Sterilization, Disinfection, and Antisepsis

Question 1

sterilization

Answer 1

• describes a process that destroys or eliminates all forms of microbial life and is carried out in health care facilities by physical or chemical methods
• reduces numbers of microorganisms on a device to a level that is insufficient to transmit infectious organisms

Question 2

disinfection

Answer 2

• describes a process that eliminates many or all pathogenic microorganisms, except bacterial spores, on inanimate objects
• doesn’t necessarily kill all microorganisms
• reduces numbers of microorganisms on a device to a level that is insufficient to transmit infectious organisms

Question 3

Health care associated infections

Answer 3

• over a quarter of all hospital acquired HAIs are caused by four types of infections:
• pneumonia
• bloodstream infection
• urinary tract infection
• surgical site infection

Question 4

high level disinfection

Answer 4

• destroys all microorganisms except high number of bacterial spores
• pasteurization and liquid immersion in chemical sterilants (used for heat sensitive semi-critical items such as GI endoscopes, bronchoscopes

Question 5

intermediate level disinfection

Answer 5

• destroys vegetative bactera, mycobacteria, most viruses, most fungi, not bacterial spores
• hospital disinfectants with label claim regarding tuberculocidal activity used in non critical patient care items or surfaces with visible blood
• chlorine based products

Question 6

low level disinfection

Answer 6

• destroys vegetative bacteria, some fungi and viruses, not sports or mycobacteria
• no tuberculocidal claim-phenolics, quants, 70-90% alcohol

Question 7

antisepsis

Answer 7

• the reduction of microorganisms on living skin/tissue

- do not kill spores and can’t be used as disinfectants

Question 8

HAI risk factors

Answer 8

• use of indwelling medical devices such as bloodstream, endotracheal, and urinary catheters
• transmission of communicable diseases between patients and HCWs
• surgical procedures
• injections
• contamination of healthcare environment
• overuse or improper use of antibiotics

Question 9

challenges to avoiding HAIs

Answer 9

• reprocessing of medical devices is a challenge w
• endoscopes are probably the most challenging reprocessing task in health care
• flexible endoscopes have intricate sophisticated small parts that are difficult to clean before they can be disinfected
• 23.0% of 71 internal channels grew more than 10^6 CFU and 78% of facilities didn’t sterilize forceps

Question 10

Ignaz Semmelweis

Answer 10

• professor of obsetrics
• thought particles from cadavers were spreading disease
• said they should soak hands in chlorine (1847)
• people called him crazy
• died in mental institution

Question 11

Florence Nightingal

Answer 11

-showed mortality rate in most hospitals was over 50%

Question 12

Joseph Lister

Answer 12

• 1865 Pasteur said decay was caused by organisms in air that cause fermentation-lister made connection with wound sepsis
• used carbolic acid to sterilize wounds
• ward remained clear of sepsis for 9 months
• 1869-spray techniques for aseptic surgery

Question 13

decontamination

Answer 13

• removal of debris, blood, and proteins and most microorganisms
• not necessarily rendering device safe to handle by HCWs who are not wearing protective attire

Question 14

critical items

Answer 14

• instruments or object that are introduced directly into the bloodstream of into other normally sterile areas of the body
• want sterilization

Question 15

semicritical items

Answer 15

• non-invasive flexible and rigid fiber optic endoscopes, endotracheal tubes, anesthesia breathing circuits and cytoscopes
• come into contact with mucous membranes or non intact skin, should be free of everything except spores
• high level disinfectant

Question 16

non-critical items

Answer 16

• those that either do not ordinarily touch the patient and touch only in tact skin
• have to be careful about MRSA

Question 17

cidal

Answer 17

• killing of microoganism
• germicides
• kill microbes but not necessarily their endospores

Question 18

static/stasis

Answer 18

-inhibit growth or multiplication of microorganism

Question 19

Resistance

Answer 19

• there is a scale of how resistant bacteria and viruses are to various disinfectants
• lipid enveloped viruses most susceptible, prions most resistant

Question 20

conditions influencing the effectiveness of physical and chemical microbial agens

Answer 20

• population size
• type of microbe
• physiological state of microbe
• concentration or intensity of antimicrobial agent
• duration of exposure
• temperature
• environmental factors
• amount of organic contamination
• pH

