Micro Exam 5

Define the following:
- Vaccines
- Vaccination
- Immunization

• Biologically derived agents designed to stimulate a immune response

• Purpose: Stimulate the body’s immune system to recognize and fight off specific pathogens

  • Preventing or reducing the severity of disease upon further infection

Define the following:
- Vaccines
- Vaccination
- Immunization

• The act of administering a vaccine

Define the following:
- Vaccines
- Vaccination
- Immunization

• The process by which an individual become immune to a disease (often through vaccinations)

• Active vs. Passive Immunity

What is the importance of vaccines?

• Protecting individuals from preventable diseases 

  • Significalntly reducing morbidity and mortality rates

• Protecting the community (Herd immunity)

• Eradicating and controlling diseases

  • Eradication: permanent reduction to zero of the incidence of infection (smallpox)

  • Control: reducing the spread of infectious diseases (flu)

• Reducing healthcare cost

  • CDC estimated a savings of $540 billion in the last 30 years

How does herd immunity work?

• Breaks the chain of transmissions

  • Higher immunity % = fewer individuals who can be infected and transmit the pathogen (R0)

• Protecting the Vulnerable

  • Protecting individuals who cannot be vaccinated (Newborns, Elderly, Immunocompromised, People with vaccine component allergies)

• Reducing Outbreaks

  • If herd immunity is high, there is less likely a change of a large outbreak occurring

• Disease elimination and eradication

  • In some cases, high herd immunity can erradicate certain diseases (smallpox and polio)

What is R0?

• Metric that describes the average number of secondary infections that a single infected individual would generate

  • R0>1: one infected person will infect more than 1 individual

    • Indicates that the diseas has the potential to spread quickly

    • Ex. Measles (R0 12-18); Mumps (R0 10-12); COVID 19 (R0 2-3; omicron variant R0 8.2)

• R0=1: one infected person will infect one individual

  • Indicates disease will remain stable in the population (endemic)

• R0<1: one infected person will infect less than one individual

  • Indicates the disease will eventually die out

How do vaccines influence the R0 of an infectious disease?

• Reducing the susceptible population 

• Lowering the R0 to <1

• Achieving herd immunity 

  • Herd Immunity Threshold (HIT): proportion of the population that needs to be immune to prevent sustained spread

  • HIT=1 - (1/R0)

    • Ex. R0 = 4 (1-(¼)) = 75%

      • I.e. We need 75% to be immune to prevent the spread

Detail each of the types of vaccines discussed during the lecture. Include the advantages and disadvantages of each: Rotavirus Vaccine (1998/1999)

• Linked to increased risk of a serious bowel obstruction  in infants

• Vaccine was changed and the new form does not have this issue

Detail each of the types of vaccines discussed during the lecture. Include the advantages and disadvantages of each: RSV vaccine (1960s)

• Worsened RSV in children who were later exposed to RSV virus naturally (during clinical trials)

• 2023, FDA approved the first RSV vaccines for older adults and infants (maternal vaccination)

Detail each of the types of vaccines discussed during the lecture. Include the advantages and disadvantages of each:HIV vaccine (1980s onward)

• Many attempts, with some promising clinical trials but no vaccine available yet

• Due to high variation of the HIV virus

Detail each of the types of vaccines discussed during the lecture. Include the advantages and disadvantages of each: Live Attenuated Vaccines

• Contain live but weakened (attenuated) forms of pathogens 

  • Attenuated pathogen can still replicate within the host (slower and less replication)

  • Replication triggers a robust and long lasting immune response 

  • Ex. MMR

• Advantages

  • Often provide lifelong immunity with one or two doses.

  • Elicit a broad immune response (humoral and cell-mediated).

• Disadvantages

  • Potential for reversion to virulence (extremely rare)

  • Not suitable for immunocompromised individuals due to the risk of uncontrolled replication

  • May require refrigeration (cold chain), posing logistical challenges

  • Possible mild symptoms resembling the disease

Detail each of the types of vaccines discussed during the lecture. Include the advantages and disadvantages of each: Inactivated Vaccines

• Contains killed (innactive) pathogens 

  • Inactivation destroys the pathogen’s ability to replicate but preserves its antigens (stimulating an immune response)

  • Ex. Polio Vaccine

• Advantages

  • Generally safer than live vaccines

  • More stable and easier to store

  • Can be used in immunocompromised individuals

• Disadvantages

  • Stimulate a weaker immune response compared to live vaccines.

