Control of Microorganisms Various Physical & Chemical Methods

2. CCoonnttrrooll ooff MMiiccrroooorrggaanniissmmss
VVaarriioouuss PPhhyyssiiccaall && CChheemmiiccaall
MMeetthhooddss

3. MMaannyy mmiiccrroooorrggaanniissmmss aarree bbeenneeffiicciiaall..
SSoommee aarree hhaarrmmffuull..
MMiiccrroobbiiaall aaccttiivviittiieess –– ffoooodd ssppooiillaaggee aanndd ddiisseeaassee..
IInnttrroodduucceedd ccoonncceepptt ooff mmiiccrroobbiiaall ccoonnttrrooll
IIggnnaazz SSeemmmmeell WWeeiiss [[ HHuunnggaarriiaann PPhhyyssiicciiaann ]]
JJoosseepphh LLiisstteerr [[ EEnngglliisshh PPhhyyssiicciiaann]]
 MMiiccrroobbiiaall ggrroowwtthh ccoonnttrroolllleedd bbyy pphhyyssiiccaall &&
cchheemmiiccaall mmeetthhooddss..
KKiillll oorr iinnhhiibbiitt ggrroowwtthh..

4. TERMINOLOGY RELATED TO THE CONTROL
OF MICROBIAL GROWTH
• Sterilization: A treatment that kills or removes
all living cells, including viruses and spores,
from a substance or object.
• Disinfection: A treatment that reduces the total
number of microbes on an object or surface,
but does not necessarily remove or kill all of
the microbes (Chlorination).
• Sanitation: Reduction of the microbial
population to levels considered safe by public
health standards.

5. STERILIZATION
DISINFECTANTS
SANITATION

6. • Antiseptic: A mild disinfectant agent suitable
for use on skin surfaces.
• Germicide: “the agent kills” microbes. For
example, a bactericide agent kills bacteria,
fungicide, virucide, sporocide.
• Bacteriostatic: “the agent inhibits growth.” For
example, a fungi static agent inhibits the
growth of fungi, but doesn’t necessarily kill it.
( Refrigeration)
• Degerming: Removal of microbes from skin.
• Antimicrobial Agent: Agent kills micro
-organisms or inhibit their growth.

7. ANTISEPTIC DEGERMING
BACTERIOSTATICS

8.  Conditions influencing
1. Temperature
2. Type of Microbe
3. Physical State
 Actions
Kill
Inhibit Microbes
Damage Plasma Membrane
 Gram Positive Bacteria – Disinfectants and antiseptics
greater effect.
 Gram Negative Bacteria – Pseudomonads grow in some
disinfectants and antiseptics.
 Endospores resistant to chemical agents & physical
methods.

9. PPHHYYSSIICCAALL MMEETTHHOODDSS
• Damaging cell components.
• Enzymes, DNA, Cytoplasmic membranes
disrupt.
Used in food industry.
Preparation of culture media lab ware,
sterilization of instrument.

10. PPHHYYSSIICCAALL MMEETTHHOODDSS
Heat
Temperature
Desiccation
Osmotic Pressure
Filtration
Radiation

11. HHEEAATT
Kills microbes by denaturing enzymes.
Heat resistance varies among different
microbes.
Thermal Death Point (TDP)
Thermal Death Time (TDT)
Decimal Reduction Time (DRT)

12. TThheerrmmaall
DDeeaatthh
PPooiinntt
Thermal Death Point (TDP)
• Lowest temperature to kill
all the bacteria in 10 minutes.
• Thermal death is useful in
purifying water.
• Boiling - Kills many
Vegetative Cells.
• Inactivates Viruses Within 10
Minutes
• No effect on spores.

13. TThheerrmmaall DDeeaatthh TTiimmee
Thermal Death Time (TDT)
• Time required to kill all the
bacteria at a given
temperature.
• Developed for food
canning.
• Applications in cosmetics
and pharmaceuticals.

14. DDeecciimmaall RReedduuccttiioonn TTiimmee
Decimal Reduction Time (DRT)
• Length of time.
• 90% of a bacterial population killed at a given
temperature
• Reduces the number of organisms to 1/10 the
initial level.
• Used in Commercial Sterilization.

