2. Disinfectants
⢠Definition
⢠Antiseptics
⢠Properties of an ideal disinfectant:
ď Broad spectrum
ď Non toxic
ď Fast acting
ď Odourless
ď Surface compatibility
ď Economical
ď Easy to use
ď Solubility and miscibility
ď Not affected by physical factors
ď Stable on storage
3. Classification
⢠Acids and alkalies
⢠Halogens
⢠Heavy metals
⢠Phenol and its derivatives
⢠Alcohols
⢠Aldehydes
⢠Quaternary ammonium compounds
⢠Dyes
⢠Detergents and soaps
4. Acids and Alkalies
⢠H+ and OH- ion concentrations
⢠Strong as well as weak acids
⢠Alakalies like NaOH, NH4OH
Halogens
⢠Cl, Br, I, F
Chlorine:
⢠Organic, inorganic, gas
⢠Formation of hypochlorous acid
Cl2 + H2O â HCl + HClO
2 HClO â 2HCl + O2
5. ⢠Oxygen â Oxidising agent
⢠Clorine combines with proteins and enzymes
⢠Calcium hypochlorite and sodium hypochlorite
⢠Open wounds, atheleteâs foot
Iodine:
o Sporicidal, fungicidal, virucidal
o Weak Iodine Solution BP, Aqueous Iodine
Solution BP
o Iodophores
o Oxidising agent â Innactivates metabolic
compounds
6. Heavy Metals
⢠Mercury, silver, copper
⢠Combine with cellular components
Enzyme
⢠Coagulate cytoplasmic proteins
8. Phenol and its derivatives
⢠Distillation of coal tar
⢠Lister (1867) â Antiseptic surgery
⢠Evaluation Standard
⢠Cresol with soap solution and an alkali (Lysol)
⢠Hexylresorcinol â mouth washes, gargles,
cough drops
⢠Disruption of cells, precipitation of cell
proteins, inactivation of enzymes, leakage of
amino acids
14. Dyes
⢠Acridine dyes
o Acriflavine, Proflavine, Enflavine
o Effecitve against Gram positive bacteria
o Impair DNA complexes
o Burns, ophthalmic applications, bladder irrigation
⢠Triphenylmethane dyes
o Brilliant green, Malachite green, Crystal violet
o Inhibit Gram positive bacteria
o Crystal violet â fungicide
o Interfere with cellular oxidation processes
16. Detergents and Soaps
⢠SAA, wetting agents, emulsifiers
⢠Cationic (SAA) â Quat. Amm. Compounds
e.g. cetrimide, benzalkonium chloride
⢠Anionic compounds â e.g. Sodium lauryl
sulphate, soaps
⢠Non-ionic detergents - not used
⢠Amphoteric compounds â detergents +
disinfectants
e.g. Tego Compounds ( AA of high mol. wt.)
17. Factors affecting Disinfectant Action
⢠Concentration of disinfectant
⢠Temperature
⢠Time of contact
⢠pH of environment
⢠Surface tension
⢠Formulation of disinfectant
⢠Chemical structure of disinfectant
⢠Type and number of micro-organisms
⢠Interfering substances
⢠Potentiation, synergism, antagonism of disinfectants
21. pH of Environment
⢠Change in pH â rate of growth, potency of
disinfectant, ability to combine
⢠pH 6-8 â optimum
Surface Tension
⢠Surfactant property improves contact
⢠Adsorption, wetting, spreading
⢠Soap with crude phenol
22. Formulation of Disinfectant
⢠Chlorhexidine and QUATS â 70% alcohol
⢠Iodine â alcohol/ KI
⢠Iodine with SAA
⢠Concentrated solution â convenient, economic
Chemical Structure of Disinfectant
⢠Substitution of an alkyl group up to 6 carbons
â para position to phenolic âOH group
⢠Halogenation of phenol
⢠Nitration of phenol
23. Type and No. of MO
⢠Bacterial spores
⢠Aldehyde â sporicidal
⢠Aldehydes and halogens + β-propiolactone â Virucidal
⢠Iodine, formaldehyde, alcohol, phenolic compounds â
acid fast bacteria
Interfering Substances
⢠Blood, body fluids, pus, milk, food residues,
colloidal proteins
⢠Adsorption/ chemical reaction/ shielding
⢠Oils/ fats
25. Evaluation of Disinfectants
⢠Tube dilution and agar plate method
⢠Filter paper and cup plate method
⢠Ditch-plate method
⢠Phenol coefficient method
⢠Kelsey Sykes method
26. Tube dilution and agar plate method
(Serial dilution method)
⢠Chemical agent added in to nutrient broth/
agar medium
⢠Inoculation
⢠Incubation
⢠Turbidity/ colonies
⢠Activity compared
28. Cup plate/ Cylinder plate/filter paper disc method
⢠Agar inoculated with MO poured in petri dish
⢠Solidified, holes of 9mm diameter
⢠Antimicrobial agent placed
⢠Incubated
⢠Diameter of zone of inhibition observed
29. Ditch-plate method
⢠Ditch prepared in agar plate
⢠Antimicrobial solution added
⢠Test MO streaked
⢠Width of zone of inhibition â relative activity
30. Phenol Coefficient Test
⢠Phenol as a reference
⢠MO added in rising dilutions of phenol and disinfectant
⢠U.K. â Salmonella typhi
⢠U.S.A. â S. typhi, Staphylococcus aureus, Pseudomonas
aeruginosa
o Rideal-Walker test (RW Test)
o Chick- Martin test (CM Test)
o United States Food and Drug Administration Test (FDA
Test)
o The US Association of Official Agricultural Chemist
Test (AQAC Test)
31. RW Test
⢠Rideal-Walker broth, S. typhi
⢠Dilutions of phenol and disinfectant prepared
⢠5ml dilution inoculated with 0.5ml of culture
⢠TT placed in water bath (17.5â°C)
⢠Transferred to 5ml sterile bath after 2.5, 5, 7.5,
10 minutes
⢠Incubated at 37â°C for 48 to 72 hrs
⢠Examined
34. Advantages:
⢠Inexpensive, quick
⢠Reproducible
⢠Eliminate useless products
⢠Standard for crude preparations
Disadvantages:
⢠Only one MO
⢠One concentration, fixed death time, temperature
⢠Organic matter
⢠Tissue toxicity
⢠Sampling errors
⢠Effect of dilution
⢠Phenolic disinfectants only
35. Kelsey â Sykes method
⢠S. aureus, P. vulgaris, E. coli, P. aeruginosa
⢠Clear/ dirty conditions
⢠Final concentration â 109/ml
Result:
o No growth occurs in 2 or more of 5 tubes of
18 min samples
o Not more than 5 colonies from 5 drops
36. Time (Min) Procedure
0
8
10
18
20
28
3ml of Disinfectant + 1ml of bact. Suspension, Shake
Transfer 1 drop to each 5 tubes with liquid medium or 5 drops
to agar plate
Add 1ml of bact. Suspension, shake
Transfer 1 drop to each 5 tubes with liquid medium or 5 drops
to agar plate
Add 1ml of bact. Suspension, shake
Transfer 1 drop to each 5 tubes with liquid medium or 5 drops
to agar plate