Transcript Microbes in Air and Bioaerosols

Microbes in Air and
Bioaerosols
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Definition-Microorganisms or particles, gases, vapors, or
fragments of biological origin (i.e., alive or released from a
living organism) that are in the air.
Bioaerosols are everywhere in the environment.
Some bioaerosols, when breathed in, can cause diseases
including pneumonia, asthma, rhinitis (e.g. cold, hay fever),
and respiratory infection.
Some bioaerosols can also infect the eyes and via
ingestion (swallowed)
Bioaerosols
Airborne Microbes and Aerosols
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Airborne transmission is possible for essentially all
classes of microbes: viruses, bacteria, fungi and
protozoans.
Any respiratory pathogen able to survive aerosolization
and air transport is considered a potential cause of
airborne disease.
Aerosols: Airborne particles, either solid or liquid,
about 0.5 to 20 microns in diameter, that remain
airborne for extended periods of time.
Droplets: >20 (usually 100+) microns in diameter; settle
rapidly or evaporate to form droplet nuclei in the
aerosol size range.
Some Examples of Bioaerosols
Living Source
Examples
Microorganisms (microbes):
 Bacteria
Legionella, Actinomycetes, endotoxins
 Fungi
Histoplasma, Alternaria, Pencillium,
Aspergillus, Stachybotrys aflatoxins,
aldehydes, alcohols
 Protozoa
Naegleria, Acanthamoeba
 Viruses
Rhinoviruses (colds), Influenza (flu)
 Algae
Chlorococus
Green plants
Ambrosia (ragweed) pollen
Arthropods
Dermatophagoides (dust mites) feces
Mammals
horse or cat dander
Diseases Caused by Bioaerosols:
Diseases Caused by Bioaerosols:
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Result from exposure to antigens (of indoor bioaerosols)
that stimulate an allergic response by the body's immune
system.
Susceptiblity varies among people.
Diseases usually are diagnosed by a physician.
Once an individual has developed a hypersensitivity
disease, a very small amount of the antigen may cause a
severe reaction.
Hypersensitivity diseases account for most of the health
problems due to indoor bioaerosols.
Hypersensitivity or Allergic Diseases
1. Hypersensitivity or Allergic Diseases
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Building-related asthma:
◦ symptoms -an hour of exposure or 4-12 hours after exposure.
◦ by airborne fungi such as Altemaria, glycoproteins from fungi,
proteases from bacteria, the algae Chlorococus, ragweed
pollen, dust mites, and dander from cats.
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Allergic rhinitis: stuffiness of the nose, clear discharge
from the nose, itchy nose, and sneezing. Itching and puffy
eyes.
◦ All the indoor bioaerosols listed under building-related
asthma except the bacteria proteases also cause rhinitis.
1. Hypersensitivity or Allergic Diseases
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Hypersensitivity pneumonitis (extrinsic allergic alveolitis):
◦ Can be an acute, recurrent pneumonia with fever, cough, chest
tightness, and fluids entering the lungs.
◦ to shortness of breath, fatigue, weight loss and thickening and
scarring of the lungs.
◦ microorganisms associated with hypersensitivity pneumonitis:
fungi such as Penicillium and Sporobolomyces, bacteria such
as Thermoactinomyces, and protozoa such as Acanthamoeba.
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Humidifier fever: fever, chills, muscle aches, and malaise
(general feeling of being unwell), but no lung symptoms.
◦ The symptoms usually start within 4-8 hours of exposure and
end within 24 hours without long-term effects
Legionella: Legionellosis and Pontiac Fever
Reservoirs and amplifiers:
Hot water systems
 circulating water ventilation systems (cooling towers)
 Plumbing (e.g., shower heads).
 Hot tubs, whirlpools, etc.
 Produce fresheners
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Cleveland Auto plant outbreak, March, 2001:
 Plant cooling tower is considered a possible source of the
outbreak.
 But, more than 100 other internal water sources -- favorite
breeding grounds for the Legionella bacteria -- were also
under investigation….
Pontiac fever: also caused by Legionella.
 A "flu-like" illness with fever, chills, headache,
myalgia (pain in the muscles), cough, nausea,
and breathlessness.
 Pneumonia does not occur.
 Usually lasts 2-5 days.
 Same sources as for Legionnaires' disease
Legionnaire’s Disease and Pontiac Fever
Legionnaire's disease:
 Bacterial pneumonia caused by Legionella pneumophila.
 A type of pneumonia that affects the lungs and may also affect the
stomach and intestines, kidneys, and central nervous system.
 Incubation period: 2-10 days after exposure
 Frequently requires hospitalization
 Aerosol exposure from contaminated cooling towers, evaporative
condensers, whirlpools, shower heads, faucets, & hot water tanks.
When inhaled, aerosol particles derived from aqueous fluids pick
up moisture (water) while traveling in the respiratory
passageways, thereby increasing in size.
◦ Increased size changes deposition site
H2O
H2O
H2O
Hydroscopicity and Aerosol Deposition in
the Respiratory Tract
Agents of Respiratory Infectious Diseases
Viruses: influenza, measles (rubeola), chickenpox (herpes
varicella-zoster) and rhinoviruses (colds); Hantavirus
(from a rodent; mouse)
Bacteria: Legionella spp., tuberculosis and other
mycobacteria (Mycobacterium spp.), anthrax (Bacillus
anthracis), and brucellosis (Brucella spp.).
