Antimicrobials

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Antimicrobials

• CHAPTER 11
• Disinfectants and Antiseptics
• Dr. Dipa Brahmbhatt VMD MpH
• dbrahmbh_at_yahoo.com

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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

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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

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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)

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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

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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)

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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)

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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

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Material Safety Data Sheets

• Always request and keep MSDS
• Filing of MSDS and container labeling are
  important components of each facilitys 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

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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

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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

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Types of Disinfecting Agents

• Phenols
• Quaternary Ammonium Compounds
• Aldehydes
• Ethylene oxide
• Alcohols
• Halogens
• Biguanide

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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, dont use on
  open wounds (not good antiseptic), chronic
  application pruritus, seborrhea sicca

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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 110 solution or 130

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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. Dont 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

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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

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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

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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

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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

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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

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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

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Dental Treats impregnated with Chlorhexidine
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ALCOHOL IODINE IODOPHOR CHLORINE CHLORHEXIDINE QUATERNARY AMMONIUM COMPUNDS GLUTARALDEHYDE
Bactericidal
Lipid Enveloped virucidal
Nonenveloped virucidal - -
Sporicidal - - -
Effective in presence of soap -
Effective in hard water -
Effective in presence of organic material - - - -
Do not mix in water makes it ineffective
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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-ro
  ut/castssed.htm