  • Often require multiple doses (booster shots)

  • Immune response is primarily humoral (antibody-mediated).

Detail each of the types of vaccines discussed during the lecture. Include the advantages and disadvantages of each: Subunit Vaccines

• Contains specific antigen components of pathogens to prompt targeted immune responses

  • Antigens are carefully selected to elicit a protective immune response.

  • Ex. Hepatitis B vaccine

• Advantages

  • High safety profile

  • Targeted immune response

• Disadvantages

  • May require adjuvants to enhance immunogenicity

  • Can be more complex and expensive to produce

  • May not elicit as broad an immune response as live vaccines

Detail each of the types of vaccines discussed during the lecture. Include the advantages and disadvantages of each: Recombinant Vaccines

• Produced using genetic engineering techniques

  • Antigen genes are inserted into the genome of another organism (yeast, bacteria)

    • Host organisms then produces the antigen in large quantities

  • Ex. Human papillomavirus (HPV) vaccine

• Advantages

  • High purity and safety

  • Can be used to produce vaccines against pathogens that are difficult to culture

• Disadvantages

  • May require adjuvants

  • Complex production process

Detail each of the types of vaccines discussed during the lecture. Include the advantages and disadvantages of each: Conjugate Vaccines

• Designed to improve the immunogenicity of polysaccharide antigens

  • Polysaccharides often elicit a weak immune response 

    • Polysaccharide antigens are chemically linked to a protein carrier

    • Converts the polysaccharide into a T-dependent antigen

      • Make immune response stronger and longer lasting

  • Ex. Haemophilus influenzae type b (Hib) conjugate vaccine.

• Advantages

  • Significantly enhance the immune response to polysaccharide antigens

  • Provide long-lasting protection

• Disadvantages

  • More complex to produce than some other vaccine types

Detail each of the types of vaccines discussed during the lecture. Include the advantages and disadvantages of each: Toxoid Vaccines

• Used to protect against diseases caused by bacterial toxins

  • Bacterial toxins are purified and then detoxified (inactivated) to create toxoids.

    • Toxoids still retain their antigenic properties, stimulating the immune system to produce antibodies that neutralize the toxin.

  • Ex. Tetanus toxoid vaccine.

• Advantages

  • Highly effective at preventing diseases caused by bacterial toxins.

  • Very safe.

• Disadvantages

  • Protection is specific to the toxin, not the bacteria.

  • May require booster doses to maintain immunity.

Detail each of the types of vaccines discussed during the lecture. Include the advantages and disadvantages of each: mRNA Vaccines

• mRNA molecules encoding the antigen are encapsulated in lipid nanoparticles and delivered to cells.

  • Host cells translate the mRNA into the antigen.

  • Ex: COVID-19 vaccines (Pfizer-BioNTech, Moderna).

• Advantages

  • Rapid and inexpensive to design and produce

  • Can elicit both humoral and cell-mediated immunity

  • Can be modified quickly (if the pathogen mutates)

• Disadvantages

  • mRNA vaccines may require cold or ultra-cold storage

  • Long-term effects are still being studied

Detail each of the types of vaccines discussed during the lecture. Include the advantages and disadvantages of each: Viral Vector Vaccines

• Use a harmless virus (the vector) to deliver genetic material encoding the antigen from another pathogen

  • Vector virus is modified so that it cannot cause disease

    • Once inside the host cells, the gene is expressed, and the antigen is produced, triggering an immune response

  • Ex. COVID-19 vaccines (AstraZeneca, Johnson & Johnson)

• Advantages

  • Can elicit strong humoral and cell-mediated immunity.

  • Can be used to deliver large or complex antigens.

• Disadvantages

  • Pre-existing immunity to the vector can reduce vaccine effectiveness.

  • Potential for rare adverse events (e.g., blood clotting with some adenovirus vectors)

Who was the person who developed the first true vaccine? What was that vaccine for?

