Microbiology Laboratory


Written by MicroDok

The microscopical examination of urogenital specimens may involve one of the following procedures:

  • Gram smear.
  • Wet preparation.

NOTE:  Most urogenital specimens come in swab stick form. A sterile non – toxic cotton swab stick is used to obtain or collect urogenital specimens from patients.


AIM:  To detect the presence of pus cells, bacteria, and yeast cells from urogenital specimens.

MATERIAL/APPARATUS: urogenital specimen, glass slide, immersion oil, microscope, Gram staining reagents.


  1. Gently roll the swab stick containing the urogenital specimen on a clean glass slide. In this way, a smear of the urogenital specimen is made, and it will also help to avoid any damage that will be done to the pus cells containing the bacteria.
  2. Heat fix the smear on the slide.
  3. Perform Gram staining technique.
  4. Allow the Gram stained slide to dry.
  5. Add a drop of immersion oil on the slide.
  6. Examine the slide with the ×10/oil immersion objective of a microscope.
  7. Look out for pus cells and bacteria as you view the slide.


  • For Gram smear from suspected gonorrhea: Look for pus cells containing Gram negative diplococcic or intracellular Gram negative diplococci. If the pus cells are damaged, the Gram negative diplococci will be extracellular i.e. placed outside the pus cells. This is presumptive diagnosis for gonorrhea especially in males that are symptomatic to the infection. Gram stained smear does not always indicate the presence of gonorrhea in women because women are asymptomatic to the infection. Thus culture is required to diagnose gonorrhea in women.
  • For vaginal smear from candidiasis or bacterial vaginosis patients: Look for large Gram positive yeast cells that could be Candida albicans or other species of Candida. This is indicative of the presence of candidiasis infection. Also look out for Clue cells (epithelial cells with adhering Gram negative short bacilli and Gram variable coccobacilli) that could be Gardnerella vaginalis. This is indicative of bacterial vaginosis.

AIM: To detect the presence of yeast cells, Trichomonas vaginalis, pus cells, red blood cells (RBC’s) from urogenital specimens as an aid in the diagnosis of Trichomoniasis and Vaginal candidiasis.

MATERIAL/APPARATUS: Urogenital specimen (e.g. vaginal swab), test tubes, test tube rack, physiological (normal) saline, glass slide, cover slip, microscope, bulb pipette.


  1. With the bulb pipette, obtain about 1 – 2 ml of normal saline.
  2. Dispense the normal saline into a clean test tube standing on a test tube rack.
  3. Immerse the cotton swab stick containing the urogenital swab into the test tube.
  4. Allow to stand for about 60 seconds.
  5. Bring out the swab stick and make a wet preparation on a clean glass slide. Ensure that only a thin preparation is made.
  6. Cover the preparation with a cover slip.
  7. Examine slide with ×40 objective lens of a microscope. Ensure that the condenser iris of the microscope is sufficiently closed in order to give a good contrast.

NOTE: Wet preparation of urogenital specimens are usually done or carried out after Gram smear and culture must have been undertaken. This is to ensure that the specimen is not contaminated before culturing and Gram smearing.


Trichomonas vaginalis is motile. Look out for motile T. vaginalis and report. Look out for yeast cells, RBC’s, and pus cells.

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