Question 21

physical methods of microbial control

Answer 21

• heat-incineration, dry heat, moist heat (below 100-pasteurization, 100=boiling, above 100=autoclave
• radiation-UV, ionizing
• Filtration

Question 22

autoclaving

Answer 22

• steam under pressure
• 121 C/15 psi for 15-90 min
• 132 C /27 psi for 4-20 min
• minimal time required
• loading and packing critical to performance
• non toxic to patient staff and enviro
• rapidly microbicidal
• penetrates medical packaging, device lumens
• can’t use for heat sensitive instruments
• microsurgical instruments damaged by repeated exposure

Question 23

flash sterilization

Answer 23

• process of sterilizing unwrapped instruments
• uses steam for 3 min at 270 F (132 C) at 27-28 psi
• not routine, only OR

Question 24

pasteurization

Answer 24

does not achieve sterility but kills pathogens that might be present in milk, dairy products, beer-mycobacterium, salmonella

• classic-63 C 30 min
• flash-high temp short time (HTST) 72 C 15 sec rapid cooling
• ultra high treatments (UHT) 140 C less than 1 sec, rapid cooling

Question 25

filtration

Answer 25

• excellent way to sterilize solution of heat sensitive materials
• membrane filters of .1 mm thickness-cellulose acetate, cellulose nitrate, polycarbonate, polyvinylidene, difluoride
• pore size .45 or .22 mm for bacteria
• .01 mm for spirochetes, mycoplasma, viruses, and large proteins

Question 26

masks

Answer 26

• physical barrier between your mouth and nose and environment
• N95 are 95% efficient at filtering out particles that are greater than 3 micrometers in diameter
• droplets emitted by sneezing, coughing, talking are 5 micrometers or bigger, so these work well for flu or TB
• must be fit properly every time they are used

Question 27

ionizing radiation

Answer 27

• gamma, x, high E electron beams
• ionization of water forms highly reactive hydroxyl radicals
• uses-pharmaceuticals, disposable dental and medical supplies (syringes, gloves, sutures)

Question 28

nonionizing radiation

Answer 28

• UV-thymine dimers inhibit replication of DNA
• not penetrating
• damages eyes, skin cancer, burns

Question 29

irradiated blood products

Answer 29

• irradiated RBCs help to prevent graft versus host disease

- prevents proliferation of leukocytes and T cells so the graft can’t attack the host

Question 30

irradiated food

Answer 30

• destroys bacteria by damaging DNA
• prolongs shelf life of food in cases where microbial spoilage is the limiting factor
• treatment of hamburger eliminates the residual risk of a contamination by e coli

Question 31

phenol and phenolics

Answer 31

• exert antimicrobial activity by injuring PM, inactivate enzymes and denature proteins
• carbolic acid irritates skin and smell
• used to intermediate and low level disinfection
• triclosan-only good for gingivitis and may be contributing to antibiotic resistance

Question 32

hexachlorophene (pHisoHex)

Answer 32

• most active against gram pos bacteria (staph aureus)
• toxic in newborns
• now used for staph skin decolonization in patients undergoing prosthetic or cardiac valve implant surgery

Question 33

chlohexidine

Answer 33

• not a phenol deriv
• frequently used for disinfection of skin and mucous membranes
• chloraprep
• used for surgical hand scrubs and preop skin prep
• low toxicity, strong affinity to skin or mucous membranes
• killing effect by damaging PM
• effective against most vegetative bacteria but not sporicidal
• can be used in oral rinses
• some people allergic, some conferring resistance

Question 34

aldehydes

Answer 34

• work by forming covalent crosslinks with a number of organic functional groups on proteins
• formalin-37% aq solution of formaldehyde gas
• glutaraldehyde-used to sterilize hospital instruments
• less irritating and more effective that formaldehyde
• Cidex-bacteriocidal,tuberculocida, virucidal in 10 min, sporucidal in 3-10 hours
• only liquid disinfectant that can be considered a sterilant

Question 35

gaseous chemosterilizers

Answer 35

• ethylene oxide, propylene oxide
• denaturation of proteins by alkylation
• sterilize without heat
• sterilization of medical supplies and equipment:disposable plastic syringes, lensed instruments, artificial heart valves, heart lung machine, mattresses
• formaldehyde gas rarely used
• ethylene oxide requires aeration time to remove ETO residue- toxic, carcinogen, flammable