• Edward Jenner (1796)

  • In the UK it was common that milk maids never developed smallpox because they were previously exposed to cowpox

  • After training as a physician, Dr. Jenner carried the first true vaccination 

    • Inoculated an 8 year old boy with cowpox

    • 8 weeks later, Dr. Jenner the inoculated the child with smallpox

    • The child do not develop any symptoms of smallpox

  • By 1803, it was established medical procedure througout england to vaccinate people with cowpox

Detail the stages of the pre-clinical phases of vaccine development: Exploratory Stage

• (2-5 years)

  • Focus: Identify potential antigens that could be used in a vaccine

    • Involves the understanding the disease, the pathogen causing it, and how much the immune system respond

Detail the stages of the pre-clinical phases of vaccine development: Pre-clinical Stage

• (1-2 years)

  • Focus: Testing the vaccine candidate in the lab and on animals to assess its safety and immunologicity

    • In vivo and in vitro testing (human cells and animal models)

    • Evaluating safety and immunogenicity (short term)

    • Develop formulation and manufacturing process

Detail the stages of the clinical phases of vaccine development: Phase 1

• (approx 2 years)

  • 20-100 healthy adult volunteer

  • Focus on safety and dosage

Detail the stages of the clinical phases of vaccine development: Phase 2

• 2-3 years)

  • 100-300 diverse volunteers  (randomized and controlled)

    • Includes individuals that are similar to the intended recipient of the vaccine

    • Evaluation of safety and immunogenicity; dosage refinement 

Detail the stages of the clinical phases of vaccine development: Phase 3

• (5-10 years - Can be shorter, especially in urgent situations)

  • 1000s of volunteers (different geographic locations and diverse)

    • Randomized, placebo-controlled, and often double-blinded to minimize bias

    • Evaluating efficacy and long-term safety

Detail the stages of the post clinical phases of vaccine development: Regulatory Review and Approval

(up to 2 years)

• Submit a Biologics License Application to the regulatory authority

  • Data is reviewed from pre-clinical and clinical

    • Regulatory authority conduct their own tests and inspect manufacturing facilities.

Detail the stages of the post clinical phases of vaccine development: Manufacturing and Scaling Up

• Manufacturing process is scaled up to produce large quantities of the vaccine

• Must adhere to strict regulatory requirements and Good Manufacturing Practices (cGMP) 

Detail the stages of the post clinical phases of vaccine development: Quality Control and Post-Market Surveillance

• Monitor vaccine safety and effectiveness after it is released to market

How was the COVID-19 vaccine produced so quickly?

• due to pandemic

  • Prior research and existing technology

    • mRNA vaccines had been studied for decade

    • Other coronaviruses (SARS and MERS) had already been studied

      • Giving a head start in understanding COVID-19

  • Global collaboration and data sharing

    • Scientists from different nations all collobatorated and shared information

  • Unprecedented funding 

    • Governments and private organizations invested heavily (Operation Warp Speed = Billions$)

  • Streamlined regulatory process

    • FDA implemented faster review processes

What is the 3Cs model of vaccine hesitancy

• Confidence (Lack of trust in):

  • Vaccine safety and efficacy 

  • Healthcare providers

  • Health authorities

  • Pharmeceutical industry

• Complacency: Low perceived risk of vaccine-preventable diseases

  • Disease is not seen as a threat

  • Belief that natural immunity is better

• Convenience: Barriers to accessing vaccines:

  • Availability, affordability, accessibility

  • Logistical challenges (e.g., appointment scheduling)

  • Health system factors

How do “we” address vaccine hesitancy?

• Communication is key

  • Addressing concerns with empathy (don’t talk down to people)

  • Providing clear and accurate information

  • Using simple language

Improving vaccine access and convenience

• Expanding clinic hours

• Offering vaccination in non-traditional settings (schools, pharmacies, community centers)

• Reducing out-of-pocket costs

• Implementing reminder systems (text messages, phone calls)

• Public education campaigns

  • Use of trusted messengers (doctors, scientists, community leaders)

  • Clear and concise messaging

  • Addressing common myths and misconceptions.

• Community engagement and outreach

  • Working with community leaders and organizations.

  • Tailoring interventions to specific cultural and social contexts.

  • Building trust through dialogue and participation.

• Building trust and transparency

  • Open communication from public health agencies

  • Acknowledging and addressing past mistake

What are the future areas of vaccine research discussed in the lecture?

• Universal Influenza Vaccines:

  • Vaccines that provide broad protection against multiple strains of influenza

• Cancer Vaccines: 

  • Exploring both preventative vaccines (e.g., HPV) and therapeutic vaccines designed to stimulate the immune system to target and destroy existing cancer cells.

• Newer Vaccine Platforms:

  • DNA Vaccines: Introducing DNA encoding for antigens into cells.

  • Virus-Like Particle (VLP) Vaccines: Mimicking the structure of viruses but lacking genetic material.

