Deck 22: Anaerobes of Clinical Importance

Question 1

What organism mostly commonly causes gas gangrene?

A) Clostridium difficile
B) C. tetani
C) C. perfringens
D) C. botulinum

Answer 1

C
Myonecrosis,or gas gangrene,usually occurs when organisms contaminate wounds,through either trauma or surgery.C.perfringens,C.histolyticum,C.septicum,C.novyi,and C.bifermentans are members of the histotoxic group and can cause myonecrosis.C.perfringens,however,is the most common cause.

Question 2

What are two important factors that must be taken into consideration when transporting specimens for anaerobic culture?

A) Making sure there is enough specimen in a tightly closed container
B) Minimum exposure to oxygen and drying out
C) Minimum exposure to oxygen and making sure the specimen is transported in a tightly closed screw-cap container
D) Drying out and proper nutrition

Answer 2

B
Regardless of the type of specimen submitted for anaerobic bacteriology,it must be transported and processed as rapidly as possible and with minimum exposure to oxygen.Specimens are usually collected from a warm,moist environment that is low in oxygen.Thus it is important to avoid "shocking" the anaerobes by exposing them to oxygen or permitting them to dry out.

Question 3

A patient goes to the dentist with an abscess.The physician cultures the tooth.Which of the following bacteria can possibly cause this infection?

A) Bacteroides fragilis
B) Porphyromonas asaccharolytica
C) P. gingivalis
D) Mobiluncus

Answer 3

C
Anaerobic gram-negative bacilli are frequently found in mixed infections,causing abscesses and sepsis.B.fragilis often is isolated from soft-tissue infection.P.asaccharolytica is widely distributed in human tissues and fluids,whereas P.gingivalis and P.endodontalis are associated primarily with oral infections.

Question 4

What disease does Clostridium perfringens cause?

A) Botulism
B) Tetanus
C) Food poisoning
D) Toxic shock syndrome

Question 5

What is an anaerobe?

A) An organism that can live with very little oxygen
B) An organism that does not require oxygen to live
C) An organism that requires some oxygen but moderate concentrations of CO₂ to live
D) An organism that requires small amounts of oxygen and carbon dioxide to live

Question 6

Which of the following is considered a better specimen for anaerobic culture than a swab?

A) Aspirate
B) Washing
C) Scraping
D) Lavage

Question 7

The four major groups of anaerobic gram-negative bacilli include all the following EXCEPT:

A) Bacteroides fragilis
B) Porphyromonas
C) Prevotella
D) Mobiluncus

Question 8

All of the following are non-spore-forming,anaerobic,gram-positive bacilli EXCEPT:

A) Actinomyces
B) Bifidobacterium
C) Eubacterium
D) Clostridium

Question 9

What type of bacteria are those in the genus Clostridium?

A) Anaerobic cocci
B) Spore-forming anaerobic bacilli
C) Spore-forming anaerobic cocci
D) Anaerobic bacilli

Question 10

What disease does Clostridium tetani cause?

A) Botulism
B) Tetanus
C) Food poisoning
D) Myonecrosis

Question 11

All of the following organisms are found on the skin EXCEPT:

A) Propionibacterium
B) Peptostreptococcus
C) Eubacterium
D) Clostridium

Question 12

What disease does Clostridium botulinum cause?

A) Botulism
B) Tetanus
C) Food poisoning
D) Myonecrosis

Question 13

Anaerobes outnumber aerobes in all of the following locations EXCEPT:

A) Skin
B) Oral cavity
C) Gastrointestinal (GI) tract
D) Genitourinary tract

Question 14

What is an obligate anaerobe?

A) An organism that requires some oxygen but moderate concentrations of CO₂ to live
B) An organism that requires small amounts of oxygen and carbon dioxide to live
C) An organism that grows only in the absence of molecular oxygen
D) An organism that can live with very little oxygen

Question 15

An immunosuppressed patient notices sinus tracts that are draining pus.He also notices that there appear to be small,hard "nuggets" in the pus.What disease will his doctor most likely diagnose?

A) Gas gangrene
B) Pseudomembranous colitis
C) Actinomycosis
D) Myonecrosis

Question 16

Bacterial vaginosis is a synergistic infectious process involving all the following bacteria EXCEPT:

A) Eubacterium
B) Bacteroides
C) Gardnerella
D) Peptostreptococcus

Question 17

An elderly patient in a nursing home is recovering from bacterial pneumonia.The patient has been on a lengthy regiment of antibiotics to kill the organism causing the disease.A few days later,the patient is diagnosed with pseudomembranous colitis.What organism is the most likely cause?

