1. Rapid Testing in Microbiology
Infinity and Beyond:
Rapid Testing in Microbiology
Presented By:
Heather Wilson, MT (ASCP)
Microbiology Supervisor

2. The Evolution of Rapid Testing in Microbiology
(from culture to rapid testing)
Organisms previously detected only in culture are now able to be identified with “Rapid Tests”.
Bacteriology
Staphylococcus aureus (SA)
methicillin-resistant Staphylococcus aureus (MRSA)
Escherichia coli O157:H7 (E.coli O157)
Virology
Influenza and Respiratory Syncytial Virus (RSV)
Parasitology
Malaria

3. Traditional Testing and TAT
Bacterial Culture
Requires inoculation of the specimen onto media and hour incubation.
Isolated pathogens are then manually worked up for identification based on colony morphology, Gram stain, nutritional requirements, metabolic and enzymatic capabilities.
Gram stain of primary specimen provides rapid presumptive identification of pathogens present but must be followed up with culture for identification and antibiotic susceptibilities.

4. Use of selective and differential media
Selective medium types
support the growth of one group of organisms, but inhibit the growth of another; such as antimicrobials or dyes.
Differential medium types
- distinguish microorganisms based on biochemical reactions; such as fermenting lactose or enzymatic reactions resulting in color change.
MRSA ChromAgar

5. Organism Identification and Antibiotic Susceptibility Testing (AST)
API test strips manual biochemical tests requiring an additional 24 hour incubation.
BioMerieux VITEK® 2 is an Automated bacterial identification and antibiotic susceptibility testing.
BioMerieux VITEK® MS is an automated microbial identification system that uses an innovative mass spectrometry technology — Matrix Assisted Laser Desorption Ionization Time-of-Flight, or MALDI-TOF
VITEX MS
API Strip
VITEX 2

6. Viral Culture
Requires inoculation of the specimen into viral cell lines.
Tube cultures are incubated and maintained for up to 21 days.
- examined for Cytopathic Effect (CPE)
- viral ID is confirmed with indirect fluorescent antibody (IFA) staining.
normal monolayer monolayers with CPE
Shell vial cultures are incubated 1-5 days.
- viruses are detected by indirect fluorescent antibody (IFA) staining.

7. Direct Immunofluorescence Assay (DFA) directly tests for the presence of an antigen in patient specimen using a fluorescent labeled antibody (TAT ~4 hours except for weekends and holidays).
Requires experienced tech to read cell cultures and interpret IFA / DFA slides.

8. Parasitology Exam for Malaria
Requires preparation of thick and thin blood smears stained with Giemsa stain (TAT ~ 4 – 6 hours except for weekends and holidays).
Gametocytes & rings in a thick smear Rings in thin blood smears
Requires precise microscopy skills, experienced tech to interpret smear.

9. All of these traditional testing approaches :
Require highly trained technologists to perform the test
Are labor intensive
Have a lengthy turn around times
Have staffing limitations

10. What workflows and instrumentation make rapid testing possible?
Technologist staffing in our Specimen Receiving Area is 24/7.
Technologists are supported by CLAs enabling them to focus on the rapid tests.
The Cepheid GeneXpert Infinity System
automated real-time PCR analyzer
On-demand processing
The BinaxNOW Malaria Test
rapid membrane enzyme immunoassay
qualitative detection specific for P.falciparum
The SHIGA TOXIN QUIK CHEK Test
rapid membrane enzyme immunoassay
qualitative detection of Shiga toxin 1 (stx1) and Shiga toxin 2 (stx2).

11. The Cepheid GeneXpert Infinity System
Automated Real Time PCR platform
Self contained single use cartridges

12. Influenza A, Influenza B and RSV (bed placement)
Tests performed:
Influenza A, Influenza B and RSV (bed placement)
MRSA PCR (used to remove patients from contact precautions)
SA Nasal Complete (pre-op screening)
Minimal specimen processing
Automated
- Sample Extraction
- Purification
- Detection of nucleic acid target
Random access
Interfaced to SunQuest
– results auto file to patient medical record.
Results in ~1 hour

13. The BinaxNOW Malaria Test
Malaria is a serious sometimes fatal disease (mostly P.falciparum)
- caused by a parasite
- transmitted by an infected anopheles mosquito.
- four malarial species capable of infecting humans P.falciparum
P.vivax
P.ovale
P.malariae
Typical symptoms
- high fever, chills, headache, muscle ache, flu- like symptoms.
- can lead to kidney failure.
Detects antigen specific for P.falciparum (0.1% parasitemia level)
- and detects common pan-malarial antigen
Test is performed on EDTA blood sample
- Add sample & wash reagent sample migrates
- Add wash reagent incubation
Easy to read results in ~30 minutes

14. The SHIGA TOXIN QUIK CHEK Test
E.coli is a normal gut flora
The strain E.coli O157
- an enteric pathogen
- produces Shiga toxin
- causes hemorrhagic colitis, bloody diarrheal illness
- potentionally life threatening complication - Hemolytic Uremic Syndrome (HUS)
Transmission
- contaminated water or food
- contact with infected animals or persons.
Treatment
- Non-specific supportive therapy, including hydration.
- Antibiotics should not be used
- increase the risk of HUS.
Test is performed on direct fecal specimens
- diluted stool / conjugate incubation
- wash step
- substrate incubation
Easy to read results in ~30 minutes

15. The use of these rapid tests result in earlier diagnosis and treatment of patients.
Questions?