ANTISEPTICS &

DISINFECTANTS

Joseph Lister (1827 - 1912)

father of modern antisepsis

• 1867 - “Antiseptic Principle of the Practice of Surgery” - carbolic acid (phenol) as antiseptic

Antiseptics – applied to living tissue to kill microbes or

to inhibit their growth

Disinfectants – to kill or inhibit microbes on inanimate

objects

• Defined by their intended use and not by their chemical content

Ideal Antiseptic

• broad spectrum of activity, Cidal and not merely static

• residual activity

• low toxicity

• high penetrability

• active in the presence of pus and necrotic tissue

• Chemically stable, non staining

• Cheap

Ideal Disinfectants• fast action• should not corrode instrument or

metallic surfaces• Non irritating to tissues, should not

delay healing• active in the presence of organic

material (blood, sputum, feces)• compatible with soaps and detergents• residual surface activity• odorless

Order of killing

Sensitive - • Vegetative bacteria• Lipophilic viruses (lipid containing, enveloped)• Fungi• Hydrophilic viruses (non-lipid, non-enveloped)• Mycobacteria (Mycobacterium tuberculosis)• Resistant – Bacterial spores

Clinical Applications• before and after surgery

• during catheterization or other invasive implants

• in immunocompromised states -

immune defect, cytotoxic drug therapy, extreme old or young age, extensive skin damage (burn and wound)

Mode of Action of Antiseptics

• The most important actions are observed on the cytoplasmic membranes & the respiratory system of microorganisms.

• Oxidation of bacterial protoplasm

• Denaturation of bacterial proteins

The antiseptic activity depends on:-

- conc of agent and contact time- Temp and pH- Some antiseptics are inactivated by heat

and light- The presence of pus and necrotic tissue- may be absorbed by plastics and can be

unstable in diluted solutions- The major risk is the contamination by

resistant microbes.

General side effects of antiseptic

-Cutaneous irritation

-Allergic reactions

• On skin and mucous membranes, repeated application leads to diminution of normal flora, which can be replaced by another virulent infectious germs.

Principal Groups of Antiseptics and disinfectants

I . Phenols & Derivatives.

II. Oxidizing agents

III. Quarternary Ammonium compounds.

IV. Halogens.

V. Alcohols.

VI. Chlorhexidine.

VII. Dyes

VIII. Metallic salts

Phenol (Carbolic acid)

• Phenol - first to be used in clinical practice (Joseph Lister, 1867)

• denatures proteins• highly corrosive and toxic • not considered effective against bacterial or

fungal spores• seldom used as antiseptic but is a preferred

disinfectant• cheap

Uses• To disinfect urine, feces, pus,

sputum

Toxicity• Buccal, esophageal and gastric

burns – if swallowed• Excitation• Convulsions• Respiratory paralysis• Vascular collapse

Other phenolic compounds

Cresol- (lysol)• Methyl phenol• More active• Less damaging to tissues• Disinfection of utensils, excreta and

washing handsChlorxylenol – (Dettol)• Non corrosive, non-irritating to intact

skin• For surgical antisepsis

Hexachlorophene – chlorinated phenol

• Bacterial lysis

• Commonly incorporated in soap and other cleaning antiseptics for surgical scrub

• Effective for furunculosis and carbuncles

• Action is slow but persistent due to deposition on the skin as a fine film

• Odorless, non irritating to skin

Oxidizing agents

Potassium Permanganate

• Antiseptic and disinfectant

• Liberates oxygen which oxidizes bacterial protoplasm

• Slow action and high conc cause burns and blistering

• As antiseptic - 1:4000 to 1:10000 sol (Condy’s lotion) for gargling, douching, irrigating cavities, urethra nad wounds

• As disinfectant – disinfect water (wells, ponds), for stomach wash in alkaloidal poisoning

Hydrogen peroxide• wide germicidal activity• Liberates nascent oxygen –oxidizes necrotic

matter and bacteria• decomposed by catalase or other

peroxidases in tissues – loosening and removing slough, ear wax etc.

