BACE - Biotechnician Assistant Credentialing Aseptic Technique and Contamination Questions and Answers

Question 1

A biotechnician is preparing to work with a mammalian cell culture inside a horizontal laminar flow hood. Which of the following actions is MOST critical to maintaining aseptic conditions?

Accepted Answer

Arranging materials to prevent blocking airflow from the HEPA filter to the critical work area.

Answer

In a horizontal laminar flow hood, HEPA-filtered air flows from the back of the hood horizontally across the work surface towards the operator. Placing non-sterile items (like hands or equipment) between the filter and the sterile work area (e.g., an open cell culture flask) will blow contaminants directly onto the sterile materials. Therefore, organizing the workspace to maintain an uninterrupted path of clean air is the most crucial action for preventing contamination.

Question 2

During a bacterial transformation procedure, a student flames the mouth of a glass culture tube before and after pipetting a liquid medium. What is the primary purpose of this action?

Accepted Answer

To create an upward convection current that prevents airborne contaminants from entering the tube.

Answer

Passing the mouth of a container through a flame creates a warm updraft. This convection current forces air to flow up and away from the opening, making it more difficult for airborne contaminants like dust, spores, and bacteria to fall into the sterile container while it is open.

Question 3

Which of the following is considered a source of chemical contamination in a cell culture, rather than biological contamination?

Accepted Answer

Endotoxins from gram-negative bacteria

Answer

Endotoxins are lipopolysaccharides from the outer membrane of gram-negative bacteria and are considered chemical contaminants. While they originate from a biological source, they are non-living toxic molecules that can negatively impact cell growth and function. Mycoplasma, yeast, and other cell lines are all living biological contaminants.

Question 4

A technician needs to sterilize a heat-sensitive liquid solution containing a protein that would be denatured by autoclaving. Which method would be most appropriate for this task?

Accepted Answer

Filtration using a 0.22 µm filter

Answer

Filtration is the ideal method for sterilizing heat-sensitive liquids. A filter with a pore size of 0.22 micrometers (µm) is small enough to physically remove most bacteria, but allows the liquid and its dissolved components, like proteins, to pass through without being damaged by heat. Autoclaving and dry heat would destroy the protein. Ethanol is a disinfectant, not a sterilant for solutions.

Question 5

While streaking bacteria on an agar plate using a metal inoculation loop, a technician realizes they forgot to flame the loop after the initial streak. What is the MOST likely outcome of this error?

Accepted Answer

There will be excessive, confluent growth across the entire plate instead of isolated colonies.

Answer

The purpose of flaming the loop between streaking different sections of an agar plate is to dilute the bacteria, reducing the number of cells being spread. By failing to sterilize the loop, the technician carries a high concentration of bacteria into each new section, resulting in heavy, overlapping (confluent) growth instead of the desired well-isolated individual colonies.

BACE - Biotechnician Assistant Credentialing Exam Practice Test

BACE - Biotechnician Assistant Credentialing Exam Practice Test

BACE - Biotechnician Assistant Credentialing Aseptic Technique and Contamination Questions and Answers