MicrobiologyLesson 3 of 3 in the course Control of Microbial Growth

Disinfectant Efficacy: Germicide Levels and Evaluation Tests

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

This lesson introduces how disinfectants are classified by the range of microbes they can control, what conditions influence their activity, and how the historical phenol coefficient compared chemical agents.

Disinfectants are grouped according to the types of microorganisms they can inactivate. These categories describe general activity; actual results can also depend on the product and conditions of use.

All flashcards

What does a zone of inhibition show in disk-diffusion testing?
A clear area around a disk where bacterial growth is inhibited.
What does a use-dilution test evaluate?
Whether microorganisms survive on a contaminated surface after disinfectant exposure.
Why is a neutralizing compound added during an in-use test?
It inactivates carried-over disinfectant so it cannot hide viable microbes.
How can live HPV on a surface be assessed when routine culture is unsuitable?
Use a stain that attaches to viral RNA and microscopy to identify infected cells.
What can CRE outbreaks linked to endoscopes reveal about infection control?
Established protocols or device designs may need reassessment despite staff compliance.

Quiz questions

  1. What does a phenol coefficient above 1.0 indicate?Answer: The agent was more effective than phenol in the historical comparison.
  2. In disk-diffusion testing, what might a small inhibition zone indicate besides limited antimicrobial activity?Answer: The agent may have diffused poorly through the agar.
  3. After disinfectant exposure in a use-dilution test, what does turbidity in the fresh medium indicate?Answer: Surviving microorganisms grew after transfer from the treated cylinder.
  4. What passing result is required by the described AOAC use-dilution standard?Answer: At least 59 of 60 replicates show no growth.
  5. Why does a comparable disk-diffusion zone provide stronger evidence when the same organism and conditions are used?Answer: It reduces differences caused by organism choice and test conditions.

Based on Microbiology by Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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