02/23 Diagnostic Bacteriology Flashcards
What four things should you do in order to maximize recovery and reduce contamination of a biological specimen?
1) Collect sample before antibiotic therapy
2) Use aseptic technique and avoid contamination with normal flora
3) Do NOT send swabs - tissue or fluid only! (some exceptions)
4) Use appropriate containers and storage conditions
What types of analytical procedures does the microbiology lab perform?
Gram stain
Specimen plated on media and incubated for 18-24 hours
Identify culture growth with biochemical, serological, and antimicrobial tests
What is included in the preliminary bacteriological report? What about the final report?
Preliminary report - Gram stain results and quantity of growth
Final report - direct Gram stain result, identification of bacteria, antimicrobial profile
How should you collect, transport, test, analyze, and report on a CSF sample?
Collection - avoid skin flora, collect 1-5 mL
Transport - send STAT in a sterile tube, do NOT refrigerate
Lab test - STAT gram stain, plate and incubate
Analysis - identification and susceptibility tests
Report - call positive Gram stain and culture results immediately
How should you collect, transport, test, analyze, and report on a respiratory sample?
Collection - collect 2-5 mL of sputum, NOT saliva (requires a deep cough)
Transport - sterile specimen cup
Lab test - Gram stain, plate if there are less than 10 squamous epithelial cells per field
Analysis - look for growth of predominanting pathogen, perform identification and susceptibility tests
Report - quantity of potential pathogen
When is it appropriate to send a swab?
For a throat culture
How should you collect, transport, test, analyze, and report on a urine sample?
Collection - instruct patient to cleanse well and do a clean catch
Transport - sterile specimen cup, refrigerate
Lab test - streak plates for colony count using a calibrated loop
Analysis - greater than 100,000 cfu/mL is positive
Report - identify predominating pathogen, do NOT identify mixed flora
How should you collect, transport, test, analyze, and report on a genital sample, i.e. for N. gonorrhoeae?
Collection - inoculate with special media at beside and place in a CO2-generating bag
Transport - send to lab immediately, do NOT refrigerate
Lab test - media incubated up to 3 days
Analysis - biochemical tests
Report - any quantity of N. gonorrhoeae
How should you collect, transport, test, analyze, and report on a stool sample?
Collection and transport - send in clean container, do NOT send if patient has been hospitalized for more than 3 days
Lab test - plate on selective media (MacConkey, Hektoen, etc.)
Analysis - confirm presence of specific pathogen with biochemical and serological tests
Report - to clinician and State Laboratory of Public Health in cases of Shigella/Salmonella
How should you collect, transport, test, analyze, and report on a wound sample?
Collection - cleanse the area and send fluid or tissue, NO swabs
Transport - use an anaerobe tube if indicated
Lab test - Gram stain, plate aerobically or anaerobically
Analysis - use Gram stain to guide speciation
Report - mixed flora if there are more than 3 types of pathogens
How many blood culture samples should you ideally obtain from a patient?
Two
How much blood should you collect per culture?
Adults - 20-30mL
Children - 0.5-5mL
How long does it take to disinfect the site where you plan to take a blood sample?
At least 45 seconds - 15 seconds of scrubbing with chlorhexidine, 30 seconds to dry
What organisms are considered contaminants in a SINGLE blood culture?
Coagulase-negative staph Micrococcus sp. Viridans strep Corynebacterium sp. Propionibacterium sp. Lactobacillus sp. Bacillus sp. Non-pathogenic Neisseria sp.