  • Self-Amplifying RNA Vaccines: RNA that can replicate within cells, leading to increased antigen production.

  • Nanoparticle-Based Vaccines: Encapsulating antigens or genetic material in nanoparticles for enhanced delivery and immunogenicity.

Disinfection

• process of killing or inhibiting the growth of microbes (Associated with inanimate objects)

Sterilization

• the destruction of all microbes (Associated with human tissue and skin)

Antisepsis

• use of chemical or physical agent to kill microbes on the skin and living tissues

  • Aseptic: an environment or procedure free from contamination

Degerming

• the removal of microbes from a surface by mechanical means (e.g. scrubbing)

Sanitization

• disinfection of places or items used by the public

Pasteurization

• using heat to kill pathogens

  • Does not sterilize but is used to reduce number of microbes

-static

• an agent that inhibits growth (doesn’t kill)

-cidal

• an agent that kills

Antimicrobial

•  substance that inhibits the growth of a microbial organism

High-Level Disinfectant

• Most potent disinfectant (including spores and M. tuberculosis)

• Can kill ALL microorganisms

• Disinfection of critical and semi-critical medical devices

Intermediate-Level Disinfectant

• Has a broad range of microogranisms (do not kill spores)

• Disenfection of non-critical surfaces and some semi-critical devices (high-level disinfectants are not feasible)

Low-Level Disinfectant

• Kills most vegetative bacteria, some fungi, and some viruses (not spores or M. tuberculosis)

• General cleaning and disinfection of non-critical surfaces

Detail how the following macromolecules can be targets of disinfectants and antiseptics
- Lipids
- Proteins
- Nucleic Acids

• Plasma membrane is composed of a phospholipid bilayer

  • When the phospholipid bilayer is disrupted, the plasma membrane’s structure deteriorates 

  • Leading to cell death

• Surfactants are very effective for disrupting the plasma membrane

  • Composed of polar molecules with hydrophobic and hydrophilic regions

  • Bind to and penetrate the phospholipid bilayer

    • This causes openings to form

  • Also affect virus envelopes

    • Damage to the envelope causes the loss of capacity to infect

Detail how the following macromolecules can be targets of disinfectants and antiseptics
- Lipids
- Proteins
- Nucleic Acids

• Proteins are crucial for cells (structure and function)

• Require a specific 3-D shape to function (conformation)

• Loss of conformation is called denaturation

  • Causes loss of function and can result in cell death

  • Involves the breaking of bonds that aid in the formation of a proteins shape

  • Ex. heat and strong solvents

• Metallic ions can also inhibit enzymatic function

  • Blocking enzyme active site

Detail how the following macromolecules can be targets of disinfectants and antiseptics
- Lipids
- Proteins
- Nucleic Acids

• Nucleic acids are required for cell survival

• Various agents 

  • Disturb nucleic acid synthesis

  • Irreversibly bind to DNA, preventing gene expression

  • Are mutagenic and cause lethal mutations

• Radiation can interfere with DNA and RNA function

  • Irradiation with gamma rays, ultraviolet radiation, and X-rays causes mutations

  • Mutations can result in permanent inactivation of nucleic acids

What is microbial death?

• Permanent loss of reproductive capability 

• Microbial death is hard to identify

  • No apparent signs (except lysis)

• Microbial death rates are used to evaluate the efficacy of an antimicrobial agent

  • Death rate is logarithmic

What factors affect microbial death rate?

• Number of microbe: the greater the number of organisms, the longer it will take to kill

• Duration of exposure: depends on microbe and agent

• Temperature: the lower the temperature, the longer it will take to kill

• Environment matters: organic material can inhibit accessibility of the antimicrobial agent to the organism

• Concetration of agent: Too low or high concentration is ineffective

• Presence of endospores or cysts: both evade destruction

Detail the following chemical agents for controlling microbial growth
- Phenol and phenolic compounds
- Alcohols
- Halogens
- Oxidizing agents
- Surfactants
- Heavy metals
- Aldehydes
- Gaseous agents

• Phenolic compounds are derived from phenol

  • Greater efficacy and fewer side effects than phenol

• Low-level to intermediate-level disinfectants and antiseptics that:

  • Denature proteins

  • Disrupt the plasma membrane

  • Remain very effective in the presence of organic material

  • Remain active for prolonged periods

• Commonly used as disinfectants in health care settings and laboratories

Detail the following chemical agents for controlling microbial growth
- Phenol and phenolic compounds
- Alcohols
- Halogens
- Oxidizing agents
- Surfactants
- Heavy metals
- Aldehydes
- Gaseous agents

