Anaerobes Flashcards
Explain the purpose and procedure for the aerotolerence test:
Both a BAP and CHOC plate should be used to determine whether microbes are strict anaerobes or only facultative. The same org. is placed on two plates and incubated aerobically and anaerobically.
Only anaerobe plate grows - anaerobe
Both plates grow - facultative
What is the purpose and principle of BBE agar and EYA agar and the important anaerobe involved?
BBE:
EYA:
Describe reaction if org has: Lecithinase C-
Lipase C- Protease C -
BBE: Bacteroides Bile - Esculin Agar, selective/differential - Bacteroides fragilis, Turns black due to the orgs ability to hydrolyze esculin
EYA: Egg Yolk Agar - CDC Formation, differential C used to detect lecithinase, lipase, and protease activity
If org has:
Lecithinase - makes media opaque around the growth streak
Lipase - Sheen on or around the colonies
Protease - Clearing of the agar around the streak
Commonly for Clostridium
Explain the historical significance of the Nagler test and the test that has replaced this test:
On the EYA agar, C. perfringens antitoxin type A is smeared on 2 of the plate and the org. is inoculated across both sides of the plate. A pos test result is the lack of lecithinase activity on the half plate with the antitoxin.
A reverse CAMP test is performed by some labs. Arrow points the opposite direction
What are the bacteriostatic and bactericidal effects of O2 on anaerobes?
Bacteriostatic:
Bactericidal:
Bacteriostatic: If O₂ is introduced the org is busy trying to reduce the O₂ and uses energy that is needed for metabolism, so can’t reproduce = static growth rate
Bactericidal: Superoxide anions, hydroxyl radicals and H₂O₂ all build up causing a tidal effect because anaerobe orgs have few enzymes to protect themselves from these byproducts of O₂
Why do anaerobes need an environment that has a low redox potential?
Media-
In vivo (body)-
Media- there are certain anaerobic growth enzymes that require fully reduced sulfhydryl groups to be present to sustain life
In vivo (body)- sulfhydryl groups are provided by other normal flora that are present
Where are anaerobes located in/on the body in their environment?
Body
Environment
Body - all NF colonizes sites: skin, upper resp., female genital tract, GI tract
Environment - Soil, fresh and salt water
List the 5 most commonly found anaerobes in infections, along with their gram stain and morphology:
- Bacteroides fragilis (gram neg rod)
- Porphyromonas/Prevotella (pigmented, gram neg rod)
- Fusobacterium nucleate (gram neg rod)
- Clostridium species (gram pos rod)
- Actinomyces israelii (gram pos rod)
Discuss the following methods for the presumptive ID of anaerobes. Be specific about the differences between aerobic and anaerobic methodologies:
2) SPS Disk
Sodium polyanethol sulfonate
-Peptostreptococcus anaerobius is suscepetible
Discuss the following methods for the presumptive ID of anaerobes. Be specific about the differences between aerobic and anaerobic methodologies:
3) Nitrate disk
Nitrate to nitrite
Discuss the following methods for the presumptive ID of anaerobes. Be specific about the differences between aerobic and anaerobic methodologies:
4) Bile disk
to test if org can grow in 20% conc. of bile
-Gram neg rod (20%) bile resistant is B. fragilis
Discuss the following methods for the presumptive ID of anaerobes. Be specific about the differences between aerobic and anaerobic methodologies:
5) Catalase
Clostridium-
Bacillus-
Clostridium- Cat neg
Bacillus- Cat pos
Discuss acceptable automated or biochemical procedures for definitive identification of anaerobes:
- Gas liquid chromatography match peaks and time of peaks with known organisms
- Biochemical based mini-systems 24-48 hrs
- Enzyme base mini-systems can read in 4 hrs. Ex: vital, rapid ana II, MICROSCAN rapid anaerobe
Describe clostridial food poisoning caused by C. botulinum and C. perfringens:
C. botulinum
C. perfringens
C. botulinum - botulinum toxin produced by the org is ingested in contaminated food and absorbed in SI. It attached to neuromuscular junction of affected nerves causing paralysis which can appear from 2 hrs to 8 days. Antitoxin is used for treatment. Spores most often found in honey can cause infant botulism
C. perfringens - Mild, self limited GI tract illness approximately 8-12 hrs after ingestion of contaminated food. Type C is by far more severe
What anaerobe is responsible for pseudomembranous colitis? What is the most likely reason for this occurring?
C. difficile
Following antimicrobial therapy or from hospital workers not washing hands
Describe both colony morphology and gram stain morphology of Clostridium perfringens:
Large gram pos rods (gram variable)
Double zone of beta hemolysis
How would you identify C. perfringens?
Presumptive:
Definitive:
Presumptive: Egg yolk agar shows lecithinase pos
Nagler test is pos, Reverse CAMP test pos, Brucella/Blood agar - double zone beta hemolysis, Gelatin hydrolysis and DNase pos
Definitive: enzyme base mini-system
List the non-spore forming anaerobic gram positive bacilli:
Actinomyces Eubacterium Lactobacillus Bifidobacterium Mobiluncus Propionibacterium
Identify Propionibacterium and Actinomyces israllei by their chemical reactions, morphology and clinical pathogenicity. Which one is considered anaerobic diptheroids?
Propionibacterium
Actinomyces israllei
Propionibacterium: Normal skin flora and can cause subacute bacterial endocarditis and bacteremia and some species of actinomycosis. Presumptive ID: Cat pos, Spot indole pos, anaerobic gram pos diphtheroid, pleomorphic gram pos rod, gelatin hydrolysis pos.
Actinomyces israllei: seldom obligate anaerobes, colonies are rough spider like or wooly, Cat/spot indole/gelatin neg
Compare and contrast actinomycosis and myonecrosis and the organisms responsible for each:
Chronic granulomatous infection with lesions that erupt from infected sinus and drain pus containing sulfur granules and is caused by Actinomyces
Myonecrosis is a condition of necrotic damage, specific to muscle tissue. It is often seen in infections with C. perfringens
List the anaerobic gram negative bacilli by genus:
Bactericides
Prevotella
Porphyromonas
Fusobacterium
Bacteroides fragilis
Catalase: Indole: DNase: Penicillin: Rifampin: Kanamycin: Vancomycin: Pigment: Bile Solubility:
Catalase: +/= Indole: = DNase: = Penicillin: R Rifampin: S Kanamycin: R Vancomycin: none Pigment: = Bile Solubility: R
Fusobacterium
Catalase: Indole: DNase: Penicillin: Rifampin: Kanamycin: Vancomycin: Pigment: Bile Solubility:
Catalase: = Indole: + DNase: = Penicillin: S/R Rifampin: S Kanamycin: S Vancomycin: none Pigment: = Bile Solubility: S
Porphyromonas
Catalase: Indole: DNase: Penicillin: Rifampin: Kanamycin: Vancomycin: Pigment: Bile Solubility:
Catalase: = Indole: + DNase: = Penicillin: S/R Rifampin: S Kanamycin: R Vancomycin: S Pigment: + Bile Solubility: S
Prevotella
Catalase: Indole: DNase: Penicillin: Rifampin: Kanamycin: Vancomycin: Pigment: Bile Solubility:
Catalase: = Indole: + DNase: + Penicillin: S/R Rifampin: S Kanamycin: R Vancomycin: R Pigment:+ Bile Solubility: S
