USMLE ID microbiology exam with
100% correct answers 2024
Generalized transduction differs most substantially from specialized transduction
because?
A: Generalized transducing particles are infectious
B: Generalized transducing particles lack bacteriophage DNA
C: Generalized transduction involves phage integration into the chromosome
D: Specialized transduction incorporates random pieces of bacterial DNA
E: Specialized transduction utilizes an oriV site for site-specific recombination - D:
Specialized transduction incorporates random pieces of bacterial DNA
he minimum biological requirement for resistance plasmid conjugation is that the R
plasmid must encode?
A: Insertion sequences
B: Nicking/unwinding enzymes
C: Sex (conjugation) pilus
D: Site that can act as an oriT
E: Transposons - D: Site that can act as an oriT
Which of the following is correct regarding immune response to intracellular bacteria?
a. NK cells are effective primarily through their production and induction of cytokines
a-b. S typhimurium and F tularensis inhibit the formation of the phagolysosome
c. neutrophils are more active than macrophages at phagocytosing IC bacteria
d. pattern recognition molecules TLR and NLR have little role
e. soluble mediators are effective at clearing granulomatous formations
f. Th1 and Th2 cell responses are equally effective against intracellular bacteria - b. S
typhimurium and F tularensis inhibit the formation of the phagolysosome
,USMLE ID microbiology exam with
100% correct answers 2024
Pyroptosis is a result of the following:
a. extracellular bacteria triggering TLR activation of the inflammasome that recruits
caspase 3, which activates pro-IL-1 and pro-IL-6 and causes this inflammatory form of
cell death
b. intracellular bacteria inhibition of phagolysosome formation
c. cytotoxic storm activated by NK cells in response to extracellular bacteria
d. intracellular bacteria triggering NLR activation of the inflammasome that recruits
capsase 1, which activates pro-IL-1 and pro-IL-18 and causes this inflammatory cell
death - -d. intracellular bacteria triggering NLR activation of the inflammasome that
recruits capsase 1, which activates pro-IL-1 and pro-IL-18 and causes this inflammatory
cell death
For which of the following groups of organisms would you expect complement to play
the MOST significant role in immune protection?
a. gram-positive intracellular bacteria
b. gram-negative intracellular bacteria
c. toxin-producing extracellular bacteria
d. gram-negative extracellular bacteria
e. normal intestinal flora - d. gram-negative extracellular bacteria
A 32-year-old woman presents to the emergency department with abdominal pain, fever
and watery, bloody diarrhea. History includes a suspicion of eating an undercooked egg
the day before. Physical exam reveals a dehydrated febrile patient in need of rest. The
laboratory cultures Salmonella enterica from a stool sample using selective medium.
,USMLE ID microbiology exam with
100% correct answers 2024
Which of the following characteristics of this species contributes to its evasion of innate
immunity?
a. survival and replication within the phagosome
b. production of C5a peptidase
c. production of Protein A
d. inhibition of type I interferon signaling
e. expression of a capsule - a. survival and replication within the phagosome
A 62-year old man presents with a fever, cough and complaints of rust-colored sputum.
His chest X-ray shows a dense left lower lobe infiltrate with a left pleural effusion. The
laboratory cultures a gram-positive diplococcus species from a sputum sample. Which
of the following are among the immune evasion mechanisms that characterize this
organism?
a. phagosome escape
b. inhibition of NK cell activation
c. production of an IFN-g receptor mimic
d. production of a capsule
e. inhibition of type I interferon signaling - d. production of a capsule
Listeria monocytogenes is an intracellular pathogen associated with the ingestion of
contaminated meat and dairy products and can cause severe perinatal infections. If a
pregnant woman acquires her first infection with Listeria late in pregnancy, which of the
following would be impaired or absent in the newborn that might otherwise limit
infection? (two answers)
a. CD4+ and CD8+ T cells
, USMLE ID microbiology exam with
100% correct answers 2024
b. maternal IgG neutralizing antibodies
c. type I IFN
d. complement-dependent bacterial lysis
e. IL-4 - a. CD4+ and CD8+ T cells
b. maternal IgG neutralizing antibodies
Which of the following microbes is an opportunistic bacterial pathogen of relatively low
virulence that does not typically cause serious disease in healthy individuals who have
intact skin and mucous membranes?
a. Viridans streptococci
b. Staphlycoccus epidermidis
c. Candida albicans
d. Salmonella typhi
e. Cytomegalovirus
f. Pseudomonas aeruginosa - b. Staphlycoccus epidermidis
A 2-year-old child has a history of infections with prolonged episodes of diarrhea. His
mother reports that he seems to be sick constantly, and that he had oral thrush from
shortly after birth until 3 months of age and numerous upper respiratory tract infections
before the age of 6 months. Since then, he has been hospitalized twice with bacterial
pneumonia. His family history includes a maternal uncle and a male cousin who died of
pneumonia or diarrhea-associated infectious diseases in infancy. The patient has
shown mild-moderate lymphopenia throughout his life, but otherwise normal blood cell
counts. His Ig levels are low normal, but his CD4+ T cell counts (500/ml) are well below
normal for his age. He has made
100% correct answers 2024
Generalized transduction differs most substantially from specialized transduction
because?
