SUBMITTED BY

SHAILJA(1475)

BACTERIOLOGY OF AIR AND WATER

PRESENTED BY

SHAILJA (1475)

oBACTERIOLOGY OF AIRo It is defined as the branch of microbiology

dealing with the study of bacteria present in the air and the infections caused by them.

• 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

Airborne transmissiono Size of particle <5 micrometer in sizeo 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 meterso Susceptible individuals may become infected

even if some distance from infected persono Bacteria involved are- Mycobacterium

tuberculosis,

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

Measurment of air contaimination

Sedimentation settle plate metodSlit sampler

MEASUREMENT OF AIR CONTAMINATIONSedimentation ‘settle plate’ methodSlit sampler

Sedimentation ‘settle plate’ methodDefinitionA 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.MethodOpen 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.InterpretationThis 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.

Slit sampler

Definition

A means of estimating the number of bacteria present in the air by passing a known volumeOf 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.

BACTERIOLOGY OF MILKTypes 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.

Gas forming bacteria: Coliform bacilli are the commonestOthers 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.

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.

Milkborne diseasesThe most important diseases that can be transmitted by milk are ;TuberculosisBrucellosisStreptococcal infections Staphylococcal infectionsSalmonellosisQ-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.

• 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.

PATHOGENIC ORGANISMS SPREAD THROUGH MILK

Bacteria derived from infected cow

Bacteria disease in cow Disease in human 1.M.tuberculosis 1. Tuberculosis2.B.anthracis 2. Anthrax 1. Anthrax3.Brucella abortus 3. Brucellosis 2. Undulant(remittent) fever4.Streptococcus spp. 4. Mastitis 3. Sore throat,scarlet fever5.S.aureus 5. Mastitis 4. Diarrhea,vomiting6.Salmonella spp. 6. Bacteremia 5. Enteric fever, food poisning7.Coxiella burnetti 7. Q-fever 6. Q-feverM.bovis

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

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

Bacteriological Examination of milk

Routine bacteriological examination of the milk consists of the following;

Viable countTest for coliform bacilliMethylene blue reduction testPhosphatase testTurbidity test

Viable countMethod: 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 millionPer 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 deteriorationIn the conditions of production.

Test for Coliform bacilliMethod:this is performed by inoculating varying dilutions of milk into MacConkey’s fluid mediumAnd 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.

Methylene blue reduction testMethod: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.

Phosphatase testMethod: 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 precipitatedIf 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.

Examination for specific pathogens in milkTubercle bacillusBrucella TUBERCLE BACILLUS

Milk centrifugation 3000rpm,30min Sediment Inoculation Two guinea pigs

Observation for 3 months for tuberculosis

Tubercle bacilli may be inoculated in culture

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-ringOr the whey agglutination tets.

Prevention of contamination of milk PASTEURIZATION OF MILKIt 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) method2)Flash or HTST(High temperature and short time method)3)UHT(Ultra-high temperature method)

Holder(Vat) methodThe 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 methodThe milk is heated at 72deg.c for 15-20sec followed by cooling quickly to 13deg.c or lower.

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. Or100deg.c for 330min. for their destruction.

Vaccines of the non-sporing bacteria are heat inactivated in special vaccine baths at 60deg.c for 1hr.

UHT(Ultra-high temperature) methodMilk 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.

THANK YOU