Chapter 6
This is the chapter that is entirely made up of notes, Martinellians.
Terms
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- Ionizing
- (most energy) short wavelength (gamma, X) cause free radicals in organisms-used only on medical supplies
- Peroxygens
- H2)2, benzoylperoxide, and peracetic acid OXIDIZE microbial cells
- bisphenols
- skin antiseptics vs. Gm.+ staph/strep ex. hexachlorophene
- autoclaving
- steam at 11 C and pressurea t 15 psi kills all microbes and endospores in 15 minutes-used for equipment and media; pressure cooker gives similar results
- Cl2
- forms hypochlorous acid when mixed w/H20; increase/decrease Legionella in air conditioner towers
- Phenolics
- cresols, bisphenols, bignanides (not really a phenol) (phenol only used in sm. concentration due to irritation) damage plasma membrane and denature proteins
- Yersima enterocolitica
- Gram negative, rod, gastroenteritis
- Surfectants
- soap, quats-cationic antiseptic; decreases surface tension of molecule in a liquid
- Deinococcus radiodurans
- endrues high amounts of radiation; being used to clean up radiation sites
- disinfectant
- kills microbes on non-living surfaces
- osmotic pressure
- due to salting/sugaring food-dries out microbes by increasing osmotic pressure-water leaves the cell (shrink)
- pasteurization
- HTST; high temp, short time (72C, 15 sec) kills pathogens; UHT-ultra high temp, short time (141C, 2 sec) sterilizes; needs no refrigeration
- phenol
- chemical that eliminates microbes in living tissue
- incineration
- flaming/burning-directly on loops, objects
- bignanides
- NOT a phenol, but similar chemical ex. chlorhexidine (non-toxic)
- most heat denatures faster with
- H20-achieves sterilization
- Dr. Semmelweiss
- proved childbirth fever was transmitted by doctors' hands
- refrigeration
- 0-7C is bacteriostatic except to psychotrophs
- Heat
- kills by denaturing (breaking bonds of) proteins (enzymes)
- boiling
- 100C kills in 10 minutes, except Hepatitis in 30; endospores in 15 hours
- Cold
- slows growth by decreasing enzyme action
- vegetative pathogens
- growing, but not reproducing, or producing endospores
- physical methods
- temp; filtration; drying radiation
- hot air sterilization
- 170C, 2 hours
- Deep freezing
- (-50C to -95C) and lyophilization (freeze drying) preserves microbes by dormancy
- TDP
- thermal death point
- TDT
- thermal death time-lowest amount of temperature and time needed to kill spec. microbes
- bactericide
- kills bacteria
- halogens
- I2 + Cl2-both germicidal; I2 decreases protein fn; combined with iodospohore (organic molecule); it's used as a skin antiseptic (Betadine, povidone)
- Filtration
- seperates microbes from medium by passing through pores (HEPA, cellulose filters)
- microbial death by any method is
- at a constant rate
- sterilization
- only process that kills all forms of both microbes and endospores
- soap
- emulsifies dirt on skin; anionic ( - )
- dry heat
- sterilization (needs more time w/out water which conducts heat better than air)
- chemical methods
- phenolics; halogens; alcohols; aldehydes; heavy metals; surface-actives; acids; peroxygens
- heavy metal
- denatures proteins by olgodynamic action Ag, Cu, Zu, Hg used as antiseptics and disinfectants
- ethylene oxide gas sterilizers
- very effective, carcinogenic
- cresols
- disinfectants on inanimate objects (lysol)
- Dr. Lister
- used phenol as 1st antiseptic
- How does one choose control methods?
- based on microbe type and environment
- Nonionizing
- wavelength causes thymine dimers in DNA; less radiation, used in food
- control methods
- work by damaging cells structure such as DNA, RNA, or protein
- microbial environment
- amount of H20; temp; pH; concentration of the microbe and controlling agent; presence of organic material
- evaluating effectiveness by use of dilution tests or filter paper
- uses the ability to kill broad spectrum of microbes
- Aldehydes
- denatures proteins-Formaldehyde + Glutaraldehyde used to sterilize medical instruments
- resistant microbes
- bacterial endospores and protozoan cysts, mycobacteria and nonenveloped viruses
- Dessication
- keeping canvas dry decreases microbial growth/reproduction; mycobacteria and viruses and fungal spores are resistant
- bacteriostats
- decline bacterial growth
- Radiation
- ionizing, nonionizing; increases microbial death by damaging DNA
- Peroxide
- not good for open wounds since human cells contain catalase which breaks it down, but it can be used on nonliving surfaces
- Alchohol
- bacteria/fungi-cidal, but ineffective vs. endospores + nonenveloped viruses, 70% Ethanol (Isopropyl) is better than 95%
- quats-cationic antiseptic
- kills bacteria, fungi, + environmental viruses; Pseudomonas is resistant ex. cepacal, benzalkonium chloride