Microbiological safety for pathologists

1. Microbiological safety for pathologists Dr David Mitchell Centre for infectious Diseases and Microbiology Westmead Hospital, Sydney Narrator: Dr Wendy Pryor

2. 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

3. Risks for pathologists by speciality

4. Autopsy-associated infections • Risk recognised for centuries • ~2% of total lab-associated infection • Commonest cause of lab-acquired TB • Newly recognised infections

5. Potential routes of transmission during autopsies/tissue processing • direct contact • penetrating injury • contamination of mucous membranes • inhalation

6. 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

7. Blood-borne viruses

8. 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 • 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

9. 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.

10. 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

11. Tuberculosis

12. Tuberculosis • Most important infectious risk in autopsies • Relative risk for pathologists is ~10X that of non-clinical 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

14. Testing for TB disease and infection Mantoux or tuberculin skin test (TST)

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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)

21. Standard N95 masks and respirator for high risk cases

22. To protect yourself Always use • Standard precautions • Personal protective equipment • Safe work practices with every case

23. Always…… If there’s an incident Report it right away!