Disinfection and Sanitation: Farm Hygiene

The lecture is a compilation of disinfectants, their characteristics, and uses in the context of Farm Hygiene

1. Disinfection and Sanitation
FARM HYGIENE: LECTURE 2
Dr. Pankaj Dhaka
Assistant Professor
School of Public Health and Zoonoses
GADVASU, Ludhiana, India

3. A TRIBUTE TO IGNAZ SEMMELWEIS
•Known as -early pioneer of
antiseptic procedures
•Described as "saviourof mothers”
•Semmelweis discovered that the
incidence of puerperal fever could
be drastically cut by use of hand
disinfection in obstetrical clinics

4. A HYGIENIC AND SCIENTIFIC HAND WASHING
CONTINUES TO BE BEST PRAYER IN THE HOSPITAL

5. DISINFECTANTS andANTISEPTICS
▪“Antimicrobial pesticides”(E.g., sanitizers, disinfectants and sterilizers)
▪Disinfectants: substances used to control, prevent, or destroy harmful
microorganisms (i.e., bacteria, viruses, or fungi) on inanimate objects and
surfaces.
▪Antiseptics are applied to the surface of living organisms or tissues to
prevent or stop the growth of microorganisms by inhibiting the organism or
by destroying them.
▪Sanitizinglowers the number of germs on surfaces or objects to a safe
level, as judged by public health standards or requirements.

6. DEFINITIONS
Cleaningremoves germs, dirt, and impurities from
surfaces and objects…using soap (or detergent) and
water to physically remove [them]”
Degreaser: More powerful soap/detergent specially
formulated to penetrate layers of dried on body oils
and other greasy debris
Soap/detergent: Cleaning agent which works by
suspending dirt and grease.

7. ✓Broad spectrum
✓Rapid activity (short contact time)
✓Works in any environment
✓Long shelf life
✓Non-polluting
✓Non-toxic
✓Non-irritating
✓Non-corrosive
✓It shouldn’t allow emergence of resistant pathogens
✓Relatively inexpensive
For an effective disinfection protocol, consideration should be given to the microorganism
being targeted, the characteristics of aspecific disinfectant, and environmental issues.
Characteristics of an Ideal Disinfectant

8. DEGREE OF RESISTANCE OF MICROBES
TO DISINFECTANTS

9. MICROORGANISM CONSIDERATIONS
•Microorganisms vary in their degree of susceptibility to disinfectants
•Gram-positive bacteria are more susceptibleto chemical disinfectants
than Gram-negative bacteria; while mycobacteria or bacterial
endospores are more resistant
•Hydrophilic, non-enveloped viruses (adenoviruses, reoviruses,
rotaviruses) are more resistant to disinfection than lipophilic,
enveloped viruses (coronaviruses, orthomyxoviruses, paramyxoviruses)
•Some microorganisms are also effective at creating a biofilmthat
enhances their ability to persist in the environment and avoid the action
of disinfectants

10. BIOFILMSINTERFERE IN EFFECTIVE
ANTIMICROBIAL ACTION
▪“Biofilms are microbial
communities that are tightly
attached to surfaces and cannot
be easily removed
▪Bacteria within biofilms are up to
1,000 times more resistant to
antimicrobials than are the same
bacteria in suspension

11. DISINFECTANT CONSIDERATIONS
Disinfectant concentration:
-static versus –cidalaction
Application method
Wiping, brushing, spraying etc.
Contact time
70% isopropyl alcohol can destroy Mycobacterium
tuberculosis in 5 minutes
3% phenol requires 2-3 hours
Stability and storage
Safety precautions

12. ENVIRONMENTAL CONSIDERATIONS
Organic load
Surface topography
Temperature
Relative humidity
pH
Efficacy of glutaraldehyde best at a pH greater than 7
QACs have the greatest efficacy at pH of 9-10
Water hardness-reduce the effectiveness of certain
disinfectants (i.e., QAC, phenols)

