Study guide: Specimen Collection, Processing, and Microscopic Examination

Pre-analytical - The quality and condition of the collected specimen is performed by ___ team, not lab.

The consequences of poor specimen collection includes the failure to ___ infectious agent or administration of ___ therapy.

medical; detect; inappropriate

Principles of specimen collection

• Collect during ___ phase of illness/symptoms

• Note exact anatomic ___ selection

• Use correct collection device w/ ___ contamination!

• Quantity

• Use proper transport medium to maintain ___ and minimize leaks/spills

• Label specimen accurately (Name, ID, date + time, site)

• Transport in timely manner or store appropriately

• Notify lab in advance if unusual pathogens suspected

acute; site; minimal; viability

Analytical phase begins upon lab ___ the specimen.

1. macroscopic and microscopic observations

2. Specimen preparation

3. Selection of culture media

4. Incubation and atmospheric conditions

5. Culture workup

receiving

Post-analytical phase is the ___ of laboratory findings.

• post accurate and timely info (prelim results)

• interpretive statements when needed

• STAT/critical results

communication

What are the 3 forms of specimens?

Swab, tissue, fluid

Large volumes of sterile body fluid may need to be ___ to be worked up properly.

concentrated

2 swab collection device is ___ for swab specimens to plate directly to media and to make direct smear.

preferred

Tissue needs to go through ___ (ground up and mixed with saline into a slurry for proper plating).

homogenization

Routine plating media include:

• ___ agar plate

• ___ medium for fastidious organisms

• Selective and differential medium for ___ gram-___ bacilli

• Selective medium for gram-___ organisms

• Additional selective media or enrichment broths for specific pathogens needed

• Broth to supplement media with specimens from sterile body fluids, tissues, lesions, wounds, and abscesses

Nonselective; enriched; enteric; neg; pos

Incubation is performed at ___-___C (we are this temp inside, thus we want cultures to grow the same way).

Cultures are held in incubation for ___-___ hrs.

• Common pathogens demonstrate obvious growth within ___ hrs

• Slow growers can take ___ hrs

35; 37; 48; 72; 24; 72

Anaerobes/broth are held in incubation for ___-___ days (some take a full week!)

5; 7

While incubating, it is important to use appropriate atmospheric condition for suspected bacterium.

• ___ – ambient air

• ___ – no oxygen

• ___ – increased CO2

• ___ – reduced O2

aerobes; anaerobes; capnophiles; microaerophiles

The specimen ___ dictates the usual suspect list in culture workup.

source

Culture workup involves these questions that are guided by the specimen’s source:

• Is there contaminating normal flora or is the specimen from a ___ site? (if bacteria are found in sterile site, it gets worked up)

  • What is the usual ___ of the expected normal flora?

• What are the most likely ___ present in this specimen?

  • What is the colonial morphology?

• Which ___ is demonstrating growth, and what is the purpose of that medium?

• Interpret antimicrobial ___ testing (what can I tell is available or not available to treat this infection?)

sterile; appearance; pathogens; medium; susceptibility

STAT/Critical results:

• Pos ___ cultures

• Pos ___ gram stain or culture

• Pos ___ antigen test or culture

• Pos blood smear for ___

• S. pyogenes from a ___ site

• S. agalactiae or HSV from genital site of a ___ woman at term

• Detection of significant pathogen

blood; CSF; cryptococcal; malaria; sterile; pregnant

Transport medium is used to maintain ___ of specimen until processing – does not promote ___ of organisms.

Improper transport can lead to loss of organisms or overgrowth, which may cause misleading culture results or failure to detect the infectious agent.

integrity; multiplication

What are the common transport swab collection systems? What do they have to absorb fatty acids or toxins produced by bacteria?

Amie’s and Stuart’s; charcoal

O&P (Ova & Parasites) is a stool transport media.

Formalin is used to ___ and the fixative is used to make ___ with.

• fixative contains modified polyvinyl alcohol with zinc

preserve; slides

Unpreserved urine must be refrigerated within ___ hrs, where it is stable up to ___ hrs at 2-8C.

2; 24

Urine is preserved in ___ ___. It is stable for up to ___ hrs at room temp, best if ___.

Boric acid; 48; refrigerated

___ transport medium is for stool testing delays longer than ___ hrs. (must get into preservative within 2 hrs of collection).

Clary-Blair; 2

Cotton tipped swabs ___ certain species.

Other swab disadvantages include ___ (not enough pathogen on swab), contamination, and ___ (gel matrix/plug should prevent this).

inhibit; quantity; drying

Aspirate collection is done by taking a syringe and taking specimen from the point ___ where causative agent is down in tissue.

Preferred for ___ site collections! Swabs are only able to get ___ stuff off of wound, leading to contaminated results. Aspirate collection gets right to source and protects any ___ in the syringe!

source; wound; superficial; anaerobes

Critical/Invasive specimens are considered level ___ priority – includes amniotic fluid, blood, brain, CSF, heart valves, and pericardial fluid.

These are specimens that we are not going to ___ and we will work up immediately.

1; recollect

Microscopic observation is particularly done with a ___ stain, guides therapy choices when therapy must be initiated ___ culture results are available.

gram; before

Systemic evaluation of slides:

• Is there evidence of contamination by normal microbial flora? (sterile site w/ many diff morphologies = suspicious for ___)

• Necrotic ___ in the background? (broken WBCs or degraded tissues = indicative of ___ process)

• Evaluate organisms for shape, size, and gram reaction

• Monomicrobial vs Polymicrobial

contamination; debris; infectious

Monomicrobial – infection caused by single species

• Commonly seen in ___

• ___ sites tend to only be monomicrobial when they get infected

sepsis; sterile

Polymicrobial – infection caused by multiple species

• ___ are good examples of this type of infection – it’s a mixture of anything that got ___ into the tissue from exterior environment!

• Due to ___ normal or altered flora (from surgical wound infections or aspiration pneumonia).

Wounds; implanted; displaced

Situations where useful info is not provided from gram stain:

• Throat (tons of normal flora expected from ___ resp.)

• Stool (tons of bacteria not very ___ of anything on gram stain)

• N. gonorrhoeae on ___ specimens (vagina can have normal flora that look like N. gonorrhoeae)

upper; indicative; vaginal