module 2 safety precautions for afb culture and dst of m. tuberculosis 1
TRANSCRIPT
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Module 2
Safety precautions for AFB culture and DST of
M. tuberculosis
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Learning objectives
At the end of this module, you will be able to:
explain airborne transmission of TB; adhere to safe practice;explain the biosafety levels of laboratories for TB
activities;work safely in biological safety cabinets;use adequate protective personal equipment; use appropriate disinfectants;cope with accidents in the TB laboratory;handle chemicals safely in the laboratory . .
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Content outline
• Transmission of TB• Biohazards in a TB laboratory• Minimum WHO recommendations for TB culture / DST
facilities• Standard safe practice in a TB laboratory• Personal protective equipment• Disinfectants active against M. tuberculosis• Safe disposal of infectious waste• Coping with accidents • Chemical safety
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Transmission of tuberculosis
Mycobacterium tuberculosis is almost always transmitted by patients with active pulmonary disease:
• TB patient expels bacilli in small droplets of respiratory secretions.
• Secretions quickly evaporate leaving “droplet nuclei” less than 5 μm in diameter.
• Droplet nuclei of this size, containing 1–3 bacilli, can remain suspended in the air.
• Following inhalation, droplet nuclei are able to reach deep into the lungs to produce infection.
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Coughing
Sneezing
Talking
Singing
Aerosol formation: spread of droplets
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Specimens must be collected outside the laboratory
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Biohazards in the laboratory: be aware!
• Inhalation hazards: handling of liquids containing TB bacill generates infectious aerosols: – pipetting– working with loops– centrifugation– opening tubes– vortexing suspensions
• Ingestion hazards
• Inoculation hazards
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Importance of laboratory safety
for preventing
laboratory-acquired infection
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Conclusion of of the survey::•DST is associated with the higher risk..•Smear microscopy alone does not pose a higher risk than clerical work.
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Medical fitness of laboratory staff• In accordance with national laws and practices, health
surveillance of TB laboratory workers should be performed:
– before enrolment in the TB laboratory;– at regular intervals thereafter;– after any biohazard incident.
• Workers should be educated about the symptoms of TB and provided with ready access to free medical care if symptoms arise.
• Confidential HIV counselling and testing should be offered. Reassignment of HIV-positive workers away from high-risk environments should be considered.
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Biological safety cabinet
The biological safety cabinet, or BSC, is the single most important equipment for containing and quickly eliminating infectious aerosols generated during culture/DST procedures.
For proper functioning, the BSC must be well maintained.
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HEPA filter
• HEPA = high-efficiency particulate air.
• Traps and removes 99.97% of airborne particles equal to or larger than 0.3 µm in diameter.
• Evaluation of the performance of the HEPA filter and regular maintenance of the BSC are critical for protection
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Work in a BSC
BSC work zone should be divided into three areas to minimize contamination over items: – a clean area: supplies;– working area: specimen;– contaminated area:
waste container.
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Work in a BSC
• Organize a realistic workload in the BSC. Do not overload, e.g. no more than 6–8 specimens for processing at a time, according to centrifuge capacity.
• All needed material should be present in the BSC so that work is not interrupted and moves in and out of the BSC are minimized.
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Is flame allowed in the BSC?
• Avoid continuous flame = permanent source of heat
• Use intermittent burner
• Can be used in BSC I or II
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Biosafety levels
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WHO recommendations for BSL2 (specimen processing for TB cultures)
• BSCs should be ducted or vented to the outside.
• Air from BSCs must not be allowed to recirculate into the room in TB laboratories.
• An adequate budget for regular maintenance and servicing is essential.
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WHO recommendations for handling TB cultures
In addition to BSL2 recommendations:
• Isolation of the laboratory (containment room).
• Anteroom with a double-door entry; may consist of a BSL2 room
• Ventilation: directional airflow, controlled ventilating system.
• Autoclave on site (but not mandatory in the containment room).
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Laboratory for handling TB cultures
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Which biosafety level for TB laboratory activities?
Microscopy in a well-ventilated room
Culture = specimen processing in a BSC in a BSL2
Culture identification and DST = BSL2 containment room with ventilation:
directional airflow from functionally clean to dirty areas, controlled ventilating system ensuring 6 to 12 air exchanges per hour.
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Standard practices
• Limited access to the laboratory.
• No eating, drinking, smoking, etc.
• No mouth-pipetting, no chewing pencils, etc.
• Assume that ALL specimens are potentially infectious.
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Standard practices
• Hand-washing (dry with disposable paper).
• Work surfaces to be decontaminated at least once a day.
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Good microbiological techniques
• Good microbiological techniques (GMT): working methods applied to minimize exposure to pathogens via, for example, aerosols, splashes, accidental inoculation.
• GMT are fundamental to laboratory safety.
• Specialized equipment may support good laboratory practice but does not replace it.
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Personnel qualifications: proper trainingFor culture procedure:
• TB disease and transmission;• wearing and use of protective equipment and clothing;• handling of infectious materials;• laboratory design, including air flow conditions;• use of BSC, centrifuge (operation, identification of malfunctions,
maintenance);• preventing and coping with incidents;• good laboratory practice and good microbiological techniques;• organization of work flow procedures; • waste management;• importance of laboratory results for patient management;
• importance of laboratory results for the national TB programme.24
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Personal protective equipment
• Masks/respirators
• Gloves
• Gowns
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Personal protective equipment – masks
• Surgical masks prevent the spread of microorganisms from the wearer (protection from exhalation).
