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
Pathology speciality
Biohazard
Mode of transmission
Clinical chemistry
Blood-borne viruses
Percutaneous exposure
Haematology
Histopathology TB
Inhalation during autopsy/tissue processing
Microbiology
TB, brucella, histoplasmosis, meningococcus
Inhalation of culture
Typhoid, shigella
Contamination of hands
All pathologists and laboratory staff are at risk from various biohazards and infectious diseases. Blood borne viruses are a hazard for all because of potential exposure to blood and body fluids. This is usually via the percutaneous route, most commonly through sharps injury or possibly by contamination of broken skin or mucous membranes. Tuberculosis is a particular hazard for anatomical pathologists because of possible exposure during autopsies and processing of tissues. The route here is by inhalation.
Microbiologists, including Trainees, are at the highest risk of biohazards because They’re in the business of amplifying pathogens and therefore they have potential exposure to large numbers of potentially pathogenic organisms on a day to day basis. They can be exposed to pathogens via inhalation when handling specimens or cultures of organisms such as Mycobacterium tuberculosis, Brucella, Histoplasma and meningococcus. They may also be at risk from contamination of hands and subsequent ingestion of gastrointestinal pathogens like typhoid and shigella.
Microbiologists are also more likely to be exposed to viruses.  
In Australia there have been a few laboratories in Australia that have had cases of brucellosis acquired in their microbiology departments in the past ten years or so. There have also been a few cases of typhoid fever acquired by microbiologists during this time and a histopathologist has acquired tuberculosis, so these things are actually a risk and do happen, though rarely.

4. Autopsy-associated infections
Risk recognised for centuries
~2% of total lab-associated infection
Commonest cause of lab-acquired TB
Newly recognised infections
The potential infectious risks of handling cadavers and performing autopsies has been recognised for centuries.
Historically, autopsy-associated infection accounted for ~2% of total laboratory-associated infection in surveys.
Autopsies were (and still are) the commonest cause of laboratory associated tuberculosis infection.
Whilst the prevalence of autopsy-associated infection has declined, the emergence of newly recognised infections (e.g. HIV, CJD, VHF, SARS, AI) over the past 25 years has increased interest (and anxiety) in this issue.

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
If you were not immune to hepatitis B and you had a needle stick injury with hepatitis B e antigen positive blood, then your risk of acquiring hepatitis B is about 40 %. On the other hand if the source blood is e antibody positive, then the risk is about 5%. Much less but still significant.
So, the take home message for hepatitis B is to be vaccinated. After you’ve had your course of vaccine, which you’ve probably already had at some stage in your medical career, you should make sure you check your antibody levels to confirm that you’re immune. In a couple percent of people the vaccine doesn’t take, and these people require some special management. So you need to know this.
The other take home message with hepatitis B is that if for some reason you weren’t immune to hepatitis B and you were potentially exposed, there’s something we can do about it as long as we do it within 72 hours. We can reduce the numbers in terms of transmission by about 90%. So, if you do have an accident, whether it’s a needle stick injury or whatever – report it, (a) because we can often do something about it to reduce the risk of transmission, (b) so that the paperwork is done and if the worst came to the worst and you did acquire an infection, then you could be compensated because you could then prove it was associated with exposure, and (c) the laboratory can make sure that the way you had that accident doesn’t happen again to someone else.

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.
The risk of transmission of HIV is actually quite low – about 1 in 250 per needle stick injury, which is much lower than for hepatitis B. But once again, there’s something we can do about it. If you’re exposed to HIV positive blood and you start on anti-retroviral drugs, then the studies suggest that we can reduce this already low risk by about 80%. So, once again, report it and get some treatment. There are also some measures you can take to protect others from being infected by you.

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
For hepatitis C, the risk of transmission following a needlestick injury is about 3% . There is no prophylaxis for hepatitis C exposure, but there’s certainly evidence that early treatment will reduce the risk of chronic carriage and therefore subsequent liver disease. So, once again, it’s important to report it.

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
Some newly recognised prion agents pose a theoretical risk to pathologists at autopsy because prions are not inactivated by formalin or standard autoclaving. There have been reports of pathologists with Creutzfeldt-Jakob disease, but it is not certain whether they are at greater risk than the general population.
High risk tissues (classical and variant CJD): brain, spinal cord, pituitary, dura mater, retina, optic nerve
Lower risk tissues (especially variant CJD): cornea, CSF, nerve ganglia, lymphoid tissue (e.g. 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
Summary of Australian infection control guidelines for autopsies:
Suspected cases should only be processed in an appropriate facility
Wear appropriate disposable personal protective equipment
Use a hand saw for removing the brain
Use disposable instruments
Clean contaminated surfaces with sodium hydroxide
Process tissue in a biosafety cabinet
Fix tissue in formalin and then in formic acid
Reference: Infection control Guidelines for the prevention of transmission of infectious diseases in the health care setting
Department of Health and Aging, 2004.

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!