Environmental Testing - 23F --Food Microbiology Laboratory (Combined)

Environmental Testing HS https://e.centennialcollege.ca/d2l/le/content/1047309/viewContent/12761770/View 2023-10-28, 3 : 50 PM Page 1 of 3

Reflect in ePortfolio Download Print BI 218 Food Microbiology ENVIRONMENTAL TESTING Originated by: Allan Richardson Revised by: Samiha Mohammad Sharif & Yvonne Henry Uncontrolled when printed 1 THEORY: The microbiological technician in a food or pharmaceutical company must regularly monitor the various areas of the warehouse, production area and the laboratory to test the air quality, effectiveness of surface disinfectants, and to look for abnormal bacterial or fungi contamination. EQUIPMENT AND SUPPLIES: Surface testing • 4- TSA + 1% tween 80 • 2- RODAC: TSA + 1% Tween 80 (18 mL per plate) • 2- 5 mL saline • Sterile swabs • Sterile spreaders • Disinfectants: 70% alcohol / 1% bleach • 10 x 10 cm templates • Vortex mixer • 1 mL pipettes • Microscope slides + microscope + staining reagents Air testing • 2- TSA plates • Air samplers: Vacuum samplers (charged night before lab) OBJECTIVE: • To assess the microbial content o f a specific area of the laboratory environment • T o determine the microbial quality of the air and various surfaces using a variety of testing methods METHODS: Day 1 PROCEDURE A: SURFACE TESTING SWAB TECHNIQUE METHOD 1. Label 2 sterile saline buffer tubes; 1 - Before and 1 - After 2. Moisten a swab in the sterile buffer , and squeeze out excess a gainst the inside of the tube 3. Choose an area of the lab to test, and swab in a tight zig - zag pattern 3 - ways using the 10 x 10cm template 4. Replace the swab in the “Before” tube, breaking off the stick below the area touched with your fingers a. R emember to note down the volume in the tube - this is important for your final calculation 5. Shake the tube vigorously or v ortex mix for 1-2 minute s to loosen cells from the swab 6. Make 2 spread plates with TSA + Tween, using 0.1mL sample sizes (i.e., make duplicates) a. Note: 1 mL spread plates are not perf ormed as they take too long to dry 7. In - situ disinfectant test a. Choose one of the disinfectants and clean the same area surface tested previously b. When the surface has dried, repeat steps 2 to 6 using the “After” tube and 2 new TSA + Tween plates using again 0.1 mL sample size in duplicates 8. Incubate all plates at 25 o C for up to 1 week 9. Prepare a Gram stain from the saline buffer for both Before and After samples a. When staining f rom a broth or liquid sample, not additional dH 2 0 is needed 10. Heat fix , stain, and observe under the microscope (should see a “diverse” sample) BI 218 Food Microbiology ENVIRONMENTAL TESTING REPLICATE ORGANISM DIRECT AGAR CONTACT (RODAC) METHOD 1. Close to the test area, gently roll 1 RODAC plate ( TSA + Tween) across the surface a. Note: Do not use the exact same area tested in Procedure A as this has already been disinfected 2. Clean the area with your chosen disinfectant and repeat t he test with another RODAC plate 3. Incubate all plates at 25 o C for up to 1 week PROCEDURE B: AIR SAMPLIN G FALL - OUT PLATE METHOD 1. Label one TSA plate with your chosen testing site, time of exposure, date, and name 2. Remove the lid of the petri plate of TSA , and leave it sitting out for 30 minutes 3. Collect and close plate with lid, and leave it for incubation at 25 o C for up to 1 week VACUUM METHOD 1. Perform air sampling using any sampler that is available using TSA plate, or TSA/RBC strip respectivel y a. A djus t samplers to the desired time and volume and note down the time and volume: TIME: _________________ VOLUME SAMPLED: _____________________ 2. Incubate plates and strips for 1 week at 25 o C Day 3: RESULTS 1. Count the number of total colonies on all plates , distinguishing between moulds and bacteria 2. Individually, record the detailed colony morphologies of 5 different bacterial colonies from any of the test method plates 1 of 2 Automatic Zoom https://e.centennialcollege.ca/d2l/le/content/1047309/viewContent/12761770/View 2023-10-28, 3 : 50 PM Page 2 of 3