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Microbiology for Dentists > 43. Control of Microorganisms > Flashcards

43. Control of Microorganisms Flashcards

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1
Q

Chain of infection

A
  • means of transmission
  • portal of entry
  • susceptible host
  • pathogen
  • resevoir
  • portal of exit
  • back to means of transmission
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2
Q

How to control the chain of pathogens

A
  • stop the connections
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3
Q

Explain targeted precautions

A
  • use standard infection control precautions
  • patient specific - medical history
  • agent specific
  • procedure specific - risk assessment, aerosol generating or not
  • if you don’t leads to an outbreak scenario
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4
Q

Standard precautions in dentistry

A
  • hand hygeine
  • PPE
  • sharps safety
  • sterilization/disinfection
  • surgery design
  • dental unit waterlines
  • waste management
  • vaccines/screening
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5
Q

List infectious agents

A
  • respiratory viruses
  • blood borne viruses
  • bacteria
  • prions
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6
Q

Examples of respiratory viruses

A
  • common colds (rhinovirus)
  • influenza A
  • SARS-CoV-2
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7
Q

Examples of blood borne viruses

A
  • HBV
  • HCV
  • HIV
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8
Q

Examples of infectious bacteria

A
  • mycobacterium tuberculosis
  • MRSA
  • pseudomonads
  • Legionella pneumophilia
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9
Q

Major infectious concerns in dental clinic

A
  • blood borne viruses
  • respiratory viruses
  • mycobacterium tuberculosis
  • MRSA
  • psuedomonas
  • Legionella
  • prions
  • seasonal virus like norovirus, common cold
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10
Q

What do we have lesser resistance to?

A
  • enveloped viruses the least
  • gram positive bacteria
  • large, non-enveloped viruses
  • vegetative protozoa and helminths
  • vegetative fungi a bit more
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11
Q

What do we have greater resistance to?

A
  • prions the most
  • bacterial spores
  • protozoal cysts/helminth eggs
  • mycobacteria
  • small, non-enveloped viruses
  • fungal spores
  • gram negative bacteria
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12
Q

Routes of transmission for infectious agents

A
  • patient to patient
  • patient to dentist
  • dentist to patient
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13
Q

What is nosocomial transmission?

A
  • originating or taking place in hospital, acquired in hospital especially in reference to infection
  • secondary to the original cause of treatment
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14
Q

What is iatrogenic transmission?

A
  • due to action of physician or therapy
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15
Q

What is idiopathic transmission?

A
  • of unknown cause
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16
Q

Examples of nosocomial infections

A
  • UTIs
  • pneumonia
  • GI infections
  • catheter-associated UTIs
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17
Q

Examples of iatrogenic transmission

A
  • medical errors
  • poor prescribing handwriting
  • prescription drug interactions
  • improper medical treatment
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18
Q

Transmission requires what 3 things?

A
  • a source of infection like index case (person to person) or contamination
  • a vehicle (like blood, saliva, contaminated instruments)
  • a route (one of 6)
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19
Q

3 ways people can be a source of infection

A
  • overtly infected
  • incubating a disease
  • healthy carriers
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20
Q

How is an overtly infected person a source of infection?

A
  • large numbers of microbes or infectious agents can be liberated
  • patients with serious acute infections are not common
  • like COVID-19, influenza, HIV, colds
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21
Q

How is a person incubating a disease a source of infection?

A
  • prodromal stage of infection (early onset symptoms)
  • sometimes no signs of disease
  • can be highly infectious (COVID-19, measles, mumps, chickenpox)
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22
Q

How can healthy carriers be a source of infection?

A
  • convalescent carriers - past sufferers, persistant resevoirs of infection like strep sore throat, Hep B or diphtheria
  • asymptomatic carriers with no past history maybe a sub-clinical infection like Hep B, COVID-19
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23
Q

Sources other than people of infection

A
  • environmental micro-organisms
  • normal commensal microflora
  • issues like compromised patients, cutting tissue, overt pathogens like HIV, Hep B, opportunistic pathogens
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24
Q

How do environmental micro-organisms cause disease?

