Analytical Food Microbiology. Ahmed E. Yousef

       In many teaching laboratories, each student (or a group of students) is assigned a storage drawer (or a similar compartment) containing materials commonly used in the laboratory. Students should be sure that the drawer contains all the materials indicated in the course instructions and that all materials are returned and stored at the end of each session. Typical tools contained in this storage space may include inoculating loop, inoculating needle, microscope slides, cover slips, microscope lens cleaner, lens cleaning paper, lens oil, wax marking pencils or permanent markers, pipette bulbs, bibulous paper, and matches or a striker for lighting the Bunsen burner. Some of the consumable materials may be used up during the course of the term and students should learn where replacement materials are kept. At times, the items from a storage location may be misplaced. If this occurs, the student should not take supplies from someone else’s drawer.

       Some laboratory communal supplies may also be used up during the course of the school term. These items may include paper towels, disinfectant solutions, Gram stain reagents, other staining agents or reagents, adhesive tape, and other frequently used materials. Students should determine where these items are stocked so that they can replenish supplies.

       Students should know where to obtain distilled water. In most laboratories, special distilled water taps are used; these are often located near the regular hot‐ and cold‐water taps. The distilled water taps are frequently spring‐loaded to prevent anyone from leaving the tap open and wasting water. Often these taps have a tab on the handle labeled “DW.”

       At the beginning of every laboratory session, the student should determine the location of all water baths, incubators, or other equipment that will be shared during that session. Students should collect all media and supplies required to perform the experiment. Many microbiological growth media look similar; therefore, caution should be taken to carefully and correctly label media. Students should not collect more media than will be used during the exercise. Careful reading of the laboratory exercise should allow students to determine the correct number of plates and tubes needed for each exercise.

       The microbiology laboratory contains many materials that are potentially dangerous if used outside the laboratory environment. Students should never remove slides, plates, or tubes from the laboratory. After use in the laboratory, materials are either prepared for reuse or discarded. Each laboratory has a system for material disposal, protocols for which items are reused and which are discarded, locations where reusable materials should be placed at the end of the laboratory, expectations for what to clean manually by students, etc. Students must be familiar with proper disposal and proper clean up to ensure that materials are not wasted, biohazard containers do not contain excess materials, and everyone’s safety is preserved.

       Used culture tubes should not be returned to the laboratory exercise set‐up area, unless the instructor specifically tells students to do so. Only unused media should be returned to the set‐up area.

       Reusable materials may include some glassware, such as test tubes, bottles, and flasks. This reusable glassware should then be placed in the designated location for each type of item. Depending on their contents, tubes, bottles, and flasks may need to be autoclaved before washing. These items should be separated from items that do not require autoclaving. Some other items, such as blender jars, may not require autoclaving and may be manually washed by students. These items should be washed according to the designated protocol and placed in the designated drying area.

       Non‐reusable materials are disposed of in either hazardous or non‐hazardous waste containers. Paper towels used with disinfectant to wipe off laboratory benches may be placed in the containers for non‐hazardous waste (i.e., regular trash). Gauze or lens paper used to clean microscope lenses before or after use is also safe to be placed in the regular trash. Items that have not been exposed to microorganisms do not require special disposal.

       Biohazard containers (e.g., special marked bags in cardboard boxes or cans with plastic liners) are used to discard contaminated materials. These materials include all disposable gloves, culture‐containing disposable Petri plates, and disposable test tubes. Contaminated materials (i.e., those exposed to laboratory microorganisms) are typically autoclaved or incinerated. Contaminated broken glassware should be disposed of in the sharps container. Broken, uncontaminated glassware should be placed in a receptacle designated for that purpose (e.g., the broken glass box). If syringes are used for a laboratory exercise, they should be disposed of in the sharps container designated by the instructor.

       Spilling or splashing of cultures can happen. In case of small spills, the student needs to encircle and flood the area with excess disinfectant, allow disinfectant to sit for the proper amount of time, and wipe the area with paper towels or other provided absorbent towels, wiping toward the center to prevent spread of the contaminant. These towels are considered contaminated and should be disposed of in the biohazard container. In case of larger spills, the instructor should be notified immediately. Any broken glassware should be disposed of in a sharps container. Appropriate disposable gloves should be worn during the cleaning process and should be discarded after the spill has been addressed.

       It is recommended that students tape their inoculated agar plates together at the end of each exercise or keep them in a designated group container (small plastic bin) to make retrieving the group’s plates easier at the beginning of the subsequent session and make them easier to handle and inspect by instructors. Plates should be placed in the correct orientation and in the designated location for incubation.

      1 Carefully read the laboratory exercise and understand why and how it is executed.

      2 Summarize the practical steps to be carried out during the session on a single sheet of paper. This “exercise summary” should be one of only two papers allowed on the bench during the execution of the exercise. The second is a blank paper for writing observations and recording results. As indicated earlier, the exercise summary (plus the recording sheet) are ideally kept in a plastic sleeve