MICROBIOLOGY AND PARASITOLOGY: A
TEXTBOOK AND LABORATORY MANUAL
FOR THE HEALTH SCIENCES
2ND EDITION
• AUTHOR(S)FE A. BARTOLOME, AND
ELIZABETH P. QUILES
TEST BANK
1)
Reference: Ch. 1 — The Science of Microbiology
Question Stem: A new graduate working in a clinical laboratory
receives a blood culture flagged positive for small, pleomorphic
organisms on Gram stain that do not grow on standard blood
agar but amplify using PCR targeting 16S rRNA. The supervisor
asks which concept best explains why molecular methods
,detected the organism when culture failed. Interpret the
laboratory and methodological implications.
Options:
A. Viable but nonculturable (VBNC) state of the organism
B. Media contamination prevented growth on blood agar
C. Gram stain misinterpretation; organism is actually a
eukaryote
D. PCR is nonspecific and produced a false positive
Correct Answer: A
Rationales:
Correct (A): The VBNC state describes bacteria that are alive but
fail to grow on routine culture due to stress or specific growth
requirements. Molecular detection (16S rRNA PCR) identifies
nucleic acid independent of culturability, explaining positive
PCR with negative culture. This is an important diagnostic
limitation when interpreting negative cultures.
Incorrect (B): Media contamination would more likely introduce
extraneous growth rather than selectively prevent growth of
the target organism and would not explain a positive molecular
signal with negative culture.
Incorrect (C): Pleomorphic organisms and a positive bacterial
16S rRNA PCR argue against a eukaryotic organism; Gram stain
artifacts can occur but would not produce a 16S result.
Incorrect (D): While PCR contamination/false positives occur,
laboratory correlation (sterility controls, sequencing of
amplicon) distinguishes true VBNC detection from PCR artifact.
,Teaching Point: Molecular methods detect microbial nucleic
acids even when organisms are nonculturable.
Citation: Bartolome, F. A., & Quiles, E. P. (Year). Microbiology
and Parasitology. 2nd Ed., Ch. 1.
2)
Reference: Ch. 1 — The Science of Microbiology
Question Stem: An outbreak investigation finds several patients
on a surgical ward developed wound infections with the same
organism. Epidemiologic typing shows identical profiles;
investigators note that the same technician performed
preoperative skin prepping using an alcohol-based product but
failed to let it dry. Which microbiology principle most likely
explains how transmission occurred?
Options:
A. Residual antiseptic selection led to resistant organisms
causing infection
B. Incomplete antiseptic contact time reduced microbial kill,
permitting transmission
C. Alcohol-based antiseptics facilitate biofilm formation on skin
surfaces
D. Preoperative antisepsis is irrelevant; infections originated
from surgical instruments
Correct Answer: B
, Rationales:
Correct (B): Antiseptic efficacy depends on proper application
and contact/dry time; failing to allow alcohol to evaporate
reduces killing of skin flora, permitting viable organisms to
remain and be introduced into surgical wounds. This explains
epidemiologic clustering tied to technique.
Incorrect (A): Short contact time is unlikely to select for
resistant organisms in the short term; selection requires
repeated sublethal exposures over time.
Incorrect (C): Alcohols disrupt membranes and do not promote
biofilm formation; biofilms are more relevant on devices.
Incorrect (D): While instruments are a common source, the
shared technician and technique provide a direct transmission
explanation consistent with identical typing.
Teaching Point: Proper antiseptic contact time is essential to
effective skin disinfection.
Citation: Bartolome, F. A., & Quiles, E. P. (Year). Microbiology
and Parasitology. 2nd Ed., Ch. 1.
3)
Reference: Ch. 1 — The Science of Microbiology
Question Stem: A medical student uses a light microscope with
an ocular of 10× and objective of 100× (oil immersion). The
instrument’s resolving power is insufficient to separate two
closely spaced bacterial cells. Which change would most
TEXTBOOK AND LABORATORY MANUAL
FOR THE HEALTH SCIENCES
2ND EDITION
• AUTHOR(S)FE A. BARTOLOME, AND
ELIZABETH P. QUILES
TEST BANK
1)
Reference: Ch. 1 — The Science of Microbiology
Question Stem: A new graduate working in a clinical laboratory
receives a blood culture flagged positive for small, pleomorphic
organisms on Gram stain that do not grow on standard blood
agar but amplify using PCR targeting 16S rRNA. The supervisor
asks which concept best explains why molecular methods
,detected the organism when culture failed. Interpret the
laboratory and methodological implications.
Options:
A. Viable but nonculturable (VBNC) state of the organism
B. Media contamination prevented growth on blood agar
C. Gram stain misinterpretation; organism is actually a
eukaryote
D. PCR is nonspecific and produced a false positive
Correct Answer: A
Rationales:
Correct (A): The VBNC state describes bacteria that are alive but
fail to grow on routine culture due to stress or specific growth
requirements. Molecular detection (16S rRNA PCR) identifies
nucleic acid independent of culturability, explaining positive
PCR with negative culture. This is an important diagnostic
limitation when interpreting negative cultures.
Incorrect (B): Media contamination would more likely introduce
extraneous growth rather than selectively prevent growth of
the target organism and would not explain a positive molecular
signal with negative culture.
Incorrect (C): Pleomorphic organisms and a positive bacterial
16S rRNA PCR argue against a eukaryotic organism; Gram stain
artifacts can occur but would not produce a 16S result.
Incorrect (D): While PCR contamination/false positives occur,
laboratory correlation (sterility controls, sequencing of
amplicon) distinguishes true VBNC detection from PCR artifact.
,Teaching Point: Molecular methods detect microbial nucleic
acids even when organisms are nonculturable.
Citation: Bartolome, F. A., & Quiles, E. P. (Year). Microbiology
and Parasitology. 2nd Ed., Ch. 1.
2)
Reference: Ch. 1 — The Science of Microbiology
Question Stem: An outbreak investigation finds several patients
on a surgical ward developed wound infections with the same
organism. Epidemiologic typing shows identical profiles;
investigators note that the same technician performed
preoperative skin prepping using an alcohol-based product but
failed to let it dry. Which microbiology principle most likely
explains how transmission occurred?
Options:
A. Residual antiseptic selection led to resistant organisms
causing infection
B. Incomplete antiseptic contact time reduced microbial kill,
permitting transmission
C. Alcohol-based antiseptics facilitate biofilm formation on skin
surfaces
D. Preoperative antisepsis is irrelevant; infections originated
from surgical instruments
Correct Answer: B
, Rationales:
Correct (B): Antiseptic efficacy depends on proper application
and contact/dry time; failing to allow alcohol to evaporate
reduces killing of skin flora, permitting viable organisms to
remain and be introduced into surgical wounds. This explains
epidemiologic clustering tied to technique.
Incorrect (A): Short contact time is unlikely to select for
resistant organisms in the short term; selection requires
repeated sublethal exposures over time.
Incorrect (C): Alcohols disrupt membranes and do not promote
biofilm formation; biofilms are more relevant on devices.
Incorrect (D): While instruments are a common source, the
shared technician and technique provide a direct transmission
explanation consistent with identical typing.
Teaching Point: Proper antiseptic contact time is essential to
effective skin disinfection.
Citation: Bartolome, F. A., & Quiles, E. P. (Year). Microbiology
and Parasitology. 2nd Ed., Ch. 1.
3)
Reference: Ch. 1 — The Science of Microbiology
Question Stem: A medical student uses a light microscope with
an ocular of 10× and objective of 100× (oil immersion). The
instrument’s resolving power is insufficient to separate two
closely spaced bacterial cells. Which change would most
