Etiket Arşivleri: Antiseptics

Antiseptics and Disinfectants

  • ANTISEPTICS & DISINFECTANTS

  • Sterlization

  • Freeing of an article, surface or medium by removing or killing all micro-organisms including vegetative form of bacteria, spores, viruses, fungii

  • Disinfection

  • Destruction or inhibition of growth of all pathogenic organisms (bacteria, viruses, fungii) on non living surfaces

  • If spores are also killed process is Sterlization

  • Antiseptics

  • These are chemical substances

which inhibit the growth or kill micro-organisms on  living surfaces such as skin & mucous membrane.

  • Properties of good antiseptic/ disinfectant

1.Cidal

2.Non  staining &  good odour

3.Active against all pathogens

4.Active in presence of pus, blood & exudates

5.Rapid acting

6.Non irritating to tissues / non corrosive

7.Non absorbable

8.Non sensitizing/

  • Mechanisms of action of antiseptic and disinfectants

  • Oxidation of bacterial protoplasm

–Potassium permagnate, H202, Halogens

  • Co-agulation (denaturation) of bacterial proteins & disrupt cell membrane

–Phenols, chlorhexidine, alcohols, aldehydes

  • Detergent like action ↑ permeability of bacterial cell membrane

–Cetrimide, soaps

  • Classification

  • Phenol derivatives:

–phenol, cresol, hexachlorophene, chlorohexylenol (dettol)

  • Oxidizing agents:

–Hydrogen peroxide.

  • Halogens:

–Iodine,  chlorine,  chlorophores.

  • Biguanides:

–Chlorhexidine.

  • Quaternary ammonium:

–Cetrimide.

  • Phenol

  • Earliest used, reference standard

  • Protoplasmic poison,

–injures tissues & cells at high conc causes skin burn

  • MOA:

–denaturating bacterial protiens.

  • USES :

–To disinfect urine, faeces, pus, burns.

  • Extremely irritating, corrosive

  • CRESOL (Lysol)

  • Methyl Derivative of phenol, less damaging to tissues than phenol.

  • 3-10 times more active

  • used for disinfection of utensils, excreta & for washing hands.

  • Chloroxylenol (Dettol)

  • Phenol derivative

  • Does not co-agulate proteins,

  • Non corrosive,Non irritating to skin

  • Commercial 4.8 % solution used for surgical antisepsis

  • Skin cream and soap: 0.8%

  • Mouth wash 1%

  • Hexachlorophene

  • Commonly incorporated in soap

  • Effectively only against Gm+ve

  • Slow but persistant action

  • >2% preparations banned

  • Oxidizing agents

  • Potassium permagnate:

– Purple crystals, highly water soluble, liberates oxygen which oxidizes bacterial protoplasm.

–Used for gargling, irrigating wounds, urethra (condy`s lotion diluted solution of 1:4000  to 1:10,000 )

–High conc cause burns

–It is also used to disinfect water in ponds.

–Stomach wash in alkaloidal poisoning

  • Oxidizing agents

Hydrogen Peroxide

–liberates nascent  oxygen which oxidizes necrotic matter & bacteria.

–Helps in loosening  &  removing  slough,  ear wax etc.

Benzoyl Peroxide

–Widely used drug for acne.

–liberates O2 in presence of water which kills bacteria, specially anaerobes

  • Halogens

  • Iodine,

  • Iodophores,

  • Chlorine,

  • Chlorophores

  • Iodine

  • Rapidly acting broad spectrum (bacteria, fungi,virus)

  • Acts by iodinating and oxidizing microbial protoplasm.

  • Used for cuts, degerming skin before surgery.

  • Adverse effect: cause burns & blisters

  • Iodophores

  • Known as povidine iodine.

  • Non toxic, non staining prolonged action.

  • Used on boils, furunculosis, burns, ulcers, tinea, surgical srub, disinfecting surgical instruments, non specific vaginitis.

  • Chlorine

  • potent germicide. Kills pathogens in 30 sec. used to disinfect urban water supplies.

  • 0.1 to 0.25 ppm

  • Cholorophores

(1)  Chlorinated lime (bleaching powder)

–obtained by action of chlorine on lime.

–used to disinfect drinking water

(2)  Sodium hypochlorite

– Powerful  disinfectant used in dairies for milk  cans.

–Too Irritant to be used as antiseptic.

–Root canal therapy in dentisry

  • Biguanides

Chlorhexidine: (Savlon)

– Acts by disrupting bacterial cell membrane & denaturation of bacterial proteins

– Non irritant ,more active against gram +ve     bacteria.

