mb w12 (methods of infect control)

Differentiate Static/Cidal

q on quiz on static vs. cidal!

• Bacteriostatic – arresting the growth or multiplication of bacteria.

• Fungistatic – inhibition of the growth of fungi.

• Virustatic – arresting the growth or multiplication of viruses.

• Bactericidal – destructive to bact (kills), doesn’t nec kill bact endospores.

• Fungicidal – an agent that destroys/kills fungi.

• Virucidal/Viricidal – capable of neutralizing or destroying a virus.

Terms

Sepsis

• Life-threatening organ dysfxn caused by body's dysreg response to infection.

• Can lead to tissue damage, organ fail, septic shock, & death if not

treated promptly.

Asepsis

• Practices used to prevent contam by microorgs

• Helps reduce risk of infec in HC & lab settings.

• Includes hand hygiene, sterilization, disinfection, and use of sterile

technique.

More Terms

Antiseptic - ALIVE

• chemical agent that inhibits growth or activity of

  microorganisms on living tissue. A substance that prevents or arrests the

  growth or action of microorganisms either by inhibiting their activity or by

  destroying them; term used especially for preparations applied topically to

  living tissue

Antisepsis

• is the application of a chemical agent externally on a live surface

  (skin or mucosa) to destroy organisms or to inhibit their growth. Thus all

  antiseptics could be used as disinfectants, but all disinfectants cannot be

  used as antiseptics because of toxicity.

Disinfectant - DESK

• agent usually chemical, but may be a physical agent, such

as x-rays or ultraviolet light, that destroys microorganisms but may not kill

bacterial spores; refers to substances applied to inanimate objects.

q on diff between sterilization & disinfect

Sterilization

• proc that kills/removes all orgs (& their spores) in a material/object

Sterility

• state of being sterile

Sanitization

• to make sanitary, as by cleaning or disinfecting

Sanitary

• free from elements, such as filth/pathogens, that endanger health

Sanitation

• proc by which # of microorgs on inanimate objects is reduced to safe lvl

• gen refer to a cleaning proc

Disinfection

• proc that kills/removes pathogenic orgs in a material/object, EXCLUDING bact spores, so they pose no infect threat

Microbial Resistance

“ Understanding the effects of particular physical, chemical, and mechanical agents on microorganisms makes it possible to use those agents, singly or in combination, to destroy microorganisms or reduce their numbers to tolerable levels.”

Effectiveness depend on…

• quant of microorgs present

• type of microorg/disease-causing agent

• factors affecting microbial control & its effectiveness

(temp, pH, presence of org matter, osmotic pressure, atmospheric conds (O2 avail))

Factors affecting microbial control

1. Size & density of the microbial pop

• larger pops may reduce the effectiveness of disinfection/sterilization

• high density can prevent full penetration of the agent, allowing some microorganisms to survive.

• smaller, less dense populations are more easily destroyed.

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2. Time of Exposure

• Microorganisms require sufficient contact time with a lethal agent for effective killing.

• Longer exposure generally results in a progressive reduction of microbial numbers.

• Given enough time and sufficient killing power, all microorganisms can eventually be destroyed.

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3. Microorg Susceptibility

• Not all microorganisms are killed instantly; susceptibility varies.

• Identifying the contaminating organism helps determine the required exposure time.

• There is no universal “rule of thumb”; complete destruction may take 15 mins to 10+ hrs dep on microorg & agent.

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4. Intensity/Conc of Antimicrobial Agent

• effectiveness of an agent depends on its concentration or intensity.

• each chemical agent has an optimal microbicidal concentration.

• ex: 70% isopropyl alcohol is more effective than 90%, because water in the solution helps denature proteins and penetrate cells.

Factors affecting microbial control

Presence of spores

• microbial populations often contain spores, which are highly resistant.

• The success of sterilization depends on effectively destroying spores.

• Most chemical agents are designed to reduce microbial populations, and rarely achieve full sterilization on their own.

Type & Age of Microorgs

• different microorganisms have varying susceptibility to physical and chemical agents.

• Some viruses and fungi are more resistant than vegetative bacterial cells.

• Non-enveloped viruses are typically more resilient than enveloped viruses.

1. Protein Vulnerability

• susceptibility of proteins in vegetative bact cells to denaturation

(by phys/chem agents largely determs their vulnerability)

2. Gram-Pos Bacteria

• Staphylococci and enterococci are more resistant to disinfectants than other Gram-positive bacteria.

