Forensic Biology & Its biological significance.pdf
Antiseptics & disinfectants
1. ANTISEPTICS & DISINFECTANTS
Disinfection is destruction of all
microbes but not their spores. If spores
are also killed, then this is called
sterilization.
Antiseptic is the killing of microbes and
can be used on living tissues. The word
germicide can be used for drugs either.
2. MECHANISM OF ACTION
• Oxidation of bacterial protoplasm
• De-naturation of bacterial proteins
• Detergent like action
• Competition with essential substrates for imp. enzymes in
bacterial cell.
An ideal germicide should have
wide antibacterial spectrum
Chemically stable
Rapid action
Non irritating to tissues
No interference with wound healing even in presence of
pus, exudates and tissue degradation products
4. ACIDS
• Boric acid & benzoic acid have weak
bacteriostatic & fungistatic activity. Aqueous
solution of boric acid are used for irrigating eyes,
bladder, vagina & large wounds.
ALCOHOLS
Ethyl alcohol is used to clean the skin before
injections & surgeries. Isopropyl alcohol is more
potent and more toxic than ethanol. It is used in
68-72% concentration as skin antiseptic
5. ALDEHYDES
• FORMALDEHYDE: It is a gas at room temperature used
for fumigation, the 40% aqueous solution is
noncorrosive and has a broad antimicrobial spectrum. It
has a pungent odour & is highly irritant to respiratory
mucosa & eyes.
Mechanism of action of formaldehyde : act by
alkylation(transfer of an alkyl group from one molecule
to another) of chemical groups in proteins & nucleic
acid.
Uses :
I. Used for fumigation & sterilization of instruments
which cannot be moistened with solution
II. 40% solution(100% formalin) in h20 is used for
disinfection of surgical instruments and gloves.
6. SURFACTANTS
• Surfactants are chemicals that lower surface
tension of solution & are termed as detergents,
They maybe anionic(-vely charged) cationic(+vely
charged ion) ampholytic (type of amino acid that
changes its charge depending on the pH of
aqueous solution) or polysorbates (any of several
emulsifiers used in the preparation of some
pharmaceuticals and foods)
• Anionic surfactants : eg soaps
• Cationic surfactanats: eg. Cetrimide
7. PHENOL DERIVATIVES
• Phenol is one of the oldest antiseptics introduced by LORD
LISTER IN 1867. It is bactericidal & fungicidal but has poor
action against spores & viruses. It acts by denaturing the
bacterial proteins. It also has a mild anaesthetic effect. It is
a protoplasmic poison. Protoplasmic poisons are
substances that if a healthy living cell is exposed to in
significant amounts, the cell will be adversely affected,
damaged, or killed.
• Uses :
A. Disinfection of urine, faeces, sputum of patients
B. Antipruritic effect because it is an anaesthetic
• Cresol is methylphenol. It is used for disinfecting utensils
& excreta
8. HALOGENS
• It is a powerful bactericidal, sporicidal, fungicidal
and viricidal agent.
• Disadvantages: Irritating, painful, stains the area
and may delay wound healing
• Uses of iodine :
I. As a tincture: used before surgeries to clean the
skin
II. Mandl’s paint : treatment of tonsilitis &
pharyngitis
III. Iodine ointment : in ringworm infections
9. IODIZING AGENTS
• Hydrogen peroxide : It is a colourless and
odourless liquid. On application there is
effervescence & helps in removing tissue
debris, ear wax etc. Action of duration is short.
It is also a deodrant
• Uses : cleansing wounds, abscesses & for
irrigation
10. DYES
• Gentian violet : effective against gram positive
organisms and fungi. Staining is the only
disadvantage. It is non irritant and potent
antiseptic. 0.5-1% solution is used topically on
burns & boils, eczema(Eczema symptoms
include itchy, red, and dry skin caused by
inflammation)
• Brilliant green : action is similar to gentian
violet.
11. Metals
• Zinc salts : have astringent & mild antiseptic
properties. Zinc ointment is used as an
ointment or lotion eczema, impetigo &
psoriasis.
• Mercury compounds: act by inhibiting
sulphydryl enzymes of bacteria. They are not
commonly used.
