Antimicrobials

CHAPTER 11CHAPTER 11

Disinfectants and AntisepticsDisinfectants and Antiseptics

Dr. Dipa Brahmbhatt VMD MpHDr. Dipa Brahmbhatt VMD MpH

dbrahmbh@yahoo.comdbrahmbh@yahoo.com

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

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

Terminology - Disinfectants vs Antiseptics

• Disinfectants Disinfectants are chemical agents 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)• AntisepticsAntiseptics are chemical agents that kill or inhibit the

growth of microorganisms on animate objects (living tissue)

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

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)

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)

• 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

Disinfectant – Ideal Agent

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

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

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

Types of Disinfecting Agents

Phenols

Quaternary Ammonium Compounds

Aldehydes

Ethylene oxide

Alcohols

Halogens

Biguanide

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

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

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 Iodophors – complexes of iodine and neutral polymer such as PVA – Iodophor scrubs Iodophor scrubs (have detergent products added: clean dirty (have detergent products added: clean dirty

surfaces and low level disinfection)surfaces and low level disinfection) e.g. Betadine®, Polyvinyl e.g. Betadine®, Polyvinyl pyrrolidine (Providine®)pyrrolidine (Providine®)

– Cleansing skin before surgeryCleansing skin before surgery

– Iodophor solutions Iodophor solutions (diluted with water)(diluted with water) and tinctures and tinctures (diluted (diluted with alcohol): higher conc. of iodine : both irritating and cytotoxicwith alcohol): higher conc. of iodine : both irritating and cytotoxic

– Iodophor solution: clean abscessIodophor solution: clean abscess

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

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

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

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

PhenolsPhenols– 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

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

Dental Treats impregnated with Chlorhexidine

ALCOHOL IODINEIODOPHOR

CHLORINE CHLORHEXIDINE QUATERNARYAMMONIUMCOMPUNDS

GLUTARALDEHYDE

Bactericidal ++ +++ ++ +++ ++ +++Lipid Envelopedvirucidal

++ ++ +++ ++ + +++

Nonenvelopedvirucidal - + +++ + - ++Sporicidal - + + - - ++Effective in presence of soap

++ +++ ++ + - ++

Effective in hard water +* ++ ++ + - ++Effective in presence of organic material

- - - +++ - ++

* Do not mix in water; makes it ineffective

References

• Romich, J.A. Pharmacology for Veterinary Technicians, 2nd edition. 2010.

• Bill, R.L. Clinical Pharmacology and Therapeutics for the Veterinary Technician, 3rd edition. 2006.

• http://ahdc.vet.cornell.edu/clinpath/modules/ua-rout/castssed.htm