The document discusses the microbiology of air and bioaerosols. It defines bioaerosols as microorganisms and their byproducts suspended in the atmosphere. It describes the history of the field beginning with Darwin's observations of dust particles and Pasteur's early research isolating airborne microbes. It also outlines the types of microbes found indoors and outdoors, how they are transmitted through the air, and factors like temperature, humidity and altitude that influence their presence. Finally, it discusses bioaerosols as human health hazards and different sampling methods used to study airborne microbes.

1. MICROBIOLOGY
OF AIR

2. • Introduction: Aero Microbiology
• History
• Why Aero Microbiology
• Types of Microorganisms in air
• Sources and transmission of microbes
• Factors influencing air microflora
• Bioaerosols as human hazards
• Bioaerosols Sampling Methods

3. • The aero microbiology is the study of microorganisms in air and hence
they are called as bioaerosols or biological aerosols.
• Bioaerosol is a kind of colloidal system consisting of microorganisms
and their by-products, which are suspended in the atmosphere.
• Since they are found in air they have a high opportunity to travel in air
with the help of wind and precipitation.

5. • Charles Darwin was the first to observe the transport of dust particles
but Louis Pasteur was the first to research microbes and their activity
within the air.
• Prior to Pasteur’s work, laboratory cultures were used to grow and
isolate different bioaerosols.
• Pasteur also developed experimental procedures for sampling
bioaerosols and showed that more microbial activity occurred at
lower altitudes and decreased at higher altitudes

7. • The microbiology of air is significant in
many places such as hospitals, food
processing, air conditioning and many
other places.
• The bio-aerosol in hospital indoor air is
highly influenced by the number of
occupants, their activity and the
ventilation. Since exposure levels are
high, this may be an issue in the
immunocompromised patients.
• In air conditioning and metal systems:
fungi like Cladosporium have enzymatic
activity capable of metabolizing diesel, jet
fuels, creosote and hydrocarbons, it
produce a noxious smell that impact the
quality of indoor air.

8. Microflora of air can be divided in 2 headings.
1. Outdoor Microflora
Fungi – Cladosporium,
Sporobolomyces
Spores of yeasts- Basidiospores,
Ascospores
Bacteria- Bacillus anthracis, Clostridium, Sarcina
Major airborne bacteria is Bacillus anthracis. It is
a gram positive rod shaped bacteria that utilizes
spore formation to resist environmental stresses

9. • .
Fungi – Aspergillus fumigatus
Bacteria- Staphylococcus, Bacillus.
Aspergillus fumigatus, which is a major
airborne fungal pathogen.This pathogen is
capable of causing many human diseases
when conidia are inhaled into the lungs
An example of a viral airborne pathogen is the Avian
Influenza Virus, which is a single stranded RNA virus that can
infect a broad range of animal species as well as humans and
cause the Avian Influenza.

10. Air microorganisms discharges in three forms classified on
the basis of size and moisture content.
1. Droplets
2. Droplet nuclei
3. Infectious dust

11. DROPLETS
• Airborne liquid spheres(mists) greater than5 microns in
diameter, that are discharged from the nose or mouth by
sneezing, coughing, talking or simply exhaling air.
• These droplets consists of both mucus and saliva.

12. • Airborne particles that remain when the water fraction has evaporated away from
a mucous droplet.
• These are of below 5 microns usually 1-4 microns in diameter typically travel a
long distance.
• These droplets are so small that the downward forces of gravity is countered by
the fluid resistance of the air and as a result these droplets tend to remain
suspended in the air and move with the ambient air currents.
DROPLET
NUCLEI

13. Infectious dust
• These are the dried aerosol droplets settle out rapidly from air.
• Nasal and throat discharges from a patient can also
contaminate the surfaces and dry.
Airborne diseases are transmitted by 2 types of
droplets depending on their size.
1. Droplets larger than 100 micrometre in diameter.
2. Air borne infection

