CONTROL OF MICROORGANISMS BY CHEMICAL METHODS

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. 
Uses: Phenolics substances may be bactericidal or Bacteriostatic depending upon concentration used. Spores & viruses are most resistant .The antimicrobial activity of phenol is reduced at alkaline pH by organic materials, low temperature etc. 

Mode Of Action: 
                       Specific mode of action is unclear.  However depending upon the concentration phenol & its derivatives causes disruption of cell wall, denaturation of protein, enzyme inactivation, leakage of cells. To know more please visit this site http://www.icm.tn.gov.in/drug%20formulary/DISINFECTANTS%20&%20ANTISEPTICS(13).htm

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