3. Gram-Neg Bact

Pseudomonas spp.

• Opportunistic pathogens in surgical sites and burn patients

• Multiply rapidly in liquid soaps, weak disinfectants, and water containers

• Many strains of Pseudomonas aeruginosa are universally resistant to penicillin; antimicrobial testing is required to select an effective drug

Klebsiella spp.

• Opportunistic pathogen, especially in immunocompromised patients or those on antibiotics

• Can cause pneumonia

• More resistant to disinfectants than many other Gram-negative bacteria

microbial orgs differ in susceptibiltiy

Pseudomonas aeroginosa

persistance

• can survive in the human respiratory tract for long periods and often causes acute infections in open wounds, especially after surgery.

resistance to detergents

can survive exposure to some detergents and cleaning products, contributing to its persistence in moist environments, making it difficult to eliminate through routine hygiene

enzymatic defence* (if she tested would be this)

• bacterium secretes SdsA, an enzyme that cleaves SDS (sodium dodecyl sulfate/SLS), a detergent found in toothpaste, shampoo, and shower gels

mechanism

• SDS normally kills bacteria by disrupting their cell membranes. SdsA inactivates SDS, allowing P. aeruginosa to survive

nutrient use

• some strains can metabolize breakdown products of SDS/SLS as

  a carbon source

Sodium Lauryl Sulfate (SLS)

• anionic surfactant found in many toothpastes, shampoos, and cleaning products

• reduces surface tension & helps remove debris & microorgs

• can disrupt bacterial cell mems &denature prots. Some microorganisms, such as Pseudomonas aeruginosa, can produce enzymes that degrade SLS and reduce its antimicrobial effects.

• sodium Laureth Sulfate (SLES) is a related surfactant that is generally less irritating than SLS.

Microorgs of Concern in Microbial Control

spores of thermophilic Bacillus species

• resp for food spoilage

• more resistant to heat & disinfects THAN mesophilic Bacillus species

spores of Clostridium botilinum

• exhibit max resistance after 4-8 days of aging

Pyschrotrophs

• microorgs than can grow at 0°C (refrigeration temps)

• have optimal growth range of 25–30°C

• common causes of food spoilage in cold storage

review

Which factor makes a large microbial population more difficult to eliminate?

A. Increased mutation rate

B. Greater penetration of antimicrobial agents

C. More microorganisms must be destroyed and some may be protected within the population

D. Increased oxygen requirements

Why is 70% isopropyl alcohol generally more effective than 90% alcohol?

A. It evaporates faster.

B. It contains less water.

C. Water enhances penetration and protein denaturation.

D. It destroys bacterial spores.

Which group of microorganisms is most likely responsible for food spoilage in refrigerated foods?

A. Psychrotrophs

B. Mesophiles

C. Thermophiles

D. Halophiles

Which bacterial genus is known for surviving in moist environments and weak disinfectants?

A. Streptococcus

B. Lactobacillus

C. Pseudomonas

D. Neisseria

Some strains of Pseudomonas aeruginosa can:

A. Form endospores

B. Use breakdown products of SDS as nutrients

C. Survive only in dry environments

D. Destroy viruses

Which statement best explains why some Gram-negative bacteria are more difficult to control than many Gram-positive bacteria?

A. They produce endospores.

B. They lack a cell wall.

C. Their outer membrane can increase resistance to disinfectants and antimicrobial agents.

D. They are always anaerobic

Will test on this hierarchy**

Properties of Contam Materials

material limitations:

• plastic/rubber items

• may not tolerate high temperatures used in sterilization

organic material:

• accum blood/tissue/organic debris on instrument surfs can protect microorgs, increasing the time & effort required for effective disinfect/sterilization

Environmental Conds

temp

• higher temp generally enhance effectiveness of disinfectant

oxygen

• some chem agents require O2 to react & kill microorgs

pH

• effectiveness of some disinfectants is influenced by pH, with certain

  agents working better under acidic conditions

pressure

• Increased pressure, such as in autoclaving, allows steam to reach higher temperatures, improving microbial killing, including spores

“The synergistic effect of heat, oxygen, and acid pH often lowers the time of exposure to an antimicrobial agent required for disinfection or sterilization.”

