Selection of the most appropriate antimicrobial compound for specific practical applications depends on:
- Properties of chemical agents
- Types of microorganisms
- Intended application
- Toxicity of agents
- Cultural state.
Factors Affecting Choice of Antimicrobial Agent
1. Properties of chemical agents: The process of killing or inhibiting the growth of microorganisms using an antimicrobial agent is a chemical reaction. The rate and extent of a chemical reaction are generally influenced by the concentration of the chemical, temperature, pH, and formulation.
2. Environment: Organic matter, blood, body fluids, pus, milk, colloidal proteins, and food residues, mainly reduce the effectiveness of antimicrobial agents. Organic matter can have a drastic effect on antimicrobial activity by adsorption or chemical inactivation. Dried organic deposits may inhibit the penetration of the chemical agent.
3. Types of microorganisms: The types of microorganisms present and the levels of microbial contamination (bioburden) both have a significant effect on the outcome of chemical treatments. Long exposure times or higher concentrations of antimicrobials may be required for higher bioburden. Chemical agents are not equally effective against bacteria, fungi, viruses, and other microorganisms. Vegetative bacteria and fungi are sensitive to antimicrobial agents. Mycobacterium tuberculosis and other mycobacteria are resistant to many bactericides. Spores are more resistant than vegetative cells.
4. Intended application: The intended application of an antimicrobial agent, whether for preservation, antisepsis or disinfection will influence its selection and also affect its performance. Many chemicals adversely affect the instruments at the time of disinfection. Chemicals may cause corrosion of metals and also affect the clarity of lenses or change the texture of synthetic polymers.
5. Toxicity of agent: Control Of Substances Hazardous to Health (COSHH) Regulations specify the precautions required in handling toxic agents. Phenolics, formaldehyde, and glutaraldehyde are mainly toxic antimicrobial agents. Toxic volatile substances are kept in covered containers to reduce the level of exposure to the irritant vapor and they are used with an extractor facility. Alcohols, chlorine compounds, and phenolics mainly affect the eyes and skin. Aldehydes mainly affect the respiratory system and also produce contact dermatitis.
6. Cultural state: When the bacterial cells are actively dividing in the log phase of growth, they are more sensitive to antimicrobial agents. The sensitivity may be due to a minor interference with the replication of nucleic acids and with protein synthesis having a profound effect on the continuation of high metabolic activity. All microorganisms are more susceptible to chemicals at the point of division.
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