Biological Hazards in Medical Laboratories

This module gives an overview

of how bacteria and viruses

can cause injury, illness,

disease, and even death to

medical laboratory workers.

What You Will LearnWhat You Will Learn

Bacteria ExposureBacteria Exposure

• Center for Disease Control (CDC) data indicates these bacteria have a high chance of exposure potential:– Mycobacterium tuberculosis– Bacillus anthracis– Bordetella pertussis– Brucella sp.– Neisseria meningitidis

Many labs also culture other types of dangerous bacteria.

Bacteria ExposureBacteria Exposure

• In the lab bacteria can become airborne by:

– Mouth pipetting

– Manipulation of cultures

– Centrifuge, test tube fractures/cracks

Bacteria ExposureBacteria Exposure

• Tuberculosis:– Present in sputum, gastric lavage, CSF,

urine and lesions of persons with active disease (not latent)

– Bacilli survive in heat-fixed smears

– Transmitted via airborne droplet: from infected person’s respiration, in preparation of frozen sections and in preparation of liquid cultures.

Bacteria ExposureBacteria Exposure

• Tuberculosis:– Surveillance: PPD skin testing based

on laboratory’s risk level

– Prior vaccination with BCG not considered when interpreting PPD skin test. It is impossible to differentiate between BCG mediated response and latent infection.

Bacteria ExposureBacteria Exposure

• Tuberculosis:– 90% of all persons infected with TB

will never develop active TB disease

– TB infected or exposed people are NOT contagious

– Only contagious if they have ACTIVE TB disease

Bacteria ExposureBacteria Exposure

• Anthrax:– Present in blood, skin lesion exudate,

CSF, pleural fluid, rarely in urine and feces

– Aerosolized during handling– Direct and indirect contact of intact or

broken skin with cultures and contaminated lab surfaces

• Requires prompt diagnosis• Vaccine is available

Bacteria ExposureBacteria Exposure

Anthrax Story:• Lab in Texas was processing environmental samples for

anthrax in support of CDC bioterrorism investigation. • A worker had cut his face shaving. The next day, he

was moving vials containing aliquots of confirmed anthrax from the biological safety cabinet to a freezer in the next room. The worker did not use gloves. He washed his hands after handling the vials.

• Within one day, his facial cut worsened … on day 5, he was admitted to the hospital and treated for cutaneous anthrax.

• Most likely source was the surface of the vials.• No workers in the lab were immunized

against anthrax.

From April 5, 2002 MMWR (Morbidity and Mortality Weekly Report from CDC)

Bacteria ExposureBacteria Exposure

• Pertussis (whooping cough):

– Hazard is aerosol generation during the manipulation of cultures

– Incidence on the rise

– May be mild or classic in adults

– Most lab cases related to research labs

Bacteria ExposureBacteria Exposure

• Pertussis (Whooping cough):

– No pertussis containing vaccine is currently licensed for persons 7 years of age or older

– If exposed, antibiotics used as prevention

Bacteria ExposureBacteria Exposure

• Brucellosis:– The most commonly reported lab-associated

bacterial infection– Present in blood, CSF, semen and occasionally

urine of infected persons – Aerosols generated during lab procedures

• Vaccine for cattle only, no vaccine for humans

Bacteria ExposureBacteria Exposure

• N. meningitis:

– Present in pharyngeal exudates, synovial fluid, urine, feces, CSF

– Aerosols from laboratory procedures on isolates

– Vaccine available

– Post-exposure antibiotics• Rifampin or ciprofloxacin given orally; or• Ceftriaxone given IM

The use of post-exposure antibiotics have prevented outbreaks.

Bacteria ExposureBacteria Exposure

Meningitis Story:• Two microbiologists contracted meningitis, both died.

• #1: 3 days before symptoms, the patient had prepared a gram stain from the blood culture of a patient who was subsequently shown to have meningococcal disease. The microbiologist had also handled and subcultured agar plates w/ CSF. At this lab, aspiration from blood culture bottles was performed at an open lab bench.

• #2: Microbiologist who worked at state public health lab and worked on several n meningitides isolates. Performed slide agglutination tests. Used BioSafety Level 2 precautions.

• In 15 years, 16 cases of meningitis in lab personnel,50% were fatal.

From MMWR 2/22/02

Other Pathogen ExposureOther Pathogen Exposure

• Fungal agents:– Coccidiomycosis and Histoplasma

– Hazard because spores are <5 microns and can be aerosolized and inhaled

– Spores resistant to drying and remain viable for long periods

Other Pathogen ExposureOther Pathogen Exposure

• Parasitic agents:

– Intestinal (giardia, toxoplasma), tissue and organs (trichinosis), blood (malaria)

– Ingestion is primary hazard

– Also can enter body through breaks in the skin

Other Pathogen ExposureOther Pathogen Exposure

• Prions:– Transmissible spongiform encephalopathies– Present in CNS– Resistant to conventional inactivation– No known treatment

Diseases include Creutzfeld-Jakob Disease and similar diseases.First US case of new variant CJD has been reported in Florida.These diseases are not communicable via contact or aerosol between persons.No reported lab cases yet, however incubation can be as long as 10 years. Highest concentration in CNS and its coverings – thus potential exposure is during autopsy or post-mortem examinations.Highly resistant to conventional inactivation procedures including irradiation, boiling, dry heat and chemicals.