• Bactericidal, fungicidal, and virucidal (enveloped viruses)

  • Have no effect on fungal spores and bacterial endospores

• Intermediate-level disinfectants

  • Denature proteins and disrupts the plasma membrane

  • Routinely used as a degerming agent to prepare sites for injection

• Alcohol is often used to carry other antimicrobial chemicals

  • This is referred to as a tincture

Detail the following chemical agents for controlling microbial growth
- Phenol and phenolic compounds
- Alcohols
- Halogens
- Oxidizing agents
- Surfactants
- Heavy metals
- Aldehydes
- Gaseous agents

• Group of five chemically related elements in Group 17 (VIIA)

  • Four have antimicrobial activity: Iodine, chlorine, bromine, fluorine

• Intermediate-level antimicrobial chemical agents

• Halogens are effective against:

  • Bacterial and fungal cells

  • Fungal spores

  • Some bacterial endospores

  • Protozoan cysts 

  • Many viruses

  Types of __________

  • Iodine

    • Well-known antiseptic

    • Used medically as a tincture or as an iodophor

      • Betadine is an example of an iodophor

        • Routinely used to prepare skin for surgery

        • Also used to treat burns

  • Chlorine 

    • Found in drinking water, swimming pools, and wastewater treatment

    • It is major ingredient in disinfectants such as chlorine bleach

    • It is used to disinfect kidney dialysis equipment

    • Chloramines are combinations of chlorine and ammonia

      • Used in wound dressings, skin antiseptics, water supplies

      • Less effective than chlorine as disinfectants/antiseptics

      • Release their chlorine atoms more slowly, therefore last longer

Detail the following chemical agents for controlling microbial growth
- Phenol and phenolic compounds
- Alcohols
- Halogens
- Oxidizing agents
- Surfactants
- Heavy metals
- Aldehydes
- Gaseous agents

• High-level disinfectants and antiseptics that impair bacterial metabolism

  • Release hydroxyl radicals, which kill anaerobic organisms

• Very effective against infections of deep tissues

  • Routinely used in deep puncture wounds

• Most commonly used are:

Hydrogen peroxide, ozone, peracetic acid

• Hydrogen peroxide 

  • Common household antiseptic

  • Bacterial catalase can break it down but the amount of peroxide used overwhelms the amount of catalase produced by bacteria

• Ozone 

  • Very reactive form of oxygen

  • It is generated when O2 is exposed to electrical discharge

  • Some cities use ozone for water treatment

    • Expensive to produce and difficult to maintain the necessary concentration

• Peracetic acid 

  • Peroxide form of acetic acid and an extremely effective sporicide

  • It is used to sterilize surfaces and medical and food-processing equipment

    • Not affected by organic contaminants

    • Leaves no toxic residue

Detail the following chemical agents for controlling microbial growth
- Phenol and phenolic compounds
- Alcohols
- Halogens
- Oxidizing agents
- Surfactants
- Heavy metals
- Aldehydes
- Gaseous agents

• Soap molecules have different properties

  • One end of a soap molecule is ionic and hydrophilic

  • One end is a fatty acid and hydrophobic

    • Dissolves oily deposits into tiny drops

    • Mix with water and are washed away

• Soaps are good degerming agents but poor antimicrobial agents

  • Can be made more potent by adding antimicrobial triclosan

Detergents:

• QUATS (quaternary ammonium compounds) contain ammonium cations

  • Low-level disinfectants/antiseptics

  • Used in many industrial and medicinal applications (mouthwash)

• Disrupts the plasma membrane

  • Bactericidal, Fungicidal, Virucidal (enveloped viruses)

  • Not useful for nonenveloped viruses, mycobacteria, or bacterial endospores

• Are inhibited by the presence of organic contaminants

Detail the following chemical agents for controlling microbial growth
- Phenol and phenolic compounds
- Alcohols
- Halogens
- Oxidizing agents
- Surfactants
- Heavy metals
- Aldehydes
- Gaseous agents

• Ions of heavy metals are inherently antimicrobial due to protein denaturation

  • Low-level bacteriostatic agents

• Heavy metals include:

  • Arsenic

  • Zinc

  • Mercury

    • Not used anymore - toxic to humans

  • Silver:

