Air microbiology study of microbes suspended in air. Microflora of air depend on the location and environmental condition at particular place. There are different types of air trapping devices like Slit Sampler, Andersons samplers, Impingers etc. Air borne diseases mainly spread by droplet infection, contact with infected things . Air borne diseases are discussed and concluded with control of air borne microbes.

1. AIR MICROBIOLOGY
SUMANGALA.C.H.

2. CONTENTS
1. INTRODUCTION
2. MICROFLORA OF AIR
3. AIR SAMPLING TECHNIQUES
4. AIR BORNE DISEASES
5. CONTROL OF AIRBORNE
MICROBES

3. Aerobiology coined by F.C.Meier in 1930.
• Study of microbes suspended in air.
• Microbes present in air as:
1. Bioaerosol: Aerosol of biological
origin.example bacteria.
2.Droplet nuclei: Dry residues formed by
evaporation of droplets coughed or sneezed
into atmosphere.

4. AIR MICROFLORA
In air we have allochthonous populations.
(transient)
INDOOR AIR MICROFLORA
Air inside building is indoor air.
• Common Fungi Penicillium, Aspergillus.
• Common Bacteria Staphylococcus ,Bacillus,
Clostridium
• Hospital: important indoor environment for
spread of pathogens Candida and
Mycobacterium
• Library: Cellulose degrading fungi like
Aspergillus, Penicillium, Rhizopus
Trichoderma.

5. OUTDOOR AIR MICROFLORA
• Air in atmosphere found outside buildings is
outside air.
• The number and kinds of microbes in air
vary from place to place depending on
human population , location etc.
• Fungi: Aspergillus, Cladosporium, Alternaria,
basidiospores and ascospores of yeasts.
• Bacteria: Bacillus,Clostridium,Micrococcus
and Staphlococcus.

6. AIR SAMPLING TECHNIQUES
 Based on principle of Sedimentation
a. Gravity Slide Method
 Glass slide coated with petroleum jelly and
exposed to air for 24 hrs.
 Then observed directly under microscope
for pollens and microbes.
This gives Total count.

7. b. Settle Plate Method
 Petriplate containing Agar medium
exposed to air for 10 mins at different
places and incubated.
 After incubation number of colonies are
counted.
 This gives Viable count.

8.  Impactors
Solid surface is used for particle collection.
a. Slit sampler:
Air is drawn through narrow slit and
particles are impacted on Agar medium.
 After incubation colonies are counted.

9. b. Burkard Spore Trap.
Air is passed through a slit orifice and
impacted on adhesive tape supported on a
clock driven drum.
Drum makes one complete revolution in
seven days.
 After seven days tape removed and cut
and observed under microscope.

10. c. Rotorod
 Portable air sampler made of pair of rods
mounted on a shaft.
Battery operated motor rotates it at
constant speed.
Outer surface of rod is covered with cello
tape smeared petroleum jelly.
After exposure strips cut and observed
under microscope.

11. d. Andersons sampler
 This apparatus consists of series of six plates
through which air sample is passed through a
circular opening.
 Each plate has 400 holes .
 Below the perforated plate lies a Petriplate with
Agar medium .
After certain time plates are removed and
incubated and observed for the development of
colonies.

12.  Impingers
Air borne particles are collected by
bubbling sampled air through a liquid.
a.Porton Impinger
Narrow glass flask with a glass stopper.
Stopper bears a side arm to which suction
is applied.
Through apex of stopper an intake tube
terminate in a jet.
0.5 to 1 micrometer diameter cells
collected in porton impinger.

13. b . Preimpinger:
Glass bulb with half filled collecting fluid.
When connected to porton impinger
particles upto 4 micrometer diameter
penetrates the preimpinger.

14.  Filteration
Air is filtered through a membrane filter
and observed under microscope
or the filter disc is placed on Agar
medium and incubated and no of
colonies are counted.

