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 "saviour of 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 and ANTISEPTICS
▪ “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.
▪ Sanitizing lowers the number of germs on surfaces or objects to a safe
level, as judged by public health standards or requirements.

6. DEFINITIONS
Cleaning removes 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 a specific 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 susceptible to 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 biofilm that
enhances their ability to persist in the environment and avoid the action
of disinfectants

10. BIOFILMS INTERFERE 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 –cidal action
 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
▪ Amphoteric surfactants
▪ Bromides, chlorides, Chlorhexidine,
Iodides
▪ Phenolic compounds
▪ Quaternary ammonium compounds
▪ Ammonium hydroxde
▪ Aldehydes

16. Chemical compound
Gram +
Bacteria
Gram -
Bacteria
TB-like
Bacteria
Fungi Virus
Best pH range
for activity
Activity when
organic matter
present
Common
uses **
Chlorhexidene SA* SA SA SA Most Wide range Good E/P/F
Formaldehyde and
aldehydes
++ ++ ++ ++ ++ Wide range Good E/P/F
Chlorine
Chloramines
++ ++ SA ++ SA Acid Very poor CS/E
Iodophors ++ ++ SA ++ SA Acid Fair to poor CS/E
Sodium hydroxide ++ ++ SA ++ ++ Alkaline Good P
Quaternary
ammoniums
++ + No SA SA Alkaline Fair 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% peracetic acid
 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, peroxygen compounds 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. Boric acid (4-6%),
2. Sodium hydroxide (1, 2 and 5%)
3. Calcium hydroxide (lime water, slaked lime) of animal houses
4. Formaldehyde (5-10%) can be used for washing floor of animal houses
5. Glutaraldehyde 2% aqueous solution is useful for sterilization of instruments
6. Quaternary ammonium compounds; cetavlon; savlon are detergents and soaps, are used
mainly for washing. They remove grease, dirt and other organic matter
7. Bleaching powder (calcium hypochlorite), Copper sulfate (5mg/lit) and Potassium
permanganate (1-2mg/lit) are commonly used disinfectants
8. Calcium oxide is used in the burial pits to dispose the carcass and for land application
9. Calcium hydroxide (slaked) mixed with 5% phenol is commonly used in white washing of
the walls of farm houses as disinfectant
10. Phenol (0.5 to 5%) and Sodium carbonate (2.5-4%) can be used for farm buildings
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 loopful of bacterial suspension brought into contact with the disinfectant
 A loopful of 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 inoculum size (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
▪ Phenol is 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 Rideal Walker 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. • An in-use test can 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