoprim
Macrolides like azithromycin target the 50S ribosomal subunit to prevent the translocation of
peptides during protein synthesis.
11. Which bacterial feature allows for the colonization of the human stomach by
Helicobacter pylori?
A. Acid-resistant spores
B. Urease production
C. High-affinity iron transporters
D. Biofilm formation
H. pylori produces urease, which converts urea into ammonia and CO2, neutralizing stomach
acid in the immediate microenvironment of the bacteria.
12. What is the primary mode of action of beta-lactam antibiotics?
A. Inhibition of DNA gyrase
B. Disruption of the cell membrane
C. Inhibition of transpeptidase (peptidoglycan cross-linking)
D. Inhibition of folic acid synthesis
Beta-lactams bind to penicillin-binding proteins (PBPs), which are transpeptidase enzymes
responsible for cross-linking the peptidoglycan chains.