    • Occasionally used in surgical dressings, burn creams, and catheters

  • Copper

Detail the following chemical agents for controlling microbial growth
- Phenol and phenolic compounds
- Alcohols
- Halogens
- Oxidizing agents
- Surfactants
- Heavy metals
- Aldehydes
- Gaseous agents

• Compounds containing a terminal –CHO group

  • Aldehydes cross-link to organic functional groups

    • Denature proteins and inactivate nucleic acids

• Two highly reactive aldehydes are used as antimicrobials

  • Glutaraldehyde: used in liquid form

    • Effectively kills bacteria, viruses, and fungi

    • 10 min = disinfect most objects

    • 10 hrs = sterilize most objects

• Formaldehyde: used in both liquid form and gaseous form

  • Used by health care workers (formalin)

  • Is an irriatnt for mucous membranes and is carcinogenic

Detail the following chemical agents for controlling microbial growth
- Phenol and phenolic compounds
- Alcohols
- Halogens
- Oxidizing agents
- Surfactants
- Heavy metals
- Aldehydes
- Gaseous agents

• Many items cannot be sterilized with heat or chemicals

• They can be sterilized using highly reactive antimicrobial and sporicidal gases

  • Ethylene oxide (most frequently used) 

  • Propylene oxide

  • Β-propiolactone

• Ethylene oxide is used in hospitals and dentists’ offices for sterilizing instruments and equipment

• Gases rapidly penetrate and diffuse into any space

  • Over time, they can denature proteins and DNA

  • Kill everything they come in contact with and cause no damage to inanimate objects

• Gaseous agents also have disadvantages:

  • Explosive, poisonous, and potentially carcinogenic

  • Disinfection with gaseous agents takes considerable time

  • Need for continuous cleanup

Detail the three ways (we discussed) that are used to evaluate disinfectants and antiseptics: Phenol Coefficient

• Phenol was first used as a disinfectant by Joseph Lister in 1867

• It is still considered the benchmark disinfectant that others are compared with

• Comparison is reported as the phenol coefficient

  • Phenol coefficient of 1.0 = same effectiveness as phenol

  • Greater than 1.0 = efficiency greater than phenol

  • Less than 1.0 = efficiency less than phenol

Detail the three ways (we discussed) that are used to evaluate disinfectants and antiseptics: Disk Diffusion Method

• Uses tiny disks of filter paper soaked in the agent

  • An agar plate is inoculated and the disks are placed at various positions

• Inhibition of growth around the disk is called the zone of inhibition

  • Sizes of the zones may reflect differences in concentration and diffusion rates

• Cannot distinguish between microbicidal and microbistatic

Detail the three ways (we discussed) that are used to evaluate disinfectants and antiseptics: Dilution Method

• A series of solutions of different concentrations of the disinfectant are prepared

  • Time-consuming

  • Can tell whether the agent is microbistatic or microbicidal

• Cultures of the test organism are dried down on stainless steel cylinders

  • Each cylinder is dipped for 10 minutes into one of the solutions

  • Cylinders are removed and rinsed with water to remove any remaining chemical

  • Cylinders are placed into a tube of growth medium

    • Incubated and observed for growth

Detail the following physical agents for controlling microbial growth
- Heat
- Refrigeration, Freezing, And Freeze-Drying
- Filtration
- Osmotic Pressure
- Radiation

• Usually lethal to most pathogenic microbes

• Two types of heat can be used:

  • Moist heat: from hot water, boiling water, or steam

    • Ex. autoclaving, pressure cooking, Pasterurization

  • Dry heat: from hot air with low moisture

    • Ex. Ovens

Temperatures of 150–180˚C for 2–4 hours ensure the destruction of spores, as well as vegetative cells

• Exposure to very-high-temperature dry heat reduces microbes to ash and gases

• Adequate sterilization with heat depends on:

  • Temperature and length of time

• Higher temperatures require shorter treatment times

  • Thermal death time (TDT) is the shortest length of time needed to kill all organisms at a specific temperature

  • Thermal death point (TDP) is the lowest temperature needed to kill all organisms in 10 minutes

• Moist heat can be as effective as dry heat in a much shorter time at lower temperature

  • It quickly denatures proteins which halts microbe metabolism and causes death

Mosit Heat: Pasteurization

• Used to reduce microbial load

  • Destroys pathogens

  • Preserves flavor and nutritive value in foods

  • Does not sterilize

• Accomplished in two ways:

