Exam 3: Ch 9 Flashcards
Destruction of pathogenic organisms on inanimate objects; may not destroy endospores.
Disinfection
The destruction of pathogenic organisms on living organisms
Antisepsis
Physical removal of microorganisms from surfaces, like washing hands and taking a bath
Degerming
Reduction of microbes to a level deemed safe by public health guidelines as in restaurants
Sanitization
The destruction of all forms of life including endospores (strictly speaking not possible because prions are tough to destroy)
Sterilization
Bacterial contamination
Presence of bacteria in blood
Presence of actively reproducing bacteria in blood
Sepsis
Bacteremia
Septicemia
- cide suffix
- static or -stasis
To kill, biocides, germicide, fungicide, etc
Inhibit the growth and reproduction of; fungistasis, bacteriostatic
Factors affecting this rate are: number of microbes, environment, time, type of microbe
Rate of microbial death
Lowest temperature that will kill all cells in a liquid in 10 minutes
Thermal death point (TDP)
Physical Method
The minimum time for all bacteria to be killed in a particular volume of liquid at a set temperature
Thermal death time (TDT)
Physical Method
The time, in minutes, in which 90% of the bacteria will be killed
Decimal reduction time (DRT)
Physical Method
Common household items like baby bottles have this done at 100C for 10 minutes. Kills most pathogens. Hep B requires 2 hours.
Boiling
Moist heat
Protein denaturation
Dishes, etc
Steam under pressure at 121C, 15 psi, 15 minutes destroys all microbes including endospores, except prions
Autoclave
Moist heat
Protein denaturation
Medical uses
Low temperature treatment of dairy, wine, and beer at 63C for 30 minutes (classical method)
Pasteurization
Moist heat
Protein denaturation
High temperature short time (HTST) pasteurization
72C for 15 seconds
Beverages
Ultra-high temperature pasteurization (UHT)
140C for less than 1 second, maybe 3
Flaming, incineration, hot-oven sterilization at 170C for 2 hours.
Dry heat or hot air sterilization?
Burning to ashes
Oxidation
Instruments, glassware, needles, loops
Cause of death used for liquids sensitive to heat (serum and antiseria)
Membrane filter with pore sizes 22-44 um retain bacteria
HEPA (high efficiency particulate air) filter used in vents, operating rooms, and wards for immune compromised and burn patients
Causes bacteriostatic effect except in the care if psychrotrophs, which will alter the appearance and taste of food with time
Refrigeration (0-8C)
Food-borne pathogen L. monocytogenes, turkey cold cuts
Causes organisms to become dormant. The trichinosis roundworm is killed with several days of this method.
Freezing
Freeze-drying (shell freezing using chilled acetone). Water removed by high vacuum at low temperature.
Lyophilization
Causes the disruption and cessation of metabolism (eg drying of meat and fruit practiced for hundred of years)
Certain microbes and endospores remain viable and are important in hospital settings
Dessication
The use of high concentrates of salts and sugars creates a hypertonic environment and caused water to leave the cell- plasmolysis.
Fungi tolerate this better than bacteria, like growth of molds on jams.
Osmotic pressure
Destruction of DNA, gamma rays, X rays, or high energy electron beams. Marked with irradiation (Radora) logo
Ionizing radiation
Wavelength shorter than 1 mm
Used by USPS to sterilize mail after 9/11, sterilizing medical supplies and more recently for food preservation.
Causes damage to the DNA. Thymine dimer formation.
Non-ionizing radiation
Wavelength greater than 1nm so that it does not have enough energy to force electrons out of orbit.
UV lamp used in operating rooms and labs.
Microbes killed indirectly by heat, but uneven heating of pork has caused outbreaks of trichinosis
Microwaves
Comparison of action of unknown chemical disinfectant with that of phenol; old and obsolete method
Phenol coefficient to evaluate disinfectants and antiseptics
Metal carrier rings dipped into cultures of test bacteria; then dried at 37C. Dried cultures are placed in disinfectants at concentration recommended by the manufacturer for 10min at 20C. Carrier rings placed in a medium that will permit the growth of any surviving bacteria.
Dilution test
Salmonella choleraesuis, S. aureus, Pseudomonas aeruginosa
Carbolic acid used in antiseptic surgery; disadv. skin irritant and strong odor.
Phenol
Derivative of phenol with added halogens or functional groups. Less odorous and non-irritating to skin.
Cresols–used for outdoor latrines
Lysol -very good surface disinfectant.
Phenolics
Injures lipid membranes such as those of agents of TB and leprosy, enzyme denaturation
Contains 2 phenolic groups. Disadvantage is prolonged use associated with brain damage in infants
Bisphenols
Broad spectrum but mostly gram positive. Hexachlorophene containing Phisohex used in hospital nurseries during Staphylococcal and Streptococcal skin outbreaks.
Hand soaps and skin lotions, Triclosan
A bisphenol contained in antibacterial soaps, toothpaste and found in cutting boards and handles of kitchen knives.
Triclosan
Used as antiseptic as in surgical scrubs and preop scrubbing for surgical patients (e.g. Chlorhexidine)
Biguanides
Chlorhexidine disrupts the plasma membrane.
Both gram + and -
Nontoxic.
Destroys enzymes and cellular proteins. Strong oxidizing agents.
Halogens
Iodine, chlorine, bromine, fluorine
Used against all kinds of bacteria, endospores, fungi, and some viruses
As tincture and iodophor (e.g. Betadine and Isodine are povidone iodines); oldest antiseptic.
Iodine
Widely used in treatment of municipal water supply. Forms hypochlorous acid in water; strong oxidizing agent.
Chlorine
Bleach
70% ethanol or isopropyl. Works by denaturation of microbial proteins, needs water for this to happen. Dissolves envelopes of viruses.
Alcohols
Bacteria, fungi, and enveloped viruses but not endospores.
Swabbing, most common are ethanol and isopropanol.
Oligodynamic action. AgNO3 drops against ophthalmia neonatorum. Ag-impregnated catheter tips (vs. S. epidermidis catheter infections. Ag-sulfadiazine for burn patients. Mercurochrome contains mercuric chloride->Hg-cumulative poison.
Heavy metals
Denaturation of enzymes and essential proteins.
surface-active agents->surfactants (e.g. detergents and soaps for degerming; emulsify skin oils).
Cationic detergents
Quaternary ammonium compounds. Pseudomonas aeruginosa not only survive but grow in quats.
Zephiran and Cepacol
Mostly effective against gram +
Bactericidal, bacteriostatic, fungicidal, virucidal for enveloped viruses
Skin, instruments, utensils, rubber
Sorbic and benzoic acids. Nitrates and nitrites->meat preservative inhibit endospore-forming C. botulinum but carcinogenic.
Food preservatives
Organic acids
Metabolic inhibition on molds and some bacteria
Parabens in cosmetics
Formaldehyde and glutaraldehyde – destroy and coagulate proteins.
Aldehydes
Used in sterilizing surgical, dialysis and respiratory equipment. Sporicidal in 3-10hrs
Ethylene oxide on plastics (materials destroyed by heat)
Gaseous sterilants
Protein denaturation
Ozone used with chlorination-give drinking water fresh taste.
H2O2 – disinfectant.
Peracetic acid – sterilant.
Peroxygens
Oxidation
Range varies with application
Microbes from most resistant to least resistant
Prions→Endospores → Mycobacteria → Protozoan cysts → Protozoa →Gram-negative bacteria → Fungi → Nonenveloped viruses → Gram-positive bacteria → Enveloped viruses