15. RRaattee ooff MMiiccrroobbiiaall DDeeaatthh
• Bacteria usually die at a Constant Rate .
• Plotted logarithmically this will give a Straight Line

16. AUTOCLAVING

17. PASTEURIZATION
• Process used in preserving heat sensitive
foods.
• Milk, beer, and other
beverages.
• 63 °C for 30 Minutes.
• Wine - Pasteur
• Milk - VH & F soxhlet .
• Reduction of microorganism in milk.
• Pasteurization is not a method of sterilization.

18. Two different process
• High Temperature Short Time (HTST) process
- 72°C for 15s ( Quick heating and cooling).
• Ultra High Temperature (UHT) sterilization
- heating at 140°C for 3 seconds.
• Milk kept at room temperature for 2 months.
• Minimal changes in flavor.
• Equivalent Treatments – Different methods
produce same effect.
• Mycobacterium – Tuberculosis

19. LLooww TTeemmppeerraattuurreess
• Decreasing temperature decreases chemical
activity.
• Low Temperature are Not Bactericidal.
• Restrict enzyme activity.
• Ordinary Refrigerator Temperature 0° – 7°C .
• Do not Reproduce.
• Survive, Restrict rate of growth.
• Use – Food Preservation, Drug, Culture
Preservation.

20. DRY HEAT STERILIZATION
Direct Flaming – Burning contaminants
Incineration - Burns and Physically Destroys Organisms
Used for
a. Needles
b. Inoculating Wires
c. Glassware
d. Body Parts
Hot Air Sterilization – Oxidation
160° C for 2 Hours or 170° C for 1 hour
Used for
a. Objects That Won’t Melt
b. Glassware
c. Metal

21. FFIILLTTRRAATTIIOONN
• The passage of a liquid or gas through a filter with pores
small enough to retain microbes.
• Separate bacteria from suspending liquid.
• Filter – Nitrocellulose, acetate.
• Bacteria, virus large protein.
• High efficiency particulate air filters.
• Filterable viruses.

22. Two types of Filters:-
• Depth Filters – Fibrous or granular material.
• Thick layer filled with twisting channels.
• Microorganisms sucked through thick layer.
• Microbes removed by physical screening.
• Membrane filters – Circular filters
• Porous membrane – 0.1mm thick
• Made of cellulose acetate, cellulose nitrate,
polycarbonate.
• Variety of pore size.

23. HHEEPPAA FFIILLTTEERRSS
• HEPA filters - High-Efficiency Particulate Air Filters
• Filtration of small particles.
• Capture a minimum of 99.97% of 0.3 microns
contaminants.

24. HHEEPPAA FFiilltteerrss
• Filtration is the primary method of eliminating
pathogens from the air supply.
1. Operating Rooms
2. Burn Units
3. Hospitals, Surgical Mask.
4. Pharmaceutical Manufacturing Facilities

25. DDEESSIICCCCAATTIIOONN
• Removing water from microbes.
• Viruses & Endospores can resist.
• Disruption of metabolism.
• Use – Food Preservation.
• Stops Growth / Microbes are still viable.
• Freeze-drying ( Lyophilization) – remove water from
specimen.
• Gonorrhea bacterium – with stand for only 1 hour.
• Tuberculosis bacterium – viable for months
( Mycolic acid).
• Powdered milk – 85% water is removed.

26. OOSSMMOOTTIICC PPRREESSSSUURREE
• Plasmolysis
• High zone of salt & sugar.
• Salt – Preservation of fish, meat, food.
• High osmotic pressure.
• Low availability of sugar solution to prevent
microbial growth.
• Honey, high sugar content preserved.
• Loss of H2O.

27. RRAADDIIAATTIIOONN
Its Efficiency is Dependent on the Wavelength,
Intensity, and Duration.
Two types :-
Ionizing
 Destruction of DNA by gamma rays & high energy electron
beams.
 Use –
Sterilizing pharmaceuticals medical & dental supplies.
Food preservation and other industrial processes.
 More penetrating.
 Food is exposed to high levels of radiation to kill insects,
bacteria and mold.

28. Non – Ionizing
 Damage to DNA by UV light.
 Effective germicide wave length 260nm.
 Poor penetration
 UV radiation is only useful for disinfecting
outer surfaces.

