Antiseptics & Disinfectants, Pt. 2 Flashcards
What biguanide is used as an antiseptic? What activity does it have and lack?
Chlorhexidine, a synthetic cationic antiseptic compound
better activity against Gram-positive than against Gram-negative
lacks sporicidal activity
What is the mechanism of action of Chlorhexidine? What major benefits does its use have?
disrupts bacterial cell membranes and precipitates cells contents
- retains activity in the presence of blood and other organic material
- extremely low toxicity even when used on intact skin of newborns
What is polyhexamethylene biguanide (PHMB)? What common uses does it have?
polymeric biguanide with activity against Gram-positive and Gram-negative bacteria, including methicillin-resistant Staph. aureus, Pseudomonas aeruginosa, and Streptococcus equi
- eye, mouth, and vaginal infections
- contact lens disinfectants
- ear flush
What kind of antimicrobial activity do formaldehyde and formalin have? What is its mechanism of action?
effective, but slow bactericide (M. tuberculosis), virucide (FMD), and fungicide requiring 6-12 hours of contact time
inactivates microorganisms by alkylating amino and sulfhydryl groups of proteins and nitrogen rings of purines
(formaldehyde = gas/liquid; formalin = 37% aqueous formaldehyde)
Does organic matter affect formaldehyde/formalin action? What is it commonly combined with?
NO
alcohol —> chemical sterilant for surgical instruments (noncorrosive!)
What does the National Institute for Occupational Safety and Health require for the handling of formaldehyde/formalin?
handled as potential carcinogens, limiting worker exposure time
How does glutaraldehyde compare to formaldehyde? What is its mechanism of action?
better bactericidal, virucidal, and sporicidal activity
alkylates sulfhydryl, hydroxyl, carboxyl, and amino groups on RNA, DNA, and proteins
What are the 4 major benefits to using glutaraldehyde?
- wide spectrum
- retains biocidal activity in the presence of organic material
- noncorrosive to metal, rubber, and plastic
- doesn’t damage lensed instruments
How must glutaraldehyde solutions be used?
in well-ventilated areas —> high air concentrations can be irritating to eyes and nasal passage
What use is inappropriate for formaldehyde and glutaraldehyde?
antiseptic —> caustic nature (requires protective gloves to be worn when used as a disinfectant)
What oxidizing agents are commonly used as antiseptics and disinfectants? What are they not suitable for use?
hydrogen peroxide and potassium peroxymonosulfate
routine wound care —-> damages fibroblasts
What has hydrogen peroxide been formulated to contain?
surfactants and stabilizers to improve antimicrobial activity
- marketed as a powder and is stable in solution for about 1 week
What 4 microbes is potassium peroxymonosulfate effective against? What is it most commonly used for?
- viruses
- Gram-positive and Gram-negative bacteria
- fungi (mold and yeast)
- Mycoplasma
- pools or hot tubs
- high-level disinfectant in laboratories, dental care facilities, and hospitals
What step is important for clearing organic material? What is commonly used in this step?
physical cleaning before disinfection
chlorine and iodine-based disinfectants or QACs
What organic materials typically reduce antimicrobial activity? In what 2 ways do they do this?
blood, pus, feces, soil, food, milk
- chemical reactions with the compound leave a smaller amount available for killing
- spatial nonreactions leave make the compound unable to reach the organism
What disinfectant is less affected by organic material contamination? How does this affect its use?
glutaraldehyde
useful for instruments whose surface or design makes it impossible to be thoroughly cleaned
How does the level of microbial contaminations affect necessary antiseptic/disinfection exposure time? Which bacteria are most susceptible?
higher contamination = longer exposure to biocide
- Gram-positives are less resistant due to their less lipid-rich cell wall
- Gram-negatives are more resistant
What is one of the most resistant Gram-negative bacteria?
Pseudomonas aeruginosa
Why are Mycobacteria especially resistant?
unusual, hydrophobic nature of their cell wall
How can efficacy against bacterial spores improve?
increase temperature, most successful with moist heating, or autoclaving at 115 C
What are biofilms? How does this affect their response to antimicrobials?
slimy layer consisting of organic polymer matrix containing ions, nutrients, polysaccharases, proteases, β-lactamases, and microbes
bacteria in biofilms are less sensitive to disinfectant inactivation due to decreased diffusion through the matrix
How do bacteria become resistant to antiseptics and disinfectants? What 2 bacterial species are showing increasing resistance?
acquire genes due to survival after being treated with concentrations higher than the necessary killing concentration (can confer resistance to antibiotics!)
