Orientation to the Microbiology Laboratory


Basic Techniques of Biotechnologies
  Orientation to the Microbiology Laboratory
    The Microscope
    Handling and Examining Cultures

Some of the laboratory experiments included in this text may be hazardous if you handle materials improperly or carry out procedures incorrectly. Safety precautions are necessary when you work with any microorganism, and with chemicals, glass test tubes, hot water baths, sharp instruments, and similar materials. Your school may have specific regulations about safety procedures that your instructor will explain to you. If you have any problems with materials or procedures, please ask your instructor for help.

Safety Procedures and Precautions
The microbiology laboratory, whether in a classroom or a working diagnostic laboratory, is a place where cultures of microorganisms are handled and examined. This type of activity must be carried out with good aseptic technique in a thoroughly clean, well-organized workplace. In aseptic technique, all materials that are used have been sterilized to kill any microorganisms contained in or on them, and extreme care is taken not to introduce new organisms from the environment. Even if the microorganisms you are studying are not usually considered pathogenic (disease producing), any culture of any organism should be handled as if it were a potential pathogen. With current medical practices and procedures, many patients with lowered immune defenses survive longer than they did before. As a result, almost any microorganism can cause disease in them under the appropriate circumstances.

Each student must quickly learn and continuously practice aseptic laboratory technique. It is important to prevent contamination of your hands, hair, and clothing with culture material and also to protect your neighbors from such contamination. In addition, you must not contaminate your work with microorganisms from the environment. The importance of asepsis and proper disinfection is stressed throughout this manual and demonstrated by the experiments. Once these techniques are learned in the laboratory, they apply to almost every phase of patient care, especially to the collection and handling of specimens that are critical if the laboratory is to make a diagnosis of infectious disease. These specimens should be handled as carefully as cultures so that they do not become sources of infection to others. An important problem in hospitals is the transmission of microorganisms between patients, especially by contaminated hands. Well-trained professionals, caring for the sick, should never be responsible for transmitting infection between patients. Appropriate attention to frequency and method of hand washing (scrubbing for at least 30 seconds) is critical for preventing these hospital-acquired infections (also known as nosocomial infections).

In general, all safety procedures and precautions followed in the microbiology laboratory are designed to:
  1. Restrict microorganisms present in specimens or cultures to the containers in which they are collected, grown, or studied.

  2. Prevent environmental microorganisms (normally present on hands, hair, clothing, laboratory benches, or in the air) from entering specimens or cultures and interfering with results of studies.
Hands and bench tops are kept clean with disinfectants, laboratory coats are worn, long hair is tied back, and working areas are kept clear of all unnecessary items. Containers used for specimen collection or culture material are presterilized and capped to prevent entry by unsterile air, and sterile tools are used for transferring specimens or cultures. Nothing is placed in the mouth.

Personal conduct in a microbiology laboratory should always be quiet and orderly. The instructor should be consulted promptly whenever problems arise. Any student with a fresh, unhealed cut, scratch, burn, or other injury on either hand should notify the instructor before beginning or continuing with the laboratory work. If you have a personal health problem and are in doubt about participating in the laboratory session, check with your instructor before beginning the work. Careful attention to the principles of safety is required throughout any laboratory course in microbiology.

General Laboratory Directions
  1. Always read the assigned laboratory material before the start of the laboratory period.
  2. Before entering the laboratory, remove coats, jackets, and other outerwear. These should be left outside the laboratory, together with any backpacks, books, papers, or other items not needed for the work.
  3. To be admitted to the laboratory, each student should wear a fresh, clean, knee-length laboratory coat.
  4. At the start and end of each laboratory session, students should clean their assigned bench-top area with a disinfectant solution provided. That space should then be kept neat, clean, and uncluttered throughout each laboratory period.
  5. Learn good personal habits from the beginning: Tie back long hair neatly, away from the shoulders. Do not wear jewelry to laboratory sessions. Keep fingers, pencils, and such objects out of your mouth. Do not smoke, eat, or drink in the laboratory. Do not lick labels with your tongue. Use tap water or preferably, self-sticking labels. Do not wander about the laboratory. Unnecessary activity can cause accidents, distract others, and promote contamination.
  6. Each student will need matches, bibulous paper, lens paper, a china-marking pencil, and a 100-mm ruler (purchased or provided). A black, waterproof marking pen may be used to mark petri plates and tubes.
  7. Keep a complete record of all your experiments, and answer all questions at the end of each exercise. Your completed work can be removed from the manual and submitted to the instructor for evaluation.
  8. Discard all cultures and used glassware into the container labeled CONTAMINATED. (This container will later be sterilized.) Plastic or other disposable items should be discarded separately from glassware in containers to be sterilized.
    Never place contaminated pipettes on the bench top.
    Never discard contaminated cultures, glassware, pipettes, tubes, or slides in the wastepaper basket or garbage can.
    Never discard contaminated liquids or liquid cultures in the sink.
  9. If you are in doubt as to the correct procedure, double-check the manual. If doubt continues, consult your instructor. Avoid asking your neighbor for procedural help.
  10. If you should spill or drop a culture or if any type of accident occurs, call the instructor immediately. Place a paper towel over any spill and pour disinfectant over the towel. Let the disinfectant stand for 15 minutes, then clean the spill with fresh paper towels. Remember to discard the paper towels in the proper receptacle and wash your hands carefully.
  11. Report any injury to your hands to the instructor either before the laboratory session begins or during the session.
  12. Never remove specimens, cultures, or equipment from the laboratory under any circumstances.
  13. Before leaving the laboratory, carefully wash and disinfect your hands. Arrange to launder your lab coat so that it will be fresh for the next session.