Infection control in the dental setting Dr Kate Miller College of - - PDF document

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Infection control in the dental setting

Dr Kate Miller College of Public Health, Medical and Veterinary Science James Cook University McGregor Rd. Smithfield 4878 kate.miller1@jcu.edu.au

Learning Objectives

At the end of this lecture students should be able to:

• 1. Discuss basic principles of effective control of

microbial growth

• 2. List the main methods used

to destroy and inactivate microorganisms

• 3. Explain

why infection control is important in healthcare settings

Why is infection control important?

• Both patients and dental health care personnel

(DHCP) can be exposed to pathogens

• Eg. blood-borne viruses (BBV), respiratory tract viruses
• http://www.abc.net.au/news/2015-07-02/dental-

health-hiv-hepatitis-scare-sydney-may-affect- thousands/6588534

• Proper procedures can prevent transmission of

infections among patients and DHCP

• Treat all patients as potential carriers
• Have effective cleaning, disinfection and sterilisation

procedures

• Need to “break” the chain of infection

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Potential sources of infection from patients and staff

SOURCES OF INFECTION Patients in the acute phase of an infection EASILY RECOGNISED Influenza, common cold Patients in the prodromalphase of an infection NOT EASILY RECOGNISED Measles, mumps, chickenpox Healthy carriers of pathogenic organisms NOT EASILY RECOGNISED Includes convalescent carriers and asymptomatic carriers HIV, hepatitis B and C, herpes viruses

Bagg, et al. Figure 30.3

Typhoid Mary

• Lived from 1869-1938 Known carrier of typhoid bacteria

(Salmonella typhi)

• First identified asymptomatic carrier
• Shed bacteria in faeces and urine (no symptoms)
• Worked as a cook moving around the New York city region.
• Worked for 8 families, members of 7 fell ill with typhoid fever.
• Infected at least 53 people with 3 deaths (underestimate)
• Disease: severe diarrhoea and fevers
• Spread by faecal-oral route. Need vigorous scrubbing with soap

and hot water to remove the bacteria from the hands

• Suspected as a carrier by medical profession
• Typhoid Mary is a generic term for a healthy carrier of a

dangerous disease.

Modes of transmission

• Direct
• Unprotected contact with infectious lesions or other skin

infections

• Herpes, gonorrhea, ringworm
• Droplet
• Coughing and sneezing (<1 metre)
• Colds, influenza, TB, whooping cough, SARS, chicken pox,

measles, mumps

• Exchange of bodily fluids
• HIV, hepatitis, cytomegalovirus, EBV

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Modes of transmission

• Indirect
• Airborne
• Pathogens carried >1 metre
• Dental aerosols, Air conditioning units
• Spore-forming bacteria, fungal spores, oocysts/cysts (can tolerate

drying out), Legionnaires disease

• Contaminated objects (fomites)
• Microbes are transferred to an object or surface (fomite) then to a

susceptible host

• Medical instruments, clothing, taps, door handles, telephones,

computer keyboards

• Microbes transmitted on fomites include Vancomycin-resistant

Enterococcus, methicillin-resistant Staph. aureus, Strep. pyogenes, Pseudomonas aeruginosa, rhinoviruses, rotavirus, Candida, Athlete’s foot

Potential routes of transmission in the dental surgery

Bagg, et al. Figure 30.1

• Contaminated saliva or

blood

• Contaminated

instruments and surfaces

• Inhalation of airborne

pathogens

• Aerosols
• Improper sterilisation

If Saliva were Red https://www.youtube.com/watch?v=hLHMEF6RAtY Saliva contains up to 108 microorganisms per ml

Key elements of infection control

• Medical history
• Dental instrument decontamination (for reusable devices)
• Disinfection of laboratory items
• Use of disposables
• Decontamination of surgery surfaces
• Personal protective equipment
• Avoidance of needlestick and other sharps injuries
• Immunisation of staff
• Effective ventilation
• Safe waste disposal
• Effective training of staff
• Effective management of infection control
• Audit

Bagg, et al. Figure 30.4

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Standard precautions in healthcare settings

• Standard

Precautions (sometimes called Universal Precautions) = all patients/samples treated as potential carriers/hazards

• Standard precautions are applied at all times
• We need them because:
• people may be placed at risk of infection from others who carry

infectious agents;

• people may be infectious before signs or symptoms of disease are

recognised or detected, or before lab tests are confirmed in time to contribute to care;

• people may be at risk from infectious agents present in the

surrounding environment including environmental surfaces or from equipment; and

• there may be an increased risk of transmission associated with

specific procedures and practices.

