Specimen Workup 7 - Quality Control

What is quality assurance

Overarching program designed to monitor and evaluate the ongoing and overall quality of testing, and policy/procedure effectiveness

What are examples of policies + procedures controlled in the micro lab

collection of specimens, QC reporting.

What is quality control

Procedures for monitoring and evaluating quality of analytical testing process of test methods = ensures accuracy and reliability of patient test results

Use of written protocols for specimen collection

Allows for collectors/patients to collect quality specimens with limited/no contamination from normal flora

What is included in specimen collection protocols

Container type, preservatives, storage temps

Use of written protocols for lab staff

Provides reference to lab staff for lab procedure performance (acceptance, processing)

Examples of microbiology QC

Equipment, media, stain, antimicrobials checks + ID tests

Chemical controls for Anaerobe testing

Methylene blue - strip turns white in anaerobe conditions

Chemical controls for CO2 environment

Fyrite CO2 testing device for [CO2]

Biological control for strict anaerobe

Clostridium hemolyticum

Biolgical control for CO2 growth

Neisseria gonorrhoeae

Biological control for Microaerophillic growth

Campylobacter jejuni

Who provides storage and shelf date guidelines for media

Manufacturer - lab must follow

What do you do with outdated media

Dispose of it

What portion of a lot is taken for sterility testing

5% of <100 plates, or up to 10 for a large batch

How to test media for sterility

Incubate in environment + temp it is used in for 48 hours

- CHOC placed in CO2, Campy in 42C for microaerophillic conditions

How is performance testing done on new media

use specific inoculum to assess nutrient quality and reliability of selective agents

Performance testing organisms for MacConkey agar

Pos: E.coli 25922 - dry pk

Neg: P.mirabilis 12453 - wt, no swrm

Performance testing organisms for Martin Lewis

Positive: N. gonorrhoeae - growth

Negative: E.coli 25922 - no growth

Performance testing organisms for STEC

Positive: E.coli O157:H7 35150 - mauve

Negative: E.coli 25922 - no growth

Upon receipt of reagents into the lab, what must the lab do

Date bottles, check expiry dates, and follow manufacturer instructions for storage (temperature, dark, etc.) to ensure reliable results

Before each use, what must be checked on reagents

Color and clarity - check for contamination with an organism

When is QC performed on reagents

- New lot when first put into use

- Daily testing for reactive/difficult to interpret results

- Weekly testing for reliable and easy to interpret results

- As tested for frequently used reagents

How often is QC for antimicrobial discs done

Weekly - ensures zone sizes and MICs stay within tolerance limits

Short term storage for antimicrobials

1 week - keep in fridge

Long term storage for antimicrobials

Keep in freezer as per manufacturers requirement

Why can desiccant be used for antimicrobial discs

Disks will lose potency if they adsorb water

How does internal proficiency testing work in micro labs

Supervisor or QC tech introduces known specimens into regular flow of micro specimens accompanied by routine worksheet/req

Use of internal proficiency testing

- Used to check for errors in equipment and material use

- Reveals mis-interpretation of procedure manual guidelines and detects delays in testing and reporting

- Checks sensitivity of routine methods to detect pathogens and staff's ability to isolate and ID routine organisms

What programs/associations may send samples for external proficicney testing?

- College of American Pathologists (CAP)

- American Society for Clinical Pathologists (ASCP)

- College of Physicians and Surgeons of Alberta (CPSA)

How does testing external proficiency specimens work

Specimens labelled QC are processed routinely - procedures + results obtained are compared and evaluated by pathologist and supervisor with critiques and computer printouts supplied by associations

Use of external proficiency testing

Determines lab's ability to ID difficult or unusual organisms, verifying accuracy

What is a common cause of QC failing

Working culture fails, as organisms can mutate with repeated sub culture

How to prevent QC organism subculture mutation

Organisms are kept as stock, semi stock, and working cultures

Sources of stock cultures

-American Type Culture Collection (ATCC)

- Proficiency testing isolates

- Patient isolates

Where are ATCC strains purchased from

Center for Disease Control (CDC) in Atlanta Ga

What is a semi-stock culture

Stock culture (lyophilized) is reconstituted in suitable diluent and subbed to appropriate media.

After second subbing, heavy suspension of organism is inoculated to new freezer vials

Use of freezing a bunch second subbing vials

New vials removed when required and organism is not subjected to too many freeze-thaw conditions (which can cause mutations)

What media are organisms frozen in for Semi-stock cultures

Glycerol, chopped meat, or TSB to protect from -70C-80C temps

What is working culture

Small amount of organism is subcultured to an appropriate media and incubated. Cultures are ready to use when testing requires.

How often are working cultures replaced

Re-subbed daily or weekly when required

New isolate thawed every month

What does CLSI stand for

Clinical and Laboratory standards institute

What does ATCC stand for

American Type Culture Collection

What QC organisms are used for ALA testing

Positive: Haemophilus parainfluenzae

Negative: Haemophilus influenzae

What QC organisms are used for Oxidase testing

Positive: Pseudomonas aeruginosa, Neisseria gonorrhoeae

Negative: Escherichia coli

What QC organisms are used for DNAse testing

Positive: Moraxella catarrhalis

Negative: Other Moraxella sp.

What QC organisms are used for TSB broth @42C

Positive: Pseudomonas aeruginosa

Negative: Pseudomonas fluorescens, Pseudomonas putida

What QC organisms are used for ONPG (Enteric Bench)

Positive: Shigella sonnei

Negative: Other Shigella sp. (flexneri, boydii, etc.)

What QC organisms are used for Butyrate disk

Positive: Moraxella catarrhalis

Negative: Neisseria mucosa

What QC organisms are used for BCSA

Positive: Burkholderia cepacia

Negative: Stenotrophomonas maltophilia

What QC organisms are used for BCYE

Positive: Legionella pneumophilia

Negative: Non-fermentative bacilli

What QC organisms are used for PYR

Positive: Enterococcus faecalis, Streptococcus pyogenes

Negative: Streptococcus bovis, Streptococcus agalactiae

What QC organisms are used for Spot Indole

Positive: Escherichia coli

Negative: Proteus mirabilis

What QC organisms are used for Hektoen (HEK)

Positive: Salmonella (green with black centers)

Negative: Escherichia coli (yellow or Ng)

What QC organisms are used for Salmonella Shigella plates

Positive: Shigella sonnei (clear/wt colonies)

Negative: Escherichia coli (no growth)

What QC organisms are used for Catalase

Positive: Staphylococcus aureus, Enterococcus faecalis (weak pos)

Negative: Streptococcus pyogenes