Lab 10 Anaerobes Flashcards
How should anaerobic specimens be collected from wounds?
Specimens from deep wounds or abscesses should be aspirates of the fluid or pus with a sterile needle and syringe. Bubbles should be carefully expelled from the syringe, and then the needle should be removed and the syringe aseptically capped for transport (not ideal due to possible leakage, but a good way to send the specimen quickly to the lab without transport media, within 15 minutes) .
What do you do if there is a delay in getting the anaerobic specimen to the lab?
If there is a delay, the specimen should be transferred to anaerobic transport media such as commercial vials containing semisolid holding medium, an atmosphere of 5% CO2 , a reducing agent, and a resazurin indicator to give visual indication of anaerobiosis (or blood culture media or, if the specimen is a swab, charcoal transport media). This is not done frequently in labs.
Clarify what is not done frequency both or one of the options.
What type of container is typically used to send anaerobic specimens to the lab (surprisingly)?
Most frequently, the aspirated material or tissue are sent to the lab in a wide-mouthed sterile container, and processed ASAP.
What mediums should be used to culture specimens suspected of having both aerobic and anaerobic organisms?
- an enriched medium for aerobes eg. BA, Choc
- a selective medium for aerobes -optional -eg. Mac
- an enriched medium for anaerobes eg. AnO2 BA with Vitamin K (BAK)
- an enriched, selective medium for anaerobes eg. AnO2 BA with kanamycin and vancomycin ( LKV), AnO2 BA with phenylethyl alcohol (PEA)
- enrichment medium for aerobes and anaerobes eg CM (cooked meat), thioglycollate, FAB (Fastidious anaerobic broth)
Note: Plates require careful streaking for isolation and immediate incubation of the AnO2 plates.
How are anaerobe jars prepared and monitored for the correct atmosphere by?
- an anaerobic pack for creating the right environment.
- a chemical indicator- resazurin (white if AnO2 , pink if O2 ) or methylene blue (white - blue), and/or
- a biological indicator such as Fusobacterium nucleatum.
How long are anaerobes cultured for before being examined and why?
Many anaerobes are slow growers, therefore AnO2 plates are routinely incubated for at least 48h before being examined. Growth curve might be interrupted too early if jar opened at 24 hours
What tool should always be used to assist with the examination of an anaerobic plate?
Examination of anaerobic cultures should always be done using an adequate light source and magnification to be able to visualize even the tiniest of colonies. Pure subcultures are essential for identification.
What are the two types of anaerobic bacteria in terms of tolerance of O2?
Anaerobic bacteria grow better when incubated in an anaerobic atmosphere than when incubated in any atmosphere containing oxygen. They can be further classified as:
Strict- can tolerate less than 0.5% O2
Moderate- can tolerate between 2 – 8 % O2
What is the usual atmosphere in an anaerobe jar?
The atmosphere in anaerobe jars is usually 5 to 10% H2; 5 to 10% CO2; 80 to 90% N2; and 0% O2.
What gases are produced an anaerobic jar?
H2 and CO2 are produced by a gas-generating unit and kept in the cylindrical polycarbonate plastic jar with a flange at the top so the air-tight lid can be clamped firmly.
What kind of anaerobic indicators are used in the anaerobic jars to ensure the right environment?
- Chemical
–resazurin: white = anaerobic; pink = not anaerobic
-methylene blue: white = anaerobic; blue = not AnO2 - Biological- Fusobacterium nucleatum- If growth = anaerobic conditions ok.
What are unacceptable specimens for anaerobic processing in the micro lab?
- Mislabeled, lack of specimen date, site, etc.
- Dry swab
- Specimen frozen
- Specimen too long in transport
- Specimen leaking
- Specimen sent in the syringe with the needle still attached
- Unsuitable samples (see B &S’s Diagnostic Microbiology Chapter 40)
-sputum
-secretions
-feces
-throat swab
-gastric contents
-urethral swab
-nasopharyngeal swab
-vaginal or cervical swab
-rectal swab
-voided or catheterized urine
-superficial wound swabs
What are primary media to be planted for anaerobes? (Bit of a repeat question)
- BAK (Brucella blood agar with Vitamin K)
- PEA (Phenyl-ethanol agar)
- LKV (Laked kanamycin vancomycin agar)
- BBE (Bacteroides Bile Esculin agar): optional (we will not plant as primary media)
- THIO (Thioglycolate Broth) or FAB: if specimen is NOT a swab
How long is the broth held on for?
Hold any broth medium (e.g. Thio) for 5 - 7 days or until final report done.
Will you see aerobic bacteria growing on your anaerobic plates?
MOST AEROBIC ORGANISMS ARE FACULTATIVE ANAEROBES (THEY GROW BOTH AEROBICALLY OR ANAEROBICALLY), SO YOU ARE GOING TO SEE THEM ON YOUR ANAEROBIC PLATES TOO.
