Antiseptics and disinfectants are nonselective, anti-infective agents applied topically. Their activity ranges from simply reducing the number of microorganisms to an acceptable level of cleanliness (sanitization) to destroying all microorganisms (sterilization) on the treated surface. In general, antiseptics are applied on body tissues to suppress or prevent microbial infection, whereas disinfectants are germicidal compounds applied to facility surfaces. Both are generally applied after the surface has been cleaned, usually with soap.
Sometimes the same compound may act as an antiseptic and a disinfectant, depending on its concentration, conditions of exposure or the number of organisms present. To achieve maximal efficacy, it is essential to use the proper concentration of the compound for the purpose intended. The logic “if a little is good, twice as much is better” not only is uneconomical but may have toxicologic implications. The converse—being parsimonious and using too little—may ultimately lead to the emergence of disinfectant-resistant organisms.
Topical anti-infective agents are used extensively in surgery for antisepsis of the surgical site and the surgeon’s hands, and to disinfect surgical instruments, apparel, and hospital premises. Other common uses are as disinfectants for home and farm premises and food-processing facilities, in water treatment, in public health sanitation, and as antiseptics in soaps, teat dips, dairy sanitizers, etc. Antiseptics also have been used to treat local infections. In most cases, however, systemic antimicrobial agents are preferred based on superior penetration and potency in the infected area.
Ideally, antiseptics and disinfectants should have a broad spectrum and potent germicidal activity, with rapid onset and long-lasting effect. They should not be prone to development of resistance in target microorganisms. They should withstand a range of values for several environmental factors (eg, pH, temperature, humidity) and must retain activity even in the presence of pus, necrotic tissue, soil, and other organic material. High lipid solubility and good dispersibility increase their effectiveness. Antiseptic preparations should not be toxic to the host tissues and should not impair healing. Disinfectants should be nondestructive to applied surfaces. They should be readily biodegradable, neither accumulating in the environment nor reacting with other chemicals to produce toxic residues. Offensive odor, color, and staining properties should be absent or minimal.
Most antiseptic and disinfectant compounds exert their antimicrobial effect by denaturing intracellular proteins, altering cellular membranes (often by extracting membrane lipids), or inhibiting enzymes. Although most classes of antiseptics and disinfectants have been in use for decades, the emergence of microbial resistance to some agents, especially in the hospital environment, has led to continued research into the development of new compounds.
In veterinary clinics, animal shelters, farms, and laboratory animal facilities, special attention should be given to the use of products that have proven efficacy against a broad spectrum of microorganisms and viruses, and that are licensed for use with animals (and comply with local regulations). Whether a chosen disinfectant is toxic to the animals concerned, or to their human caretakers, should also be considered.
Disinfection: Process and Facility Design Factors
Disinfection is the first line of defense against an infectious disease outbreak ( see Biosecurity Biosecurity ) in a veterinary hospital, shelter, cattery, kennel, or farm. No matter how good the disinfectant, if the premises are badly designed, or if the staff has a poor comprehension of aseptic technique, then disinfection will be ineffective. Premises and furnishings intended for large numbers of occupants should be designed for ease of cleaning.
Clever building design can facilitate disinfection. Rounded corners where floors meet walls enable more thorough disinfection. Microbial-resistant surfaces and equipment that cannot be colonized by bacteria or fungi should be chosen wherever possible, such as those fabricated from micropatterned or superhydrophobic materials. Well-ventilated spaces and UV light exposure can also reduce microbial contamination in a facility.
The staff of veterinary hospitals, specific-pathogen-free (SPF) laboratory animal facilities, quarantine and rescue shelters, and—to some extent—farms should be required to have a thorough understanding of the principles of hygiene and aseptic technique. Checklists can be employed to ensure that staff complete all required steps for antisepsis and disinfection, every time. Convenience and ease-of-use should be borne in mind when determining the placement and number of hand sanitizing stations and disinfection equipment. Anecdotal examples in which the staff were a cause of infection transmission include the following:
The staff at an SPF kennel with an outbreak of parvovirus-related deaths among pups were using scrapers to push feces from one pen to another in their cleaning routine, unaware that they were spreading parvovirus from one pen to another. Cessation of this practice stopped the outbreak.
In a veterinary hospital with an outbreak of feline infectious peritonitis due to feline coronavirus shed in the feces, dusty, particulate, sawdust-based cat litter was being emptied from used litter trays into bins placed directly beside open bins containing the new, clean cat litter.
Facilities should also be designed to minimize animal stress, because stressed animals shed more pathogens. Transmission of infectious disease by intermediate and paratenic hosts must also be taken into account when designing a disinfection protocol, and measures must be taken to prevent insect or rodent incursion into premises.