Antisepsis and Sterilization Flashcards
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
extended)
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
