Laboratory Safety and Procedures

The video tutorial guides lab assistants through testing milk samples for bacterial contamination, emphasizing lab safety and the use of disposable lab supplies. It compares Petrifilm plates with Petri dishes and explains the process of testing pasteurized and raw milk. The tutorial also covers sampling techniques in a dairy processing plant to identify contamination sources, particularly E. coli, and demonstrates how to analyze samples using Petrifilm plates.

Which of the following is NOT a basic lab safety procedure?

• Cleaning equipment after use

• Wearing gloves and safety glasses

• Eating and drinking in the lab

• Washing hands before and after handling materials

Why are disposable lab supplies sometimes preferred over reusable ones?

• They are harder to use

• They are more expensive

• They require more cleaning

• They present less opportunity for contamination

What is the main advantage of Petrifilm plates over Petri dishes?

• They need preparation before use

• They require more space in the incubator

• They are made of glass

• They have built-in biochemical confirmation

What is the primary purpose of pasteurization?

• To make milk thicker

• To add flavor to the milk

• To reduce the overall number of bacteria

• To increase the shelf life of milk

How can milk become contaminated?

• By boiling the milk

• Through bacteria on cows' udders

• By freezing the milk

• By adding sugar

What is the purpose of using a Bunsen burner in the lab?

• To maintain a sterile working environment

• To dry the samples

• To melt the Petrifilm plates

• To heat the samples

Why should samples be kept cool before testing?

• To prevent bacteria from multiplying

• To increase the number of bacteria

• To make the samples easier to handle

• To change the color of the samples

What type of agar is used to specifically grow E. coli bacteria?

• Nutrient agar

• Agar film on Petrifilm plates

• MacConkey agar

• Blood agar

How do you estimate the number of bacterial colonies on a Petrifilm plate?

• Measure the diameter of the colonies

• Count all colonies directly

• Count colonies in a square and multiply by 20

• Weigh the Petrifilm plate

What should be done with disposable lab equipment after use?

• Wash and reuse them

• Store them for future use

• Dispose of them in an autoclave or by incineration

• Throw them in the regular trash