13. CLEANING BEFORE DISINFECTION
•Cleaning alone may remove over 90% of bacteria from surfaces
•Scrub and flush away all forms of organic mater
•Pressure washing is preferable
•Warm water with detergent facilitates removal of caked material & grease
•Troughs, drinkers and inaccessible corners require particular attention
•Rinse thoroughly
•Apply the chosen disinfectant and leave this in contact with surfaces for as
long as possible (sufficient contact time)

14. APPLICATION METHOD
•Object surfaces or walls of a building may be treated with a
disinfectant solution by wiping, brushing, spraying or misting
•Portable items should be soaked in a container of disinfectant
•Fumigation may be used in some situations but is inefficient in
buildings with ill-fitting doors and windows, or damaged roofs
Thorough cleaning and washing prior to the application of any
disinfectant is essential

15. Types of Disinfectants Used in
Animal Disease Control Programme
▪Hot water
▪Acid-anionic surfactants
▪Amphotericsurfactants
▪Bromides, chlorides, Chlorhexidine,
Iodides
▪Phenoliccompounds
▪Quaternary ammonium compounds
▪Ammonium hydroxde
▪Aldehydes

16. Chemical compound
Gram +
Bacteria
Gram -
Bacteria
TB-like
Bacteria
FungiVirus
Best pH range
for activity
Activity when
organic matter
present
Common
uses **
Chlorhexidene SA* SA SA SA MostWide rangeGood E/P/F
Formaldehyde and
aldehydes
++ ++ ++ ++ ++ Wide rangeGood E/P/F
Chlorine
Chloramines
++ ++ SA ++ SA Acid Very poorCS/E
Iodophors ++ ++ SA ++ SA Acid Fair to poorCS/E
Sodium hydroxide++ ++ SA ++ ++ AlkalineGood P
Quaternary
ammoniums
++ + No SA SA AlkalineFair CS/E
Phenols
++ ++ + SA SA Acid +Good E/P/F
Information About Common Disinfectants
*SA-some activity
**E-equipment;P-premises;F-footbaths;CS-clean surfaces (Adapted from Purdue University Extension Bulletin PIH80)

17. Common Disinfectants Used in Veterinary Practice

18. SELECTION OF CHEMICAL DISINFECTANTS
FOR SPECIFIC INFECTIOUS AGENTS
Bacillus anthracis
1% peraceticacid
10 % formaldehyde
4% glutaraldehyde
3 % Hydrogen peroxide
Brucella abortus
2% formaldehyde
2.5 % Sodium hypochlorite
2-3% Caustic soda
Foot and mouth disease
▪4% Sodium Carbonate
▪4% Sodium Hydroxide
Mycobacteria
▪2% alkaline
glutaraldehyde
solution

19. USE OF DISINFECTANT IN FARM OPERATIONS
Animal waste during an outbreak
Formaldehyde solution (formalin) at 5% concentration
Exotic disease alternative treatments include peracetic acid and sodium hydroxide
Farm building
After through cleaning followed by rinsing, suitable disinfectants for routine use include
phenolic compounds, halogens, peroxygencompounds and aldehydes
Transport vehicles
High pressure cleaning with warm water containing detergent, followed by rinsing with hot water
Dry application of phenolic compounds or halogens to all parts of the vehicle including
bodywork and wheels

20. 1.Boricacid(4-6%),
2.Sodiumhydroxide(1,2and5%)
3.Calciumhydroxide(limewater,slakedlime)ofanimalhouses
4.Formaldehyde(5-10%)canbeusedforwashingfloorofanimalhouses
5.Glutaraldehyde2%aqueoussolutionisusefulforsterilizationofinstruments
6.Quaternaryammoniumcompounds;cetavlon;savlonaredetergentsandsoaps,areused
mainlyforwashing.Theyremovegrease,dirtandotherorganicmatter
7.Bleachingpowder(calciumhypochlorite),Coppersulfate(5mg/lit)andPotassium
permanganate(1-2mg/lit)arecommonlyuseddisinfectants
8.Calciumoxideisusedintheburialpitstodisposethecarcassandforlandapplication
9.Calciumhydroxide(slaked)mixedwith5%phenoliscommonlyusedinwhitewashingof
thewallsoffarmhousesasdisinfectant
10.Phenol(0.5to5%)andSodiumcarbonate(2.5-4%)canbeusedforfarmbuildings
Common disinfectants used in animal shelters

