Dr David MitchellCentre for infectious Diseases and Microbiology

Westmead Hospital, Sydney

Narrator: Dr Wendy Pryor

Microbiological safety for pathologists

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

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

Microbiology Blood-borne viruses Percutaneous exposure

TB, brucella, histoplasmosis, meningococcus

Inhalation of culture

Typhoid, shigella Contamination of hands

Risks for pathologists by speciality

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 exposurecommence vaccine course

HBV vaccine3 doses IM 0, 1 month, 6 monthsconfirm post course immunity (anti-HB(s) antibody level) routine booster not neededusually 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 exposurebaseline 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

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: NSWMortuary 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 tissuescornea, 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!