IMC 104 B – MICROBIOLOGY (STEELE) MIDTERM |
QUESTIONS AND ANSWERS | VERIFIED ANSWERS PLUS
RATIONALES | EXAM ALREADY GRADED A+ | LATEST
EXAM
1. Which of the following is a Gram-positive bacterium?
A. Escherichia coli
B. Staphylococcus aureus
C. Neisseria meningitidis
D. Pseudomonas aeruginosa
Answer: B – Staphylococcus aureus is Gram-positive due to its thick peptidoglycan cell wall
which retains crystal violet stain.
2. The main function of bacterial pili is to:
A. Produce toxins
B. Adhere to surfaces
C. Motility through flagellar movement
D. Photosynthesis
Answer: C – Pili primarily function in attachment and sometimes in genetic exchange, while
motility is primarily via flagella.
3. The term “antiseptic” refers to:
A. Substances that kill bacteria on living tissue
B. Substances that kill bacteria on inanimate surfaces
C. Antibiotics used internally
D. Vaccines
Answer: A – Antiseptics are chemical agents applied to living tissue to reduce microbial load
without harming the host.
4. Endospores are produced by which genera of bacteria?
A. Clostridium and Bacillus
B. Staphylococcus and Streptococcus
C. Escherichia and Salmonella
D. Neisseria and Haemophilus
Answer: A – Clostridium and Bacillus species can form endospores to survive extreme
conditions.
5. Which staining technique differentiates bacteria based on cell wall composition?
A. Gram stain
,B. Acid-fast stain
C. Capsule stain
D. Flagella stain
Answer: D – Flagella staining shows motility structures, but Gram stain is correct for cell wall
differentiation.
6. Which organism is known for causing tuberculosis?
A. Mycobacterium tuberculosis
B. Streptococcus pyogenes
C. Escherichia coli
D. Bacillus subtilis
Answer: A – Mycobacterium tuberculosis is acid-fast and causes TB, requiring Ziehl-Neelsen
staining.
7. The primary role of normal flora in humans includes:
A. Producing antibiotics
B. Preventing colonization by pathogens
C. Causing disease
D. Generating energy for the host
Answer: B – Normal flora competitively inhibits pathogenic bacteria and supports immune
system development.
8. Which of the following is a fungal infection of the skin?
A. Candidiasis
B. Tinea pedis
C. Tuberculosis
D. Influenza
Answer: B – Tinea pedis (athlete’s foot) is a superficial fungal infection caused by
dermatophytes.
9. What type of immunity is provided by vaccination?
A. Passive natural immunity
B. Active artificial immunity
C. Passive artificial immunity
D. Innate immunity
Answer: B – Vaccines stimulate the immune system to produce memory cells and antibodies
actively.
10. Which virus is associated with causing cervical cancer?
A. HIV
B. HPV
,C. Influenza
D. Hepatitis C
Answer: B – Human papillomavirus (HPV) can lead to cervical dysplasia and cancer.
11. Bacteria that require oxygen for growth are called:
A. Obligate anaerobes
B. Facultative anaerobes
C. Obligate aerobes
D. Microaerophiles
Answer: C – Obligate aerobes need oxygen for cellular respiration and growth.
12. Which structure protects bacteria from phagocytosis?
A. Flagella
B. Capsule
C. Cell wall
D. Endospore
Answer: B – Capsules prevent engulfment by immune cells, enhancing virulence.
13. Which of the following is an example of a zoonotic disease?
A. Measles
B. Rabies
C. Influenza A
D. Chickenpox
Answer: B – Rabies is transmitted from animals (e.g., bats, dogs) to humans.
14. The first step in bacterial infection is typically:
A. Invasion of host tissue
B. Attachment to host cells
C. Toxin production
D. Spore formation
Answer: B – Adhesion via pili or fimbriae is required for colonization.
15. Which test differentiates Staphylococcus aureus from other staphylococci?
A. Coagulase test
B. Catalase test
C. Gram stain
D. Oxidase test
Answer: A – S. aureus is coagulase-positive; most other staphylococci are coagulase-negative.
, 16. Gram-negative bacteria have:
A. Thick peptidoglycan layer
B. Outer membrane with lipopolysaccharide
C. No cell wall
D. Teichoic acids
Answer: B – Gram-negative bacteria have a thin peptidoglycan wall and an LPS-containing
outer membrane.
17. Which of the following is an example of an opportunistic pathogen?
A. Streptococcus pneumoniae
B. Pseudomonas aeruginosa
C. Mycobacterium leprae
D. Clostridium botulinum
Answer: B – Pseudomonas can cause infection in immunocompromised hosts.
18. Penicillin targets:
A. Bacterial ribosomes
B. DNA replication
C. Peptidoglycan synthesis
D. RNA polymerase
Answer: C – Penicillin inhibits transpeptidase, disrupting bacterial cell wall synthesis.
19. Which of these is a common bacterial cause of urinary tract infections?
A. Escherichia coli
B. Streptococcus pyogenes
C. Neisseria gonorrhoeae
D. Staphylococcus epidermidis
Answer: A – E. coli from the gut flora is the most frequent cause of UTIs.
20. The acid-fast stain is primarily used for:
A. Gram-positive cocci
B. Mycobacteria
C. Fungi
D. Protozoa
Answer: B – Mycobacteria have mycolic acids that retain carbol fuchsin in acid-fast staining.