Physical Factors

• knowing the environ conds that favor microbial growth help determ how to apply phys agens to destroy microorg effectively

• many microorgs grow optimally within narrow ranges of temp, osmotic pressure, & atmospheric conds

• application: by altering these conds (ex: inc temp, adjust humidity, change O2 avail), we can inhib growth or ehance microbial destruct

Dry Heat Sterilization

method - use intense heat to sterilize metal instruments & glassware

requirements:

• instrum must be clean & free of oil/grease/org debris (can insulate microorg & reduce effectiveness)

• hot air must circulate around all surfaces

typical parameters: testable*

• 160–165°C for 2 hours

• 170–180°C for 1 hour

limitations:

• time-consuming = less practical for high vol/urgen sterilization needs

Moist Heat Sterilization

121.5°C for 20 min**

advantages over dry heat:

• faster & more effective

• work at lower temps & shorter exposure times

boiling:

• kills vegetative cells in 20-30 min

• spores need 30min-6hr of boiling

• heat-resistant endospores, mycobacteria, and some viruses

  may survive

key consideration:

• some thermophilic microorganisms and bacterial endospores can survive temperatures that would kill many other microorganisms

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method

• steam under pressure is the most efficient form of moist

mechanism

• pressure allows steam to reach higher temperatures, effectively killing microorganisms

typical parameters:

• 15 psi

• 121.5°C (121 °C -134 °C)

• 20 min

effectiveness

consideration

Heat Sterilization

chem vapour sterilization

• method

• mech

guidelines

BCCOHP provides infection prev & control (IPAC) guidance for OH profs

key sterilization reqs:

• weekly biological monitoring (spore testing) for each sterilizer

• daily monitoring & documentation of sterilizer, noting proper function or any malfxns & corrective action.

• external chemical indicators on every packaged instrument

• mechanical indicators (time, temp, pressure) reviewed for each sterilization cycle

• exposure management protocols for incidents involving blood-borne pathogens

IPAC guidance is a living doc & should be reviewed reg to ensure complaicne with currect evidence-based best practices

review

Physical methods of microbial control are effective because they:

A. Increase microbial growth rates

B. Alter environmental conditions beyond what microorganisms can tolerate

C. Always destroy bacterial endospores

D. Work only on bacteria

Which characteristic is a major limitation of dry heat sterilization?

A. It requires higher temperatures and longer exposure times than steam sterilization.

B. It cannot destroy bacterial spores.

C. It cannot be used on metal instruments.

D. It requires liquid chemical sterilants.

What is the primary advantage of moist heat over dry heat?

A. It destroys all spores during boiling.

B. It works at lower temperatures and shorter exposure times.

C. It does not require cleaning of instruments.

D. It is effective only against viruses.

Why is pressure used in an autoclave?

A. Pressure directly kills microorganisms.

B. Pressure dries instruments more quickly.

C. Pressure allows steam to reach higher temperatures.

D. Pressure removes organic debris.

What is a major limitation of chemical vapour sterilization?

A. It cannot destroy bacterial endospores.

B. It requires microorganisms to be actively growing.

C. It can only be used on plastic instruments.

D. Tightly wrapped or sealed packages may prevent adequate vapour penetration.

Which method is considered the gold standard for verifying that a sterilizer is

functioning effectively?

A. External chemical indicator

B. Biological monitoring (spore testing)

C. Mechanical monitoring (time, temperature, pressure)

D. Visual inspection of instrument packages

BCCOHP recs

instrumenting reprocessing areas

• bccohp rec a clear separation of contam & clean areas within instrument reprocessing area

one-way workflow should be maintained:

1. receiving, cleaning, & decontamination

2. inspection, preparation, and packaging

3. sterilization

4. cooling & drying

5. storage

goal

• prev cross-contam by ensuring instruments move in single direct (diry>clean>sterile storage)

reqs:

• sterilizer monitoring & documentation (cycle time, temp, &

  pressure)

• approp use PPE

• testing liquid chemical sterilants/high-level disinfectants according to

  manufacturer instructions

• no eating or drinking in contaminated instrument processing areas

best practices

• dedicated clinic-only uniform-scrub

• routine DUWL maint & flushing protocols

why matter?

• verify sterilization effectiveness

• prevent cross contam

• protect patients & oral health profs

• support compliance w bccohp IPAC standards

other methods of sterilization

Ethylene Oxide (EtO) Gas

• Gaseous sterilization, primarily used in hospitals and larger clinics, rarely in private dental offices.

