Exam 4 - (CH 22) Anaerobes of Clinical Importance Textbook Review Questions

Question 1

Microaerophilic organism require the oxygen concentration be reduce to
A. 1%.
B. 5% or less.
C. 20% or less.
D. 50% or less.

Answer 1

B. 5% or less.

Question 2

All clostridia are capable of producing
A. oxidase.
B. spores.
C. hydrogen peroxide.
D. botulism.

Answer 2

B. spores.

Question 3

Clostridium tetani produces this neurotoxin that prevents the release of neurotransmitters.
A. Tetanospasmin
B. Risus sardonicus
C. Trismus
D. Alpha toxin

Answer 3

A. Tetanospasmin

Question 4

Actinomyces spp. are typically considered endogenous microbiota of the
A. skin.
B. genitourinary tract.
C. oral cavity.
D. None of the above.

Answer 4

C. oral cavity.

Question 5

Most strains of Porphyromonas will not grow on kanamycin and vancomycin with laked sheep blood (KVLB) agar because of their sensitivity to
A. amoxicillin.
B. cefepime.
C. cefuroxime.
D. vancomycin.

Answer 5

D. vancomycin.

Question 6

A double zone of hemolysis on a sheep blood agar (SBA) plate incubated anaerobically is suggestive of
A. Bacteroides fragilis.
B. Fusobacterium.
C. Clostridiodes difficile.
D. Clostridium perfringens

Answer 6

D. Clostridium perfringens

Question 7

A bile-tolerant, gram-negative anaerobic bacillus indicates that the isolate is likely a member of the ___________ group.
A. Actinomyces
B. Porphyromonas and Prevotella
C. Bacteroides fragilis
D. Clostridioides difficile

Answer 7

C. Bacteroides fragilis

Question 8

Bilophila wadsworthia is a bile-resistant anaerobe that will grow on Bacteroides bile esculin (BBE) agar with this characteristic appearance.
A. Fish eye
B. Wagon wheel
C. Fried egg
D. Star

Answer 8

A. Fish eye

Question 9

Lipases catalyze the
A. hydrolysis of peptide bonds.
B. degradation of collagen.
C. splitting of host phospholipids.
D. hydrolysis of ester linkages.

Answer 9

D. hydrolysis of ester linkages.

Question 10

Clostridioides difficile fluoresces this color under UV light.
A. Chartreuse
B. Red
C. Light orange
D. Purple

Answer 10

A. Chartreuse

Question 11

Match the following infectious diseases with their associated causative organism:

Myonecrosis _____
Tetanus _____
Botulism _____
Pseudomembranous colitis _____
Actinomycosis _____

a. Clostridium botulinum
b. Clostridium perfringens
c. Clostridium tetani
d. Clostridium botulinum
e. Actinomyces spp.

Answer 11

Myonecrosis = Clostridium perfringens
Tetanus = Clostridium tetani
Botulism = Clostridium botulinum
Pseudomembranous colitis = Clostridium botulinum
Actinomycosis = Actinomyces spp.

Question 12

An organism that can live in reduced concentrations of oxygen but prefers an anaerobic environment is known as a( n):

a. Capnophile
b. Obligate anaerobe
c. Facultative anaerobe
d. Aerotolerant anaerobe

Answer 12

d. Aerotolerant anaerobe

Question 13

Some anaerobes are particularly susceptible to oxygen because they lack the enzyme:
a. Amylase
b. β-Lactamase
c. Superoxide dismutase
d. Glucose-6-phosphate dehydrogenase

Answer 13

c. Superoxide dismutase

Question 14

Endogenous anaerobes least likely to be involved in cases of bacteremia are:

a. Bacteroides
b. Clostridium
c. Eubacterium
d. Fusobacterium

Answer 14

c. Eubacterium

Question 15

Which of the following specimens would be unacceptable for anaerobic culture?

a. Aspirated pus
b. Cerebrospinal fluid
c. Tissue from biopsy
d. Urethral swab

Answer 15

d. Urethral swab

Question 16

A gram-positive bacillus was isolated from a wound specimen and had the following characteristics: double zone of β-hemolysis, lecithinase positive, lipase negative, spot indole negative. What is the most likely identification of this organism?

