Infectious Disease Intro PT2

Question 1

When diagnosing an infection what are the steps

Answer 1

a) History
- Signs and symptoms: severity
- Source of infection
- Try to determine what organism it could be
b) Physical examination (will be different for each one)
- Try to localize infection
- Ex. (measles: rash)( meningitis: neck stiffness) (pneumonia: cough and sputum production; chest sounds)
c) Laboratory
- WBC and differential
- ESR and CRP
- Renal/hepatic function
- Electrolytes…
- Microbiology

Question 2

What is the goal of using microbiology in the lab

Answer 2

a) Gram stain
- Is it gram + or -
- Cocci vs bacillus
- Presence of WCB
b) Culture
- Organism is grown and the biochemical profile is determined
c) MALDI-TOF MS
- Vaporizes bacterial samples with laser and this ionized mass is then separated by mass and charge-> creates a fingerprint of the organism-> compared to a database to identify
d) Sensitivity test
- Determines which antibiotics the organism is susceptible to
e) Immunologic testing (serology)
- Useful when the organism cannot be cultured or treatment has already begun
f) Antibody testing
- Detects presence of antibodies directed against the pathogen
g) Antigen detection
- Detects presence of antigen in the sample
- Bacterial, fungal or viral
h) Polymerase chain reaction (PCR)
- Detects very low amounts of specific DNA in specimens
i) Electron microscopy
- see viruses

Question 3

What is a gram stain

Answer 3

• Quick and easy to get an idea of organism
  
  • Gram + or -
  • Cocci vs bacillus
  • Presence of WBC (if no WBC then could maybe just be colonization)
  • Is it even a bacteria
  • However not all organisms stain well (TB)

Question 4

What is a culture test

Answer 4

• Best method for revealing organism
  
  • Organism is grown and the biochemical profile is determined (coagulase + or -/ oxidase + or -)
  • Not all organisms grow well
  • Contamination issues