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Microbio Ch 11
Microbial Control
44
Microbiology
Not Applicable
10/20/2016

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Term
Controlling Microorganisms
Definition
Physical, chemical, and mechanical methods to destroy or reduce undesirable microbes in a given area (decontamination) ; Primary targets are microorganisms capable of causing infection or spoilage: a) Vegetative bacterial cells and endospores, b) Fungal hyphae and spores, yeast, C) Protozoan trophozoites and cysts, D) Worms, E) VirusesF) Prions
Term
Relative Resistance of Microbes
Definition
picture
Term
Highest resistance
Definition
Prions, bacterial endospores
Term
Moderate resistance
Definition
Pseudomonas sp., Mycobacterium tuberculosis, Staphylococcus aureus, Protozoan cysts
Term
Least resistance
Definition
Most bacterial vegetative cells, Fungal spores and hyphae, yeast, Enveloped viruses, Protozoan trophozoites
Term
Sterilization
Definition
a process that destroys all viable microbes, including viruses and endospores ex) autoclaving, ionizing radiation (correctly applied)
Term
Disinfection
Definition
a process to destroy vegetative pathogens, not endospores; inanimate objects ex) 5% bleach, boiling water
Term
antiseptic
Definition
disinfectants applied directly to exposed body surfaces ex) iodophors, antibacterial soap, chlothexidine
Term
Sanitization
Definition
any cleansing technique that mechanically removes microbes ex) dishwashing, laundering clothes
Term
Degermation
Definition
reduces the number of microbes through mechanical means ex) surgical handscrub
Term
Microbial Death
Definition
Microbes are “dead” when they no longer replicate.; Hard to detect, microbes often reveal no conspicuous vital signs to begin with ; Permanent loss of reproductive capability, even under optimum growth conditions
Term
Factors That Affect Death Rate
Definition
number of microbes; nature of microbes in the population; temperature and pH of environment; concentration or dosage of agent; mode of action of the agent; presence of solvents, organic matter, or inhibitors
Term
Practical Concerns in Microbial Control, Selection of method of control depends on:
Definition
Does the application require sterilization? ; Is the item to be reused? ; Can the item withstand heat, pressure, radiation, or chemicals? ; Is the method suitable?; Will the agent penetrate to the necessary extent? ; Is the method cost- and labor-efficient and is it safe?
Term
Antimicrobial Agents’ Modes of Action
Definition
Cellular targets of physical & chemical agents: 1.The cell wall (cell wall becomes fragile and cell lyses; example: some antimicrobial drugs, detergents, alcohol) ; 2.The cell membrane (loses integrity; Examples: detergent or surfactants); 3. Protein and nucleic acid synthesis---prevention of a) replication, transcription or translation, ,b) peptide bond formation, c) protein synthesis (examples: chloramphenicol, ultraviolet radiation, formaldehyde) 4)Proteins --disrupt or denature proteins( examples: alcohols, phenols, acids, heatProtein Denaturation)
Term
Moist heat
Definition
lower temperatures and shorter exposure time; coagulation and denaturation of proteins.. time to sterilize 15 min (121C)
Term
Dry heat
Definition
moderate to high temperatures; dehydration, alters protein structure; incineration.. time to sterilize 600 min (121C)
Term
Thermal Death Measurements
Definition
Bacterial endospores most resistant – usually require temperatures above boiling
Term
Thermal death time (TDT
Definition
– shortest length of time required to kill all test microbes at a specified temperature
Term
Thermal death point (TDP)
Definition
lowest temperature required to kill all microbes in a sample in 10 minutes
Term
MOIST HEAT METHODS
Definition
Steam under pressure – sterilization ; Autoclave – 15 psi/121oC/10-15 min ; Steam must reach surface of item being sterilized; Item must not be heat or moisture sensitive ; Mode of action – 1. denaturation of proteins 2. destroys membranes and DNA
Term
Boiling Water
Definition
Boiling at 100oC for 30 minutes to destroy non-spore-forming pathogens
Term
Pasteurization
Definition
heat is applied to kill potential agents of infection and spoilage without destroying the food flavor or value ; 63°C–66°C for 30 minutes (batch method) ; 71.6°C for 15 seconds (flash method) ; Not sterilization – kills non-spore-forming pathogens and lowers overall microbe count; does not kill endospores or many nonpathogenic microbes
Term
Dry heat
Definition
using higher temperatures than moist heat; baking ; Incineration – flame or electric heating coil--Ignites and reduces microbes and other substances; Dry ovens – 150–180oC – coagulate proteins ; Using Heat for Sterilization and Disinfection
Term
Cold --Microbiostatic
Definition
slows the growth of microbes; Refrigeration 0–15oC ; Freezing <0oC ; Used to preserve food, media, and cultures ;
Term
Desiccation
Definition