–Used in for surgical scrub, neonatal bath, mouth wash &  general skin antiseptic.

–Most widely used antiseptic in dentisry 0.12-0.2% oral rinse or 0.5 -1 % tooth paste

  • Quarternary ammonium antiseptics

    cetrimide

  • Detergents: Cidal to bacteria, fungi & viruses.

  • Act by altering permeability of cell membrane

  • Efficiently remove dirt and grease

  • Widely used as antiseptics & disinfectants for

surgical   instruments, gloves etc

  • Combined with chlorhexidine (savlon)

  • Soaps

  • Anionic detergents

  • Weak antiseptics with cleansing action

  • Washing with soap and warm water one of the most effective methods of preventing disease transmission

  • Affect only Gm+ bacteria

  • Alcohols

  • Ethanol

–Antiseptic, cleansing agent at 40-90% conc.

–Act by precipating bacterial proteins

– Irritant, should not be applied on mucous membrane, ulcers, open wounds.

  • Aldehydes (Formaldehyde)

  • Used for fumigation.

  • 37 % aqueous solution called as formalin.

  • Protoplasmic poison , denaturates protiens.

  • Used for preserving dead tissues.

  • Use as antiseptic  restricted due to bad odour & irritation

  • Glutaraldehyde is a better sterlizing agent

  • Acids

Boric acid

  • weak antiseptic , bacteriostatic.

  • used for mouth wash, irrigation eyes, glossitis.

  • Adverse effect: vomiting ,abdominal pain on systemic absorption.

  • Metallic salts

SILVER COMPOUNDS

  • Silver sulphadiazine is active against pseudomonas seen in burns patient.

  • Silver nitrate highly active against gonococci

ZN SALTS

  • Mild antiseptic, used as eye wash, ear drops.

  • Dyes

Gentian violet:

– Active against bacteria (gram + ve), fungi

–Used on chronic ulcers, furunculosis, bed sores, ring worms.

Acriflavine

–Active against  gram +ve bacteria & gonocci

–suitable for chronic ulcers & wounds

–Do not retard healing, non irritant

  • Ectoparasiticides

  • These are drugs used to kill parasites that live on body surfaces

lice → cause pediculosis (hair infection)

mites → cause scabies(skin infection)

  • Drugs used are

(1)  PERMETHRIN

(2)  LINDANE

(3) BENZYL BENZOATE

(4) IVERMECTIN

(5) CROTAMITON

(6) SULFUR

  • Permethrin

  • Broad spectrum causes neurological paralysis in insects.

  • 100 % cure rate nearly

  • Single application needed in most  cases.

  • Few patients experience itching ,burning.

  • first drug of choice for scabies & pediculosis.

Scabies:    apply  all over the body except face & head . Wash  after 8- 12 hrs.

 Head louse:    massage about 30 g in to scalp  and wash  after  10 min.

  • Lindane

  • Broad spectrum insecticide which kills lice and mites by penetrating their chitinous cover

  • Properties similar to permethrin.

  • Cure rate low & resistance seen.

  • Disadvantage: being lipid soluble CNS toxicity like vertigo , convulsions seen.

  • Application similar to permithrin.

  • combination with benzyl benzoate is more effective.

  • Benzyl benzoate

  • Oily liquid with aromatic smell.

  • Cure rate 76 – 100% ; second application required after 24 hrs.

  • Toxicity is low. Application similar to permethrin.

  • Use has declined due to skin irritation.

  • Contra indicated in children because of neurological symptoms & skin irritation.

  • combination with lindane highly effective.

  • Crotamiton

  • low cure rates

  • Better results if applied for 5 days in children

  • Less irritation and toxicity

  • May be preferred in children as second choice

  • Ivermectin

  • Anti helminthic drug which has been recently found effective against scabies & pediculosis.

  • A single 0.2 mg /kg ( 12mg in adults) has 91- 100 %  cure rate.

  • Contra indicated in children < 5yrs , preganant & lactating women.

Evaluating the Effectiveness of Antibiotics, Antiseptics, and Disinfectants

Antiseptics, disinfectants, and antibiotics can be referred to as chemical anti-microbial agents, in contrast to physical antimicrobial agents such as heat and radiation. Microbiologists usually distinguish between antiseptics and disinfectants in the following way. Antiseptics are preparations of chemicals that are meant to be applied to the skin or other living tissue. Examples are chemical preparations designed to treat wounds or infected throats. Alcohol, probably the most widely used antiseptic, denatures proteins, extracts lipids, and dehydrates cells, all of which probably contribute to the effectiveness of alcohol as an antiseptic. Iodine is another excellent antiseptic, though its effects on microbes are not understood. Heavy metals are also used in antiseptic preparations; for example, laws require that silver nitrate be applied to the eyes of newborn humans, especially to prevent the transmission of gonococci from mother to infant.

