Anaerobes (Basics) Flashcards
Obligate anaerobes
microorganism that cannot grow in the presence of oxygen, growing only in conditions with very little or no oxygen present
Facultative anaerobes
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
Moderately Obligate anaerobe
an anaerobe that cannot grow in the presence of even 0.5% oxygen and is thus unable to grow on the surface of agar
Aero Tolerance Test
Organism is plated to agar at both aerobic conditions (Chocolate plate) and anaerobic conditions (Blood agar plate)
Superoxide dismutase
catalyzes the conversion of superoxide radicals to less toxic hydrogen peroxide and molecular oxygen
Catalases and peroxidases
converts hydrogen peroxide to oxygen and water
How do you collect anaerobic specimens?
Needle aspirations
Fluids
Biopsies
Swabs when anaerobic transport media is used
Blood culture bottles
What is in Anaerobic media?
○ Supplements that provide a source of CO2
Reducing agents that absorb O2
What supplements provide a source of CO2?
Hemin
Blood
Vitamin K
Sodium bicarbonate
What are the reducing agents that absorb O2?
Thioglycollic acid
Sodium thioglycollate
L-cystine
Primary Isolation of Anaerobes
Nonselective anaerobic blood agar plate
Anaerobic selective media
Enriched broth media, enriched thioglycolate broth
CDC anaerobic blood agar (AnBAP)
Nonselective plate used for primary isolation of all anaerobes:
obligate anaerobes
facultative anaerobes
Anaerobic phenylethyl alcohol blood agar (PEA)
Selective isolation of anaerobes from specimens that most likely contain more that one organism
What does PEA inhibit?
Inhibits facultative anaerobes like Enterobacteriaceae
Anaerobic kanamycin-vancomycin blood agar (KV)
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
What are incubation requirements for anaerobes?
Anaerobic environment needed
Incubation at 35-37C
When are anaerobes examined?
Examined at 48H and then held an additional 2-5 for slow growing organisms
What species of anaerobes are gram negative? Which are gram positive?
Gram negative: Bacteroides, Porphyromonas, Prevotella spp (coccobacilli). Fusobacterium spp (Gram - rods)
Gram positive: Clostridium spp, Propionibacterium spp (bacilli). Peptostreptococcus spp (cocci)
What is a distinctive thing about anaerobe cultures?
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
What is a positive reaction for egg yolk agar for both Lipase and Lecthinase? What do they mean?
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
