Microbio Practicals Flashcards
What are the time frames for direct examination tests?
Direct examination can take hours for microscopic and minutes for macroscopic tests.
What is the time frame for culture tests?
Culture tests usually take days, but mycobacteria and other fastidious organisms can take weeks.
What is the time frame for antibody detection tests?
Antibody detection tests may be rapid (<24 hours), but it takes a minimum of 2 weeks from exposure to develop antibodies.
What is the time frame for other tests?
Other tests are usually rapid, but may need to be sent to a specialist reference laboratory.
What are the types of techniques in examination?
- Direct Examination
- Culture
- Serology
- Others
What does Direct Examination include?
Macroscopic: appearance, colour, smell
Microscopic: a. Gram stain, b. Acid fast stains, c. Wet film, d. KOH preparation for fungi, e. India ink for cryptococcus, f. Dark ground for syphilis
What is the Gram stain result for positive and negative stains?
Positive stain: purple
Negative stain: pink
What should be sent if pus is present in culture (2)?
Send a few mLs of pus.
What are the types of samples to transport?
Swab - transport medium.
Fluid - e.g. urine, CSF, joint aspirate.
Faeces.
What types of media are used in the laboratory?
Solid media: Blood agar (aerobic & anaerobic), Selective media, Enriched media.
Liquid media: no quantitation but allows growth of small numbers of bacteria. Dilutes out inhibitory substances
What is the minimum requirement for Blood Culture?
Usually minimum of two broths (aerobic & anaerobic).
Pour plates
What to do if fastidious organisms are suspected?
Discuss with laboratory.
What does Serology involve?
Paired sera acute and convalescent > 10 days apart
IgM
Single high convalescent - less reliable.
What are the types of techniques under ‘Others’?
Toxin detection
Antigen detection
Molecular biological techniques, e.g. PCR
What are the basic gram film characteristics of key bacteria?
Gram +ve Cocci, Gram -ve Cocci, Gram +ve Bacilli, Gram -ve Bacilli