This document discusses the bacteriology of air and water. It defines bacteriology of air as the study of bacteria present in air and infections caused by them. It describes two main modes of transmission for airborne infections: airborne transmission for particles under 5 micrometers that can remain suspended in air, and droplet transmission for larger particles that only travel short distances. It also discusses methods to measure air contamination like sedimentation plates and slit samplers. Finally, it covers the bacteriology of milk, types of bacteria found in milk, milkborne diseases, and examination methods for milk.

1. SUBMITTED BY
SHAILJA(1475)
BACTERIOLOGY OF AIR
AND WATER
PRESENTED BY
SHAILJA (1475)

2. o BACTERIOLOGY OF AIR
o It is defined as the branch of microbiology dealing
with the study of bacteria present in the air and
the infections caused by them.

3. • AIRBORNE INFECTIONS
 Transmission of infection produced by respiratory
droplets less than 5micrometer in size.
• DROPLET INFECTIONS
 Transmission of infection produced by respiratory
droplets larger than 5micrometer in size

4.  Airborne transmission
o Size of particle <5 micrometer in size
o Droplets are produced during coughing ,talking
,sneezing ,invasive procedures(bronchoscopy
,suction aspiration)
 Characteristics of droplets includes;
o Droplets remain suspended in air for long periods
o Travel several meters
o Susceptible individuals may become infected even
if some distance from infected person
o Bacteria involved are- Mycobacterium
tuberculosis,

5.  Droplet transmission
 Size of the droplet should be greater than 5 micrometer
 Droplets are produced during coughing ,sneezing , talking , invasive
procedures (bronchoscopy)
 Characteristics of droplets :
 1. droplet nuclei arise due to evaporation
 2. they are present in air for short time and travel only short distances
 3.Close contact needed for this mode of transmission
 4. bacteria involved are
• streptococcus pygonenase
• Neisseria meningipidis
• Corynebacterium diphtheria
• Haemophilus influenza type e
• Bodetella pertussis
• Yersinia pestis(pneumonic plague)
• Mycoplasma pneumonia

6. Measurment of air contaimination
Sedimentation settle plate metod
Slit sampler

7. MEASUREMENT OF AIR CONTAMINATIONSedimentation ‘settle plate’ method
Slit sampler
Sedimentation ‘settle plate’ method
Definition
A means of estimating the number of bacteria present in the air by permitting
bacteria to ‘settle’
On open petri dishes(containing culture media) over a fixed duration.Droplet
nuclei require more time to settle than larger particles.
Method
Open plates of culture media are exposed for specific periods,for example half
to one hour;then the plates are incubated at 37degree Celsius for 24 hours and
the number of colonies counted.when pathogenic staphylococci and streptococci
are looked for,blood agar plates are used;when fungi are sought,Sabouraud agar
plates are used in addition.
Interpretation
This method provides an idea of the relative number and species of
microorganisms present in air and is specially used for testing the quality of air
in surgical theaters and hospital wards.

8. Slit sampler
Definition
A means of estimating the number of bacteria present in the air by passing a
known volume
Of air through a ‘slit’.
Since the plate exposure method has many limitations , a more elaborate
method , the slit sampler,has been introduced.In this , a known volume of air
is directed onto a plate through a slit 0.25mm wide,the plate being
mechanically rotated so that the organisms are evenly distributed over it.

9. BACTERIOLOGY OF MILK
Types of bacteria in milk
Acid forming bacteria:
The commonest are lactic streptococci including S.lactis and Enterococcus
faecalis.
Lactobacilli are also found.
These ferment lactose in the milk,producing acids , mainly lactic acids ,
which lead to formation of smooth gelatinous curd.
Alkali forming bacteria:
These consist of the Alcaligenes spp, some aerobic spore bearers and the
Achromobacer species.
These render the milk alkaline.

10. Gas forming bacteria:
Coliform bacilli are the commonest
Others are Cl.perferingens and Cl.butyricum.
Acid and gas are produced.
A smooth gelatinous curd riddled with gas bubble is
formed.
Coliform bacilli are responsible for the ropiness in milk.
Proteolytic bacteria
Spore bearing aerobs , such as bacillus subtilis and
bacillus cereus,Proteus vulgaris,Staphylococci and
Micrococci come under this category.

11. Inert bacteria
These are the bacteria that produce no visible changes in milk.
These include some cocci of the udder , members of the Achromobacter group
and the most of the pathogenic organisms in milk.
Human milk
Breast milk contains small numbers of S.epidermidis, S.mitis, Gaffkya
tetragena and S.aureus.
A few other species may also be found in some samples.

12. Milkborne diseases
The most important diseases that can be transmitted by milk are ;
Tuberculosis
Brucellosis
Streptococcal infections
Staphylococcal infections
Salmonellosis
Q-fever
Diseases of less importance include;
Cowpox and milker’s nodes-transmitted during milking rather than through
ingestion of milk.
Foot and mouth disease,anthrax and leptospirosis have been transmitted on rare
occasions.
Tickborne encephalitis virus may transmitted through goat milk.
Milkborne infectious hepatitis have been reported.

13. • Occasionally, milk may be contaminated with
Streptobacillus moniliformis from the nasal secretion
of rats and with Campylobacter jejuni from animal
feces.
• Yersinia enterocolitica is not uncommon in milk and
may give rise to gastroenteritis if present in large
numbers.

