Controlling microbial growth

Methods of controlling microbial growth

Physical and Chemical

Physical

1. Sterilization

2. Sterilization by Irradiation

3. Sterilization by Filtration

4. Low temperature

Types of Sterilization by heat

Dry heat

Moist heat

Boiling

Pasteurization

Chemical

Alcohol

Oxidizing Agents

Halogens

Alkalies

Acids

Gases

Quarternary Ammonium Compounds

Soaps

Sterilization

purpose is to destroy all microorganisms and their spores on inanimate objects

Disinfectant

purpose is to destroy or irreversibly inactivate microorganisms (but not their spores) on inanimate objects

Antiseptic

chemical germicide for use on the skin or tissues and should not be substituted for disinfectant

Bacteriostatic

inhibits/ suppresses growth of bacteria

Bactericidal

kills bacteria

Sterilization by Heat

Kills microorganisms by denaturing/coagulating their proteins and enzymes

Indicators of Effectiveness

Thermal Death Time (TDT)

Thermal Death Point (TDP)

Decimal Reduction Time (DRT)

Thermal Death Time (TDT)

minimum time it takes to kill a population of microbes at a specific temperature

Thermal Death Point (TDP)

lowest temperature that is required to kill a population of microbes when applied for a specific time.

Decimal Reduction Time (DRT)

Time in minutes at which 90% of bacteria is killed within a given period of time. canning industr

Most effective method of sterilization (Autoclave)

Requires moist heat at 121C, 15-30min

Kills microorganisms by coagulating their protein

Moist heat

Tyndallization

Autoclaving

2 method of moist heat

Temperatures of about 160C for 60minutes – necessary to kill most spores

Use primarily on glassware, metals and fatty substance which are not permeable to water

Ex: Hot Air Oven

Dry heat

Heating to 100C at boiling point

Kills vegetative forms of bacteria (water-borne), most virus, and fungi within 1 minute

Hepatitis virus can survive up to 30 minutes of boiling

Endospores can survive up to 20 minutes of boiling

Boiling

Tyndallization

AKA Fractional sterilization

the steaming process performed at 100°C done in steam sterilizer for 15-20 minutes followed by incubation at 37°C overnight and this cycle is repeated for successive 3 days

Use to kill spores

Uses Arnold Sterilizer

Autoclave

Most reliable method of heat sterilization

More modern

Use to sterilize culture media and surgical supplies

121C, 15min, 15lbs pressure

121 C, 15 min, 15 lbs pressure

setting for autoclaving

Pasteurization

process of food preservation in which packaged and unpacked foods (e.g., milk and fruit juices) are treated with mild heat, usually to less than 100 °C (212 °F), to eliminate pathogens and extend shelf life

destroys or deactivates microorganisms and enzymes that contribute to food spoilage or the risk of disease

Less than 100 C (212 F)

Pasteurization setting

High-temperature short-time (HTST) pasteurization

Ultra-high-temperature (UHT) pasteurization

Types of pasteurization

High-temperature short-time (HTST) pasteurization

for milk; (71.5 °C (160.7 °F) for 15 seconds) which ensures safety of milk and provides a refrigerated shelf life of approximately two weeks

71.5 °C or 160.7 °F

for milk;________________for 15 seconds) which ensures safety of milk and provides a refrigerated shelf life of approximately two weeks

Ultra-high-temperature (UHT) pasteurization

milk is pasteurized at 135 °C (275 °F) for 1–2 seconds, which provides the same level of safety, but along with the packaging, extends shelf life to three months under refrigeration

135 °C or 275 °F for 1–2 seconds

milk is pasteurized at _________________, which provides the same level of safety, but along with the packaging, extends shelf life to three months under refrigeration

Irradiation

UV rays with shorter WL are more effective in killing bacteria

Mercury vapor lamps with WL 240-280 = used to sterilize rooms

WL 240-280

Mercury vapor lamps with __________= used to sterilize rooms

Filtration

Use if heat is not feasible (some carbohydrates solutions, serum, body fluids)

Removes microbes by passage of liquid or gas through a screen like material with small pores

A typical microfiltration membrane pore size range is 0.1-10 µm, with the most commonly used being 0.2 µm and 0.45 µm, which is sufficient to eliminate bacteria and fungi

0.1-10 µm, 0.2 µm and 0.45 µm

A typical microfiltration membrane pore size range is _____, with the most commonly used being _______, which is sufficient to eliminate bacteria and fungi

High Efficiency Particulate Air filter (HEPA)

use in operating rooms to eliminate bacteria; mostly filters particles that are 0.3um; capture pollen, dirt, dust, moisture, bacteria (0.2–2.0 μm), viruses (0.02–0.3 μm), and submicron liquid aerosol (0.02–0.5 μm

capture pollen, dirt, dust, moisture, bacteria

mostly filters particles that are 0.3 μm;

bacteria

(0.2–2.0 μm)