Fungi: diseases: histoplasmosis, cryptococcosis,
blastomycosis, coccidiodomycosis, and aspergillosis
Protozoans: Pneumocystis carinii pneumonia; prevalent
in immunodeficient hosts such as AIDS patients.
Acanthamoeba encephalitis; primary amebic
meningoencephalitis (PAM)
Reservoirs of Airborne Microbes
Reservoirs: sources of air microbes
Wide range, overall
Depends on the microbe
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humans,
animal,
soil
dust
water
air
Airborne Microbes and their Reservoirs
Viruses:
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Mostly humans but some animals
Some rodent viruses are significant: ex: Lassa Fever Virus and
Hantavirus.
Bacteria:
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Humans (TB & staphylococci),
other animals (brucella and anthrax),
water (Legionella)
soil (clostridia).
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soil and birds (Cryptococcus and Histoplasma)
dead plant material
wet surfaces (wood and other building materials)
indoor air (mycotic air pollution)
stagnant water for the opportunistic fungi (e.g., Aspergillus sp.).
Fungi:
Amplifiers:
Places where microorganisms multiply or proliferate.
 Most reservoirs are potential amplifiers
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Amplifiers of air microbes
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Devices causing microbes to enter airborne state or be
aerosolized; often the reservoir or amplifier.
Any device able to produce droplets and aerosols:
◦ Humans and other animals: coughs and sneezes, esp.
◦ Mechanical ventilation systems
◦ Nebulizers and vaporizers
◦ Toilets (by flushing)
Disseminators
◦ Showers, whirlpools baths, Jacuzzi, etc.
◦ Wet or moist, colonized surfaces (wet walls and other
structures in buildings)
◦ Environments that are dry and from which small particles
can become airborne by scouring or other mechanisms:
 Vacuuming or walking on carpets and rugs
 Excavation of contaminated soil
 Demolition of buildings
Disseminators
Factors Influencing Airborne
Infection
Factors Influencing Airborne Infection
Aerosol Factors
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Particle size; <5 um dia.; "droplet nuclei" from coughing & sneezing
◦ Deposition site: depends on particle size and hygroscopicity
◦ Chemical composition of the aerosol particle
Relative humidity (RH); dessication (loss of moisture)
Temperature: generally greater inactivation at higher temperature
Sunlight: UV inactivation of microbes
 Factors influencing air movement: winds, currents,
mechanical air handlers, etc.
 Seasonal factors: precipitation, air currents, pollen sources,
etc.
 Air pollution:
◦ chemicals inactivating airborne microbes (OAF= Open Air
Factor)
◦ enhancing their ability to cause infection in a host
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Microbe Factors:
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Size of microbe and of aerosol particle
◦ influences air transport
◦ influences deposition site: in environment and in host
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Composition:
◦ lipids, proteins (structural, enzymes), amino acids, etc.
◦ enveloped and non-enveloped viruses respond
differently to air pollution
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Protective forms:
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spores
cysts
growth phase
moisture content
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Discussed previously in this class.
Host Factors
Sampling the air microbes
Active sampling methods
 Passive sampling method
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Air Samplers - Sedimentation and Slit Samplers
Sedimentation methods: collection of aerosol particles on a
sticky surface; e.g., a petri dish containing agar or glycerol.
 Slit samplers: Sampled of air is directed through a slit
against a rotating collection surface. For bacteria, this
could be an agar medium petri plate. Rotation is intermittent
so that each impaction area represents a specific volume of
sampled air and a time series of samples can be collected.
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Sedimentation - Agar Medium Plate
Slit Sampler
Air Samplers - Stacked Sieve (Anderson type) Sampler
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Six stages, each a perforated
plate located above a petri
dish.
Diameter of air passageway is
smaller at each successive
level, collecting progressively
smaller particles.
Classifies and collects
particles according to size
Used mostly for bacteria.
Can be used for virus
sampling by collecting onto a
sticky surface in the petri
dish.
Air Sampling - Filtration Methods
Pass air through a membrane filter of small enough pore
size to trap aerosol particles.
 After collection, the filter can be plated or particles can be
washed off.
 Dessication and inefficient washing/recovery of collected
particles can be problems.
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Open Face Air Filter Cassette
with Cap
Air Samplers - Electrostatic Precipitation
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Air is drawn over
electrically charged
collection plates so that
charged particles are
attracted to and collected
on either a positively or
negatively charged,
wetted surface.
Collected particles are
washed off into the
circulating collection
fluid on the charged
plate surface.
Air Samplers - Liquid Impingers
Collects particles from sampled
air into a liquid medium.
 All glass impinger (AGI).
 Particles are drawn through a
small orifice that increases their
velocity, thereby causing them to
impinge on the bottom surface of
the container and be "scrubbed"
into the collection fluid.
 Excessive cooling and
evaporation and leakage
(particles not being retained) can
be a problem.
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Air Samplers
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High volume liquid (cyclone) scrubber: Particles in air traveling at
high speeds through a progressively smaller, helical passageway
impinge against the container walls and are collected into a
recirculating collection fluid supplied by a pump