14. PATHOGENIC ORGANISMS SPREAD THROUGH MILK
Bacteria derived from infected cow
Bacteria disease in cow Disease in human
1.M.tuberculosis 1. Tuberculosis
2.B.anthracis 2. Anthrax 1. Anthrax
3.Brucella abortus 3. Brucellosis 2.
Undulant(remittent) fever
4.Streptococcus spp. 4. Mastitis 3. Sore
throat,scarlet fever
5.S.aureus 5. Mastitis 4.
Diarrhea,vomiting
6.Salmonella spp. 6. Bacteremia 5. Enteric fever,
food poisning
7.Coxiella burnetti 7. Q-fever 6. Q-
feverM.bovis

15. Bacteria from sources external to animal
Bacteria Disease in humans
A)Non-pathogenic organisms
1. Non chromogenic lactic- 1.Non-pathogenic but may
streptococci , cause unpleasant taste
Lactobacillus spp. And odour of milk
Bacillus subtilis
2. Chromogenic bacteria 2. Non-pathogenic but may
Chromobacterium violaceum cause changes resulting in
milk of blue,red and yellow

16. B) Pathogenic bacteria
DISEASES
1.Shigella spp. 1.Dysentry
2.Vibrio cholera 2.Cholera
3. Corynebacterium diptheriae 3.Diptheria
4. S.pyogenes 4. Scarlet fever
5.Diarrheagenic E.coli 5. Diarrhea
6.Salmonella 6. Enteric fever
7. S.aureus 7. Food poisning

17. Bacteriological Examination of milk
Routine bacteriological examination of the milk consists of the
following;
Viable count
Test for coliform bacilli
Methylene blue reduction test
Phosphatase test
Turbidity test

18. Viable count
Method: This is estimated by performing plate counts with serial
dilutions of milk sample.
Raw milk always contains bacteria, varying in number from about
500 to several million
Per ml.
Significance:
The plate count gives a rough and direct assessment of the viable
bacteria in the milk.
It is easily explainable to the producer and gives a fair idea of the
improvement or deterioration
In the conditions of production.

19. Test for Coliform bacilli
Method:this is performed by inoculating varying dilutions
of milk into MacConkey’s fluid medium
And noting the production of acid and gas after
incubation.
Significance:
Contamination with coliforms comes mainly from
dust,dirty utensils and dairy workers.This method is the
useful indicator of fecal contamination,and also
contamination by dust or unclean utensils.

20. Methylene blue reduction test
Method:This is a simple substitute for the viable count.It depends on the
reduction of the methylene blue by bacteria in milk when incubated at 37
degree in complete darkness.
Significance:
The rate of reduction is related to the degree of bacterial contamination.Raw
milk is considered satisfactory if it fails to reduce the dye in 30min. Under
standard conditions.The dye test is a rough and quick test to determine the
quality of milk as it arrives from the producer.
The resazurin test is similar but the dye resazurin , on reduction , passes through
a series of colour changes-from blue to pink to colourless- the shade of colour
after incubation with milk for particular period of time ,depending on the
degree of contamination.Generally , the 10 min resazurin test is done in which
the shade of colour is noted after incubation with the milk for 10 min.

21. Phosphatase test
Method: this is a check whether milk has been pasteurised.The enzyme
phosphatase ,which is normally present in milk,is inactivated if pasteurization has
been performed properly.
Significance:
Residual phosphatase activity indicates that pasteurisation has been
inadequate.This test,
If positive after proper pateurisation of milk,shows contamination after
pasteurization.
Turbidity test
This is a check on the sterlisation of milk. If milk has been boiled or heated to the
temperature prescribed for sterlisation, all heat – coagulable proteins are
precipitated
If ammonium sulphate is then added to the milk , filtered and boiled for 5
minutes,no turbidity results.
This test distinguishes between pasteurized and sterlised milk.

22. Examination for specific pathogens in milk
Tubercle bacillus
Brucella
TUBERCLE BACILLUS
Milk centrifugation
3000rpm,30min
Sediment
Inoculation
Two guinea pigs
Observation for 3 months for tuberculosis
Tubercle bacilli may be inoculated in culture

23. Brucella
Isolation by
inoculating cream heavily on serum dextrose agar or
by injecting a centrifuged deposit of milk sample
intramuscularly
guniea pigs
after 6 weeks animals sacrificed
serum tesed for agglutinised spleen inoculated
in culture media
Brucellosis in animals can be detected by demonstrating antibodies in milk, by the milk-ring
Or the whey agglutination tets.

24. Prevention of contamination of milk
PASTEURIZATION OF MILK
It is defined as the heating of milk to such temperatures and
for such periods of time as are required to destroy any
pathogens that may be present while causing minimal
changes in the composition ,flavour and nutritive value.
Three are widely used:
1)Holder (vat) method
2)Flash or HTST(High temperature and short time method)
3)UHT(Ultra-high temperature method)

25. Holder(Vat) method
The milk is heated at 63deg.c for 30min followed by cooling
quickly to 13deg.c or lower.
Coxiella burnetti is heat resistant and may survive the holder
method.
Flash method
The milk is heated at 72deg.c for 15-20sec followed by cooling
quickly to 13deg.c or lower.

26. All non-sporing bacteria such as mycobacteria,brucella
and salmonella are destroyed.
Practically all mesophilic non-sporing bacteria are killed
by exposure to moist heat at 60deg.c for 30min.
Staph.aureus and S.faecalis require 60min.
Clostridium botulinum require 120deg.c for 4min. Or
100deg.c for 330min. for their destruction.
Vaccines of the non-sporing bacteria are heat inactivated
in special vaccine baths at 60deg.c for 1hr.

27. UHT(Ultra-high temperature) method
Milk is rapidly heated usually in two stages (the second stage
usually being under pressure)to 125deg.c for a few seconds only.
It is then rapidly cooled and bottled as quickly as possible.

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