Culture Vs. PCR

Culture Vs. PCR

Our Tests

Molecular Infectious Diseases

Common types of pathogens

Bacteria

Viral

Fungus

Parasitic

Infectious Disease Testing Procedure

Presence of an infection in patient (bacterial, viral, fungal)
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Correctly identify the pathogen
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Prescribe treatment medications to help end infection

Detection of Infectious Pathogens

1. Culture of Patient Specimen

  • Grow specimen in culture media with nutrients/ inhibitors to promote the growth of pathogens in vitro
  • 2-5 + days in culture
  • Visual identification of pathogen

2. Test for the Presence of Antibodies

  • Serves as biomarkers during an active infectious state
  • Serological testing identifies the presence of specific IgM or IgG antibodies produced by infections
  • Common immunoassays are used for Point-Of-Care (POC) Testing

3. Nuclei Acid Amplification Test (NAAT)

  • Molecular testing to amplify nucleic acid sequences (DNA and RNA) using specific primers for the identification of pathogens present in a specimen.
  • Polymerase Chain Reaction (PCR) for DNA amplification and Reverse Transcriptase Polymerase Chain reaction (RT PCR) for RNA amplification.
Culturing of Pathogens

Culturing of Pathogens

  1. Inoculation with specimen into general purpose media (blood agar, chocolate agar)
  2. Nutrients and inhibitors are added to the general media to help selectively promote with growth in culture of pathogens
  3. Grow in culture for 2-5+ days to identify pathogens

Results of Culturing

  • Culturing may be able to grow a major pathogen for identification under the appropriate culturing conditions
  • Culturing will not grow all pathogens in a specimen
  • Culturing will not identify any antibiotic resistance in any pathogen
  • Culturing results will be inaccurate if patient is currently taking antibiotics at time of specimen collection

Serological Testing for Pathogens

  1. Specimens are used to detect the presence of IgM and IgG antibodies in response to an infection.
  2. Patient antibodies in a specimen will bind to a fixed antigen glass, plates, filter paper.
  3. A reporter antigen will bind to the antigen/patient antibody complex for visual detection.

Results of Serological Testing

Person
infected

1-3
weeks

Person has detectable levels of antibodies

Results of Serological Testing

  • Unrivaled specificity and accuracy in detecting pathogen nucleic acid.
  • Swift results: Get patient outcomes within 24 hours of specimen arrival.
  • Comprehensive testing: Detect multiple pathogens simultaneously (bacterial, viral, fungal, parasitic).
  • Antibiotic resistance insight: Identify resistance genes in detected pathogens.
  • Reliable results: Unaffected by a patient’s antibiotic usage.
  • Consistent accuracy: Results independent of pathogen quantity or test timing.
  • Dependable detection: Not reliant on pathogen growth outside the body.
  • Cutting-edge technology: PCR testing uses sensitive computer technology for accurate, fluorescent results.

Molecular Testing for Pathogens

  1. DNA or RNA is extracted from patient specimen. If RNA is extracted, the RNA strand will be reverse transcribed into a complementary DNA strand.
  2. Using Polymerase Chain Reaction (PCR), DNA primers anneal and amplify DNA specific for pathogen target regions.
  3. Amplified DNA is tagged with a fluorescent dye for the identification of pathogen nucleic acid in a specimen.

Differences in Culture, Serology, and PCR in Infectious Disease Testing

Culture

  • Culture growth time: 2-5 days.
  • Limited to pathogens growing in culture.
  • Visual identification through microscopy.
  • May miss several pathogens in a specimen.

Serological

  • Test during active infection.
  • Less sensitive than other methods.
  • Relies on visual identification with IgG/antigen.
  • Identifies one pathogen at a time, may miss others.

Molecular PCR

  • PCR identifies pathogens without growth delay.
  • Results available on the same day.
  • Comprehensive reporting, beyond microscopic view.
  • Detects antibiotic resistance genes.
  • Timing-independent accuracy for active or inactive infections.