2. Introduction
Microbiology is the scientific study of
microorganisms. Microorganisms are those organisms
that are too small to see with the naked eye and
include things like bacteria, fungi, and viruses.
Air microbiology: is the study of living microbes
which are suspended in the air. It is also called aero
microbiology.
3. Cont….
The study of microorganisms and their spores invisible
to naked eye suspended in air.
Study of aero-spoliation, aerial transmission and
biological materials.
It also includes the study of diseases transmitted
through respiratory routes.
The field of aero-microbiology is important as it
involves, Formation of aerosols.
4. Cont……
Microbes are called bio-aerosols.
Microbes normally found in atmosphere within 300-
10000 feet above from the land.
There are significantly less atmospheric
microorganisms than there are in oceans and in soil.
These microbes have a chance to travel long distances
with the help of wind and precipitate and increase the
rate of infectious diseases caused by these microbes.
5. Cont…..
The important gases that effect the microorganisms
are hydrogen sulphide, sulphur dioxide, carbon
monoxide, chlorine, hydrogen fluoride, ozone , etc.
The microbial forms are bacteria, fungi and
actinomycetes , algae, spores of pteridophytes, pollen
grains, micro insects and viruses.
6. History
During 1930s the term Aero-microbiology was used to
denote the air borne spores (e.g. fungi and other
microorganisms )
Further in 1951, the term was elaborated to include
dispersion of insect population, fungal spores, bacteria
and viruses.
In 1964, the term included the research work of air
borne materials of biological significance.
7. Indoor air microbiology
It deals with microorganisms present in air in indoor
environment.
They are the microorganisms which are responsible
biodeterioraton of storage materials, equipment ,
library materials and archives.
Microbes can survive for extended period in indoors as
they have relatively less exposure to radiations.
8. Indoor air microbiology
It involves home and work place environments in
which air borne microbes create major public health
concerns.
Microbes found in different sites:
Aeromicrospora of pharmacy.
Aeromicroflora of hospitals.
Houses Aeromicroflora of storage materials.
9. Indoor air microbes
Indoor air contains more disease causing agents that
has higher chances of infections than outdoor air
especially in large gatherings like schools and theaters.
The commonest genera of fungi in indoor air are
Penicillium, Aspergillus.
The commonest genera of bacteria found in indoor air
are Staphylococci, Bacillus and Clostridium.
10. Outdoor air microbiology
The study of air in the atmosphere, which is found
outside the buildings, is referred to as outside
airoutdoor aero microbiology.
In outdoor or extramural environment, the expanse of
space and the presence of air turbulence are the two
controlling factors in the movement of bio aerosols.
11. Outdoor air microbes
The number and kind of microorganism may vary
from place to place, depending upon the human
population densities. Some of microbes include;
Algae
Protozoa
Yeasts
Molds , Mold spore are predominant,
e.g clasdosporium
Bacterial species are, Spore forming, Non spore forming.
12. Cont…..
The dominant microflora of outside air is fungi.
The two common genera of fungi
are cladosporiul and sporobolomyces.
Aspergillus, Alternaria, Phytophthora and Erysiphe
are other fungal aerosals.
13. Cont…..
Also contains besidispores, ascopres of yeast, and
fragments of mycelium and canidia of molds.
The bacterial genera include:
Bacillus and clostridium, sarcina, mirococcus, coryneb
acterium and Achromobacter.
14. Sources of air microbes
Some of the sources are listed below;
Soil
Water
Wind and tidal actions
Human beings
15. Cont….
Soil: soil microbes disturbed by the wind blow,
liberated into the air and remain suspended there for a
long period of time.
Man made actions like digging or ploughing the soil
may also release soil borne microbes into the air.
16. Cont……..
Water: water microorganisms release in the form of
water droplets or aerosols.
Splashing of water by wind action or tidal action may
also produce droplets or aerosols.
Wind and tidal actions: Air currents may bring the
microorganisms from plant or animal surfaces into air.
For example, spores of Puccini a graminis
17. Cont……….
Human beings: The main source of airborne
microorganisms is human beings.
Pathogenic flora of the upper respiratory tract and the
mouth are discharged into the air by activities like
coughing, sneezing, talking and laughing.
18. Forms of discharge
The microorganisms are discharged out in three
different forms which are grouped on the basis of their
relative size and moisture content.
droplets,
droplet nuclei and
infectious dust.
19. Droplets
Droplets are usually formed by sneezing, coughing or
talking. Each consists of saliva and mucus.
