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ch 6
Controlling microbial growth in the environment
| Antimicrobial agent | anything that either kills or inhibits the growth of a microbe. includes physical, chemicals, and chemotherapeutic agents |
| -cidal | kills microbe |
| -static | inhibits microbe |
| Aseptic | environment or procedure that is free of contaminants or microorganisms |
| What are the three methods of achieving aseptic conditions | sterilization, disinfection, antisepsis |
| Sterilization | removal or destruction of all microorganisms including viruses and endospores in or on an object |
| Sterile | any object subjected to sterilization |
| Disinfection | involves using physical or chemical agents known as disinfectants that destroy vegetative microbes and many viruses on inanimate objects. not endospores |
| Antisepsis | inhibits or destroys vegetative microbes and many viruses on living tissue. does not include endospore. |
| antiseptics | the use of chemical agents that destroy vegetative microbes on living tissue |
| Degerming | removal of microbes by mechanical means such as hand washing or alcohol swabbing |
| sanitization | removal of pathogens from objects that meet public health standards |
| Pasteurization | The heating of a substance to destroy pathogens and reduce number of spoilage microorganisms in foods and beverages |
| What is an agent called that kills bacterial? inhibits bacteria? | bactericidal and bacteriostatic |
| What is an agent called that kills fungi? inhibits fungi? | Fungicidal and fungistatic |
| What is an agent called that kills protozoa? inhibits protozoa? | protozoacidal and protozoastatic |
| What is an agent called that kills virus? inhibits? | virucidal and virustatic |
| What is an agent called that kills spores? inhibits? | sporicidal and sporistatic |
| Microbial death | permanent loss of reproductive abilities under optimal environment conditions |
| Microbial death rate | often constant for a microorganism under particular set of conditions ~90% in one minute |
| What should microbe regulating agent be? | inexpensive, accessible, fast-acting, stable during storage, capable of controlling microbial growth but harmless of humans, animals, and objects |
| factors affecting efficacy of antimicrobial methods? | site to be treated, environmental conditions, susceptibility of microorganism |
| site to be treated | some chemicals and heath cannot be used on humans, animals, or objects. also based on site of medical procedure |
| Relative susceptibility of microorganisms | some microbes more resistant than others to agents. bacterial endospores are most resistant followed by mycobacteria, and protozoa cyst |
| germicide classifications types? | High level germicide, intermediate-level germicide, and low-level germicide |
| High level germicide | kills all pathogens including endospores |
| intermediate-level germicide | kills fungal spores protozoan cyst, viruses, and pathogenic bacteria |
| low-level germicides | kills vegetative bacteria, Fungi, protozoa, and some viruses |
| Environmental conditions | temperature and pH affect microbial death rate. |
| What do organic materials do to efficacy? | they interfere with penetration of heat, chemicals, and some forms of radiation. can inactivate chemical disinfectants |
| What are the four levels of safety? | BSL1- BSL 4, 1 being relatively safe to 4 being extremely dangerous |
| Can physical and chemical methods be to treat infections inside the human body? | No but can be used to control microbial growth on non internal human tissues such as the skin |
| What are the 7 methods of microbial control? | Heat-related methods, refrigeration and freezing, desiccation and lyophilization, filtration, osmotic pressure, radiation, and degerming |
| What do Heat-related methods do? | denature proteins, interfere with integrity of cytoplasmic membrane and cell wall, and disrupt structure and function of nucleic acids |
| Thermal death point | amount of temperature it takes to kill all microbes in a broth culture in 10 minutes |
| Thermal death time | the amount of time it takes to kill or sterilize microbes in a broth culture at a set temperature |
| decimal reduction time | time it takes at a set temperature to reduce population of microbes by 90% |
| How many forms of heat-related methods are there? | Dry-heat and moist heat |
| Moist heat | used to disinfect, sanitize, sterilize, and pasteurize. it denatures proteins and destroys cytoplasmic membranes. it is more effective than dry heat, |
| What are methods of moist heat | boiling, autoclaving, pasteurization, ultra-high temperature sterilization |
| boiling | type of moist heat, kills vegetative cells of bacteria fungi protozoan trophozoites, and some viruses. boiling time is critical, endospores, protozoan cyst, and some viruses survive boiling |
| Autoclaving | pressure applied to boiling water prevents steam from escaping. boiling temperature increases as pressure increases. conditions include 121 C 15psi 15 minutes |
| pasteurization | used for milk, ice cream, yogurt, and fruit juices. it is not sterilization. |
| ultra-high temperature sterilization | 140 C for 1-3 sec then rapid cooling. treated substances can be stored at room temperature |
| Dry heat | used when moist heat is not possible, denatures proteins and oxidized metabolic and structural chemicals. requires higher temperatures and more time. |
