1. Disinfectants and Antiseptics Dr. Dipa Brahmbhatt VMD MpH
Antimicrobials
CHAPTER 11
Disinfectants and Antiseptics
Dr. Dipa Brahmbhatt VMD MpH

2. Objectives Scientific and nonscientific terminology of disinfectants
MOA: disinfectants and antiseptics
Adverse reaction of disinfectants and antiseptics and how to mitigate these
How to select agent based on bacterial resistance, organic material

3. Controlling Growth of Microorganisms
Sterilization is the removal or destruction of all microbes
achieved by steam under pressure, incineration, or ethylene oxide gas
Asepsis
An environment or procedure that is free of contamination by pathogens
Disinfection = using physical or chemical agents to reduce the number of pathogens on inanimate objects. Used for:
Noscomial infections
Urinary tract – urinary catheters
Respiratory tract – ET tubes
Surgical sites, IV catheter insertion and wounds

4. Terminology - Disinfectants vs Antiseptics
Disinfectants are chemical agents kill or inhibit the growth of microorganisms on inanimate objects
More toxic to humans
High level disinfectant: kill naked virus and spores e.g. chlorine, glutaraldehyde
Microbicidal
Bacteria and fungi: vegetative form (actively growing); spore form (static form)
Antiseptics are chemical agents that kill or inhibit the growth of microorganisms on animate objects (living tissue)

5. Terminology - Disinfectants vs Antiseptics
Sanitizers: chemical agents that reduce the number of microorganisms to “safe” level w/o eliminating microbe
Sterilizers: chemical or other agents that destroy all micoorganisms
Germicides: any chemical agent that kills microorganisms, non specific term

6. Most resistant to least resistant
Prions
Endospores: Clostridium tetani (tetanus), Bacillus anthracis, Mycobacterium avium (acid fast)
Protozoal cysts
Non-enveloped viruses: enterovirus (parvo virus) and adenovirus
Glycocalyx: Pseudomonas (gram -, biofilms are more resistant)
External fixation devices (pins and clamps), bone implant (pin/plate)
Fungi (Candida, Aspergillus)
Gram - : E.coli, Salmonella
Gram +: Staphylococcus aureus,
Streptococcus equi
Lipid enveloped virus (AI virus)

7. Disinfectant – Ideal Agent
Ideal agents should:
Broad spectrum antimicrobial activity
Be nonirritating (not cytotoxic to humans)
Not damage or stain
Stable and not easily inactivated. E.g. organic materials, cellular debris, blood. Shelf life appropriate so does not loose potency.
Be affordable (should not be most important criteria)

8. Disinfectant – Ideal Agent
Appropriate disinfectant
Type of microorganism e.g. spores, bacteria, fungi …
Lipid envelope: FIP, FeLV, Canine Distemper virus easily killed than feline distemper virus or parvoviruses
Environment: living vs. inanimate objects, organic material
Endoscopes difficult to clean, hard water/ soap can inactivate disinfectant
Dilution (Read the package insert for dilution recommendations)
Always start with the quantity of water and add the chemical concentrate to avoid splashing chemicals into
Rinse disinfected ET tubes : local tissue reaction or systemic toxicosis
Disinfectant characteristics: corrosiveness, cost, Ab spectrum

9. Material Safety Data Sheets
Always request and keep MSDS
Filing of MSDS and container labeling are important components of each facility’s hazard communication plan, which is required by OSHA
Hazard Communication Standard was enacted in 1988 to educate and protect employees who work with potentially hazardous material

10. Hazard Communication Plan
Should include:
A written plan that serves as a primary resource for the entire staff
Name of person responsible for keeping MSDS current
Location of where MSDS kept, how obtained
Procedures for labeling materials
Outline emergency and clean-up procedures
An inventory of hazardous materials on the premises
Current MSDS for hazardous materials
Proper labeling of all materials in the facility
Employee training for every employee working with these materials

11. Must be on all MSDSs: Product name and chemical identification
Name, address, and telephone number of the manufacturer
List of all hazardous ingredients
Physical data for the product
Fire and explosion information
Information on potential chemical reactions when the product is mixed with other materials
Outline of emergency and cleanup procedures
Personal protective equipment required when handling the material
A description of any special precautions necessary when using the material

13. Types of Disinfecting Agents
Phenols
Quaternary Ammonium Compounds
Aldehydes
Ethylene oxide
Alcohols
Halogens
Biguanide

14. Alcohols 70% solutions: Ethyl alcohol or Isopropyl alcohol (50%)
Most common disinfectant: sx. sites, injection sites, rectal thermometers
Denature coagulating proteins and dissolving membrane lipids
Advantages: Non-irritating, non-toxic, inexpensive, bactericidal (gram negative/ positive), enveloped viruses
Disadvantages: Ineffective on spores and nonenveloped viruses, contact time: minutes, not effective with organic material, don’t use on open wounds (not good antiseptic), chronic application: pruritus, seborrhea sicca

