Lecture 5- Intro to clinical lab Flashcards
Role of the Clinical Microbiology Laboratory?
To examine and/or culture clinical specimens for microorganisms, to make accurate species identification of significant isolates and when indicated, perform antibiotic susceptibility tests.
Importance of obtaining an accurate identification?
Overt Pathogens always require accurate speciation
ID is important for ongoing and recurrent infections
Epidemiological accuracy – references would never get updated
Significance of antibiotic susceptibility results and ID?
- Many practitioners placeéemphasis on susceptibility profile over ID
- Some microorganisms are intrinsically resistant to certain antibiotics
- i.e. cannot use Augmentin to treat Pseudomonas – ID may limit therapy options
Decribe the diagnostic cycle?
What is the turnaround time?
- The time elapsed from the time a specimen is collected until the time a final result is issued
Why is turnaround time so important for patients and doctors?
Patient – waiting to commence treatment - alleviate symptoms and/or anxiety e.g. consider possible diagnosis of UTI vs possible gonorrhea
Doctor – confirmation of correct treatment - empirical therapy is common - confirm diagnosis or exclude infection
What happen to a specimen quility over time?
It decreases with time. The longer it takes for a specimen to reach the laboratory, the more difficult it may be to isolate or identify a pathogen
Eg.
Overgrowth with normal flora
Non-survival of anaerobes or fastidious (fussy) organisms
what are the important factors that go into proper specimen collection?
Correct & clear labeling of all containers, swabs, smears AS SOON AS COLLECTED!
Collect material from the site of infection
Sufficient quantity of sample to perform all tests, esp. urine, aspirates
Sterile containers (except for faeces)
Use of transport media for swabs?
- preserves the viability of bacteria without multiplication
- the semisolid agar provides moisture to prevent drying out
- contains a reducing agent to improve recovery of anaerobes
- maintains pH
- use special tissue culture media for requests for viral studies
- charcoal containing media for gonorrhoeae (inhibits toxic fatty acids found in cotton fibers)
What is the aim of proper specimen transport?
The aim is to transport the specimen while maintaining the sample in as close to the original state as possible
This is achieved by;
Paperwork and specimen should be shipped together
Aviod extremes of tempuratures
Use leak proof containers
What is the ideal time to recieve a specimen in?
Ideally, specimens should be received within 2 hours
When would dry swab with no media be used?
Suitable for chlamydia and gonorrhoea PCR
Not suitable for MC+S (microscopy, culture & sensitivity)
When does Rejection of Specimens occour?
- Unlabeled specimens
- Samples with illegible labeling
- Mismatched details
- Insufficient material and/or leaking specimens
- Specimens for anaerobes that have been stored at 4 ̊C
- Inappropriate specimen collected
- Non-sterile container for a urine or aspirate
- Any specimen collected into formalin
What hapens in a hospital when a specimen is rejected?
- generally it should be easier to get another sample
- depends on the site of infection and the type of specimen
e.g. CSF (traumatic and difficult) vs. wound swab (easy) - patient must still be an ‘inpatient’
-patient must still be an ‘inpatient’
What happens when a specimen is rejected in a private lab?
- much more challenging to accomplish
- contact surgery, contact patient, recollect specimen, transport to lab., match to existing paperwork
- therefore, there is more pressure to accept and process an existing sample
What happens to specimens as they enter a lab?
- Small laboratories – likely to process individual specimens as they arrive
- Large laboratories – likely to process specimens in batches
What are classified as URGENT/High priority specimens?
CSF, tissue, blood cultures, sterile fluids
What are generally classed as lower priority specimens?
urine, swabs, sputum, faeces (unless marked URGENT)