Effectiveness: Kills all forms of microorganisms if adequate time, temp, & gas conc are used.

Exposure time:

• Several hours, followed by an aeration period

Post-sterilization handling:

– Items require aeration after sterilization to remove residual EtO gas.

– Plastic, rubber, or cloth goods: Must be aired for 24 hours to allow EtO gas to dissipate.

Advantages: Can sterilize heat-sensitive items that cannot withstand autoclaving.

Precautions: Toxic, flammable, and requires proper ventilation.

Ionizing

Sterilization

Biological Indicators (Spore tests) for sterilization

Microorgs used by sterilization type:

Steam Autoclave & Chemical Vapor

• Bacillus stearothermophilus (vials, ampoules, or strips)

Dry Heat Oven & Ethylene Oxide:

• Bacillus subtilis (strips)

Procedure:

– Place ampoule, vial, or strip in the center of a package; place package in

the middle of the sterilizer load.

– Run the sterilization cycle at the recommended time and temperature

After the cycle:

– Ampoules/Vials: Colour change indicates no surviving microorganisms.

– Strips: Culture to confirm no microbial growth.

Indications for Spore Testing in Dental Settings:

– Introduction of new packaging materials or trays.

– After training new personnel.

Sterilization Monitoring Methods:

1. mechanical indicators (time, temp, pressure)

2. chemical indicators (color-change indicators)

3. biological indicators (spore tests)

Microorgs Used by Sterilization Type:

• steam & chem vapor: Geobacillus stearothermophilus

• dry heat & ethylene oxide: Bacillus atrophaeus

Procedure:

• place indicator in the most challenging area of the load

• run the sterilization cycle

• incubate/submit according to manufacture instruct

Interpretation

• no microbial growth = success

• growth = failure

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Spore testing rec..

• weekly

• during initial uses of a sterilizer

• with every implantable device > tissues

• after any other change in the sterilizing procedure

• when training new personnel

What is the primary purpose of maintaining a one-way workflow in the instrument

reprocessing area?

A. To reduce sterilization cycle times

B. To prevent cross-contamination between dirty and clean instruments

C. To improve instrument organization

D. To decrease the need for biological monitoring

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Which of the following is considered a BCCOHP IPAC requirement?

A. Wearing clinic-only scrubs outside the workplace

B. Flushing waterlines between patients

C. Monitoring and documenting sterilizer cycle parameters

D. Using only disposable instruments

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What is the primary advantage of ethylene oxide (EtO) sterilization?

A. It sterilizes instruments in less than 5 minutes.

B. It can sterilize heat-sensitive items that cannot be autoclaved.

C. It is safer than steam sterilization.

D. It does not require aeration after sterilization.

Which statement about ionizing radiation is correct?

A. It is commonly used in dental offices for instrument sterilization.

B. It destroys microorganisms by damaging their DNA.

C. It is ineffective against bacterial spores.

D. It is primarily used for disinfecting environmental surfaces.

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Which statement best explains why prions require special decontamination procedures?

A. Prions are rapidly destroyed by routine autoclaving cycles.

B. Prions are highly resistant infectious proteins that may survive standard sterilization methods.

C. Prions form endospores that resist heat and disinfectants.

D. Prions are protected by a lipid envelope that prevents chemical penetration.

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Which sterilization monitoring method is considered the most reliable for confirming that

sterilization has been achieved?

A. Mechanical indicators (time, temperature, pressure gauges)

B. Chemical indicators (colour-changing tape or strips)

C. Biological indicators (spore tests)

D. Visual inspection of instrument packages

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Which of the following situations would NOT typically require additional biological monitoring

(spore testing)?