• damaging to tissues, not suitable for routine wound care

• In its concentrated form, extremely corrosive and irritating to skin, eyes and mucous membrane

HalogensIodine• oxidizes proteins and other important

biological macromolecules.• wide germicidal activity including fungi,

viruses and bacterial spores• has a characteristic odor and is corrosive• is insoluble in water and thus prepared in

alcohol (tincture) or with solubilizing surfactants (“tamed”iodine)

• limited activity when in the presence of organic matter

Uses-

• on cuts, for degerming skin before surgery

• Mandel’s paint (1.25% Iodine) – for sore throat

• Iodine ointment (Iodex 4%) – antiseptic and counter-irritant

Iodophores- soluble complexes of iodine with large molecular organic compounds

• slow continuous release of free iodine• excellent cleansing agents as well as antiseptic

and disinfectants• prolonged activity after application (4-6 hours)• less irritating, allergenic, corrosive, and non

staining

Povidone I2 –

Non-irritating, non toxic, non-stainingUsed on boils, furunculosis, burns, otitis externa,

ulcers, surgical scrubbing

Chlorine and chlorophores

• formation of hypochlorous acid (HOCl)• sodium hypochlorite (NaOCl, bleach),

chlroamine-T• provide wide germicidal activity and are

relatively nontoxic• limited activity when in the presence of

organic matter• poor residual activity• corrosive to metals and destroy many

fabrics

• fair effectiveness as sporicidal agents

• effective at low concentrations for disinfecting objects

• strong odor, light sensitive

Uses

• Disinfectant for drinking water, swimming pools.

Chlorhexidine• disrupts the cell membrane and precipitates cell

contents• active against bacteria, fungi, and Mycobacterium

tuberculosis• poorly active against viruses and bacterial spores• Long residual activity• Active in the presence of blood and other organic

materials• Nontoxic• Widely used as a presurgical antiseptic, wound

flush, mouthwash

Alcohol

• ethyl and isopropyl alcohol• solubilizes the cell membrane and denatures

proteins.• wide germicidal activity, non corrosive, but

poses a fire hazard• limited residual activity due to evaporation• alcohols provide limited activity in the

presence of organic matter • used as a 70-90% concentration• irritating to tissues

Aldehydes

• alkylates and crosslinks proteins, DNA, RNA

• formaldehyde (HCOH), glutaraldehyde

• not as antiseptics

Formaldehyde• very potent disinfectant, highly toxic to

animals• active as gas and liquid form (formalin)• very wide germicidal activity (bactericide,

fungicide, virucide, sporicide)• slow, requiring 6-12 hours’ contact time • relatively noncorrosive to metals, paint, and

fabric• slight to moderate efficiency in presence of

organic matter• slight residual activity• irritating fume and pungent odor• potential carcinogen

Glutaraldehyde

• similar to formaldehyde without some of its shortcomings

• faster effects compared to formaldehyde• moderate residual activity• to be sporicidal, need to be activated by

alkalizing agents• irritating to the eyes and nasal passages• 2% sol.- disinfects surgical instruments and

endoscopes

Quarternary ammonium antiseptics

Cetrimide (1-3%)

• fishy odour

• Most popular hospital antiseptic and disinfectant for surgical instruments

• Removes dirt, grease, blood from road side accidents

Soaps

• Anionic detergents

• Weak antiseptics

• Affect only gram positive bacteria

Dyes

Gentian violet

• Effective against gram positive bacteria and fungi

• (gram negative and mycobacteria are insensitive)

• 0.5-1% - furunculosis, chronic ulcers, bed sores, ringworm

Acriflavine and Proflavine• Orange yellow acridine dyes• Effective against gram positive bacteria

and gonococci• Efficacy not reduced by organic matter• Non-iritant chronic ulcers and wounds –

burn dressing• Triple dye lotion – gentian violet+brilliant

green+ acriflavine- burns and dressing umbilical stump in neonates

Acids

• Boric acid- bacteriostatic, weak antiseptic

• 4% - irrigating eyes, mouthwash, douche.

• Boroglycerine paint (30%) – stomatitis and glossitis

• Borocide -10% ointment cuts & abrasions

• Prickly heat powders and ear drops

• Systemic abs- vomiting, abd pain, diarhoea, visual disturbances

Metallic salts

• Silver compounds – Silver nitrate, silver sulfadiazine

• Zinc salts – Zn sulphate, Calmaine and Zn oxide

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