It has been estimated that the number of bacteria in a
single sneeze may be between 10,000 and 100,000
The size of the droplet determines the time period during
which they can remain suspended.
Most droplets are relatively large, and they tend to settle
rapidly in still air.
the droplets containing pathogenic microorganisms may
be a source of infectious disease.
20. Droplet Nuclei
Small droplets in a warm, dry atmosphere tend to
evaporate rapidly and become droplet nuclei.
The residues of solid material left after drying up of a
droplet is known as droplet nuclei.
These are small, 1-4µm, and light.
can remain suspended in air for hours or days,
traveling long distances.
may serve as a continuing source of infection if the
bacteria remain viable when dry.
21. Cont……
Viability is determined by a set of complex factors
including:
the atmospheric conditions like humidity, sunlight
and temperature, the size of the particles bearing the
organisms, the degree of susceptibility or resistance of
the particular microbial species to the new physical
environment.
22. Infectious Dust
Large aerosol droplets settle out rapidly from air on to
various surfaces and get dried.
Nasal and throat discharges from a patient can also
contaminate surfaces and become dry.
Disturbance of this dried material by bed making,
handling a handkerchief having dried secretions or
sweeping floors in the patient's room can generate
dust particles which add microorganisms to the
circulating air
23. Cont……..
Airborne diseases are transmitted by two types of
droplets, depending upon their size.
Droplet infection proper applies to, droplets larger
than 100 µm in diameter.
The other type may be called airborne infection, and
applies to dried residues of droplets.
24. Factors Affecting Microbes
Microbes are continually in the state of stress.
Oxygen stress and ionic stress.
Temperature stress.
Moisture stress/humidity.
UV-radiation stress
25. Oxygen and ionic stress:
Higher level of oxygen and its reactive forms causes
inactivation of enzymes, damage to DNA, inactivation
of nucleic acids and proteins.
Naturally occurring ions causes ionic stress,
lightening, water shearing and ion displacement.
26. Temperature
Temperature is the major factor in the inactivation of
microbes.
High temperature promotes inactivation, mainly
associated with desiccation and protein denaturation
lower temperature promotes longer survival times.
At freezing environment some organisms lose viability
because of formation of ice crystals on their surfaces.
27. Moisture content
The relative as well as the absolute humidity content of
the air play a major role in the survival of the air borne
microorganisms.
gram-negative bacteria in air survive for longer periods
at relative low humidity by regulating their metabolic
activities.
While Gram-positive at high moisture content.
28. Cont……..
at 100% relative humidity, longer exposure decreases
the viability in relation to survival.
Intracellular ionic imbalance and loss of cellular
metabolites occur when the cell is exposed to
unfavorable humidity level.
Viruses with enveloped nucleocapsids tend to have
better survival in aerosols than without.
29. Radiation stress
Shorter wavelength and X-ray causes damage to DNA
by Single strand breaks, Double strand breaks and
Alteration in structure of DNA.
It also affects Genome replication, Transcription and
Translation.
30. Significance of air microbes
When compared with the microorganisms of other
environments, air micro flora is very low in number,
they play a very significant role.
Because the air is in contact with almost all animate
and inanimate objects.
31. Cont..
The significance of air flora has been studied since
1799, in which year Lazaro Spallanzani attempted to
disprove spontaneous generation.
In 1837, Theodore Schwann, in his experiment to
support the view of Spallanzani.
Where he introduced fresh heated air into a sterilized
meat broth and demonstrated that microbial growth
couldn't occur.
32. Cont….
These two scientists formed the basis of modern day
forced aeration fermentations.
Pasteur in 1861, which first showed that
microorganisms could occur as airborne contaminants.
33. Significance in Human Health
Air acts as a medium for the transmission of infectious
agents.
An adult man inhales about 5m³ of air per day.
Most of the microorganisms present in air are
harmless saprophytes and commensals,
less than 1% of the airborne bacteria is pathogens.
34. Cont….
Even though the contamination level is very low, the
probability of a person becoming infected will be
greatest if he is exposed to a high concentration of
airborne pathogens.
35. Staphylococcus aureus
The number of S. aureus in air may vary between 0-
1/m³ and 50/m
The purity of outdoor air, however, is an essential part
of man's environment.
In the case of indoor air chance for the spread of
infectious disease is more especially in gatherings.
36. Significance in Hospitals
Hospitals are the war fields for combating against
diseases, there are certain occasions in which
additional new infectious diseases can be acquired
during hospitalization.