A. After repair of a sterilizer

B. Commissioning a new sterilizer

C. Training new personnel

D. Changing the brand of examination gloves

Tests For Sterilization

• confirms that autoclave reached designateed temp for sterilization

• routine use = applied to instrument packages (ex: indicator tape)

• mechanism = color change signals that autoclave reached

  required temp for penetration

Does NOT confirm sterilization

• only indicate that proper heat conds achieved

• actual microbial destruct depend on time, pressure, & proper loading

Review (Props of a Surface Disinfectant)

1. Non-toxic - safe for humans

2. Broad-spectrum -

3. Fast-acting -

4. Unaffected by org matter -

Sodium Hypochlorite

mech of action = destroy microorg by oxidizing microbial enzymes & cell wall components

uses

• cleaning dentures

• gen surface disinfect (chlorine compound)

stability

• unstable; use distilled water to improve stability

• prep fresh daily solns

limitations/precautions

• strong odour

• can irritate eyes & skin

• can damage clothing & surfs

advatages:

• economical

• widely available & effective

Synthetic Phenols (water/alcohol based)

• high conc =

• lower conc =

• broad spectrum activity w/ residual biocidal effect

• limitation = not effective against spores

common ex:

• lysol =

• pHiso

Quaternary Ammonium Compounds (QAC)

• cationic (pos-charge) surface-active germicides

mechanism

• disrupt phospholipid membranes on microbial plasma

  membranes, disrupting cell integrity, effective against Gram-positive

  bacteria

resistance:

• many Gram-negative opportunistic pathogens (ex: Pseudomonas spp.) show reduced susceptibility.

• spores & mycobacteria may not be destroyed

• Mycobacteria: aerobic, acid-fast rods (ex: Mycobacterium tuberculosis)

properties:

• highly stable

• non-irritating & odourless

• relatively expensive

Iodophors (iodine complexed w/ an organic material)

• compounds that contain iodine + detergent

• ex: betadine

mechanism:

• release iodine slowly (provide prolonged antimicrobial activity)

• broad-spectrum antimicrobial activity against many microorgs

Alcohols

mechanisms

• alcohols denature proteins and disrupt lipid membranes

• mem disruption especially important for effectiveness against enveloped viruses

advantages:

• safe, inexpensive, fast-acting

limitations:

• Limited activity against spores

• Ineffective against some non-enveloped viruses (e.g., echovirus, coxsackievirus)

• Alcohols are less effective in the presence of organic matter and are not recommended for disinfecting large blood spills

Glutaraldehyde

• conc = 2% solns (potent antimicrobial agents)

spectrum of activity:

• effective against acid-fact bacilli, vegetative bacteria, bact spores, fungi, virus

mechanism:

• kills microorgs by damaging prots & nucleic acids

• 10hr immersion is for cold chemical sterilization of heat-sensitive items

limitations:

• Not used as a surface disinfectant

• Produces toxic fumes

• Activated glutaraldehyde has limited shelf life and must be monitored according to manufacturer instructions.

Phenol Coefficient (PC) Test wont ask to calc but know & understand gist

• ratio of the highest dilution of the test disinfectant killing the test organism in 10 min to the highest dilution of phenol w/ the same germicidal activity

method:

standard oculum of a test org (ex: Salmonella typhi) added to serial dilutions of phenol & to dilutions of the test disinfectant

Disinfectants that Kill Viruses

high lvl disinfectant

• destroy all microorgs EXCEPT large #s of bact spores w/ routine exposure times

• prolonged exposure may achieve sterilization

• ex: Formalin (5-37%) = kill vegeatative bact/spores/fungi/virus

• ex: Glutaraldehyde (2%) = kills acid-fast bacilli/spores/fungi

intermediate lvl disinfectants

low lvl disinfectant

Clean & Disinfect Environmental Surfs

effectiveness relies on 2 actions":

1. physical removal of debris & contaminants

2. chemical inactivation of microorgs

procedure

• thoroughly clean entire surf (+crevices, irregs)

• 
  

Sterilization

Ultrasonic Cleaning

• cleaning proc only, DOESN’T disinfect/sterilize

• preps instruments for subsequent disinfect/sterilization by removing debris & org matter

• pre-cleaning essential bc bioburden interfere w sterilization

Benefits

• Achieves a high level of cleanliness

• Reduces clinician exposure to potentially pathogenic microorganisms

• Improves the effectiveness of subsequent disinfection and sterilization

• Prevents aerosol and droplet release associated with hand scrubbing

• Penetrates hinges, serrations, and grooves unreachable by brushes

• Safe method of precleaning

Mechanism

• ultrasonic waves create microscoping bubbles (cavitation) that implode & dislodge debris & tarnish from instrument surfs

Advantages

• Eliminates hand scrubbing and reduces puncture and sharps injuries

• Cleans more thoroughly, including grooves and hinges

• Less time-consuming

– Produces less spatter and aerosols (keep lid closed)

isnt it always out of 100

the essay was on edulink