Standard precautions consist of:

• hand hygiene, before and after every episode of

patient contact;

• the use of personal protective equipment;
• the safe use and disposal of sharps;
• routine environmental cleaning;
• reprocessing of reusable medical equipment and

instruments;

• respiratory hygiene and cough etiquette;
• aseptic non-touch technique;
• waste management

Dental instrument decontamination

• Legislation covering the cleaning, disinfection and

sterilisation of reusable medical devices (AS/NZS4187-2003)

• Surgical instruments must be sterile at point of use
• Procedures used during the reprocessing of

contaminated instruments must minimise risk of exposure of dental staff

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Important terms used in destruction or control of microorganisms

• Antiseptic
• Type of chemical disinfectant suitable for use of skin
• r living tissue, used to kill or remove harmful

microorganisms without damaging the tissues

• Biocide
• Chemical capable of killing microbe
• Decontamination
• Removal of possibly harmful microorganisms from

an object by cleaning or disinfecting

• Cleaning
• Mechanical removal (+ usually detergent and water)
• f material from surface of an object

Important terms used in destruction or control of microorganisms

• Disinfectant
• Type of chemical suitable for use on inanimate
• bjects
• Disinfection
• destruction or removal of most microorganisms

(usually kills bacteria, may not kill spores and viruses)

• Sterilisation
• complete destruction or removal of all

microorganisms including spores and viruses

• Sterile
• free of all living organisms

Approaches to prevent infection in healthcare settings

• Removal of microorganisms from the

environment

• Cleaning
• Disinfection
• Removal of organisms from patient care

equipment

• Often requires cleaning, disinfection or

sterilisation (sometimes all three)

• Depends on equipment type

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Instruments and infection risk

• 1. Critical instruments

Penetrate mucous membranes or contact bone, the bloodstream, or other normally sterile tissues (of the mouth)

• Surgical instruments, scalpel blades, periodontal scalers
• 2. Semi-critical instruments

Contact mucous membranes but do not penetrate soft tissue

• Dental mouth mirrors, amalgam condensers, and dental

handpieces

• 3. Non-critical instruments

Contact intact skin

• X-ray heads, bib chain, alginate spatula, protective

eyewear

Processing in JCU Dental

JCU Dental manual p.45

Cleaning

• Sites that may harbour microorganisms
• Blood
• Pus
• Mucous
• Grease
• Dirt
• Microorganisms require organic compounds and

water to reproduce

• Detergent is a solvent
• Instrument and equipment cleaning
• Environment cleaning

27/03/2020 7 Cleaning

• Instrument and equipment
• Physical removal of debris
• Manual scrubbing and/or ultrasonic bath, or automated

washer

• Detergent, disinfectant/detergent or enzymatic cleaner
• Environment
• Transmission through indirect contact
• Routine cleaning of floors, walls, furnishings important
• Details in Australian Guidelines for the Prevention and

Control of Infection in Healthcare

Disinfection

• Disinfection = Removal or destruction of harmful

microbes not usually including bacterial spores

• Does not sterilize
• Methods
• Heat
• Pasteurisation, controlled temp washers, boiling for 5 min
• Radiation
• Short wave UV
• Liquids
• Phenolic compounds, bleach, 70% alcohol, glutaraldehyde

Factors affecting liquid disinfectant activity

• Properties of organisms
• bacterial spores are highly resistant, Gram-negative more

resistant than Gram-positive, non-enveloped viruses more resistant than enveloped

• Inactivation
• presence of soil (blood, pus) or incompatibility with other

chemicals

• Dilution/volume
• Use manufacturer’s instructions for concentration and

contact time

• Contact time
• a prolonged contact time may be required for sporicidal

activity

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• Static/Cidal activity
• Static inhibits, cidal kills
• Stability
• fresh solutions prepared often (daily-weekly)
• Bacterial load
• high loads must be reduced by effective pre-treatment

cleaning

• Resistance
• From repeated prolonged exposure to some types of

disinfectants

• Change type regularly

Factors affecting liquid disinfectant activity

Skin disinfectants = antiseptics

• Alcohols
• e.g. skin wipes
• Dissolve lipids in microbe cell wall and plasma membrane
• Requires water to increase penetration and denature proteins
• Commonly used as skin prep for venipuncture/injection clean
• Chlorhexidine
• e.g. used widely, persists on skin for extended periods
• Disrupts plasma membrane
• In combination with detergents – antiseptic handwash
• Residual, low toxicity
• Iodine-containing
• e.g. surgical scrubs, disinfecting wounds
• Less irritating / good residual activity
• With detergent – surgical scrub
• Broad spectrum but not sterilisation
• Some Pseudomonasspp resistant
• Stains skin

Sterilisation

• Free from

microorganisms including bacterial spores

• Moist heat sterilisers
• Boiling ≠ sterilising
• replacement of air with

steam

• e.g. 121°C for 15min
• e.g. 134°C at 2.25 bar for 3

min

27/03/2020 9 Sterilisation methods

• Filtration
• Heat sensitive
• Ethylene oxide gas
• Heat sensitive
• Hydrogen peroxide
• Delicate instruments
• Dry heat (1800C/ 60 min)
• Incineration
• Dressings, disposable equipment
• Gamma (γ) Irradiation
• Anaesthetics, syringes, implants, single-use medical supplies

https://beta-static.fishersci.com/images/F24288~wl.jpg

Sterilisation methods

• Factors affecting sterility assurance
• High starting count of micro-organisms
• Presence of organic material to buffer the effect of the

sterilant

• Sterilisation must be monitored and validated
• Records
• Indicators

Storage of sterile and clean items

• Use date- or event-related shelf-life practices
• Examine wrapped items carefully prior to use
• When packaging of sterile items is damaged, re-clean,

re-wrap, and re-sterilise

• Store clean items in dry, closed, or covered

containment

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Infections you are likely to encounter

