MMSC 428 EXAM 4 QUESTIONS AND
DETAILED ANSWERS. EXPERT
VERIFIED FOR GUARANTEED PASS.
Anaerobes - ANS 1. Are able to replicate in the absence of oxygen.
2. Anaerobic cultures performed in clinical microbiology laboratories are used to recover
organisms in these two groups.
Obligate Anaerobes - ANS 1. Unable to grow in the presence of oxygen (oxygen is toxic). Also
called "strict" anaerobes.
Aerotolerant Anaerobes - ANS 1. Able to survive short exposures to oxygen, but unable to
perform many metabolic processes in the presence of oxygen. Also called "moderate"
anaerobes
Endogenous Anaerobes - ANS 1. Opportunistic pathogens, usually gaining access to tissues,
sterile body sites, and the bloodstream.
Anaerobes: Normal Microbiota - ANS 1. Many different sites
2. Skin, upper respiratory tract, oral cavity, GI tract, and genitourinary tract.
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,Anaerobes: Incidence of Infection - ANS 1. Infections may be localized to the colonizing site,
adjacent to the site, or distant from the colonizing site.
2. Bacteremia
3. Variety of abscesses (brain, lungs, oral, abdomen, etc)
4. Peritonitis
5. Female genital infections
6. Myonecrosis
7. Aspiration pneumonia
T/F: Many infections involving anaerobes are polymicrobial: consisting of mixtures of
anaerobes, or anaerobes and aerobes. - ANS True
Anaerobic Infections: Clues for ID - ANS 1. Presence of foul odor
2. Infection in close proximity to a mucosal surface
3. Infection following human or animal bites
4. Traumatic puncture of the bowel or genital tract (following trauma or surgery)
5. Necrotic tissue, gangrene
6. Large quantity of gas
Anaerobes: Collection of Specimens - ANS 1. Suitable specimens
- All sites not likely to be contaminated with normal microbiota can be cultured for anaerobes
2. Unsuitable specimens
- Sites that are likely contaminated by normal microbiota
Anaerobes: Suitable Specimens - ANS 1. Sterile body fluids/aspirates, blood & bone marrow,
tissues & bones, aspirated closed abscesses
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,Anaerobes: Unsuitable Specimens - ANS 1. URT and oral swabs, sputum/BAL, stool/bowel
contents/rectal swabs, voided urine, genital swabs, surface swabs from wounds, any material
collected adjacent to a mucous membrane where adequate decontamination was not
performed
Anaerobes: Collection w/ Aspirates & Tissues - ANS 1. Aspirates of fluids/purulent material
collected by needle and syringe are the specimens of choice over swabs as they are less likely to
be contaminated by endogenous microbiota and provide more material than swabs.
2. Tissues collected by biopsy and bones are also ideal specimens. Swabs are the least ideal
collection method and should only be used when aspiration is not possible or tissue cannot be
obtained.
Anaerobes: Transport - ANS 1. Provides oxygen-free environment to protect obligate
anaerobes.
2. Preservative-free vacuum collection tubes can be used for fluids. Sterile cup can be used for
larger tissues (>1 cm2) provided they are transported to the lab within a few hours. All
specimens should be transported ASAP and maintained at Room temperature.
Anaerobes: Direct Exam - ANS 1. Gram stains should be performed on all non-blood
specimens submitted for anaerobic culture for several reasons
2. The presence of multiple distinct organism morphotypes suggests that the infection is
polymicrobic.
3. Certain morphotypes may provide a presumptive identification of the causative organisms.
E.g. Large, boxcar-like GPB suggest Clostridium species. Thin, fusiform GNB suggest
Fusobacterium.
4. Gram stain helps evaluate the quality of the specimen based on the presence and number of
SECs, that would suggest specimen contamination during collection.
5. Helps to identify morphotypes that were seen in Gram stain but not recovered in culture.
Different culture media may be needed or anaerobic culture conditions were not initially met.
-Detect toxins directly in the specimen (e.g. C. difficile toxins in stool)
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, T/F: Anaerobes direct examination includes gross & microscopic exams and detect toxins -
ANS True
Anaerobes: Culture Characteristics - ANS 1. Media
a) Nutritious primary isolation media: prereduced, room temperature
1) CDC anaerobic blood agar & Brucella agar
2) Laked sheep blood with vitamin K
3) Broths
a) Thioglycollate
b) Chopped (cooked) meat
Who am I?
- I have special nutritional requirements for vitamin K, hemin, and yeast extract.
- My culture specimens should be inoculated onto one of these primary isolation agar plates. -
ANS 1. Anaerobes
Anaerobes: CDC ABAP & Brucella agar - ANS 1. Supports growth of almost all obligate
anaerobes and provides sheep RBCs, vitamin K, and yeast extract
Anaerobes: Laked sheep blood (LSB) - ANS 1. RBCs lysed through a series of freeze-thaw
cycles. Lysis releases more nutrients into the agar.
2. Selects for anaerobic GNB. Kanamycin inhibits most facultative GNB & vancomycin inhibits
most GP organisms. Yeast and kanamycin-resistant GNB may also grow "breakthrough"
T/F: Broths serve as a PRIMARY culture source. If the SECONDARY agar plates do not recover
suspected anaerobes, the broth can be subcultured to anaerobic plates for recovery. Broths
should be inoculated for SOME body fluids and tissues. - ANS False, SECONDARY, PRIMARY,
ALL
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DETAILED ANSWERS. EXPERT
VERIFIED FOR GUARANTEED PASS.