| What is the ultimate form of sterilization | incineration |
| Refrigeration and Freezing | decreases microbes metabolism, growth, and reproduction bc chemical rxns are slower at low temperatures. effective with most pathogens. organisms vary in susceptibility to freezing and some organisms able to multiply in refrigeration |
| What is most effective when freezing | slow freezing |
| desiccation | drying inhibits growth due to removal of water |
| lypholization | freeze drying used for long-term preservation of microbe cultures. prevents formation of damaging ice crystals. |
| filtration | fluids are force through filter that traps microbes that are present. used for media that cannot be autoclave sterilized. filter size dictates what is allowed through |
| osmotic pressure | high concentrations of salt or sugar in foods to inhibit growth. cells in hypertonic solution of salt or sugar lose water. |
| what organism has a greater ability than bacteria to survive hypertonic environment | fungi |
| radiation types? | ionization and non-ionization radiation |
| ionization radiation | wv are shorter than 1 nm, ex: electron beams, gamma rays, x-rays. gamma rays penetrate well but require lots of time, electron beam effective but do not penetrate well, XR takes too long |
| nonionizing radiation | wv longer than 1 nm, excites electrons but does not form ions. it affects 3d structure of proteins and nucleic acids |
| UV light | causes pyramidine dimers in DNA, does not penetrate well |
| what is nonionizing radiation most suitable for | disinfecting air, transparent fluids, and surfaces of objects |
| Chemical methods | affects microbes cell walls cytoplamsic membranes proteins or DNA. the effect varies with environmental conditions |
| what are chemical methods most effective against | enveloped viruses and vegetative cells of fungi and protozoa |
| what are the 9 most commonly used chemicals | 1. phenol and phenolics, alcohols, halogens, oxidizing agents, surfactants, heavy metals, aldehydes, enzymes, and antimicrobial drugs. |
| Phenol and phenolics | denature proteins and disrupt cell membrane. most effective with organic matter and remain active for a long time. |
| where are phenols and phenolics used | in health care setting. have disagreeable smell and may have side effects. |
| alcohols | denature proteins and disrupt cytoplasmic membrane, intermediate level disinfectant more effective than soap, ex: ethanol, isopropanol, methanol |
| What can alcohol be used for and what is it not effective against | can remove microbes from skin when swabbed prior to injection. is not effective against endospores, fungal spores |
| Halogens | damage enzymes by denaturing. an intermediate level antimicrobial |
| Where are halogens used | iodine tablets, chlorine treatment, bleach |
| oxidizing agents | kill by oxidation of microbial enzymes. high level disinfectants and antiseptics |
| examples of oxidizing agents? | peroxides, ozone, and peracetic acid, hydrogen peroxide can disinfect and sterilize surfaces but not effective in open wounds bc of catalase, ozone treatment of drinking water and air. peracetic acid effective sporicidal used to sterilize equipment |
| Surfactants | surface active chemicals that reduce surface tension of solvents. includes soaps which have hydrophilic and hydrophobic ends (degerming but not antimicrobial), detergents positively charged organic surfants |
| heavy metals | denature proteins. low level bacteriostatic and fungistatic agents. |
| example of heavy metal usage? | 1% silver nitrate once used to prevent blindness caused by neisseria. thimerosal used to preserve vaccines |
| aldehydes | crosslink functional groups to denatyre proteins and inactive nucleic acids |
| Examples of aldehydes and their function | glutaraldehyde disinfects and sterilizes, and formalin used for embalming and disinfection of rooms and instruments . also formaldehyde |
| enzymes | antimicrobial enzymes acts against microorganisms |
| examples of enzymes | humans tears, saliva, breast milk cotain lysozyme |
| what does lysozyme do | digests peptidoglycan cell wall of bacteria. can be used to control microbes in environment such as cheese. |
| what does prionzyme do | removes prions on medical instruments |
| Antimicrobial drugs | used to treat diseases and some can be used outside the body. |
| examples of antimicrobial drugs | antibiotics, semisynthetic, and synthetic chemicals |
| What methods exist to evaluate disinfectants and antiseptics | Use-dilation test and in-use test |
| what does the in-use test entail? | a swab of an object before and after a disinfectant or antiseptic is used, The swab is then inoculated in a medium culture and incubated. Growth is then observed. it is an accurate measure pf strength and application procedure for specific situation |
| What does the use-dilution test entail? | metal cylinders are dipped into broth cultures and then immersed into various dilutions of disinfectants. the cylinders are then removed washed and placed into tube of medium. ex: broth medium checks for turbidity |
| What is the standard test for evaluation antimicrobials? | the use-dilution test |
| Do products containing antiseptic and disinfecting chemicals promote or add to human health? | There is little evidence |
| besides microbial control, what may antimicrobial products lead to? | resistant microbes |
Created by:
Acrob89
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