• Masks do not provide protection to the wearer against inhaling small infectious aerosols.
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Personal protective equipment – respirators
N95/FFP2 FFP3
N95/FFP2 respirators effectively filter out more than 95% (98% for FFP3) of particles 0.3 µm or more in diameter.
Respirators have to be fitted to the face. Facial hair causes the respirator to be ineffective.
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Personal protective equipment – respirators
Respirators may be worn in settings of high MDR-TB and/or HIV prevalence, where staff may be HIV-infected and highly susceptible to infectious aerosols.
Respirators must be available in all culture/DST labs for coping with spillages outside the BSC.
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Personal protective equipment – gloves
• Gloves should always be worn while specimen processing and handling TB cultures.
• Wearing gloves can give technicians a false sense of safety.
• Frequent hand-washing and care in the handling of contaminated materials are good laboratory practices.
• Gloves should be removed at every interruption of work and should not be reused. Hands should be washed after removal of gloves.
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Personal protective equipment – gowns
• Gowns must always be worn inside the laboratory (but never outside) and should be changed regularly, at least weekly.
• Gowns should preferably be fully buttoned, long-sleeved with narrow cuffs, and back-opening.
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Remove PPE in the following order:
1.Disposable gloves
1.Respirator/mask
1.Gown/coat/suit/overalls
Removing PPE
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Personal protective equipment – conclusion
• Hand-washing and GMT are acceptable practices for most countries.
• Each country must evaluate the risks and decide on the level of personal protection equipment that is appropriate, given the available resources.
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Disinfectants
• A disinfectant is a chemical or mixture of chemicals used to kill microorganisms.
• Disinfectants are usually applied to surfaces or inanimate objects.
• Disinfectants may be used for pre-decontamination treatment, before autoclaving.
Because of their specific cell wall structure,TB bacilli are resistant to most standard disinfectants, e.g. quaternary ammonium compounds are ineffective.
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Disinfectants
The only adequate disinfectants against TB bacilli are:• Phenol, 2–5%: very irritant to skin, use derivatives.• Hypochlorite (bleach): corrosive to metals.• Alcohol 70%, no residue, use on skin and work surfaces.• Iodophores, 3–5%, iodine plus inert polymer.
• Glutaraldehyde, requires an activator, highly irritant to skin.
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Disinfectants
• Diluted solutions should be prepared daily.• Stock solutions should be stored according to
manufacturer's recommendations. • Use commercial solutions for “dirty or worst possible
situations”.• Follow national chemical safety guidelines.
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Waste disposal
• All infected materials, including closed specimen containers, should be placed in the BSC in autoclavable bags.
• All cultures and related materials should be autoclaved.
• All material handled in the BSC should be considered as infected.
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Incident: spill
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Spill in the BSC – what to do
• Cover the spill with absorbent paper towel.
• Pour over disinfectant and leave for at least 2 hours.
• Discard absorbent tissue and all clean-up material in an autoclavable bag and autoclave.
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Spill outside the BSC
• EVACUATE the room and stay outside with the door closed for at least 2 hours.
• Using appropriate respiratory protection devices, return to the accident area to clean the spill.
• Cover the spill with paper towel and pour over disinfectant. Leave for at least 2 hours.
• Once disinfection is complete, discard all waste into suitable waste containers and autoclave.
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Spill outside the BSC
Emergency spill kit should be available in all culture/DST laboratories, with:
•all personal protective equipment (overalls, over-shoes, gloves, respirators);
•Paper towels;
•large quantities of disinfectant.
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Chemical safety
• Alcohols are flammable: avoid flame
• Phenol is corrosive:– avoid direct contact with the skin or mucous
membranes;– limit exposure to phenolic fumes.
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NEVER ADD WATER TO ACIDALWAYS ADD ACID TO WATER
WATER
ACID
ACID
WATER
Chemical safety: handling acids
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SAFETY FIRST!
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True and false exercise
1. Surgical masks protect you from TB infection.
2. Remove personal protective equipment in the following order:
respirator/mask
disposable gloves
gowns/coats/suits/overalls.
3. In case of spills outside the BSC, you should evacuate the room and stay outside with the door closed for at least 30 minutes.
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Module review: take-home messages
Never smoke, eat, or drink in the laboratory. Wash your hands frequently with soap and water
before and after performing any procedures. Avoid hazards in a TB laboratory by paying
careful attention to safety procedures. Always work carefully and in a safe manner
following good microbiological technique. The additional protection conferred by
respirators must be assessed for each setting.
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Self-assessment• How is TB transmitted from person to person?
• What are the sources of infectious aerosols in a laboratory?
• What is the critical equipment for safe culture and DST?
• What personal protective equipment is recommended for TB laboratory activities?
• What are the most efficient disinfectants in TB laboratories?
• What procedures should be followed when coping with accidents?
• What precautions should be taken when handling acids?
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