CONTROL OF MICROORGANISMS BY CHEMICAL METHODS
A). PHENOLS & PHENOLICS:
Phenols & phenolics compounds are very important disinfectants. A 5% aqueous solution of phenol rapidly kills vegetative cells but spores are most resistant. Phenol was used( first) by Joseph Lister(1880s) to reduce infection in surgical incisions & surgical wounds. Phenols remains the standard against another antiseptics & disinfectants are evaluated by Phenol Coefficient Techniques. But, phenol is expensive,has pungent small & is irritating to skin. So, several phenol derivatives are used like;
- Cresol: It is phenol derivatives containing methyl group. It has germicidal activity & lower toxicity than the parent compound. Mixture of or-tho, para, & meta cresol are used commercially as wood preservatives.
- Hexylresorcinol: It is used in mouth wash & topical antiseptics & in throat lozengels.
- Bisphenols: It contains two phenolic group connected by a bridge like o-phenyl phenol, chlorohexidine triclosan etc. One bis phenol, hexachlorophene, is an ingredient of prescription lotion, pHisohex used for surgical & hospital microbial population control procedures. Gram positive Staphylococci & Streptococci which can cause skin infections in new born, are particularly susceptible to hexachlorophene so it is often used to control such infections.