Gradual removal of water from cells, leads to metabolic inhibition (not death) ; Not effective microbial control – many cells retain ability to grow when water is reintroduced ; Lyophilization – freeze drying; preservation
Term
Ionizing radiation
Definition
deep penetrating power with sufficient energy to cause electrons to leave their orbit ; breaks DNA ; Gamma rays, X-rays, cathode rays ; Used to sterilize medical supplies and food products; Application of Ionizing Radiation: Preserving food with ionizing radiation
Term
Nonionizing radiation
Definition
little penetrating power ;requires direct exposure ; UV light à pyrimidine dimers - interfere with replication ; Application of Nonionizing Radiation: Sterilizing air, water or surfaces
Term
Filtration
Definition
Physical removal of microbes by passing a gas or liquid through a filter; 0.4mm – fungi, protozoa, algae, dirt, 0.2mm – bacteria ; Used to sterilize ---heat sensitive liquids----air in hospital isolation units and industrial clean rooms
Term
Chemical Agents in Microbial Control
Definition
Disinfectants, antiseptics, sterilants, degermers, and preservatives; Some desirable qualities of chemicals: a) Rapid action in low concentration, b) Solubility in water or alcohol, stable c) Broad spectrum, low toxicity, d)Penetrating, e) Noncorrosive and nonstaining F)Affordable and readily available
Term
High-level germicides
Definition
kill endospores; may be sterilants; Devices that are not heat sterilizable and intended to be used in sterile environments (body tissue
Term
Intermediate-level germidice
Definition
– kill fungal spores (not endospores), tubercle bacillus, and viruses ; Used to disinfect devices that will come in contact with mucous membranes but are not invasive
Term
Low-level germicide
Definition
eliminate only vegetative bacteria, vegetative fungal cells, and some viruses; Clean surfaces that touch skin but not mucous membranes ;
Term
Factors that Affect Germicidal Activity of Chemicals
Definition
Nature of the material being treated; Degree of contamination ; Time of exposure ; Strength and chemical action of the germicide ; Chemical Agents Used in Health Care ;
Term
Germicidal Categories
Definition
1.Halogens 2. Phenolics 3. Chlorhexidine 4.Alcohols 5.Hydrogen peroxide 6.Aldehydes 7.Gases 8. Detergents & soaps 9. Heavy metals 10. Dyes 11. Acids and Alkalis
Term
Halogens
Definition
Chlorine – Cl2, hypochlorites (chlorine bleach), chloramines ; Denaturate proteins by disrupting disulfide bonds ; Intermediate level ; Unstable in sunlight, inactivated by organic matter ; Water, sewage, wastewater, inanimate objects ; Iodine - I2, iodophors (betadine); Interferes with disulfide bonds of proteins; Intermediate level ; Milder medical and dental degerming agents, disinfectants, ointments;. Phenolics --Disrupt cell walls and membranes and precipitate proteins ; --Low to intermediate level – bactericidal, fungicidal, virucidal, not sporicidal—Lysol; Triclosan – antibacterial additive to soaps
Term
Chlorhexidine
Definition
A surfactant and protein denaturant with broad microbicidal properties ; Low to intermediate level ; Hibiclens, Hibitane ; Used as skin degerming agents for preoperative scrubs, skin cleaning, and burns
Term
Alcohols
Definition
Ethyl, isopropyl in solutions of 50-95% ; Act as surfactants dissolving membrane lipids and coagulating proteins of vegetative bacterial cells and fungi ; Intermediate level
Term
Hydrogen Peroxide
Definition
Produce highly reactive hydroxyl-free radicals that damage protein and DNA while also decomposing to O2 gas – toxic to anaerobes ; Antiseptic at low concentrations; strong solutions are sporicidal
Term
Aldehydes
Definition
Kill by alkylating protein and DNA ---Glutaraldehyde in 2% solution (Cidex) used as sterilant for heat sensitive instruments; (High level ) ; ----Formaldehyde – disinfectant, preservative, toxicity limits use ;(Formalin – 37% aqueous solution; Intermediate to high level)
Term
Gases and Aerosols
Definition
Ethylene oxide, propylene oxide ;Strong alkylating agents ; High level ; Sterilize and disinfect plastics and prepackaged devices, foods
Term
Detergents and Soaps
Definition
Quaternary ammonia compounds (quats) act as surfactants that alter membrane permeability of some bacteria and fungi; Very low level ; soaps—mechanically remove soil and grease containing microbes
Term
Heavy Metals
Definition
Solutions of silver and mercury kill vegetative cells in low concentrations by inactivating proteins; Oligodynamic action ; Low level ; Merthiolate, silver nitrate, silver
Term
Dyes as Antimicrobial Agents
Definition
Aniline dyes, like Crystal Violet, are very active against Gram-positive species of bacteria and various fungi ; Sometimes used for antisepsis and wound treatment ; Low level, narrow spectrum of activity
Term
Acids and Alkalis
Definition
Low level of activity; Organic acids prevent spore germination and bacterial and fungal growth ; Acetic acid inhibits bacterial growth ; Propionic acid retards molds ; Lactic acid prevents anaerobic bacterial growth ; Benzoic and sorbic acid inhibit yeast
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