Practicals for Principles of Medical Microbiology for students of 3rd year Medicine.

1. LABORATORY SAFETY
MEASURES
GOVERNING THE HANDLING OF
INFECTIVE MATERIAL

2. LABORATORY SAFETY MEASURES (1)
• Coats, jackets, bags and other outer apparel should be left
outside the laboratory.
• Laboratory gowns must be worn inside the laboratory and not
outside the lab.
• Long hair should be tied back neatly and closed footwear should
be worn.
• NOTHING (fingers, pencils, pens) should be placed in the
mouth.
• Mouth pipetting is strictly forbidden in the laboratory.
• No eating, drinking or smoking allowed in the laboratory.
• The working bench should be wiped with disinfectant at the
beginning and at the end of the laboratory session.

3. LABORATORY SAFETY MEASURES (2)
• Every specimen must be regarded as dangerously infective
and treated as such.
• ALL ACCIDENTS such as spilling of infected material, cutting of
fingers, or pricking of fingers, must be reported immediately
to the laboratory instructor.
• A spilled culture can be covered with paper towels and
laboratory disinfectant poured over the towels and
contaminated area; leave for 15 minutes before mopping up.
DO NOT WIPE with coat, handkerchief or clothes.
• All waste material must be placed in the special containers
provided, and not thrown on to the floor.

4. LABORATORY SAFETY MEASURES (3)
• Sharps (e.g., used needles and disposable syringes) should be
discarded into special medical waste bins.
• All used material (e.g., cover slips, slides, pipettes) must be
placed in the containers provided containing disinfectant.
• All discarded cultures must be placed in the bucket provided,
ready for sterilization.
• Do not discard any fluid into sinks or drains. Container will be
provided to discard the fluid.
• All instruments must be sterilized immediately after use (e.g.,
inoculating wire loop).
• No slides or cultures are to be taken away from the lab.
• Hands must be washed thoroughly before leaving the
laboratory.

5. Infection in Microbiology Lab
Infection in microbiology laboratories
is generally caused by:
Inhalation
Inoculation
Ingestion of microorganisms

6. Applications of Light Microscopy
1. Bright field microscope (uses light source)
2. Dark field microscope (with a special condenser
and objective to illuminate organism against dark
background)
3. Fluorescent microscope (specimen is stained with
fluorescent dye that absorbs the energy of short light
waves then releases light of longer wavelength)
4. Phase contrast microscope (uses a modified
light microscope that permits greater contrast between
substances of different thickness or density).

7. Light Microscope

8. Light Microscope
MICROSCOPE RULES
When you have finished using your
microscope
1. Remove slides from the stage.
2. Turn light source down to 0.
3. Clean objectives if using oil.
4. Switch off.
5. Leave lowest power objective (ie x4) in
viewing position.
6. Put cover on.
7. Turn off at the power point.

9. DISINFECTION
Students will test the efficacy of different disinfectants on
Gram-negative bacteria using following method:
1. Take each of the following disinfectants in 5ml amounts into
3 sterile cotton plugged tubes as follows:
A. Dishwasher detergent “DAC”.
B. “Sekusept” disinfectant.
C. 2% Glutaraldehyde buffered solution.
2. To each tube of disinfectant add 0.5ml of E.coli suspension.
3. Mix gently by tapping the bottom of the tubes.
4. Place the tubes in a 20°C water bath.

10. DISINFECTION
5. Transfer two loopful from each disinfectant bottle into a 5 ml
sterile nutrient broth at intervals of 5 minutes, 10 minutes and
20 minutes.
6. Label the cultured broth tubes with time held in water bath.
7. Incubate the tubes for 48 hours at 37°C.
8. Record your results in the table provided as follows:
Turbid Growth Disinfectant Time
5 mins 10 mins 20 mins
Clear No growth
A. Dishwasher “DAC”
B. “Sekusept”
C. 2% Glutaraldehyde