15. Halogens - Cl Work by interfering with proteins and enzymes of
the microbe
Chlorine kills bacteria, fungi, viruses (esp. parvovirus)
A: cheap
DA: Not great for spores, bleach and deteriorate fabrics in high conc., corrosive (OK on stainless steel), chronic use: pits on metal surfaces, poorly ventilated areas: irritating to eyes/ mucous membranes, rinse surface after contact time, not effective with organic materials, contact time: several minutes, inactive if exposed to light
Found in household bleach (Chlorox®: sodium hypochlorite) NOT common leach or color-fast bleach
Routinely used in a 1:10 solution or 1:30

16. Halogens - Iodine
Adv: Commonly used as topical antiseptics: bacteri/viru/protozoa/fungi –cidal, Great for dermatophytes, spores (solution in moist and contact 15 minutes).
DA: can be inactivated with organic material but better than chlorine, conc. Iodine solution/tincture can be irritating. Don’t use in peritoneum or denuded skin. Can be corrosive in high conc. And contact time
Iodophors – complexes of iodine and neutral polymer such as PVA
Iodophor scrubs (have detergent products added: clean dirty surfaces and low level disinfection) e.g. Betadine®, Polyvinyl pyrrolidine (Providine®)
Cleansing skin before surgery
Iodophor solutions (diluted with water) and tinctures (diluted with alcohol): higher conc. of iodine : both irritating and cytotoxic
Iodophor solution: clean abscess

17. Glutaraldehyde
Chemical sterilizer: organic compounds that contain a functional group –CHO (carbon-hydrogen-oxygen), like formaldehyde
Work by affecting protein structure
Rapid; kills fungi and bacteria within minutes and spores in about 3 hours (alkaline pH).
Effective against gram-positive and gram-negative bacteria, fungi, viruses, and bacterial spores
Adv: generally not inactivated by organic material and effective on hard water, work against biofilms, sterilize equipment that cannot be heat sterilized: endoscopic equipment
DA: Toxic fumes, ventilation necessary, safety goggles and thoroughly rinse before use on living tissue

18. Quaternary ammonium compounds (QUATS)
Work by concentrating at the cell membrane and dissolving lipids in the cell walls and membranes. Disinfectant.
Effective against gram-positive , enveloped viruses NOT bacterium spores, poor efficacy: gram-negative bacteria, fungi, and unenveloped viruses e.g. benzalkonium chloride, NB: Third generation QACs work on enveloped viruses (Roccal D-plus – parvo)
ADV: Work rapidly, usually not irritating to skin or corrosive to metal
DA: reduce efficacy with organic material, soap or detergent (hence clean thoroughly before applying) and hard water, prolonged contact: skin irritation. Birds in confinement: this product causes damage to mouth, toes, eyes and respiratory tract
Organic debris, hard water, and soaps will inactivate QACs

19. Other agents
Hydrogen peroxide damages proteins and is used to kill anaerobic bacteria; can cause tissue damage, so its use is limited
Good for oral infections
Debride dead, injured, necrotic tissue and weak bactericidal
Not great antiseptic
Peroxide sterilization is better than ethylene oxide: high-level disinfectant also can destroy spores e.g. Trifectant
Soaps and detergents have limited bactericidal activity
Main functions are mechanical removal of debris
May contain ingredients effective against some bacteria
Do not work on spores and have limited antiviral properties

20. Ethylene oxide Works by destroying DNA and proteins
Is a gas used for chemical sterilization
Effective against gram-positive and gram-negative bacteria, fungi, viruses, and bacterial spores
Very slow acting
Explosive; potent carcinogen
Can sterilize objects that cannot withstand heat

21. Phenols
Work by destroying the selective permeability of cell membranes
First antiseptics developed: pine oil, lysol
Effective against gram-positive and NOT gram-negative bacteria, fungi, and some enveloped viruses
Should not be used as antiseptics because:
Can be very irritating to skin
Lesions on birds feet
Dermal ulceration: snakes
Can be absorbed systemically
Hexachlorophene :Linked to neurotoxicity ,
teratogenic and hepatoxicity

22. Biguanides Work by denaturing proteins
Effective against gram-positive and gram-negative
bacteria, fungi, and enveloped viruses
Does not work on nonenveloped viruses and spores
FeLV, FIP
Fast acting
Chlorhexidine (Nolvasan®, Hibiclens®)
Commonly used as a surgical scrub and for cleaning wounds
Can have residual activity of 24 hours
One of the most commonly used disinfectants and antiseptics
in vet med.
Also shampoos, oral care, and ear cleaning solutions

23. Dental Treats impregnated with Chlorhexidine

24. ++ +++ + - +* * Do not mix in water; makes it ineffective ALCOHOL
IODINE
IODOPHOR
CHLORINE
CHLORHEXIDINE
QUATERNARY
AMMONIUM
COMPUNDS
GLUTARALDEHYDE
Bactericidal ++
+++
Lipid
Enveloped
virucidal +
Nonenveloped -
Sporicidal
Effective in presence of soap
Effective in hard water +*
Effective in presence of organic material
* Do not mix in water; makes it ineffective

25. References
Romich, J.A. Pharmacology for Veterinary Technicians, 2nd edition
Bill, R.L. Clinical Pharmacology and Therapeutics for the Veterinary Technician, 3rd edition