Microbial Growth and Growth Control Flashcards
What do we mean by decontamination, disinfection and sterilization?
Decontamination: treatment of a surface to make it ``safe to handle´´
Disinfection: is the use of chemical/physical agent that targets pathogens
Sterilization: killing all viable organisms
What are bactericidal and bacteriostatic agents?
bactericidal agents are natural or synthetic chemical agents used to kill microorganisms.
bacteriostatic agents are natural or synthetic chemical agents used to inhibit the growth of microorganisms.
What is the difference between decontamination and disinfection?
decontamination can be as simple as wiping fragments off a surface, while disinfection involves disinfectants that kill or severely inhibit the growth of microorganisms.
Which three parts are included in physical antimicrobial control? How does each work?
Heat sterilization: at very high temperatures microorganisms denaturate.
Radiation sterilization: radiation alters bioloymers such as DNA or proteins
Filter sterilization: filter pores are too small to allow bacteria pass.
What is denaturation?
is the loss of structure and and ability to function of a protein molecule.
What do we mean by decimal reduction time (D) and thermal death time?
Decimal reduction time: the time it takes for a viable microbial to reduce ten fold
Thermal death time: the time it takes to kill all cells of a microbial population at a specific temperature.
What are the problems with endospores and heat sterilization?
Endospores are heat resistant and have much longer decimal reduction times
Describe the autoclaving process. How do heat and pressure changes and why?
The autoclave is a sealed heating device that uses steam under pressure to kill microorganisms. The autoclave places steam under a pressure of 1.1 kg/cm2 (15 lb/in2), which yields a temperature of 121°C. AIf the object to be autoclaved is bulky or large volumes of liquids are to be sterilized, heat transfer to the interior is retarded, and thus the total heating time must be extended. It is not the pressure inside the autoclave that kills the microorganisms but the high temperatures that are achieved when steam is placed under pressure.
Define sterile
1 bacterium/endospore per 1.000.000 objects
What is pasteurization?
uses heat to significantly reduce rather than totally eliminate the microorganisms found in liquids
What do we mean by radiation sterilization?
Ultraviolet radiation between 220 and 300 nm is absorbed by DNA and can cause mutations or have other serious effects on DNA that lead to death of the exposed organism.
Ionizing radiation is electromagnetic radiation of sufficient energy to produce ions and other reactive molecular species from molecules with which the radiation particles collide. Ionizing radiation is typically generated from X-ray sources or the radioactive nuclides 60Co and 137Cs. These nuclides produce X-rays or gamma rays, both of which have sufficient energy and penetrating power to kill microorganisms in bulk
How does filter sterilization work?
Filtration is accomplished by using a syringe or a pump to force the liquid through the filtration apparatus into a sterile collection vessel
What is chemical antimicrobial control?
Chemical antimicrobial control is the use of natural or synthetic chemical agents to kill or inhibit the growth of microorganisms.
How do bacteriostatic-, bactericidal-, and bacteriolytic agents affect bacterial growth and how can you differentiate between these by studying the bacterial growth curve?
bacteriostatic agents inhibit growth but once removed growth can resume, bactericidal kill bacteria but don`t lyse the dead cells, bacteriolytic kill bacteria through lysis and this affects both viable and total cell count.
Describe the mechanism of action of ethanol based disinfectants on bacteria.
it kills the microorganism by dissolving the cell wall and denaturing its proteins.