Question 36

formaldehyde gas

Answer 36

• AD-same as formalin, effective penetration
• DISAD-same as formalin, flammable, pot carcinogen, gas irritates
• uses-on site decontamination of biological safety cabinet, HEPA filters
• enclosed areas

Question 37

ETO has

Answer 37

• AD-broad spectrum, no heat/moisture, penetrates packing
• DISAD-flammable, reactive, carcinogen/mutagen, some items may need more than 24 hrs for outgassing
• uses:heat or moisture sensitive supplies, instruments, equipment

Question 38

Quaternary Ammonium Compounds

Answer 38

• Ad-combined detergent and germicidal activity, stable and working dilutions have low toxicity
• Disad-non-sporicidal, limited activity against viruses, mycobacteria, may support growth of bacteria
• uses-surface decontamination, floors, walls, equipment wipe down, antiseptic formulations available
• crestm cepacol
• can be resistant

Question 39

alcohols

Answer 39

• dehydrate cells, disrupt membranes and caus coagulation of protein
• may be used for hard surface disinfection of skin antisepsis
• isopropyl, methyl, and ethyl
• a 70% aqueous solution is more effective at killing microbes than absolute alcohols
• skin disinfectant, surface decontamination, bench top/cabinet wipedown
• inactivates most viruses with lipid envelope
• can’t penetrate protein rich materials
• flammable

Question 40

handwashing and sanitizer

Answer 40

• less time, more effective unless hands are visibly soiled
• reduces bacterial counts on hands
• more accessible than sinks
• physicians more willing than washing hands

Question 41

halogens-iodine and chlorine

Answer 41

• oxidizing agents and cause damage by oxidation of essential sulfydryl groups of enzymes
• chlorine reacts with water to form hypochlorous acid, which is microbicidal
• chlorine gas is used to bleach water
• household bleach can be used at a dilution of 1:10 in decontamination of spillage of infectious material
• disadvantage-unstable when diluted-needs to be made daily, don’t work on organic matter as well, may be corrosive

Question 42

iodine preparations

Answer 42

• tincture of iodine (2% iodine, 70% alcohol) is an antiseptic
• iodophores-iodine can be combined with neutral carriers such as polyvinylpyrrolidone to prepare iodophores such as povidone-iodine
• betadine,isodine
• iodophores permit slow release and reduce irritation of antiseptic

Question 43

heavy metals and organic acids

Answer 43

• metals combine with SH groups on proteins
• heavy metals-silver nitrate (1% for ohpthalmic prep), mercurochrome, copper sulfate, zinc chloride/oxide
• organic acid deriv-sorbic acid, benzoic acid, methylparaben, propylparaben

Question 44

h2o2

Answer 44

• acts on the microorganisms through its release od nascent oxygen, produces hydroxyl free radicals that damages proteins and DNA
• used at 6% concentration to decontaminate instruments and equipment such as ventilators
• 3% used for skin disinfection and cleaning of wounds and ulcers
• strong solutions are sporicidal
• decomposes in light, broken down by catalase, proteinaceous organic matter drastically reduces activity

Question 45

Peracetic Acid

Answer 45

• mixture of acetic acid and h2o2 in aq soln
• PAA disinfects by oxidizing the outer cell membrane of vegetative bacterial cells, endospores, yeast, and mold spores
• cooling tower water disinfectant where it prevents biofilm/legionella
• effective for sanitizing fowl carcasses without affecting skin or flesh-applied to meat
• plasma (gas phase) sterilization

Question 46

plasma sterilization

Answer 46

• beneficial for sterilizing temperature sensitive polymeric material (endoscopes)
• safe, non tixic dry, low temp sterilization in 1 hour
• generated in an enclosed chamber under deep vacuum using UV or microwaves to create free radicals in a gaseous phase
• free radicals kill bacteria

Question 47

STERRAD

Answer 47

• uses low temp h2o2 gas plasma tech to sterilize instruments and medical devices
• quick reprocessing
• express cycle for da Vinvci 3D endoscopes and other devices without lumens
• processes a wide range of instruments including multiple single channel flexible endoscopes, cameras, rigid scopes, light cords, batteries, power drills