Microbiology, part 50: Control of Growth - Microbial Control Terminology & Considerations

Hi, I'm Cathy with Level Up RN. In this video, I'm going to begin my coverage of topics from the control of microbial growth section of our microbiology flashcard deck. Specifically, I'll be going over some important terms related to microbial control, as well as factors that impact treatment effectiveness with antimicrobial agents. At the end of the video, I'm going to give you guys a little quiz to test your knowledge of some of the key facts I'll be going over in the video, so be sure to stay for that. And if you have our flashcards, go ahead and pull out your flashcards on microbial control so you can follow along with me.

Let's first go over some important terms related to microbial control. So chances are in your micro class, you're going to need to be able to differentiate between these terms on your exam. So first up, we have sterilization. Sterilization is the destruction or removal of all microorganisms, including vegetative cells, endospores, and viruses. An example of sterilization is the use of an autoclave in the hospital or laboratory to sterilize equipment. Next, let's talk about commercial sterilization. So commercial sterilization kills microbes that are responsible for spoilage of food and foodborne illness, including clostridium botulinum. However, it does not kill all microorganisms. So it uses heat that is high enough to kill harmful microbes, but not so high that it compromises food quality. Disinfection is the destruction of microorganisms, but not endospores on a surface using antimicrobial chemicals or heat. Cleaning wipes are an example of a disinfectant. Antisepsis is the application of an antimicrobial chemical on living tissue. So antisepsis would be used for things such as prepping a patient's skin for surgery. Examples of antiseptic agents include chlorhexidine and iodine. Sanitization is a treatment that reduces the microbial load on an inanimate surface. So it reduces the number of microbes to a safe level, but it does not remove all microbes. An example of sanitization is the use of a dishwasher to sanitize plates and utensils. And then finally, degerming is the reduction of microbes through the use of a mild chemical, and mechanical removal through gentle scrubbing. So washing your hands with soap and water is an example of degerming.

When treating an area with an antimicrobial agent to kill microbes or reduce the number of microbes, there are a number of factors that impact treatment effectiveness. Let's go through those now. The first factor is the number of microbes. So the more microbes there are, the harder it will be to kill them all. So if you are treating a surface with an antimicrobial agent, you may need to leave it on there longer or use a higher concentration of the agent. Next, we have environmental factors, such as temperature, nutrient levels, and the presence of biofilms. So for example, if an area to be treated has a biofilm, that biofilm provides protection for the microorganisms against the antimicrobial agent, which makes that agent less effective. Another factor is the time of exposure to an antimicrobial agent. So in general, the longer that microbes are exposed to an agent, the more effective that agent is going to be at killing the microbes. The concentration of the antimicrobial agent also matters. So in general, a higher concentration is going to kill microbes more quickly and effectively. Finally, microbial characteristics such as cell wall composition and enzymes also impact treatment effectiveness. So for example, gram-negative bacteria have a second outer membrane, which makes it harder for antimicrobial agents to penetrate that layer.

The last thing I want to talk about is decimal reduction time, or DRT, which is used to evaluate the effectiveness of a specific antimicrobial agent. So DRT is the amount of time it takes for a specific chemical to kill off 90% of a population of a specific microbial species. So a low DRT means that the microbe is more sensitive to the antimicrobial agent, and it will be killed off more quickly, whereas a high DRT means that the microbe is more resistant to the antimicrobial agent, and it will take longer to kill off the microbes.

All right. It's quiz time, and I have four questions for you, and they are all fill in the blank.

Question number one. Blank is the application of an antimicrobial chemical on living tissue.

The answer is...antisepsis.

Question number two. Blank is the destruction or removal of all microorganisms, including vegetative cells, endospores, and viruses.

The answer is...sterilization.

Question number three. Blank is the reduction of microbes through the use of a mild chemical, and mechanical removal with gentle scrubbing.

The answer is...degerming.

And number four. Blank is the amount of time required for a specific chemical to kill off 90% of the population of a specific microbial species.

The answer is ...decimal reduction time or DRT.

All right. That's it for this video. I hope it was helpful. Take care and good luck with studying.

[BLOOPERS]

To kill off 90% of a specific microbial-- so washing your hands with soap and water is an example of degerming. And are responsible for [inaudible] foodborne illness.