0.2–2.0 μm

bacteria

viruses

0.02–0.3 μm

0.02–0.3 μm

viruses

submicron liquid aerosol

0.02–0.5 μm

(0.02–0.5 μm)

submicron liquid aerosol

Low Temperature

usually inhibit or stop microbial growth and proliferation but often do not kill bacteria (BACTERIOSTATIC)

Refrigeration (4ºC) and freezing (-20ºC or less) are commonly used in the food, pharmaceuticals and biotechnology industry

4ºC and freezing -20ºC or less

Refrigeration _______________are commonly used in the food, pharmaceuticals and biotechnology industry

Alcohol

three types of alcohol are ethanol, methanol, and isopropanol'

works by denaturing and coagulating proteins, disrupting their cell wall, and killing them; dissolves lipid membranes

highly efficient against viruses and can be used in adjunct with other alcohols to obtain a powerful synergistic effect against microorganisms

Oxidizing Agents

H2O2, K-permanganate

act by oxidizing the cell membrane of microorganisms, which results in a loss of structure and leads to cell lysis and death

H2O2, K-permanganate

Oxidizing agents

Halogens

Iodide, Chlorines

destroy the cellular protein, nucleic acid, and cell wall or membrane of microorganisms

Disrupts oxidative phosphorylation, which is the most important process in cell

Chlorines – conc are made based on the nature of the contaminated surface

• Ex:

  Porous surface: 1:10 dilution

  Hard Surfaces: 1:100 dilution

  Concentrated infectious agents: 1:5 dilution

Iodide, Chlorines

Halogens

Alkalies

KOH, NaOH

produce saponification of the fatty acids within cell membranes, resulting in the loss of membrane integrity

KOH, NaOH

Alkalies

Acids

Nitric Acid, Sulfuric Acid

disrupts the amphoteric matter in microbial surface structures and increases the permeability of cell membrane, subsequently metabolic processes are hindered

Nitric Acid, Sulfuric Acid

Acids

Gases

Formaldehyde

inactivates microorganisms by alkylating the amino and sulfhydral groups of proteins and ring nitrogen atoms of purine bases

Formaldehyde

Gases

Quaternary Ammonium Compounds

• hexadecyltrimethylammonium ('cetrimide'), chlorhexidine, and benzalkonium chloride

bactericidal and fungicidal activity

permeate into the membrane and disrupt its physical and biochemical properties

Soaps

disrupt the chemical bonds that allow bacteria, viruses and grime to stick to surfaces, lifting them off the skin

Antimicrobial soaps triclosan and triclocarban

triclosan and triclocarban

Antimicrobial soaps

Antimicrobial Agents

Any chemical use to treat an infections either by inhibiting or killing pathogens

• Antibacterial

• Antifungal

• Antiprotozoals

• Antiviral

• Antibiotics – subs produced by microorganism that is effective in killing or inhibiting growth of microorganisms

• Primarily ANTIBACTERIAL

• All antibiotics are antimicrobial but not all antimicrobials are antibiotics

Antibacterial

Antifungal

Antiprotozoals

Antiviral

Antimicrobial Agents

Antibiotics

subs produced by microorganism that is effective in killing or inhibiting growth of microorganisms

Primarily ANTIBACTERIAL

Antimicrobial Agents

Ideal Qualities of Antimicrobial Agents

• kill/inhibit pathogens

• Cause no damage to the host

• Cause no allergic reactions

• Stable when stored in solid or liquid form

• Remain in specific tissue of the body long enough to be effective

• Kills the pathogens before they mutate and become resistant to it

Host Defense Mechanisms

• Mucus ( respiratory tract) – trap bacteria with the assistance of cilia

• Lysozymes – present in respiratory secretions lyses bacterial cell wall

• Saliva – possess hydrolytic enzymes that breakdown bacteria

• Gastric acid of the stomach – destroys bacteria that are acid labile

• Normal flora of the Large intestines

• Acidic pH of the urine and constant flushing action

• Vaginal lactic acid – normal flora

• Eye tears – constant flushing action

Mucus ( respiratory tract)

trap bacteria with the assistance of cilia

Lysozymes

present in respiratory secretions lyses bacterial cell wall

Saliva

possess hydrolytic enzymes that breakdown bacteria

Gastric acid of the stomach

destroys bacteria that are acid labile

Inflammatory Response

Inflammation – total changes occurring in tissue factors upon injury

Significance of Inflammation - increased blood flow WBC, other cells, plasma proteins (complement, interferons), antibodies migrate to the injured site arrest the insulting foreign organi

Inflammation

total changes occurring in tissue factors upon injury

Common Nosocomial Infections

• UTI

• Surgical wound infections

• LRTI

• Bacteremia

• Aspiration Pneumonia

UTI

Surgical wound infections

LRTI

Bacteremia

Aspiration Pneumonia

Common Nosocomial Infections