Air within the hospital may act as a reservoir of
pathogenic microorganisms which are transmitted by
the patients.
Infection acquired during the hospitalization is called
nosocomial infections and the pathogens involved are
called as nosocomial pathogens.
37. Cont..
The common microorganisms associated with hospital
infection are
Haemophilus influenza, Streptococcus pneumonia,
Streptococcus pneumonia, Staphylococcus aureus,
Pseudomonas aeruginosa, members of
Enterobacteriaceae and respiratory viruses.
38. Microorganisms in Industries
Food manufacture:
Microorganisms that have been transported through
the air and have settled on, or in, the material are
involved in various fermentation products.
Production of alcoholic beverages, vinegar,
sauerkraut, ensilage, dairy products, etc., is often due
to microbial activity
39. cont,….
Spoilage of foods and fermentation products
In industrial processes, where particular organisms are
to be grown, to supply sterile air free from
contaminating organisms is a considerable problem.
40. Bioaerosals control in laboratory
Bioaerosal containing airborne microbes can be
controlled at every point by using different mechanism
which includes:
Ventilation
Filtration
Biocidal agents
Isolation
41. Cont….
Ventilation:
It is the most common method to check build up of
airborne particles.
This can be achieved by open windows or use of air
conditioning and heating units that pump outside air
into the room.
This is cost effective and this will at least reduce the
amount of microbes inside room.
42. Cont…….
Filtration:
Unidirectional air flow filtration is also simple and
effective for bioaerosol control.
HEPA is used for this purpose and it removes virtually
all infectious particles.
Bag house filtration has also become common in
building
43. Cont..
Biocidal agents:
These are used for super heating, super dehydration,
ozonation and UV irradiation to eradicate the
microorganisms.
The most commonly used method is ultraviolet
germicidal radiation (UVGI).
44. Cont….
Isolation:
Is the enclosure of an environment through the use of
positive or negative pressurized air gradients and air
tight seals.
Isolation chamber in TB wards in hospitals provide
protection to other present inside the air from these
rooms is exhausted in to the atmosphere passing
through a HEPA filter and biocidal control chamber.
45. Cont..
This system work on negative pressurized air.
Positive –pressure isolation chambers, working on the
opposite principle force air out of the room thus
protects occupants of the room from outside
contamination.
46. The diseases that caused by
air microbes or catch by
breathing, These are called
airborne diseases.
.
47. Cont….
Airborne disease can spread when an infected person
coughs, sneezes, or talks.
certain viruses or bacteria take flight and hang in the
air or land on other people or surfaces
48. Symptoms
Airborne diseases usually result in one or more of the
following symptoms:
inflammation of nose, throat and lungs
coughing
Sneezing
runny nose
sore throat
swollen glands
Headache
loss of appetite
fever
fatigue
49. Types of airborne diseases
Many diseases are spread through the air, including :
Influenza
Tuberculosis (TB)
Measles
Mumps etc.
50. Influenza
Most of us have some experience with the flu. It spreads so
easily because it’s contagious about a day before you notice
the first symptoms.
It remains contagious for another five to seven days. If you
have a weakened immune system for any reason, you can
spread it to others for longer than that.
There are many strains of the flu, and they are constantly
changing. That makes it difficult for your body to develop
immunities.
51. Tuberculosis (TB)
TB is an airborne disease.
but this bacterial infection doesn’t spread easily. You
generally have to be in close contact with an infected
person for a long time. You can be infected without
becoming ill or infecting others.
52. About 2.5 billion people worldwide are infected with
TB. Most aren’t sick. About 9.6 million people
worldwide have active TB.
People with a weakened immune system have the
greatest risk of developing the disease.
53. Measles
Measles is a very contagious disease, particularly in
crowded conditions. The virus can remain active in the
air or on surfaces for up to two hours.
You’re able to infect others up to four days before and
four days after the measles rash appears. Most people
get the measles only once.
54. Measles is a leading cause of death among children
worldwide
It is estimated that the measles vaccine prevented 20.3
million deaths from 2000 to 2015.
55. generally starts on your face and neck, and then
spreads over the course of a few days.
56. Serious complications of measles include:
ear infections
diarrhea
dehydration It
severe respiratory infection
blindness
swelling of the brain, or encephalitis
57. Mumps
Mumps is another very contagious viral disease. You
can spread it before symptoms appear and for up to
five days after.
Mumps used to be quite common in the United States,
but rates have declined due to vaccination.
