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Microbial Diagnostics

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zijimubo1's version from 2016-12-15 02:35

Section 1

Question Answer
What is the role of the clinician in the laboratory investigation of an infectious disease?Order collection of patient's specimen and send to lab. Lab report.
Why is proper specimen collection important?Poorly collected specimen may lead to incorrect or harmful therapy if treatment is directed toward a commensal or contaminant organism.
Alternative test included what methods?Molecular methods: amplified and nonamplified
What does the non-amplified test test check for?Oligonucleotide primers that are complementary to a segment of the genome.
What technique is used in amplified test?PCR; quantitative or qualitative
What is important to assess when interpreting lab results?Changing from empiric treatment to directed therapy. Use NARROW spectrum antimicobials first.
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Section 2

Question Answer
Where should the specimen be collected from?From the actual site of infection, collected with minimum of contaminant from adjacent tissues, organs, or secretions.
Why is it important to collect sufficient quantity of a specimen?To avoid false negatives.
When is a swab culture recommended?For mucous membranes only, testing for strep throat, staph aureus nasal carriage, nasopharyngeal specimens for respiratory viruses or Bordetella pertussis.
Why should appropriate collection devices, specimen containers, and culture media be used?To ensure optimal recovery of microorganisms.
How can time delay between collection of specimen and inoculation of media be reduced?Direct inoculation at bedside or in the OR. Ex. Neisseria gonorrhoeae, corneal scrapings, or vitreous humor, and blood culture.
What specimens require special transport media with growth requirements that differ from bacteria?Viruses and chlamydia, since they are obligate intracellular pathogens.
When should cultures be obtained?Before administration of antibioitics.
Why should smears be performed in addition to cultures?Provides useful information that supplements the culture, and assesses the quality of the specimen.
What ensures a culture container is properly labeled?SPECIFICS: Name, MRN, source, date, time of collection, collector's initials.
How soon should a specimen be transported to the lab?Within 2 hrs. CSF, joint fluid, pleural fluids should be submitted sooner.
What are exceptions to the 2 hr transport?Stools, urines, and sputa can be refrigerated.
List substances that should not be refrigerated.Neisseria, CSF, genital, eye, internal ear specimens.
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Section 3

Question Answer
How many blood cultures should be drawn?2-3
How can contamination of blood cultures be reduced?Aseptic technique using venipuncture instead of vascular catheters.
How much blood should be collected?20-30 mL
What is a proper ratio for blood:broth to enhance microbial recovery?Between 1:5 and 1:10
At what time intervals should collection take place?Same time instead of random times. No benefit of arbitrary collection.
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