Microbiology Test Results: What do they mean?

Christie Massen M.S., MLS(ASCP)Microbiologist III – QA/CLIA Coordinator

North Dakota Department of Health Division of Laboratory Services - Microbiology

Objectives• Upon completion of this presentation, participants

will be able to:o Summarize various microbiological testing methods.o List the components of a laboratory report.o Interpret various microbiology test results.o Summarize antibiotic susceptibility testing and results.o Compare various serological test results.

Infectious Diseases• Bacterial• Viral• Fungal• Parasitic

Supporting Laboratory Results

• Bacterialo Identification of bacteriao Increased WBC Counto Increased Neutrophil Counto Left-shift in Neutrophil Cell

Lineo Increased CRPo Increased Sed-Rate

• Fungalo KOH Prep Testo Identification of fungal

elements

• Viralo Identification of viruso Normal or Decreased WBC

Counto Increased Lymphocyte Count

• Parasitico Identification of parasiteo Increased Eosinophil Count

Laboratory Reports

Bacterial Culture• Pros

o Identify the isolateo Very specific

• Conso Lengthyo Normal flora

• Grow and isolate bacteria• Various media• Identify a pathogen

Biochemical Testing

Identification

Antibiotic Susceptibility Testing

• Determine antibiotic susceptibility or resistance

Antibiotic Susceptibility Testing

Case 1

Case 1: Report

Case 2

Case 2: Report

Modified Hodge Test• Purpose:

o Detection of carbapenemase production in identified organisms

• Interpretation: o Positive

• Clover leaf-like indentation along the streak line

o Negative • No growth along the streak line

Case 3

Case 3: Report

Virology

Virology Culture• Cytopathic Effect (CPE)

Case 4

Case 4: Report

Parasitology & Mycology

• Direct Examination• Macroscopic and Microscopic

Molecular Testing• DNA Probes

• DNA sequencingo Nucleic acid sequences (16s)o Whole genome sequencing

• Nucleic Acid Amplification Testing (NAAT)o Polymerase Chain Reaction (PCR)o Ligase Chain Reaction (LCR)o Transcription Mediated Amplification (TMA)

PCR• Developed in 1985• First NAA method

• How it works:o DNA Polymerase replicates the target DNA molecules

• RNA can be replicatedo Heat and cool cycles utilizedo DNA Primers hybridize the target and initiate polymerization of new

DNA Moleculeso End product: Billions of copies of the target DNAo Read for presence of DNA target

Immunology Test Methods

• Test Methods:o Agglutinationo Nephlometryo Double Diffusiono Radial Immunodiffusiono Electrophoresiso Western Bloto Flocculationo ELISAo Immunoflorescence assayo Radioimmunoassay

• Detects:o Antigenso Antibodies

Antibody Review

Antibody Review

Case 5

Case 5: Report

Case 6

Case 6: Report

Case 7

Case 7: Report

Case 8

Vaccine Preventable Disease

Case 8: Report

Questions?

References• Kiser, K.M., Payne, W.C., & Taff, T.A. (2011). Clinical

Laboratory Microbiology: A Practical Approach. Upper Saddle River, NJ: Pearson Education.

• Amjad, A., Mirza, I.A., Zia, F. (2011). Modified Hodge test: A simple and effective test for detection of carbapenemase production. Iran Journal of Microbiology. Retrieved from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3330182/

• New Directions in Molecular Testing: An Educational Guide for Clinical Laboratory Professionals. Gen-Probe Inc. Retrieved from: www.gen-probe.com