15. Intrinsic factors include the nature and physiological state of microorganisms.
• Spores are relatively more abundant than the vegetative
bacterial cells.
• This is mainly due to the dormant nature of spores which
enables them to tolerate unfavorable conditions like desiccation,
lack of enough nutrients and ultraviolet radiation.
• Similarly fungal spores are abundant in the air since they are meant
for the dispersal of fungi.
• The size of the microorganisms is another factor that
determines the period of time for which they remain
suspended in air.
• Generally smaller microorganisms are easily liberated
into the air and remain there for longer period.
Intrinsic factors

16. Environmental factors
Temperature

17. Environmental factors
Humidity

18. Environmental factors
Altitude

19. • Bioaerosols – aerosols originated biologically such as metabolites, toxins, or
fragments of microorganisms that are present ubiquitously in the environment.
• Composition:
• Fungi & Bacteria
• Endotoxins
• Beta-glucans
• Mycotoxins
• Allergens
• Highest concentration in the planetary boundary layer
• Size range - 10 nanometer virus particles to 100 micrometers pollen grains
• May Cause:
• Infectious Diseases
• Allergic Diseases
• Poisoning
Bioaerosols as Human Hazards

20. • Microbes may penetrate organs via respiratory tract
• Once settled, microbes may enter through skin, or by hands to
digestive tract.
Skin diseases
Tuberculosis (Mycobacterium tuberculosis)
Diphtheria (Corynebacterium diphtheriae)
Pneumonia (Streptococcus pneumoniae)
Influenza (Orthomyxoviruses)
Cold (Rhinovirus)
Sore throat (Adenoviruses)

21. Allergic Diseases

22. Poisoning
• Major source: Mycotoxins and endotoxins
• Most common mycotoxin: Aflatoxin by Aspergillus flavus
• Has toxic, mutagenic, carcinogenic and teratogenic actions
• Bioaerosols from livestock wastes and grain dusts: elevated
concentration of mycotoxins and endotoxins may cause lung diseases.
• Inhalation of 80 mg of endotoxin in healthy individual decrease the
lung function (Kharitonov and Sjöbring, 2007)

23. Control Measures

24. Bioaerosol sampling in the context of
microbiological assessment is the
collection of air borne microorganisms.
The atmosphere is not a living habitat
for microbes, but they can spread
through it, and therefore the
atmosphere could act as a conveyor of
pathogenic microbes.
• Major methods:
• Active method
• Passive method

25. Sedimentation (settle plate technique) :
Here the petri dish with agar medium is horizontally exposed to air for a certain period.
Particles and microorganisms settle via gravity. The plates are then incubated at required
temperature and time and number of colonies are counted .

26. ACTIVE METHOD
• This method requires the use of certain bioaerosol samplers for the
collection purposes.
• Some of the commonly used bioaerosol samplers are
• Inertial Impactors
• Impingers
• The Centrifugal Sampler
• Filter Samplers
• Electrostatic precipitator

27. • Collection mechanisms for different types of inertial bioaerosol samplers.
• Inertial impaction
examples : Single-stage impactors, Cascade impactors
• Centrifugal inertial impaction
examples : Reuter centrifugal sampler, BIO.
• Liquid impingement
examples : AGI-4 and AGI-30 impingers
• Tangential impingement
example : BioSampler SKC.

28. INERTIAL IMPACTORS

29. IMPINGERS

33. • As air is heart of nature, study of air microflora is essential
• It has direct effect on human health.
• Human activities are responsible for presence of various microbes in air
• Various techniques available to control air microflora have to be
implemented

34. • Bio-aerosols in indoor environment: Composition, health effects and
analysis: Padma Srikanth, Suchithra Sudharsanam, Ralf Steinberg
• Lipopolysaccharide challenge of humans as a model for chronic
obstructive lung disease exacerbations: Kharitonov, S.A., Sjöbring, U.,
2007.
• Respiratory disease in United States farmers: Hoppin, J.A., Umbach,
D.M., Long, S., Rinsky, J.L., Henneberger, P.K., Salo, P.M., et al., 2014.

35. THANK
YOU