Antisepsis and Sterilization

Question 1

what are Koch’s postulates?

Answer 1

(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

Question 2

what is a nosocomial infection?

Answer 2

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

Question 3

what is the assumption with a nosocomial infection?

Answer 3

hospital acquired

Question 4

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

Answer 4

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

Question 5

reasons for high rates of healthcare-associated infections include:

Answer 5

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

Question 6

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

Answer 6

proper hand hygiene

Question 7

define disinfectant

Answer 7

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

Question 8

define antiseptic

Answer 8

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

Question 9

define bacteriostatic

Answer 9

agent that inhibits bacterial growth

Question 10

define bactericidal

Answer 10

agent that destroys or inactivates bacteria

Question 11

phenolics and alcohols ___ proteins and disrupt ___

Answer 11

denature; cell membranes

Question 12

iodine is a halogen that works by ___

Answer 12

iodinating and oxidizing bacterial proteins

Question 13

chlorine is another halogen that works by ___

Answer 13

oxidizing bacterial proteins

Question 14

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

Answer 14

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

Question 15

define sterilization

Answer 15

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

Question 16

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

Answer 16

physical; probability

Question 17

physical methods of control include:

Answer 17

heat, cold, filtration, radiation

Question 18

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

Answer 18

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

Question 19

describe autoclaving

Answer 19

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)

Question 20

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

Answer 20

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

Question 21

does boiling sterilize?

Answer 21

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

Question 22

does pasteurization sterilize?

Answer 22

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

Question 23

what is the purpose of pasteurization?

Answer 23

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

Question 24

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

Answer 24

slow the growth

Question 25

what are cellulose membrane filters?

Answer 25

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

Question 26

does filtration sterilize?

Answer 26

no, technically only disinfects

Question 27

does non-ionizing radiation sterilize?

Answer 27

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

Question 28

what is the drawback to non-ionizing radiation?

Answer 28

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

Question 29

does ionizing radiation sterilize?

Answer 29

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

Question 30

what is the drawback to ionizing radiation?

Answer 30

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