Laboratory Diagnosis of Bacterial Pneumonia



Diagnostic Microbiology In Action
  Microbiology of the Respiratory Tract
      Isolation and Identification of Staphylococci
      Staphylococci in the Normal Flora
    Streptococci, Pneumococci, and Enterococci
      Isolation and Identification of Streptococci
      The CAMP Test for Group B Streptococci
      Identification of Pneumococci
      Identification of Enterococci
      Streptococci in the Normal Flora
    Haemophilus, Corynebacteri and Bordetella
    Clinical Specimens from the Respiratory Tract
      Laboratory Diagnosis of a Sore Throat
      Laboratory Diagnosis of Bacterial Pneumonia
      Antimicrobial Susceptibility Test of an Isolate from a Clinical Specimen

Purpose To identify bacterial species in a simulated sputum as quickly as possible
Materials Simulated sputum in a screw-cap container, accompanied by a laboratory request for culture
  • Patient’s name: Richard Wilson
  • Age: 72 years
  • Physician’s name: Dr. F. Smythe
  • Tentative diagnosis: lobar pneumonia
Blood agar plate (BAP)
Mannitol salt agar plate (MSA)
Dropping bottle containing 3% hydrogen peroxide
Tubed plasma (0.5-ml aliquots)
Sterile 1.0-ml pipettes
Pipette bulb or other aspiration device

  1. Make a Gram stain of the simulated sputum specimen. Record the results and place the information on your work card.
  2. With your sterilized inoculating loop, inoculate a blood agar and a mannitol salt agar plate. Streak each for isolation of colonies. Incubate both plates at 35°C for 24 hours.
  3. When the “physician” calls, refer to your work card and give him or her specific information about your microscopic interpretation of the Gram-stained smear.
  4. After the plates have incubated, examine each carefully. Record colonial morphology on the work card, and make Gram stains of different colony types on each medium.
  5. Perform the catalase test on different colony types on each medium. Be careful not to scrape the surface of the blood agar plate or a false-positive reaction will occur.
  6. Perform the coagulase test with any colony on either plate that appears to be a Staphylococcus.With a sterilized inoculating loop, pick up a colony and emulsify it directly in 0.5 ml of plasma. Incubate the plasma tube and read at intervals from 30 minutes to 4 hours. If necessary, incubate the tube overnight and read the result the next day. Record the result on your work card.
  7. Prepare a final report for the “physician.”

  1. Laboratory work card (record of your work to be kept on file at least two years).

  2. Final laboratory report to “physician.”