A
  • environmental mycobacteria
  • clostridioides spp. etc
  • length of survival time in environment allows
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25
Q

Which kind of normal commensal microflora can cause infection?

A
  • staph (epidermidis and aureus)
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26
Q

Give vehicles for infections

A
  • blood
  • saliva
  • direct contact/skin
  • objects/fomites
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27
Q

Blood is the vehicle for what infections?

A
  • HIV
  • Hep-B
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28
Q

Saliva is the vehicle for what infections?

A
  • Glandular fever/infectious mononucleosis - Epstein Bar Virus
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29
Q

Direct contact is the vehicle for what infections?

A
  • staphylococci
  • non-commensal contamination
30
Q

Objects such as … can be vehicles for infection

A
  • instruments
  • clothing
31
Q

Give 6 routes of transmission

A
  • in utero
  • inhalation
  • ingestion
  • implantation
  • inunction
  • injection
32
Q

Explain in utero transmission

A
  • placenta is barrier for most microbes
  • syphilis, cytomegalovirus, rubella
  • low relevance to clinic
33
Q

Explain inhalation transmission

A
  • across most surfaces
  • aerosols
  • strep pyogenes, neisseria meningitidis, mycobacterium tuberculosis
  • high relevance to clinic
34
Q

Explain ingestion transmission

A
  • usually food and drink but in dental clinic, objects introduced to mouth
  • strep pyogenes, neisseria meningitidis, mycobacteium tuberculosis
  • high relevance to clinic
35
Q

Explain implantation transmission

A
  • often via trauma to skin
  • staph epidermidis and aureus
  • C. tetani and perfringens
  • strep pyogenes
  • high relevance to clinic
36
Q

Explain inunction transmission

A
  • microbes driven into tissue by rubbing
  • staph epidermidis and aureus
  • neisseria gonorrhoeae
  • moderate to low clinical relevance
37
Q

Explain injection transmission

A
  • often by biting insect
  • malaria/plasmodium, typhus/rickettsia, yellow fever virus, HIV, hep
  • high relevance to clinic wtih needlestick
38
Q

How do inhalation infections become easy in dental clinics?

A
  • aerosols!
  • easily produced with ultrasonic scalers, high speed handpieces, sneezing, coughing, talking, stirring liquid
39
Q

How do reduce impact of aerosils?

A
  • evacuate aerosol and splatter after dental procedures
  • masks
40
Q

Influenza is associated with coughing but may need …

A

direct contact

41
Q

TB was once considered what for dentists?

A

occupational disease

42
Q

How is the pneumonic plague transmitted?

A
  • inhalation
  • no insect vector needed
  • high mortality, rapid onset
43
Q

How can things infect you in a dental appointment?

A
  • inhalation of aerosols or droplets
  • inoculation - like sharps injuries or surgical procedures
  • absroption through mucous membranes inc. eyes
  • absorption through intact or broken skin
  • ingestion
44
Q

What masks do dentists use?

A
  • type IIR fluid-repellent surgical masks
  • disposable filtering facepiece (FFP) respirators - FFP2 and FFP3, highest level of protection from 3
45
Q

Why is sharps safety needed in dentistry?

A
  • sharps injuries most common type but preventable
  • puncturing of skin is major route of blood borne virus transmission
46
Q

What is sterilisation?

A
  • killing or removal of all viable organisms
  • inactivation or removal of all self-propagating biological entities (to include prions)
47
Q

What is disinfection?

A
  • more vague than sterilising
  • killing or removal of most viable organisms
  • reduction in viable organisms to the point where risk of infection is acceptable
48
Q

Equation for efficiency of sterilisation/disinfection

A

N = k/CT
N is number of surviving organisms
C is concentration of agent/temp
T is time applied
K is constant

49
Q

Value of K in efficiency equation depends on what?

A
  • species of microbes present
  • physiological state of microbe
  • presence of organic material (blood, saliva)
  • means absolute sterility can’t be guaranteed
50
Q

Due to k being dependent on different things, sterile means …

A

less than 1 in 10 to the 6 chance of single viable organism being present

51
Q

Methods of disinfection - reducing the microbial load

A
  • heat - boiling water or pasteurisation
  • chemical disinfection
52
Q

How does heat cause disinfection?