29. CChheemmiiccaall CCoonnttrrooll MMeetthhooddss
• Phenols and Phenolics
• Halogens
• Alcohols
• Heavy Metals and Their Compounds
• Surface-Active Agents
• Quaternary Ammonium Compounds
• Chemical Food Preservatives
• Aldehydes
• Antibiotics

30. TTyyppeess ooff DDiissiinnffeeccttaannttss
 Phenols and Phenolics
Another Name for Carbolic Acid / Lysol / Pine-Sol
- Joseph Lister
- Exert Influence By
1. Injuring Plasma membranes
2. Inactivating Enzymes
3. Denaturing Proteins
Use – Skin surface, Environmental surface, Instruments, Mucous
membranes.
Common – Cresols, Hexachlorophene.
Phenolics are Long Lasting.
No Effect on Spores.
Effective antibacterial agents, fungi and many viruses.

31. CCHHLLOORRHHEEXXIIDDIINNEE
• Damages plasma membranes.
• Use – Skin degerming, Surgical scrubs.
• Only Operates in Narrow pH Range (5-7).

32. HHAALLOOGGEENNSS
 Can be Used Alone or in Solution.
 Inactivated by Sunlight
 Alter cellular component.
 Inactive enzymes.
Chlorine
- Purifies Drinking Water
- 2-4 Drops of Chlorine per Liter / 30 Min
- Forms an Acid - hypochlorous acid – Bactericidal
- Gaseous form or in Solution as Calcium Hypochlorite.
- Good disinfectants on clean surfaces.
- Inexpensive / Chlorox.
- Never Mix with Other Cleaning Agents!
- Kills legionella species ( Legionella Pneumophila
Bacteria ).

33. Iodine
Least toxic of the disinfectants.
Combines with Amino Acids.
a. Inactivates Enzymes
b. Tincture / Alcohol
c. Iodophor
 Betadine
Wound treatment.

34. AALLCCOOHHOOLL
• Denature Proteins and Dissolve Lipids.
• Evaporates
• Fast Acting
• Wet Disinfectants
a. Aqueous Ethanol (60% - 95%)
b. Isopropyl Alcohol
• Not effective against endospore.
• Use – Thermometer, Instruments, before
injection swabbing skin.

35. HHEEAAVVYY MMEETTAALLSS
• Silver, Mercury – germicidal or antiseptic
• Silver nitrate – prevent gonococcal eye infections.
• Copper sulfate – Algicide
• Mercurochrome – Disinfects skin and mucus membrane.
• Used for Burn Treatment
- Denature Proteins
- Example / Silvadene Ointment / Silver
• Mercuric chloride – Bacteriostatic
• Copper sulphate – destroy green algae in reservoirs.
• Zinc chloride – ingredients in mouth washes.
• Zinc oxide – anti fungal in paints.

36. SSUURRFFAACCEE AACCTTIIVVEE AAGGEENNTTSS
• Include Soaps and Detergents.
• Soaps – Anionic detergents.
• Skin degerming.
• Triclocarbon – inhibit gram positive bacteria.
• Decrease Molecular Surface Tension
• Limited Germicidal Action.
• Removal of Organisms by Scrubbing.

37. CCAATTIIOONNIICC DDEETTEERRGGEENNTTSS
• Quaternary Ammonium Compounds (QUATS)
- Cationic Detergents Attached to NH4
+
- Disrupt Plasma Membranes
- Most Effective on Gram-Positive Bacteria
• Enzyme inhibition, protein denaturation.
• Fungicide, Amoebocide.
• Two popular QUATS – Zephiran.
• Cepacol – Anti microbial

38. OORRGGAANNIICC AACCIIDDSS
Chemical Food Preservatives
- Sorbic Acid
- Benzoic Acid Inhibit Fungus
- Propionic Acid
- Nitrate and Nitrite Salts / Meats
• To Prevent Germination of Clostridium
botulinum endospores.
• Calcium Propionate – Bread

39. Aldehydes
• Antimicrobial.
• Inactivate Proteins.
• Covalent crosslink formation.
• Formaldehyde – preserve biological specimens.
• Glutaraldehyde – Sterilize hospital instruments.
• Most Effective of all Chemical Disinfectants.
• Carcinogenic.
• Oxidize Molecules Inside Cells.

40. Antibiotics
 Used to Preserve Cheese.
 Used in Feed Given to Food Animals.