Module 9 - ANAEROBES

• Anaerobic bacteria comprise most normal flora of the mucous membranes.
• Suspect anaerobic bacteria in the following situations: foul odor and necrotic tissue, anaerobic body sites, abscesses, and wounds, and surgical specimens.
• Media contain supplements that enhance anaerobic growth, including Vitamin K to enhance the growth of Prevotella and Porphyromonas, and Hemin for Bacteroides and Prevotella.
• The Centers for Disease Control and Prevention (CDC) Anaerobic Blood Agar is used for general growth of all anaerobes.
• Clostridium ramosum is a red bacteria.
• Bilophilia wadsworthia is a bile resistant anaerobe that will grow on BBE Agar.
• Porphyromonas is a light orange to pink (coral) bacteria.
• Bilophilia wadsworthia may also grow on KVLB Agar.
• Clostridium difficile is a chartreuse bacteria.
• Fusobacterium is a chartreuse bacteria.
• Eggerthella lenta is a red or no fluorescence bacteria.
• Veilonella is a red bacteria that fades rapidly.
• Bacteroides Bile Esculin (BBE) Agar is a selective and differential medium used to culture and presumptively identify Bacteroides fragilis.
• Kanamycin-Vancomycin Laked Sheep Blood (KVLB) Agar is an enriched selective medium for isolation of slowly growing anaerobes such as Prevotella and Bacteroides.
• Phenylethyl alcohol (PEA) Agar is an enriched and selective medium used to grow most anaerobes, including Clostridium and Bacteroides.
• Columbia-Colistin-Nalidixic Agar with 5% Sheep Blood inhibits gram negative organisms and is used to grow most gram positive anaerobes and facultative anaerobes.
• Egg yolk Agar is used to detect proteolytic enzymes (lipase and lecithinase) produced by Clostridium.
• Isolated growing only on the plate incubated anaerobically are obligate anaerobes.
• Eggerthella/Eubacterium spp. are mostly nonpathogenic normal oral and intestinal flora.
• Propionibacterium spp. include P. acnes and P. propionicus, often called anaerobic diphtheroids, and Propionibacterium acnes is the most often found as a skin contaminant in blood cultures and is part of the anaerobic normal skin flora.
• Anaerobic conditions are achieved when the methylene blue indicator turns from blue (oxidized) to white, indicating reduction.
• Aerotolerance testing is a method used to identify possible anaerobic bacteria by inoculating a colony to an anaerobic blood agar plate and a chocolate agar plate incubated under conditions of increased CO2.
• Bifidobacterium spp. are mostly nonpathogenic normal oral and intestinal flora.
• Gram Stain identifies anaerobes as Bacilli, Cocci, and Actinomyces spp.
• Actinomyces spp. are normal flora of animal and human mucous membranes and cause abdomen and chest infections and pelvic actinomycosis in women with intrauterine devices.
• Peptostreptococcus spp. include P. anaerobius, which is inhibited by sodium polyanethol sulfonate (SPS) and was renamed Finegoldia magna.
• Peptococcus spp. include P.Niger, which is catalase positive and produces olive-green colonies that become black.
• Lecithinase activity produces an opaque zone from the cleavage of lecithin releasing insoluble fats (diglyceride).
• Lipase cleaves lipids, releasing glycerol, which floats to the top of the medium producing a blue-green sheen (mother-of-pearl) on the agar surface.
• Anaerobic Media can be used to grow anaerobic bacteria, including Broth with reducing agents, Thioglycolate and Cooked (or Chopped) Meat, and Resazurin, an oxidation-reduction indicator, may be added.
• Solid media must be placed in anaerobic conditions in order for obligate anaerobes to grow, commonly used systems include anaerobic GasPak jars and bags and anaerobic hoods.
• Gram Positive Cocci are small, gram negative cocci that reduce nitrates to nitrite, do not ferment any carbohydrates, are inhibited by kanamycin and colistin but resistant to vancomycin, and have red fluorescence under UV light.
• In the presence of palladium, a catalyst, the following reaction occurs: 2H2O + O2 - > 2H2O2.
• Gram Negative Cocci are gram negative cocci that do not reduce nitrates to nitrite, ferment carbohydrates, are inhibited by kanamycin and colistin but resistant to vancomycin, and have red fluorescence under UV light.
• Prevotella melaninogenica is a pigmented saccharolytic gram negative bacilli, is the normal flora of the oropharynx, nose, GI and urogenital tracts, causes head, neck and lower respiratory tract infections, has young colonies that appear tan and exhibit brick-red fluorescence under UV light, and older colonies that are brown to black.
• Porphyromonas is an asaccharolytic or weak fermenters, pigmented colonies, gram negative bacilli, is the normal flora of the oropharynx, nose, GI and urogenital tracts, causes infections of the head, neck, oral cavity and urogenital tract, has brick-red fluorescence under UV light, is inhibited by kanamycin and colistin, and is resistant to vancomycin.
• Gram Negative Bacilli are gram negative bacilli with GS morphology: Pale, pleomorphic gram - negative coccobacilli with bipolar staining.
• Fusobacterium is an asaccharolytic or weak fermenters, nonpigmented colonies, gram negative bacilli, is the normal flora of the upper respiratory and GI tracts, causes pulmonary, blood, sinus and dental infections in addition to brain abscesses, is inhibited by kanamycin and colistin, and is resistant to vancomycin.
• Bacteroides fragilis is a non-pigmented bacillus responsible for most anaerobic infections. It has a polysaccharide capsule as a virulence factor, is the major normal flora of the colon, and causes intraabdominal abscess. It enters normally sterile body sites, especially after surgery, trauma, or disease. It is nonhemolytic on anaerobic blood agar, produces brown to black colonies on BBE Agar, grows in 20% bile.
• Asaccharolyticus was renamed Peptoniphilus asaccharolytica.