Anaerobes (Basics)

Question 1

Obligate anaerobes

Answer 1

microorganism that cannot grow in the presence of oxygen, growing only in conditions with very little or no oxygen present

Question 2

Facultative anaerobes

Answer 2

having the ability to adapt to more than one oxygen level in the environment. Organisms are able to grow in the presence and absence of oxygen

Question 3

Moderately Obligate anaerobe

Answer 3

an anaerobe that cannot grow in the presence of even 0.5% oxygen and is thus unable to grow on the surface of agar

Question 4

Aero Tolerance Test

Answer 4

Organism is plated to agar at both aerobic conditions (Chocolate plate) and anaerobic conditions (Blood agar plate)

Question 5

Superoxide dismutase

Answer 5

catalyzes the conversion of superoxide radicals to less toxic hydrogen peroxide and molecular oxygen

Question 6

Catalases and peroxidases

Answer 6

converts hydrogen peroxide to oxygen and water

Question 7

How do you collect anaerobic specimens?

Answer 7

Needle aspirations
Fluids
Biopsies
Swabs when anaerobic transport media is used
Blood culture bottles

Question 8

What is in Anaerobic media?

Answer 8

○ Supplements that provide a source of CO2
Reducing agents that absorb O2

Question 9

What supplements provide a source of CO2?

Answer 9

Hemin
Blood
Vitamin K
Sodium bicarbonate

Question 10

What are the reducing agents that absorb O2?

Answer 10

Thioglycollic acid
Sodium thioglycollate
L-cystine

Question 11

Primary Isolation of Anaerobes

Answer 11

Nonselective anaerobic blood agar plate
Anaerobic selective media
Enriched broth media, enriched thioglycolate broth

Question 12

CDC anaerobic blood agar (AnBAP)

Answer 12

Nonselective plate used for primary isolation of all anaerobes:
obligate anaerobes
facultative anaerobes

Question 13

Anaerobic phenylethyl alcohol blood agar (PEA)

Answer 13

Selective isolation of anaerobes from specimens that most likely contain more that one organism

Question 14

What does PEA inhibit?

Answer 14

Inhibits facultative anaerobes like Enterobacteriaceae

Question 15

Anaerobic kanamycin-vancomycin blood agar (KV)

Answer 15

Selective isolation of anaerobes from specimens that most likely contain more than one organism
Vancomycin inhibits facultative and obligate gram positive anaerobes.
Kanamycin inhibits most facultative gram negative rods.
Isolation of Bacteroides, Prevotella, and some Fusobacterium

Question 16

What are incubation requirements for anaerobes?

Answer 16

Anaerobic environment needed
Incubation at 35-37C

Question 17

When are anaerobes examined?

Answer 17

Examined at 48H and then held an additional 2-5 for slow growing organisms

Question 18

What species of anaerobes are gram negative? Which are gram positive?

Answer 18

Gram negative: Bacteroides, Porphyromonas, Prevotella spp (coccobacilli). Fusobacterium spp (Gram - rods)
Gram positive: Clostridium spp, Propionibacterium spp (bacilli). Peptostreptococcus spp (cocci)

Question 19

What is a distinctive thing about anaerobe cultures?

Answer 19

extremely putrid odors- This is due to volatile and nonvolatile fatty acids being made through metabolism
Broths look bubbly and turbid with a foul smell

Question 20

What is a positive reaction for egg yolk agar for both Lipase and Lecthinase? What do they mean?

Answer 20

Lipase: Oily water or shimmering appearance on the plate. Means lipase degrades fat into fatty acid and glycerol
Lecthinase: Opaque white halos around the bacterial colonies. Mean that lecthinase breaks down lectin into water insoluble diglycerides