Temperature Lethal Effect

Temperature Lethal Effect

Temperature’s lethal effects on bacterial growth can be seen after subjecting various bacterial cultures to excessive heat in the range of 90 to 100 degrees C. Microorganisms are killed by elevated temperatures mainly because of the susceptibility of their macromolecules to heat. High temperatures cause proteins to denature and unfold which results in the loss of the tertiary structure and loss of overall function. Most proteins are enzymes which means that metabolic activity relies on their function. If these proteins are damaged the metabolic capabilities of the organism will be irreversibly damaged. Nucleic acids are also damaged by heat resulting in the loss of structure of DNA and RNA. This will lead directly to cell death. Smaller co-factors like NAD+ can also be damaged by heat and loss of these factors leads to cell damage and death. Some cells like that of Bacillus and Clostridium are more resistant to heat because of their endospores. These endospores contain calcium dipicolinate that protects the cells from heat. Endospore-specific proteins can bind to nucleic acids and prevent denaturation.

Antiseptics

We use antiseptics everyday.  An antiseptic is a chemical agent used to kill or control the growth of microorganisms.  Hospitals use sodium hypochlorite which is identical to household bleach to control microorganisms.  Medical professionals use alcohol to sterilize the skin before an injection and betadine (an organic form of iodine) on the skin before surgery.  The betadine prevents Staphylococcus aureus from causing a post surgical infection.  Cities add chlorine to the water supply to prevent the spread of pathogens such as Salmonella typhi from getting into the drinking water.  Chemical agents are also added to food to slow down spoilage by microorganisms.  This increases the shelf life of the packaged food.  Clostridium botulinum causes a deadly form of food poisoning and is controlled by adding chemicals to canned food.  Antiseptics are not to be confused with disinfectants which are used to control microbial activity on inanimate objects.

Antimicrobial Sensitivity Testing

As soon as the causative agent of an infection has been determined it is up to the physician to presribe the most effective antimicrobial agent that will kill the pathogen without harming the patient.  Antibiotics vary in effectiveness against different bacteria.  Some antibiotics are more effective against gram negative bacteria while some are referred to as broad spectrum and are effective against both gram negative and gram positive bacteria.  Antibiotics must be tested against specific organisms to determine how effective they are.  The Kirby-Bauer method of sensitivity testing is one of the most popular methods for testing antibiotics.  This test is performed by uniformly streaking a medium with the test organism.  Paper disks containing specific concentrations of an antibiotic are deposited on the agar surface.  A chemical in the disk diffuses out and forms a concentration gradient.  If the agent inhibits the growth of the bacteria there will be a zone around the disk where no growth occurs called the zone of inhibition.

Membrane Filter Technique

Conclusion

The Membrane Filter Technique is an effective, accepted technique for testing fluid samples for microbiological contamination. It involves less preparation than many traditional methods, and is one of a few methods that will allow the isolation and enumeration of microorganisms. The MF Technique also provides presence or absence information within 24 hours.

Antibiotic Sensitivity Testing

Introduction

Antibiotic sensitivity testing (AST) aims to determine the susceptibility of an isolate to a range of potential therapeutic agents. This can be with a view to individualizing the antibiotic to be administered or to monitor resistance patterns developing in that environment, gathering this information is important for revising and updating the standard antibiotic prescribing policy for a particular population or institution.

Resistance to antibiotics can either be naturally occurring for a particular organism/drug combination or acquired resistance, where mis-use of anti-microbials results in a population being exposed to an environment in which organisms that have genes conferring resistance (either spontaneously mutated or through DNA transfer from other resistant cells) have been able to flourish and spread.

Identification of an organism normally goes hand in hand with the AST test, knowing what organism you have isolated together with knowledge of the isolation site, will give an indication of what type of antibiotics should be considered. The sensitivity of an isolate to a particular antibiotic is measured by establishing the Minimum Inhibitory Concentration (MIC) or breakpoint, this is the lowest concentration (conventionally tested in doubling dilutions) of antibiotic at which an isolate cannot produce visible growth after overnight incubation.