MLAB 2434 – MICROBIOLOGY KERI BROPHY-MARTINEZ

MLAB 2434 – MICROBIOLOGY KERI BROPHY-MARTINEZ

General Concepts in Specimen Collection and Processing

General Concepts in Specimen Collection and Processing (cont’d)

Basic Principles of Specimen CollectionSpecimen should be taken in

acute phase of infection AND before antibiotics are administered

Written order must specify site of culture (example: wound on left arm)


Avoid normal flora and colonizing organisms

Collect the appropriate quantity of specimen

Package specimen in correct transport media

Label with patient information & source Transport the specimen to the lab asap

to avoid deterioration


Appropriate Collection TechniquesAspirates and tissues

• Aspirates and tissues present few problems, if collected using sterile technique

• Lesions, wounds and abscesses; cultures should be from as deep in the wound as possible


Swabs• Used only as a last resort.

Dacron/polyester swabs preferred• Steps

• Clean wound• Explore wound• Obtain fresh and quality culture

material• Should be placed in a holding

medium to protect pathogens without permitting multiplication during transport


Patient Education and Preparation If patient is responsible for collecting

specimen, good instructions are critical Urine – midstream clean catch first

morning specimen Sputum – collect sputum NOT spit,

morning specimens are preferred, deep cough

Stools – usually 3 vials and at least 4 days after barium X-rays, swabs are discouraged

General Concepts in Specimen Collection and Processing Labeling & Requisition

Specimen must have patient name, time, date, source, location

Requisitionmust accompany specimen,

include diagnosis & antimicrobial history


SafetyStandard PrecautionsSpecimen processing should be

conducted in a Class II safety cabinet (hood)


Preservation, Storage, and Transport of Specimens Concerns

• Overgrowth • Death of microorganisms: deliver to lab

within 30 minutes of collection• Inaccurate quantitation• Loss of organisms from drying• Protection from oxygen• Protection from clotting• Safety of transporter


Anticoagulants• Needed in any specimen that might

clot (blood, serum, joint fluids)• Sodium polyanethol sulfonate (SPS)

• Most common anticoagulant in micro


Preservatives• Urine – boric acid

for up to 24 hours

• Stool – phosphate-buffered saline (PBS) or O & P kit


Use of Holding and Transport Media Media should provide viability without allowing

multiplication of bacteria

Media should maintain pH, provide proper atmospheric conditions and prevent drying


Types of collection devices


Blood culture bottles


Sterile container for sputum, urine, and other specimens


Aspirates are usually collected and transported in syringes

General Concepts in Specimen Collection and Processing(cont’d)

Storage of Specimens• Urine, viral blood specimens, catheters and

swabs should be refrigerated (4oC)• Blood and CSF should be processed ASAP• Specimens for fungus cultures can be kept

at room temperature• Respiratory and stool cultures should be

processed ASAP if at all possible, but refrigerated if immediate processing is not possible

• Anaerobes, genital, ear, eye cultures can be held at room temperature


Mailing specimens Regulated by U.S. Dept. of Health and

Human Services & U.S. postal Service National guidelines issued by

Department of transportation Retraining of employees must occur

every 2 years

Packaging Infectious Substances


Unacceptable Specimens Labels on requisition and on specimen must

match (unlabeled, mislabeled)• Noninvasive vs. invasive specimens

Rejected specimens• Leaking• Syringes with needles attached• Stools contaminated with urine or barium• Anaerobic cultures on inappropriate sources• Unpreserved specimens over 2 hours old


Unacceptable specimens Refrigerated blood cultures Dried-up specimens Specimens in formalin Improper collection Delay in transport **Do not discard rejected specimen until a new

one is submitted, if original specimen is cultured, notate in patients report

Do you feel like this?


Processing of Clinical Samples for Optimal Organism RecoveryPrioritization

• Level 1- Critical/invasive ( CSF)• Level 2 – Unpreserved (sputum)• Level 3 – Accuracy of quantitation

affected (urine, no preservative)• Level 4 – Protected/Preserved (urine

with preservative)


Gross Examination of Specimens Check specimen for:

• Volume submitted• Presence of blood or mucous• General appearance: cloudy, clear

Check requisition against sample


Direct Examination TechniquesDirect Microscopic Examination

• Determine quality of specimen• Diagnose infectious disease• Guide routine culture interpretation• Dictate the need for nonroutine

processing• Guide antibiotic therapy


Smear PreparationTissuesSwabsAspirates and body fluids

• Single drop smear• Centrifuged sediment smear• Layered smear• Cytocentrifuged smear• Additives


Direct Smears NOT usefulThroats, nasopharyngeal swabsUrineFemale genital tractStools

References

Engelkirk, P., & Duben-Engelkirk, J. (2008). Laboratory Diagnosis of Infectious Diseases: Essentials of Diagnostic Microbiology . Baltimore, MD: Lippincott Williams and Wilkins.

http://catalog.bd.com/bdCat/search.doCustomer?searchText=urine+culture&typeOfSearch=0&viewPageNum=0&sortByField=Category&x=0&y=0

http://coe.berkeley.edu/news-center/publications/engineering-news/archive/engineering-news-vol-79-no-9f/need-a-study-break-here-are-a-few-ideas

http://www.firstqualitylaboratory.com/pages/specimenpreparation.html http://www.lookfordiagnosis.com/images.php?term=Polyanetholesulfon

ate&lang=1 Mahon, C. R., Lehman, D. C., & Manuselis, G. (2011). Textbook of

Diagnostic Microbiology (4th ed.). Maryland Heights, MO: Saunders.




http://www.firstqualitylaboratory.com/pages/specimenpreparation.html

http://www.lookfordiagnosis.com/images.php?term=Polyanetholesulfonate&lang=1

http://www.lookfordiagnosis.com/images.php?term=Polyanetholesulfonate&lang=1

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MLAB 2434 – MICROBIOLOGY KERI BROPHY-MARTINEZ