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 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.  

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.

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 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.

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.

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.

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: 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 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

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 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. http://www.health.gov.au/internet/main/publishing.nsf/content/icg-guidelines-index.htm

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!