A) Clostridium difficile
B) C. tetani
C) C. perfringens
D) C. botulinum

Question 18

All the following organisms are found in the gastrointestinal (GI)tract EXCEPT:

A) Bacteroides
B) Clostridium
C) Propionibacterium
D) Bifidobacterium

Question 19

What substances do organisms that use oxygen have to protect themselves from superoxide anions?

A) Hyaluronidase and proteases
B) Exotoxins and superoxide dismutase
C) Enterotoxins and lipase
D) Superoxide dismutase and catalase

Question 20

Bacterial growth requirements for oxygen and carbon dioxide can be divided into all the following categories EXCEPT:

A) Ambient air (95% O₂ and 5% CO₂)
B) Microaerophilic (5% O₂ )
C) Anaerobic (0% O₂)
D) Capnophilic (about 15% O₂ and 5% to 10% CO₂)

Question 21

What disk is used to presumptively identify Peptostreptococcus anaerobius?

A) Bile
B) Nitrate
C) Sodium polyanethol sulfonate
D) Indole

Question 22

What is the ideal anaerobic incubation system?

A) Anaerobic chamber
B) Anaerobic jars
C) Anaerobic bags
D) Candle jars

Question 23

A microbiology technologist is reading an anaerobic culture and observes a double zone of hemolysis on an anaerobically incubated sheep blood agar plate.The Gram stain of that organism was a boxcar-shaped,gram-positive bacillus.What organism is this?

A) Clostridium perfringens
B) C. difficile
C) C. ramosum
D) C. clostridiiforme

Question 24

All of the following are approaches to treating anaerobic infections EXCEPT:

A) Surgical therapy
B) Hyperbaric oxygen
C) Antitoxins
D) Enzyme inactivators

Question 25

How is the true Gram stain reaction of an anaerobe determined?

A) Special potency disks
B) Shape and colony morphology
C) Aerotolerance
D) DFA

Question 26

Aerotolerant anaerobes include all the following EXCEPT:

A) Clostridium
B) Bacteroides
C) Actinomyces
D) Bifidobacterium

Question 27

All of the following procedures should be performed on clinical specimens to recover anaerobic bacteria EXCEPT:

A) Specimen plating on appropriate tubed and plated media
B) Anaerobic incubation
C) Kinyoun stain
D) Gram stain

Question 28

How long are anaerobic cultures routinely held in the laboratory?

A) 1 to 2 days
B) 3 to 4 days
C) 5 to 7 days
D) 7 to 9 days

Question 29

All of the following reasons are cited for performing antimicrobial susceptibility testing on anaerobes by the Clinical and Laboratory Standards Institute (CLSI)EXCEPT:

A) To determine the resistance mechanisms in anaerobes
B) To assist in the management of patients with serious illnesses
C) To monitor local and regional resistance patterns
D) To determine susceptibility of anaerobes to new antimicrobials

Question 30

All of the following techniques are used for making definitive identification of anaerobes EXCEPT:

A) PRAS and non-PRAS tubed biochemical test media
B) Gas-liquid chromatography of metabolic end products
C) Preexisting enzyme-based minisystems
D) Mass spectroscopy

Question 31

How are suspected colonies of anaerobes processed?

A) Gram stain morphology and reaction is observed.
B) An aerotolerance test is set up.
C) A pure culture/subculture plate is inoculated and appropriate disks are added.
D) All of the above.

Question 32

Gram stains of specimens for anaerobic cultures should be examined for all the following reasons EXCEPT:

A) The Gram stain reveals various types and relative number of bacteria present.
B) Certain morphotypes may provide a presumptive identification and will guide media selection.
C) The Gram stain often reveals the presence of leukocytes.
D) The Clinical and Laboratory Standards Institute (CLSI) guidelines recommend Gram stains on all anaerobic specimens.

Question 33

A microbiology technologist is reading an anaerobic plate from an intestinal abscess.There is growth on the Bacteroides bile esculin (BBE)plate: gray colonies with a brown color in the area around the colonies.There is also a dark precipitate in the medium in the areas of heavy growth.The technician Gram stains the colonies and observes gram-negative coccobacilli.What is the presumptive identification of this organism?

A) Bacteroides vulgatus
B) B. fragilis
C) B. pneumoniae
D) B. denticola

Question 34

What evidence indicates the presence of anaerobes in cultures?

A) A foul odor upon opening an anaerobic jar or bag
B) Growth on the anaerobic plates, but not on the sheep blood agar (SBA) plates incubated in the CO₂ incubator
C) Colonies on kanamycin-vancomycin laked blood agar (KVLBA) that fluoresce brick-red under ultraviolet light
D) All of the above