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Flashcards in Antisepsis and Sterilization Deck (30)
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what are Koch's postulates?

(i) the microbe must be present in all disease cases
(ii) the microbe must be isolated from the infected host and grown in pure culture
(iii) when a pure culture is introduced into a susceptible host, the disease must be reproduced
(iv) the microbe must be isolated from a purposely infected host


what is a nosocomial infection?

infections whose onset and confirmation occur >48 hours after hospital admission


what is the assumption with a nosocomial infection?

hospital acquired


in addition to nosocomial infections, healthcare-associated infections include:

infections occurring within 6-12 months of systemic antibiotic treatment, residence in a long-term care facility, central IV catheterization, urinary catheterization, or any form of dialysis


reasons for high rates of healthcare-associated infections include:

high prevalence of pathogens in healthcare settings, a high prevalence of compromised patients, and the efficient transmission of pathogens from patient to patient by unknowing personnel


The single most important method to limit the transmission of nosocomial agents is ___

proper hand hygiene


define disinfectant

a physical or chemical agent used to inhibit or destroy microorganisms on inanimate objects


define antiseptic

a physical or chemical agent used to inhibit or destroy microorganisms on skin or other tissue


define bacteriostatic

agent that inhibits bacterial growth


define bactericidal

agent that destroys or inactivates bacteria


phenolics and alcohols ___ proteins and disrupt ___

denature; cell membranes


iodine is a halogen that works by ___

iodinating and oxidizing bacterial proteins


chlorine is another halogen that works by ___

oxidizing bacterial proteins


what are surfactants contain ___ groups and are so named bc they perturb ___

hydrophobic and hydrophilic; bacterial cell membranes (leading to cell death)


define sterilization

complete killing or removal of all living organisms from an item or area


sterilization is best accomplished by ___ methods and is considered achieved on the basis of ___

physical; probability


physical methods of control include:

heat, cold, filtration, radiation


which kills more rapidly, moist or dry heat? why?

moist, because reactive water molecules denature protein by disrupting hydrogen bonds formed between amino acids


describe autoclaving

subjects objects or liquids to steam plus pressure to increase the boiling temp of water above 100C; autoclaving at 15 PSI and 121C for 15 minutes will kill all bacteria, fungi, and viruses (to kill spores and cysts, time is


why does baking require higher temps and longer time than autoclaving?

bc it uses dry instead of moist heat which conducts heat less effectively (min = 160C for 2 hrs)


does boiling sterilize?

no, but it kills most everything except spores or cysts within 10 minutes


does pasteurization sterilize?

no, bacterial load is reduced by 90% and spores are not killed


what is the purpose of pasteurization?

make milk and juices safe for consumption and increase their storage life


refrigeration and freezing ___ of most all pathogens and therefore complement pasteurization as a strategy to ensure food safety and storage

slow the growth


what are cellulose membrane filters?

filters that are able to remove live and dead bacteria from liquids


does filtration sterilize?

no, technically only disinfects


does non-ionizing radiation sterilize?

because it excites electrons and leads to the formation of new covalent bonds, such as thymine-thymine dimers in DNA (ex: UV)


what is the drawback to non-ionizing radiation?

poor cell penetration properties due to long wavelength, limiting its usefulness


does ionizing radiation sterilize?

yes, shorter wavelengths (x ray or gamma ray) provide more energy and better cell penetration


what is the drawback to ionizing radiation?

transmitted energy damages DNA but also produces free radicals and creates hydrogen peroxide from cytoplasmic water