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Microbiological safety for pathologists
Dr David Mitchell
Centre for infectious Diseases and Microbiology
Westmead Hospital, Sydney
Narrator: Dr Wendy Pryor
Objectives
 Recognise most common infectious risks for pathologists
 List main routes of transmission
 List blood-borne viruses that pose laboratory risk
 Evaluate risks of infection after needlestick injury (NSI)
 Know what action to take following exposure
 Ensure you are properly screened and vaccinated
 Recognise potential risks of prions
 List general precautions to reduce risk
Risks for pathologists by speciality
Pathology speciality
Biohazard
Mode of transmission
Clinical chemistry
Blood-borne viruses
Percutaneous exposure
Haematology
Blood-borne viruses
Percutaneous exposure
Histopathology
Blood-borne viruses
Percutaneous exposure
TB
Inhalation during
autopsy/tissue
processing
Blood-borne viruses
Percutaneous exposure
TB, brucella,
histoplasmosis,
meningococcus
Inhalation of culture
Typhoid, shigella
Contamination of
hands
Microbiology
Autopsy-associated infections
 Risk recognised for centuries
 ~2% of total lab-associated infection
 Commonest cause of lab-acquired TB
 Newly recognised infections
Potential routes of transmission
during autopsies/tissue processing
 direct contact
 penetrating injury
 contamination of mucous membranes
 inhalation
Infection risk in autopsies
 Pathogens may survive after death of the host,
but rarely if ever multiply
 Risk should be lower from autopsy than
invasive surgery on same individual if alive
 Mode(s) of transmission from a cadaver
usually the same as from living host
 In some cases risk may be enhanced by
autopsy (e.g. TB) or transmission may occur in
unusual way
 If in doubt then apply the same infection
control precautions as would apply during life
Blood-borne viruses
Occupational exposure to Hepatitis B
 Risk of transmission via NSI
 ~40% (if source HB(e )Ag +ve)
 ~5%
(if source HB(e)Ab +ve)
 Management of HBV exposure (if not immune)
 HBIG within 72 hours of exposure
 commence vaccine course
 HBV vaccine
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3 doses IM 0, 1 month, 6 months
confirm post course immunity (anti-HB(s) antibody level)
routine booster not needed
usually give booster to healthcare workers after exposure
Occupational exposure to HIV
 Risk of transmission of HIV
 via NSI ~0.3%
 via mucosal splash ~0.1%
 Management of occupational exposure
 baseline bloods and serology at 3 and 6 months
 if high risk, seek expert ID advice re antiviral
prophylaxis (reduces transmission by ~80%?)
 during window period protect sexual partners,
avoid pregnancy and blood donation.
Occupational exposure to Hepatitis C
 Risk of transmission of HCV via NSI ~3.0%
(1-10%)
 Management of occupational exposure to HCV
 baseline serology and HCV serology at 3 months
 HCV PCR at 6 weeks in high risk exposures
 monitor LFTs every 2 weeks
 no prophylaxis available
 early interferon treatment of acute Hepatitis C may
reduce risk of chronic carriage and late complications
Tuberculosis
Tuberculosis
 Most important infectious risk in autopsies
 Relative risk for pathologists is ~10X that of non-clinical
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lab staff
Airborne spread when infected body cavities are opened
Possible percutaneous inoculation or splash
Observers (e.g. medical students) and embalmers at risk
Outbreaks in coroner’s offices, anatomy departments
involving clerical staff etc
Mycobacteria may remain viable despite formalin fixation
Hospitals must have a TB monitoring programme
Testing for TB disease and infection
Mantoux or tuberculin skin test (TST)
Screening policy: NSW
 Mortuary staff/pathologists - high risk
 TST at commencement of employment
 if positive - CXR and assessment
 if negative – repeat annually or after exposure
 if converts - CXR and medical assessment
 BCG – consider for high risk personnel, but
not very efficacious
 Offer TST on termination
 All must be documented in employee’s file
CJD and other prion diseases (1)
 Theoretical risk
 Pathologists do not appear to have greater risk of CJD
than general population
 Prions not inactivated by formalin fixation or standard
autoclaving
 High risk tissues
 brain, spinal cord, pituitary, dura mater, retina, optic
nerve
 Lower risk tissues
 cornea, CSF, nerve ganglia, lymphoid tissue (eg
tonsils, appendix), liver, lung, placenta, ?blood
CJD and other prion diseases (2)
 Main theoretical risk of transmission during
autopsy by percutaneous exposure to infected
tissues or instruments
 IM injection of contaminated pituitary hormone
 Blood transfusion implicated in some human
cases in UK
CJD and other prion diseases (3)
Australian Infection Control Guidelines for
autopsies:
 Suspected cases should only be processed in
appropriate facility
 Disposable personal protective equipment
 Disposable instruments
 Specific decontamination procedures
Reducing infection risks – general principles
 Well designed facilities
 Written protocols and staff education
 Standard Precautions with all cadavers and specimens
 Appropriate personal protective equipment (PPE)
 Minimise aerosols
 Hand hygiene
 Safe handling of sharps
 Decontamination of instruments and work surfaces
 Mandatory Hepatitis-B vaccination of staff
 Mandatory tuberculosis monitoring of staff
 Encourage staff to report exposure incidents
Personal protective equipment - autopsies
 All staff, all autopsies regardless of infectious
status
 surgical scrub, impervious gown, apron, overboots
 gloves (double surgical with interposed layer of
mesh)
 N95 mask (surgical masks do not protect against
infectious aerosols)
 face shield or eye goggles
 High risk autopsies:
 Consider PAPRs (powered air-purifying respirators)
Standard N95 masks and
respirator for high risk cases
To protect yourself
Always use
 Standard precautions
 Personal protective equipment
 Safe work practices
with every case
Always……
If there’s an
incident
Report it right
away!