• Actinomycosis
• AIDS
• Angular cheilitis
• ANUG/NOMA
• Avian flu
• Candidiasis
• Cat scratch disease
• Cellulitis inc Ludwig’s angina
• Denture stomatitis
• Glandular fever
• Gonorrhea
• Hand, foot and mouth
• Herpes simplex
• Herpes zoster
• Herpetic stomatitis
• Human Papilloma Virus
• Impetigo (School sores)
• Mumps
• Oral manifestations of anthrax,

botulism, smallpox, tularaemia

• Primary syphilis
• SARS
• Secondary syphilis
• Swine flu
• TB
• Varicella (chicken pox)
• Tetanus

More information in Week 6

Preventing transmission of bloodborne pathogens

Bloodborne viruses such as hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV)

• Are transmissible in health care settings
• Can produce chronic infection
• Are often carried by persons unaware they are

infected

Transmission of blood borne viruses (BBVs)

Transmission can be: Patient DHCP DHCP Patient Patient Patient

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Factors influencing occupational risk

• f bloodborne virus infection
• Frequency of infection among patients
• Risk of transmission after a blood exposure (i.e. type
• f virus)
• Type and frequency of blood contact

Occupational infection with HBV and HIV HBV HIV

Minimum volume of blood to transmit infection 0.00004ml 0.1ml Risk of infection following needlestick injury from a seropositive patient 7-30% 0.3%

Hepatitis B virus

• Hepadnaviridae family
• Enveloped DNA virus
• Transmitted by direct contact with blood or bodily

fluids

• Causes inflammation of the liver
• Can develop into cirrhosis, liver cancer
• Risk factors
• iv drug use, sex, tattooing, acupuncture, blood

transfusions, working in healthcare, congenital transfer

Concentration of HBV in body fluids

High Moderate Low/Not detectable Blood Serum Wound exudates GCF (gingivitis) Semen Vaginal fluid Saliva Urine Faeces Sweat Tears Breast milk

27/03/2020 12 HBV infections

1987 – publication of Universal Precaution guideline 1991- OSHA requirement that employers provide HBV vaccinations to HCP

Transmission of HBV from infected DHCP to patients (CDC)

• Nine clusters involving 300 cases of transmission from

dentists and oral surgeons to patients 1970–1987

• Eight dentists tested for Hep B e-Ag were positive
• associated with higher rates of viral replication and

enhanced infectivity

• Lack of documented transmissions since 1987 may

reflect increased use of gloves and vaccine

• One case of patient-to-patient transmission in a dental
• ffice in 2003
• mechanism of transmission never identified

Human Immunodeficiency Virus

• Retroviridae family
• Enveloped single strand RNA retrovirus
• Transmitted in body fluids
• Destroys CD4+ (T-helper) cells
• Weakens immune system
• Opportunistic pathogens
• Risk factors:
• Unsafe sex practices, needle-sharing, blood transfusions,

congenital transmission

https://cdn.technologynetworks.com/tn/images/thumbs/webp/640_360/reversing-hiv-latency-is-step-towards-a-cure- 329698.webp?v=10551445

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• Only one documented case of HIV transmission from an

infected dentist to patients

• patients had invasive dental work

http://www.cdc.gov/mmwr/preview/mmwrhtml/000016 79.htm (1990) http://www.aidsmap.com/Four-cases-of- transmission/page/1324553/

• No transmissions documented in the investigation of 63

HIV-infected HCP (including 33 dentists or dental students)

Pseudomonas aeruginosa

• Gram-negative bacillus
• Found in water, soil
• Opportunistic pathogen
• Found in dental water

lines

• Biofilms
• Sub-clinical infections
• Multi-drug resistant
• Intrinsic efflux pumps
• Horizontal gene transfer
• In biofilm

https://www.microbiologyinpictures.com/bacteria-photos/pseudomonas-aeruginosa-photos/pseudomonas-aeruginosa.jpg

Preventing transmission of pathogens

• Use standard

precautions and transmission precautions (Dr Ang’s lecture)

• Wear PPE

https://scontent-sea1-1.cdninstagram.com/vp/209710078d304035cf8fff81de4f400e/5AE5C187/t51.2885- 15/s480x480/e35/13260936_587494248094111_1820368296_n.jpg?ig_cache_key=MTE4OTk0MTU4MDUwNjk3NTQ3OQ%3D%3D.2

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References

Bagg J, et al. (2006) Essentials of Microbiology for Dental

• Students. Oxford University Press

JCU Dental (2020) Infection Prevention and Control manual Lamont RJ and Jenkinson HF (2010) Oral Microbiology at a

• Glance. John Wiley & Sons.

Laheij AMGA, et al. (2012) Journal of Oral Microbiology 4: 17659 http://dx.doi.org/10.3402/jom.v4i0.17659 Lee G and Bishop P (2010) Microbiology and infection control for health professionals Fourth Edition, Pearson Australia