Other Pathogen ExposureOther Pathogen Exposure

• Rickettsial Agents:– Coxiella burnetti – Q fever

• High risk of lab infection• Aerosol and parenteral exposures

– Rickettsia species• Typhus, reported in 57 lab-associated cases• Rocky mountain spotted fever, in 1976, 63

lab cases were reported, 11 were fatal• Aerosols and parenteral inoculation

VirusVirus ExposureExposure

• Some viruses are transmitted via aerosols such as:– Hantavirus– Human herpes viruses – Influenza– Pox viruses

Hantavirus: 4 persons known to have contracted hantavirus infection while handling infected rodents in the lab setting.Herpes viruses are ubiquitous – primarily an opportunistic infection. Rarely, cytomegalovirus or Epstein-Barr may be transmitted in the lab.No documentation that influenza has been contracted in the lab – as it also is ubiquitous in season.

Virus ExposureVirus Exposure

• Hepatitis A and E:– Fecally transmitted

– We hear about it in the news when infected restaurant workers may expose a community

– Although high virus titers may be present in blood during the incubation period, lab transmission not reported

Virus Exposure – Blood/Body FluidsVirus Exposure – Blood/Body Fluids

• Some pathogens are transmitted through microorganisms contained in blood and other body fluids.

• Examples are:– Hepatitis B Virus (HBV)Hepatitis B Virus (HBV)– Hepatitis C Virus (HCV)Hepatitis C Virus (HCV)– Hepatitis D Virus (HDV)Hepatitis D Virus (HDV)– Human Immunodeficiency Virus (HIV)Human Immunodeficiency Virus (HIV)

Virus Exposure – Blood/Body FluidsVirus Exposure – Blood/Body Fluids

• Blood includes:– Human blood– Human blood components, such as

packed cells and plasma– Products made from human blood, such

as: • Clotting agents for hemophilia• Immune globulins including Rh factor

immune globulins

• Potentially infectious body fluids include:

Virus Exposure – Blood/Body FluidsVirus Exposure – Blood/Body Fluids

• Semen• Vaginal secretions• Cerebrospinal

fluid • Synovial fluid • Pleural fluid

• Pericardial fluid • Peritoneal fluid • Amniotic fluid

• Saliva in dental

procedures

Virus Exposure – Blood/Body FluidsVirus Exposure – Blood/Body Fluids

• Other pathogens also transmitted through blood include:– Malaria– Syphilis– Brucellosis– Leptospirosis– Cruetzfeldt-Jakob Disease– Some fungi and ricketsii

Virus Exposure – Blood/Body FluidsVirus Exposure – Blood/Body Fluids

• Hepatitis B, C, and D

– Very infectious

– Causes liver inflammation and/or damage - mild to fatal

– Can live in a dry environment > 7 days, such as on countertop

– Highest risk of transmission through hollow bore needle stick

Virus Exposure – Blood/Body FluidsVirus Exposure – Blood/Body Fluids

• Hepatitis B, C, and D

– Hepatitis B, active and passive vaccines available

– Hepatitis C, no vaccine available

– Hepatitis D, no vaccine available, however immunization against hepatitis B also protects against hepatitis D

Virus Exposure – Blood/Body FluidsVirus Exposure – Blood/Body Fluids • Human Immunodeficiency Virus (HIV)

– Attacks the human immune system

– Can live in a dry environment for only a few hours

– No vaccine available

– Antiviral post-exposure prophylaxis effective in reducing risk

Reference: MMWR June 29, 2001/50(RR11);1-42

HIV Virus Exposure Routes

• Parenteral• Needlestick• Scalpel/glass cut

• Mucous membrane• Mouth pipetting• Eating, drinking in lab area• Not wearing appropriate PPE

• Non-intact skin• Unguarded splash• Contact with contaminated surfaces• Not covering skin breaks

HIV Virus Exposure

HIV Story:

The CDC reports as of December 2001, 51 of the 57 cases of occupationally acquired HIV infection involved sharps injuries of which nearly half involved needles used in phlebotomy or blood sampling from a vascular line, with vacuum- tube device needles accounting for the largest number of these injuries.

Other sharps injuries included broken glass from blood collection tubes and a needle for cleaning/dislodging debris in laboratory equipment.

Reference: Infection Control & Hospital Epidemiology, Feb 2003

Biosafety Guidelines

• The Centers for Disease Control (CDC) has guidelines to describe combinations of:

– Laboratory Practices and Techniques• Standard Practices• Special Practices

– Safety Equipment

– Laboratory Facilities

Biosafety Guidelines

• These guidelines are called:

CDC Biosafety in Medical and Biomedical Laboratories (BMBL)

• The BMBL guidelines describe four laboratory hazard levels or Biosafety Levels (BSL)

Biosafety Guidelines

• Biosafety Levels 1-4 provide:

– Increasing levels of personnel and environmental protection

– Guidelines for working safely in microbiological and biomedical laboratories

Biosafety Levels (BSL)

• The Four Biosafety Levels are:

• BSL1 - agents not known to cause disease (B. subtilis, E. coli).

• BSL2 - agents associated with human disease (hepatitis B, Salmonellae, Toxoplasma)

• BSL3 - indigenous/exotic agents associated

with human disease and with potential for

aerosol transmission (M. tuberculosis, C. burnetii).

• BSL4 - dangerous/exotic agents of life

threatening nature (Marbug and Ebola virus).

WISHA Rules

• Occupational Exposure to Bloodborne Pathogens – WAC 296-823

– This rule provides requirements to protect employees from exposure to blood or other potentially infectious materials, that may contain bloodborne pathogens.

– The rule covers anticipated exposure, even if no actual incidents have occurred.

Other WISHA Rules & Directives

• Protect Employees from Biological Agents 296-800-11045

• Personal Protective Equipment, 296-800-160

• WRD 11.35 Tuberculosis

Thank you for taking the time to learn about safety and health and how to prevent future injuries and illnesses.