21. Which of the following is NOT a method of sterilization?
A. Autoclaving
B. Boiling
C. Filtration
D. Pasteurization
QUESTIONS AND ANSWERS | VERIFIED ANSWERS PLUS
RATIONALES | EXAM ALREADY GRADED A+ | LATEST
EXAM
1. Which of the following is a Gram-positive bacterium?
A. Escherichia coli
B. Staphylococcus aureus
C. Neisseria meningitidis
D. Pseudomonas aeruginosa
Answer: B – Staphylococcus aureus is Gram-positive due to its thick peptidoglycan cell wall
which retains crystal violet stain.
2. The main function of bacterial pili is to:
A. Produce toxins
B. Adhere to surfaces
C. Motility through flagellar movement
D. Photosynthesis
Answer: C – Pili primarily function in attachment and sometimes in genetic exchange, while
motility is primarily via flagella.
3. The term “antiseptic” refers to:
A. Substances that kill bacteria on living tissue
B. Substances that kill bacteria on inanimate surfaces
C. Antibiotics used internally
D. Vaccines
Answer: A – Antiseptics are chemical agents applied to living tissue to reduce microbial load
without harming the host.
4. Endospores are produced by which genera of bacteria?
A. Clostridium and Bacillus
B. Staphylococcus and Streptococcus
C. Escherichia and Salmonella
D. Neisseria and Haemophilus
Answer: A – Clostridium and Bacillus species can form endospores to survive extreme
conditions.
5. Which staining technique differentiates bacteria based on cell wall composition?
A. Gram stain
,B. Acid-fast stain
C. Capsule stain
D. Flagella stain
Answer: D – Flagella staining shows motility structures, but Gram stain is correct for cell wall
differentiation.
6. Which organism is known for causing tuberculosis?
A. Mycobacterium tuberculosis
B. Streptococcus pyogenes
C. Escherichia coli
D. Bacillus subtilis
Answer: A – Mycobacterium tuberculosis is acid-fast and causes TB, requiring Ziehl-Neelsen
staining.
7. The primary role of normal flora in humans includes:
A. Producing antibiotics
B. Preventing colonization by pathogens
C. Causing disease
D. Generating energy for the host
Answer: B – Normal flora competitively inhibits pathogenic bacteria and supports immune
system development.
8. Which of the following is a fungal infection of the skin?
A. Candidiasis
B. Tinea pedis
C. Tuberculosis
D. Influenza
Answer: B – Tinea pedis (athlete’s foot) is a superficial fungal infection caused by
dermatophytes.
9. What type of immunity is provided by vaccination?
A. Passive natural immunity
B. Active artificial immunity
C. Passive artificial immunity
D. Innate immunity
Answer: B – Vaccines stimulate the immune system to produce memory cells and antibodies
actively.
10. Which virus is associated with causing cervical cancer?
A. HIV
B. HPV
,C. Influenza
D. Hepatitis C
Answer: B – Human papillomavirus (HPV) can lead to cervical dysplasia and cancer.
11. Bacteria that require oxygen for growth are called:
A. Obligate anaerobes
B. Facultative anaerobes
C. Obligate aerobes
D. Microaerophiles
Answer: C – Obligate aerobes need oxygen for cellular respiration and growth.
12. Which structure protects bacteria from phagocytosis?
A. Flagella
B. Capsule
C. Cell wall
D. Endospore
Answer: B – Capsules prevent engulfment by immune cells, enhancing virulence.
13. Which of the following is an example of a zoonotic disease?
A. Measles
B. Rabies
C. Influenza A
D. Chickenpox
Answer: B – Rabies is transmitted from animals (e.g., bats, dogs) to humans.
14. The first step in bacterial infection is typically:
A. Invasion of host tissue
B. Attachment to host cells
C. Toxin production
D. Spore formation
Answer: B – Adhesion via pili or fimbriae is required for colonization.
15. Which test differentiates Staphylococcus aureus from other staphylococci?
A. Coagulase test
B. Catalase test
C. Gram stain
D. Oxidase test
Answer: A – S. aureus is coagulase-positive; most other staphylococci are coagulase-negative.
, 16. Gram-negative bacteria have:
A. Thick peptidoglycan layer
B. Outer membrane with lipopolysaccharide
C. No cell wall
D. Teichoic acids
Answer: B – Gram-negative bacteria have a thin peptidoglycan wall and an LPS-containing
outer membrane.
17. Which of the following is an example of an opportunistic pathogen?
A. Streptococcus pneumoniae
B. Pseudomonas aeruginosa
C. Mycobacterium leprae
D. Clostridium botulinum
Answer: B – Pseudomonas can cause infection in immunocompromised hosts.
18. Penicillin targets:
A. Bacterial ribosomes
B. DNA replication
C. Peptidoglycan synthesis
D. RNA polymerase
Answer: C – Penicillin inhibits transpeptidase, disrupting bacterial cell wall synthesis.
19. Which of these is a common bacterial cause of urinary tract infections?
A. Escherichia coli
B. Streptococcus pyogenes
C. Neisseria gonorrhoeae
D. Staphylococcus epidermidis
Answer: A – E. coli from the gut flora is the most frequent cause of UTIs.
20. The acid-fast stain is primarily used for:
A. Gram-positive cocci
B. Mycobacteria
C. Fungi
D. Protozoa
Answer: B – Mycobacteria have mycolic acids that retain carbol fuchsin in acid-fast staining.
21. Which of the following is NOT a method of sterilization?
A. Autoclaving
B. Boiling
C. Filtration
D. Pasteurization
