FREE AP-MICRO Laboratory Operations and Safety Questions and Answers

Question 1

A new trainee in a microbiology laboratory is observed performing several tasks. Which of the following actions requires immediate correction by the training supervisor due to the significant risk of creating infectious aerosols?

Accepted Answer

Forcefully expelling the last drop of liquid from a pipette into a culture medium.

Answer

Forcefully expelling the last drop from a pipette is a common source of aerosol production in the laboratory. This action can create a spray of microscopic droplets containing microorganisms, which can then be inhaled by laboratory personnel or contaminate surfaces. Proper pipetting technique involves gently touching the tip to the side of the container to release the liquid without bubbling or forceful discharge.

Question 2

A reference laboratory needs to ship a pure culture of *Bacillus anthracis* to the CDC for further testing. According to IATA/DOT shipping regulations, this organism must be classified and shipped as:

Accepted Answer

A Category A Infectious Substance, UN 2814.

Answer

*Bacillus anthracis* is a high-consequence pathogen capable of causing life-threatening disease. It is explicitly listed as a Category A Infectious Substance, which includes organisms that can cause permanent disability or life-threatening disease in otherwise healthy humans. The proper shipping name is "Infectious substance, affecting humans," and it is assigned the identification number UN 2814. Category B (UN 3373) is for substances not meeting the Category A criteria.

Question 3

A technologist accidentally drops and breaks a flask containing a liquid culture of *Mycobacterium tuberculosis* outside the biosafety cabinet. Which of the following is the most critical first step in the cleanup procedure?

Accepted Answer

Alert others, vacate the area immediately, and prevent re-entry for at least 30 minutes.

Answer

For a spill involving a BSL-3 agent like *Mycobacterium tuberculosis*, the primary immediate risk is inhalation of infectious aerosols. The correct first action is to alert everyone, evacuate the area, and close it off for a period (e.g., 30-60 minutes) to allow aerosols to settle before trained personnel with appropriate PPE begin decontamination, typically using a tuberculocidal disinfectant.

Question 4

A technologist needs to subculture a mold isolate that is highly suspicious for *Coccidioides immitis*. To minimize the risk of laboratory-acquired infection, this work must be performed in which of the following?

Accepted Answer

A Class II Biosafety Cabinet.

Answer

*Coccidioides immitis* is a Biosafety Level 3 (BSL-3) pathogen when manipulated in its mold form due to the high risk of aerosolizing infectious arthroconidia. All manipulations that could generate aerosols must be performed in a certified Class II Biosafety Cabinet (BSC), which provides personnel, environmental, and product protection. A chemical fume hood only protects the user from chemical vapors, and a laminar flow bench blows air toward the user, offering no personal protection.

Question 5

Which set of parameters is most commonly used for routine steam sterilization of microbiological media and decontamination of biohazardous waste in an autoclave?

Accepted Answer

121°C for 15 minutes at 15 psi.

Answer

The standard and most widely accepted conditions for steam sterilization (autoclaving) are 121°C for a minimum of 15 minutes at 15 pounds per square inch (psi) of pressure. This combination of moist heat and pressure is effective at killing even the most heat-resistant bacterial endospores, ensuring sterility.

AP Practice Test

AP Practice Test

FREE AP-MICRO Laboratory Operations and Safety Questions and Answers