A: Generalized transducing particles are infectious
B: Generalized transducing particles lack bacteriophage DNA
C: Generalized transduction involves phage integration into the chromosome
D: Specialized transduction incorporates random pieces of bacterial DNA
E: Specialized transduction utilizes an oriV site for site-specific recombination - D:
Specialized transduction incorporates random pieces of bacterial DNA
he minimum biological requirement for resistance plasmid conjugation is that the R
plasmid must encode?
A: Insertion sequences
B: Nicking/unwinding enzymes
C: Sex (conjugation) pilus
D: Site that can act as an oriT
E: Transposons - D: Site that can act as an oriT
Which of the following is correct regarding immune response to intracellular bacteria?
a. NK cells are effective primarily through their production and induction of cytokines
a-b. S typhimurium and F tularensis inhibit the formation of the phagolysosome
c. neutrophils are more active than macrophages at phagocytosing IC bacteria
d. pattern recognition molecules TLR and NLR have little role
e. soluble mediators are effective at clearing granulomatous formations
f. Th1 and Th2 cell responses are equally effective against intracellular bacteria - b. S
typhimurium and F tularensis inhibit the formation of the phagolysosome
,USMLE ID microbiology exam with
100% correct answers 2024
Pyroptosis is a result of the following:
a. extracellular bacteria triggering TLR activation of the inflammasome that recruits
caspase 3, which activates pro-IL-1 and pro-IL-6 and causes this inflammatory form of
cell death
b. intracellular bacteria inhibition of phagolysosome formation
c. cytotoxic storm activated by NK cells in response to extracellular bacteria
d. intracellular bacteria triggering NLR activation of the inflammasome that recruits
capsase 1, which activates pro-IL-1 and pro-IL-18 and causes this inflammatory cell
death - -d. intracellular bacteria triggering NLR activation of the inflammasome that
recruits capsase 1, which activates pro-IL-1 and pro-IL-18 and causes this inflammatory
cell death
For which of the following groups of organisms would you expect complement to play
the MOST significant role in immune protection?
a. gram-positive intracellular bacteria
b. gram-negative intracellular bacteria
c. toxin-producing extracellular bacteria
d. gram-negative extracellular bacteria
e. normal intestinal flora - d. gram-negative extracellular bacteria
A 32-year-old woman presents to the emergency department with abdominal pain, fever
and watery, bloody diarrhea. History includes a suspicion of eating an undercooked egg
the day before. Physical exam reveals a dehydrated febrile patient in need of rest. The
laboratory cultures Salmonella enterica from a stool sample using selective medium.
,USMLE ID microbiology exam with
100% correct answers 2024
Which of the following characteristics of this species contributes to its evasion of innate
immunity?
a. survival and replication within the phagosome
b. production of C5a peptidase
c. production of Protein A
d. inhibition of type I interferon signaling
e. expression of a capsule - a. survival and replication within the phagosome
A 62-year old man presents with a fever, cough and complaints of rust-colored sputum.
His chest X-ray shows a dense left lower lobe infiltrate with a left pleural effusion. The
laboratory cultures a gram-positive diplococcus species from a sputum sample. Which
of the following are among the immune evasion mechanisms that characterize this
organism?
a. phagosome escape
b. inhibition of NK cell activation
c. production of an IFN-g receptor mimic
d. production of a capsule
e. inhibition of type I interferon signaling - d. production of a capsule
Listeria monocytogenes is an intracellular pathogen associated with the ingestion of
contaminated meat and dairy products and can cause severe perinatal infections. If a
pregnant woman acquires her first infection with Listeria late in pregnancy, which of the
following would be impaired or absent in the newborn that might otherwise limit
infection? (two answers)
a. CD4+ and CD8+ T cells
, USMLE ID microbiology exam with
100% correct answers 2024
b. maternal IgG neutralizing antibodies
c. type I IFN
d. complement-dependent bacterial lysis
e. IL-4 - a. CD4+ and CD8+ T cells
b. maternal IgG neutralizing antibodies
Which of the following microbes is an opportunistic bacterial pathogen of relatively low
virulence that does not typically cause serious disease in healthy individuals who have
intact skin and mucous membranes?
a. Viridans streptococci
b. Staphlycoccus epidermidis
c. Candida albicans
d. Salmonella typhi
e. Cytomegalovirus
f. Pseudomonas aeruginosa - b. Staphlycoccus epidermidis
A 2-year-old child has a history of infections with prolonged episodes of diarrhea. His
mother reports that he seems to be sick constantly, and that he had oral thrush from
shortly after birth until 3 months of age and numerous upper respiratory tract infections
before the age of 6 months. Since then, he has been hospitalized twice with bacterial
pneumonia. His family history includes a maternal uncle and a male cousin who died of
pneumonia or diarrhea-associated infectious diseases in infancy. The patient has
shown mild-moderate lymphopenia throughout his life, but otherwise normal blood cell
counts. His Ig levels are low normal, but his CD4+ T cell counts (500/ml) are well below
normal for his age. He has made