a. Clostridium perfringens
b. Clostridium ramosum
c. Clostridium septicum
d. Clostridium tetani

Answer 16

a. Clostridium perfringens

Question 17

An anaerobic, pleomorphic, gram-negative bacillus was recovered from a liver abscess. The special potency antimicrobial disks demonstrated that the organism was vancomycin resistant and colistin and kanamycin sensitive. Other results were as follows: chartreuse fluorescence, spot indole positive, and lipase positive. What is the most likely identification of the organism?

a. Fusobacterium mortiferum
b. Fusobacterium necrophorum
c. Fusobacterium nucleatum
d. Fusobacterium varium

Answer 17

b. Fusobacterium necrophorum

Question 18

True or False

Exogenous anaerobes more commonly cause infectious diseases than endogenous anaerobes.

Answer 18

False

Question 19

True or False

Clostridium spp. are especially easy to identify in Gram-stained smears of clinical specimens because they always appear as gram-positive rods with terminal or subterminal spores.

Answer 19

False

Question 20

True or False

Failure to isolate fusiform gram-negative organisms that were observed on a Gram-stained smear of a clinical specimen could be an indication that a problem exists with the primary medium used for the isolation of anaerobes or the system being used for anaerobic incubation of primary plates.

Answer 20

True

Question 21

True or False

Large, dark colonies (> 1 mm) growing on a BBE agar plate at 24 hours can presumptively be called a member of the Bacteroides fragilis group.

Answer 21

True

Question 22

True or False

A pleomorphic gram-positive bacillus that is spot indole and catalase positive can be presumptively identified as Cutibacterium acnes.

Answer 22

True

Question 23

Points to Remember

Answer 23

■ Anaerobes are organisms that do not require oxygen for life.
■ Anaerobes are important in human and veterinary medicine because they can produce serious and often fatal infections and intoxications.
■ Anaerobic infections of exogenous origin are usually caused by gram-positive, spore-forming bacilli belonging to the genus Clostridium.
■ The anaerobes most frequently isolated from infectious processes in humans are those of endogenous origin, such as members of the B. fragilis group.
■ Factors that commonly predispose the human body to anaerobic infections include trauma of mucous membranes or skin, vascular stasis, tissue necrosis, and decrease in the redox potential of tissue.
■ Significant clinical infections caused by anaerobes include mixed microbiota abscesses, tetanus, botulism, myonecrosis, antibiotic-associated diarrhea, and actinomycosis.
■ Many types of specimens are unacceptable for anaerobic bacteriology because they are likely to be contaminated with anaerobes of the endogenous microbiota.
■ Proper selection, collection, and transport of specimens for anaerobic culture are critical for quality results and maximum recovery of pathogens.
■ The anaerobes most commonly associated with infectious processes and those most often isolated from specimens include members of the B. fragilis group, certain Clostridium spp. (e.g., C. perfringens, C. ramosum, C. clostridioforme, C. septicum), Clostridioides difficle, Fusobacterium nucleatum, F. necrophorum, Cutibacterium acnes, Actinomyces israelii, Porphyromonas, Prevotella, and the anaerobic gram-positive cocci.
■ Presumptive identifications are based on Gram stain, colony appearance on different media, and results of simple, inexpensive, and rapid test procedures.
■ Definitive identifications are commonly made using preformed enzyme– based identification kits, 16S rDNA sequencing, or MALDI-TOF MS.
■ Susceptibility testing of anaerobes is not recommended for all anaerobic isolates but is warranted for specific types of serious infections and whenever especially virulent or drug-resistant anaerobes have been isolated.
■ Practical methods for anaerobe susceptibility testing include microwell broth dilution panels and the Etest.
■ Anaerobe-associated diseases may be treated by surgery, hyperbaric oxygen therapy, antitoxins, and antimicrobial therapy. Refractory CDAD can be treated with fecal microbiota transplant.