- Staphylococcus aureus - QACs and chlorhexidine
- Pseudomonas - lower-level resistance (unstable)
How do the mechanisms of antibiotics and disinfectants/antiseptics compare?
ANTIBIOTICS - well-known, single specific targets that inhibit proteins, nucleic acid synthesis, RNA polymerase, or DNA gyrase
D/A - not as well-understood and involve more general and multiple cellular targets
What are the 4 most common mechanisms of action of disinfectants and antiseptics?
- interacts with cell wall or envelope
- disrupts membrane integrity
- inhibits membrane enzymes
- alkylating agents
What is a major factor in selecting disinfectants and antiseptics? How can this lead to resistance?
EXPENSE
dilution to save on cost may reduce biocidal potency (pick biocides based on efficacy and safety, not cost)
What is surgical antisepsis? Use of what preparations are limited to intact skin? How are different concentrations used?
application of antimicrobial chemicals to skin, mucosa, and wounds to reduce the risk of infection
alcohol or detergent scrubs
concentration for wound preparations are lower than those used for intact skin
What is the purpose of surgical hand scrubs? Where are the highest microbial counts found on the hands? How does this affect surgical preparations?
remove transient flora and reduce resistant flora for the duration of surgery
subungual area (under nails) —> becomes even higher in moist environments (gloves!)
- nails should be cut short
- artificial nails and polish are discouraged
- debris should be mechanically removed from under fingernails prior to surgical scrub
What is the major factor affecting the efficacy of surgical scrubs?
duration of washing and mechanical action allowing antimicrobial products to have sufficient contact time
What duration is generally recommended for surgical scrubbing? What are 2 alternatives?
120s —> may be longer for veterinary surgeons
- initial water and soap cleansing followed by alcohol-based rub for 5 minutes
- initial cleansing followed by 5 minutes of chlorhexidine or iodophor hand scrub
Why is chlorhexidine commonly used as a surgical hand scrub? What negative effects are associated with long-term use?
active agents have residual bactericidal activity under surgical gloves
- tissue disruption
- elimination of beneficial deeper microflora
- predisposition to colonization with pathogenic bacteria
What 4 common preoperative preparations are used on the patient?
- clipping and/or shaving
- removal of gross contamination and dirt
- gentle antiseptic scrubbing beginning at the surgical site and moving outward over the entire surgical area
- final antiseptic spray left to dry to allow proper contact time
What 4 problems are common with mucous membrane (oral) surgical preparation?
- bacterial colonization is very high
- efficacy or oral antiseptics is affected by dilution effects
- inactivation of antiseptics due to salivary proteins
- increase in concentration is associated with local irritation
What are the 3 major solutions that are useful as oral antiseptics?
- povidone-iodine - reduces inflammation and the progression of periodontal disease or bacteremia after extraction
- chlorhexidine - negatively charges surfaces in the mouth
- hexetidine
What 4 things must be considered for open wound treatment?
- age
- health status
- cause
- size and extent of contamination
(any agent chosen should not impede the healing process)
Why is opinion divided concerning the utility of antiseptics in routine wound care?
- some authors affirm this practice reduces the incidence of infections
- there are reports of potential toxic and harmful effects of antiseptics on fragile healing tissue
- surface colonization of wound does not imped healing
What are 4 possible treatment options for wounds?
- chlorhexidine diacetate - wide spectrum and minimal deleterious effects on wound healing
- (hypertonic) saline - eliminates debris and lowers bacterial counts
- povidone-iodine - most effective and least tissue toxic at 1%
- Dakin’s solution (0.005% sodium hypochlorite) - bactericidal and no damage to fibroblasts
What has sodium hypochlorite (Dankin’s) solution been proposed to treat?
atopic dermatitis and recurrent pyoderma in dogs
What are disinfectants most commonly used on?
- floors
- tables
- walls
- surgical equipment
- instruments before storage
- animal housing facilities
(follow manufacturer guidelines regarding contact time, dilution, and usefulness)
What 2 disinfectants are recommended to specifically limit Salmonella infection?
- footbaths - peroxygen compounds > QACs
- formaldehyde - effective even at lower temperatures
What 2 species of Salmonella are particularly common in poultry houses? What disinfectant is recommended?
1 S. enteritis
2. S. senftenberg
glutaraldehyde
What disinfectants were effective in cleaning artificially contaminated surfaces in poultry transport containers? What ones were able to achieve 100% reduction?
halogen compounds and QACs
sodium hypochlorite or iodine-containing
What causes avian influenza? What 3 agents are recommended for clearing contamination?
avian influenza virus (Orthomyxoviridae, HPAI)
- alcohols
- phenolics
- oxidating agents
(bury or compost contaminated litter and manure)