16. AIR BORNE DISEASES
Mainly transmitted by dust containing
infectious agent or droplet nuclei .
Bacterial air borne disease
1.Diptheria - Corynebacterium diphtheriae
 Bacteria produce diphtheria toxin which
cause formation of thick gray membrane
covering throat and tonsils.
2.Tuberculosis- Mycobacterium tuberculosis
 In lungs bacteria becomes sealed to form a
calcified nodule called tubercle .

17. 3.WhoopingCough -Bordetella pertussis
Coughing with a distinctive whooping
sound when breathing in.
4.Bacterial meningitis– Streptococcus
pneumoniae , Neisseria mengitidis
 It causes inflammation of membrane of
brain and spinal cord.

18. 5.Streptococcus pneumonia-
Streptococcus pneumoniae
 Mainly inflammation of the alveoli in the
lungs.
 Entire lobes of lungs infected -lobar
pneumonia.
 Branchial tree infected -Branchopneumonia

19. Bacterial disease acquired by inhaling
particles from environment.
1.Legionellosis -Legionella pneumophila
 Spread from mist and from air conditioning
unit .
 Causes Bronchopneumonia.
2.Psittacosis -Chlamydia psittaci
 Spread from droppings of infected birds.
 Inflammatory illness of lungs.

20. Viral Air Borne diseases
Viral disease spread by droplet nuclei
and direct contact.
1.Influenza(Flu)
 Influenza virus classified under
orthomyxovirus .
 Virus bind through hemagglutinin on
to surface of epithelial cells in nose, throat
and lungs.
 The main target of virus are columnar
epithelial cells of respiratory tract.

21. 2.Measles
 Rubeola virus
classified under paramyxovirus.
Virus enters through respiratory tract or
conjunctiva of eyes.
 Lesions found in skin, conjunctiva and
mucous membrane of nasopharynx
bronchi and intestinal tract.
 Kopliks spots seen.

22. 3.German measles
Rubella virus classified under Togavirus.
 Virus transmitted under respiratory route and
replicates in nasopharynx and lymph nodes.
 Fever ,swollen lymph nodes and rashes seen.
4.Small pox
 Variola virus classified under orthopoxvirus.
 Characteristic feature rash progresses to
raised bump and pus filled blister that crust
and scab and fall after about three weeks
leaving scar.

23. 5.Chicken pox
 Varicella virus classified in herpes family.
 Characterized by pleomorphic eruption of
skin and mucous membrane.
 Eruptions passes through stages of
macule, papule, vesicle and pustule.
6.Mumps
 Mumps virus belonging to paramyxovirus.
 Characterized by swelling of parotid
glands occasionally swelling of sub
lingual glands.

24. Fungal Air Borne Diseases
 Mainly occurs by inhalation of spores.
 Initial infection is in lungs and spread to
other organs by blood stream.
 Treatment is mainly Amphotericin B and
Ketaconazole.

25. 1.Blastomycosis
Blastomycosis dermatitidis
 If only lungs involved its Pulmonary
Blastomycosis.
 Initial infection in lungs then spread to skin
where cutaneous ulcers occur.
2.Coccidiomycosis:
Coccidioides immitis
Affects lungs ,bones, skin and meninges
Some people develop painful erythematous
nodular lesions called Erythema nodosum.

26. 3.Histoplasmosis
Histoplama capsulatum
 Disease of reticulo endothelium system
 Cause the formation of Granulomas
 Can necrotize and become calcified.
4.Cryptococcis
 Cryptococcus neoformans
 Affects lungs, spread to skin ,bones and
Central nervous systems.
 Once in central nervous system Cryptococcal
meningitis occurs.

27. Control of Air Borne Microbes.
1.Dust control
Dry vacuum pick up followed by application
of suitable detergent
Oiling floors ,bed clothes etc.
2.UV radiation
Germicidal lamps
250nm -260nm radiations shows
bactericidal effect.

28. 3. Laminar Air Flow system
 Air passes through HEPA filters and
removes particles as small as
0.3micrometer.
4.Chemical techniques
 Indoor air microbial population reduced by
vapourizing or spraying of propylene
glycol, Propionolactone and triethylene
glycol.