MCB2000C
Microbiology I
Exam Q & A
2024
, 1. A patient with a history of diabetes mellitus and peripheral vascular
disease presents with a chronic ulcer on his left foot. The wound
culture reveals the presence of Pseudomonas aeruginosa, a
gram-negative rod that produces a greenish pigment and a fruity
odor. Which of the following statements is true about this
organism?
a) It is an obligate anaerobe that can cause gas gangrene.
b) It is a facultative intracellular parasite that can survive inside
macrophages.
c) It is an opportunistic pathogen that can form biofilms and resist
antibiotics.
d) It is a strict aerobe that can produce exotoxins and endotoxins.
*Answer: c) It is an opportunistic pathogen that can form biofilms and
resist antibiotics.
Rationale: Pseudomonas aeruginosa is a common cause of nosocomial
infections, especially in immunocompromised patients and those
with chronic wounds. It can adhere to surfaces and form
biofilms, which protect it from host defenses and antimicrobial
agents. It can also produce various virulence factors, such as
enzymes, siderophores, and quorum sensing molecules, that
enhance its pathogenicity and resistance.
2. A 25-year-old woman visits her gynecologist with complaints of
vaginal itching, burning, and discharge. She admits to having
unprotected sex with a new partner two weeks ago. The
gynecologist performs a wet mount of the vaginal discharge and
observes clue cells under the microscope. Which of the
following organisms is most likely responsible for this
condition?
a) Candida albicans
b) Gardnerella vaginalis
c) Neisseria gonorrhoeae
d) Trichomonas vaginalis
*Answer: b) Gardnerella vaginalis
Rationale: Gardnerella vaginalis is a gram-variable rod that can cause
bacterial vaginosis, a condition characterized by a thin, grayish-
white, fishy-smelling discharge and vaginal pH above 4.5. Clue
cells are epithelial cells covered with adherent bacteria, which
are diagnostic of bacterial vaginosis. Candida albicans is a
fungus that causes vulvovaginal candidiasis, which manifests as
a thick, white, curdy discharge and vaginal pH below 4.5.
Neisseria gonorrhoeae is a gram-negative diplococcus that
causes gonorrhea, which may present as a purulent discharge
Microbiology I
Exam Q & A
2024
, 1. A patient with a history of diabetes mellitus and peripheral vascular
disease presents with a chronic ulcer on his left foot. The wound
culture reveals the presence of Pseudomonas aeruginosa, a
gram-negative rod that produces a greenish pigment and a fruity
odor. Which of the following statements is true about this
organism?
a) It is an obligate anaerobe that can cause gas gangrene.
b) It is a facultative intracellular parasite that can survive inside
macrophages.
c) It is an opportunistic pathogen that can form biofilms and resist
antibiotics.
d) It is a strict aerobe that can produce exotoxins and endotoxins.
*Answer: c) It is an opportunistic pathogen that can form biofilms and
resist antibiotics.
Rationale: Pseudomonas aeruginosa is a common cause of nosocomial
infections, especially in immunocompromised patients and those
with chronic wounds. It can adhere to surfaces and form
biofilms, which protect it from host defenses and antimicrobial
agents. It can also produce various virulence factors, such as
enzymes, siderophores, and quorum sensing molecules, that
enhance its pathogenicity and resistance.
2. A 25-year-old woman visits her gynecologist with complaints of
vaginal itching, burning, and discharge. She admits to having
unprotected sex with a new partner two weeks ago. The
gynecologist performs a wet mount of the vaginal discharge and
observes clue cells under the microscope. Which of the
following organisms is most likely responsible for this
condition?
a) Candida albicans
b) Gardnerella vaginalis
c) Neisseria gonorrhoeae
d) Trichomonas vaginalis
*Answer: b) Gardnerella vaginalis
Rationale: Gardnerella vaginalis is a gram-variable rod that can cause
bacterial vaginosis, a condition characterized by a thin, grayish-
white, fishy-smelling discharge and vaginal pH above 4.5. Clue
cells are epithelial cells covered with adherent bacteria, which
are diagnostic of bacterial vaginosis. Candida albicans is a
fungus that causes vulvovaginal candidiasis, which manifests as
a thick, white, curdy discharge and vaginal pH below 4.5.
Neisseria gonorrhoeae is a gram-negative diplococcus that
causes gonorrhea, which may present as a purulent discharge