Anaerobes - ANS 1. Are able to replicate in the absence of oxygen.
2. Anaerobic cultures performed in clinical microbiology laboratories are used to recover
organisms in these two groups.
Obligate Anaerobes - ANS 1. Unable to grow in the presence of oxygen (oxygen is toxic). Also
called "strict" anaerobes.
Aerotolerant Anaerobes - ANS 1. Able to survive short exposures to oxygen, but unable to
perform many metabolic processes in the presence of oxygen. Also called "moderate"
anaerobes
Endogenous Anaerobes - ANS 1. Opportunistic pathogens, usually gaining access to tissues,
sterile body sites, and the bloodstream.
Anaerobes: Normal Microbiota - ANS 1. Many different sites
2. Skin, upper respiratory tract, oral cavity, GI tract, and genitourinary tract.
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,Anaerobes: Incidence of Infection - ANS 1. Infections may be localized to the colonizing site,
adjacent to the site, or distant from the colonizing site.
2. Bacteremia
3. Variety of abscesses (brain, lungs, oral, abdomen, etc)
4. Peritonitis
5. Female genital infections
6. Myonecrosis
7. Aspiration pneumonia
T/F: Many infections involving anaerobes are polymicrobial: consisting of mixtures of
anaerobes, or anaerobes and aerobes. - ANS True
Anaerobic Infections: Clues for ID - ANS 1. Presence of foul odor
2. Infection in close proximity to a mucosal surface
3. Infection following human or animal bites
4. Traumatic puncture of the bowel or genital tract (following trauma or surgery)
5. Necrotic tissue, gangrene
6. Large quantity of gas
Anaerobes: Collection of Specimens - ANS 1. Suitable specimens
- All sites not likely to be contaminated with normal microbiota can be cultured for anaerobes
2. Unsuitable specimens
- Sites that are likely contaminated by normal microbiota
Anaerobes: Suitable Specimens - ANS 1. Sterile body fluids/aspirates, blood & bone marrow,
tissues & bones, aspirated closed abscesses
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,Anaerobes: Unsuitable Specimens - ANS 1. URT and oral swabs, sputum/BAL, stool/bowel
contents/rectal swabs, voided urine, genital swabs, surface swabs from wounds, any material
collected adjacent to a mucous membrane where adequate decontamination was not
performed
Anaerobes: Collection w/ Aspirates & Tissues - ANS 1. Aspirates of fluids/purulent material
collected by needle and syringe are the specimens of choice over swabs as they are less likely to
be contaminated by endogenous microbiota and provide more material than swabs.
2. Tissues collected by biopsy and bones are also ideal specimens. Swabs are the least ideal
collection method and should only be used when aspiration is not possible or tissue cannot be
obtained.
Anaerobes: Transport - ANS 1. Provides oxygen-free environment to protect obligate
anaerobes.
2. Preservative-free vacuum collection tubes can be used for fluids. Sterile cup can be used for
larger tissues (>1 cm2) provided they are transported to the lab within a few hours. All
specimens should be transported ASAP and maintained at Room temperature.
Anaerobes: Direct Exam - ANS 1. Gram stains should be performed on all non-blood
specimens submitted for anaerobic culture for several reasons
2. The presence of multiple distinct organism morphotypes suggests that the infection is
polymicrobic.
3. Certain morphotypes may provide a presumptive identification of the causative organisms.
E.g. Large, boxcar-like GPB suggest Clostridium species. Thin, fusiform GNB suggest
Fusobacterium.
4. Gram stain helps evaluate the quality of the specimen based on the presence and number of
SECs, that would suggest specimen contamination during collection.
5. Helps to identify morphotypes that were seen in Gram stain but not recovered in culture.
Different culture media may be needed or anaerobic culture conditions were not initially met.
-Detect toxins directly in the specimen (e.g. C. difficile toxins in stool)
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
, T/F: Anaerobes direct examination includes gross & microscopic exams and detect toxins -
ANS True
Anaerobes: Culture Characteristics - ANS 1. Media
a) Nutritious primary isolation media: prereduced, room temperature
1) CDC anaerobic blood agar & Brucella agar
2) Laked sheep blood with vitamin K
3) Broths
a) Thioglycollate
b) Chopped (cooked) meat
Who am I?
- I have special nutritional requirements for vitamin K, hemin, and yeast extract.
- My culture specimens should be inoculated onto one of these primary isolation agar plates. -
ANS 1. Anaerobes
Anaerobes: CDC ABAP & Brucella agar - ANS 1. Supports growth of almost all obligate
anaerobes and provides sheep RBCs, vitamin K, and yeast extract
Anaerobes: Laked sheep blood (LSB) - ANS 1. RBCs lysed through a series of freeze-thaw
cycles. Lysis releases more nutrients into the agar.
2. Selects for anaerobic GNB. Kanamycin inhibits most facultative GNB & vancomycin inhibits
most GP organisms. Yeast and kanamycin-resistant GNB may also grow "breakthrough"
T/F: Broths serve as a PRIMARY culture source. If the SECONDARY agar plates do not recover
suspected anaerobes, the broth can be subcultured to anaerobic plates for recovery. Broths
should be inoculated for SOME body fluids and tissues. - ANS False, SECONDARY, PRIMARY,
ALL
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