A
  • boiling water kills most bacteria but not spores
  • 2 types of pasteurisation - heat to 66 degrees or 71 degrees - kills mycobacterium TB but not some heat resistant bacteria or spores
53
Q

How does chemical disinfection occur?

A
  • glutaraldehyde, chlorine compounds, phenolics, alcohol, chlorhexidine
  • activitty affected by conc, temp, pH, protein conc
  • problems with toxicity and corrosion of equipment
54
Q

Methods of sterilisation

A
  • dry heat/oven
  • moist heat
  • radiation sterilisation
  • sterilising gases/chemicals
  • filtration
55
Q

How does moist heat sterilise?

A
  • autoclave
  • tyndalisation (3 times through heating to 100 degrees, cooling, incubating cycle)
56
Q

How does radiation sterilisation occur?

A
  • cobalt 60
  • specialised environment
  • used for disposables (syringes, needles, catheters)
  • effective but may damage article
57
Q

Give 2 sterilising gases/chemicals

A
  • sulphur dioxide
  • ethylene oxide
58
Q

2 methods of filtration for sterilisation

A
  • physical removal
  • IV fluids
59
Q

Reusable surgical instrument cycle

A
  • acquistion (purchase or loan) enters cycle
  • cleaning
  • disinfection
  • inspection
  • packaging to disposal in bad
  • sterilization
  • transport
  • storage
  • use
  • transport
  • to cleaning
60
Q

3 ways to decontaminate dental instruments

A
  • manual washing
  • ultrasonics
  • washer disinfectors
61
Q

Is manual washing good?

A
  • least efficient
  • difficult to validate
62
Q

What do ultrasonics do?

A
  • instruments placed in bath with detergent
  • ultrasonic generator creates vacuum within liquid
63
Q

Washer disinfectors do what?

A
  • clean and disinfect to high and reproducible standard
64
Q

Autoclaving process

A
  • high pressure saturated steam
  • 121 degrees for 15 minutes or 134 degrees for 3-4 minutes
65
Q

Types of transmissible spongiform encephalopathies

A
  • Kuru
  • BSE (mad cow) and scrapie
  • CJD (Creutzfeldt-Jakob-disease)
66
Q

How are prions transmitted?

A
  • through infected nervous tissue
  • thought to be misfolded forms of normal protein, no nucleic acid
  • capable of propagation but not culturing
  • extreme resistance to heat, radiation and disinfectant
  • very long incubation of many years
67
Q

Dental safeguards against prions and TSEs

A
  • endodontic reamers and files are single use
  • highest standard of decontamination for all dental instruments
  • manufacturers instructions are followed and where difficult to clean single use
68
Q

High risk patients include …

A
  • symptomatic and asymptomatic
  • general control is enough unless procedures exposes neurovascular tissue
69
Q

How can the surgery be designed to control infection?

A
  • zoning - clean and dirty zones
  • good ventilation
  • dental unit cleaned after each patie and surfaces cleaned
  • dental unit and all surfaces cleaned down at end of session
70
Q

How to control infection through dental unit waterlines?

A
  • dental units contaminated with a range of microbes
  • waterlines harbour pathogens such as Pseudomonas and Legionella species
  • water static for long periods of time and heated to temps between 22 (room temp) and 37 (body temp) also encourages microbial growth
71
Q

How to control infection through safe waste disposal?

A
  • separation of clinical and domestic waste
  • yellow bags for clinical waste
  • black for general
  • sharps bin
72
Q

How to control infection by boosting host defences - immunisations?

A
  • behaviour change and immunisation
  • occupational health
  • HIV/HCV screening
  • Hep B - vaccination and sero-conversion check
  • stay up to date with diphtheria, tetanus, polio, MMR
  • reccommended an annual flu vaccine, SARS-CoV-2 vaccination/booster

Microbiology for Dentists (37 decks)

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