21. DISINFECTANT TESTS
• Carrier test
• Suspension test
• Capacity test
• Phenol coefficient test
• In-use test

22. TESTING OF DISINFECTANTS
Carrier test
A carrier such as a silk or catgut thread is contaminated by submersion in a liquid culture of the
test organism
The carrier is then dried and brought in contact with the disinfectant for a given exposure time.
Cultured in a nutrient broth
No growth indicates activity of the disinfectant tested whereas growth indicates a failing.
Suspension test
A sample of the bacterial culture is suspended into the disinfectant solution
After exposure it is verified by subculture whether this bacterial inoculum is killed or not
Suspension tests are preferred to carrier tests as the bacteria are uniformly exposed to disinfectant

23. Types of suspension tests
a) Qualitative suspension tests:
A loopfulof bacterial suspension brought into contact with the disinfectant
A loopfulof this mixture cultured for surviving organisms.
Results expressed as ‘growth’ or ‘no growth’.
b) Quantitative suspension tests.
The number of surviving organisms (B) is counted and compared to the
original inoculumsize (A).
Microbicidal effect (ME) = Log (A) -Log (B)
TESTING OF DISINFECTANTS….CONT.

24. Capacity test
A capacity test, the disinfectant is challenged repeatedly by successive
additions of bacterial suspension until its capacity to kill has been exhausted.
Best known capacity test is the Kelsey-Sykes test
TESTING OF DISINFECTANTS….CONT.

25. Phenol Coefficient Test
Determination of Phenol Coefficient:
➢Is a measure of the bactericidal activity of a chemical compound in
relation to phenol
➢Is calculated by dividing the dilution of test disinfectant by the dilution of
phenol that disinfects under predetermined conditions
Determine inhibition concentration of unknown disinfectant
A sample of the bacterial culture is suspended into various dilutions of the
disinfectant solution
After exposure it is verified by subculture in nutrient broth whether this inoculum is
killed or not
Repeat the procedure for control disinfectant phenol
Prepare phenol coefficient table

26. RIDEAL-WALKER TEST
▪Phenolis diluted from 1:400 to 1:800 and the test disinfectant is diluted
from 1:95 to 1:115.
▪Their bactericidal activity is determined against Salmonella typhi suspension
▪Subcultures are performed from both the test and phenol at intervals of
2.5, 5, 7.5 and 10 minutes.
▪The plates are incubated for 48-72 hours at 37°C.
▪That dilution of disinfectant which disinfects the suspension in a 7.5 minutes
and not in 2.5 and 5 minutes time is divided by that dilution of phenol
which disinfects the suspension in same time gives its phenol coefficient.

27. N

28. CHICK MARTIN TEST
▪This test also determines the phenol coefficient of the test disinfectant.
▪Unlike in RidealWalker method where the test is carried out in water, the
disinfectants are made to act in the presence of yeast suspension (or 3%
dried human feces) to simulate the presence or organic matter.
▪Time for subculture is fixed at 30 minutes and the organism used to test
efficacy is Salmonella typhi as well as Staphylococcus aureus

29. Rideal-Walker versus Chick-Martin Method

30. •Anin-use testcan determine whether an actively used
solution of disinfectant in a clinical setting is microbially
contaminated
•1-mL sample of the used disinfectant is diluted into 9 mL
of sterile broth medium that also contains a compound
to inactivate the disinfectant.
•Ten drops (approx. 0.2 mL) of this mixture, are then
inoculated onto each of two agar plates.
•One plate is incubated at 37 °C for 3 days and the
other is incubated at room temp. for 7 days.
•Plates are monitored for growth of microbial colonies
•Growth of five or more colonies on either plate suggests
that viable microbial cells existed in the disinfectant
solution and that it is contaminated.
•Such in-use tests monitor the effectiveness of
disinfectants in the clinical setting.
In-Use Test