  • Flash method: temperature of 71.6˚C for 15 seconds

  • Batch method: temperature of 63–66˚C for 30 minutes

• Pasteurization kills about 97-99%

  • Does not affect endospores, nonpathogenic lactobacilli, micrococci, or yeasts

Detail the following physical agents for controlling microbial growth
- Heat
- Refrigeration, Freezing, And Freeze-Drying
- Filtration
- Osmotic Pressure
- Radiation

• Cold temperatures limit the growth of microorganisms

  • They slow the rate of enzymatic reactions

  • They do not kill

• Refrigeration is used to delay the spoilage of food

  • Bacteria and molds will continue to grow

  • It is useful only for a limited period

Freezing can preserve food

• It does not sterilize

• It slows metabolic rate

• There is no microbial growth or spoilage

• Freezing can also be used to preserve microorganisms

  • Organisms to be preserved are frozen in glycerol

  • This prevents the formation of ice crystals

• Freeze-drying (lyophilization) preserves cells by removal of water

  • Organisms are frozen in liquid nitrogen and subjected to high vacuum

  • Containers are then sealed under vacuum

  • Organisms are viable in this state for years

  • It is used for long-term storage

  • Addition of water restarts the growth process

Detail the following physical agents for controlling microbial growth
- Heat
- Refrigeration, Freezing, And Freeze-Drying
- Filtration
- Osmotic Pressure
- Radiation

• Useful for sterilizing liquids

• Involves passing the liquid through membrane filters

  • Pores in the filter are too small to allow for the passage of microorganisms

  • Filters are made with specific pore sizes

• Can be used for:

  • Growth media, Drugs, Vitamins, Some commercial food preparation

• Used to sample and test water samples for fecal coliform contamination

• Filters can also purify air

  • High-efficiency particulate air filters are called HEPA filters

  • Seen in operating rooms, burn units, clean rooms of laboratories

  • Used in laboratory facilities to keep organisms from escaping

    • Filters are soaked in formalin before disposal

Detail the following physical agents for controlling microbial growth
- Heat
- Refrigeration, Freezing, And Freeze-Drying
- Filtration
- Osmotic Pressure
- Radiation

• Been used in food preservation for many decades

• High concentrations of salt or sugar or other substances are used in food preservation because:

  • Creates a hypertonic medium

  • Draws water from the organisms

  • Leads to plasmolysis and death

Detail the following physical agents for controlling microbial growth
- Heat
- Refrigeration, Freezing, And Freeze-Drying
- Filtration
- Osmotic Pressure
- Radiation

• Energy emitted from atomic activities

  • Cell’s molecules absorb some of the energy which can lead to changes in DNA structure

• Two types of radiation:

  • Ionizing radiation

    • Includes gamma rays, X-rays, and high-speed electron beams

    • Causes mutation and breakdown of chromosomes

  • Nonionizing radiation: 

    • Best seen with ultraviolet radiation

    • Leads to abnormal bonds with molecules (Thymine Dimmers)

Ionizing Radiation

• All ionizing radiation can penetrate liquids and most solid materials

  • Gamma rays are the most penetrating

• Flour, meat, fruits, and vegetables are routinely irradiated to kill microorganisms, parasites, and insects

• Sterilization of medical products by ionizing radiation is rapidly expanding

  • Drugs, Vaccines, Plastics, Syringes, Gloves, Tissue used in grafting, Heart valves

• Main risk is potential radiation poisoning of the operators

Ultraviolet Radiation

• Ultraviolet radiation disrupts cells by generating free radicals 

  • Fungal cells, Spores, Bacterial cells, Protozoans, Viruses

• Used in germicidal lamps in hospital rooms, operating rooms, food preparation areas, and dental offices

• Can be effective in reducing postoperative infection 

  • Preventing droplet transmission

  • Inhibiting growth of organisms in water, vaccines, drugs, plasma, and tissues used for transplantation

• Major disadvantages are:

  • Poor penetration, Damages human tissues, Retinal Damage, Cancer

Detail thermal death time and thermal death point

• (TDT) is the shortest length of time needed to kill all organisms at a specific temperature

Detail thermal death time and thermal death point

• (TDP) is the lowest temperature needed to kill all organisms in 10 minutes

Detail ionizing radiation and noionizing radiation

• Includes gamma rays, X-rays, and high-speed electron beams

• Causes mutation and breakdown of chromosomes

Detail ionizing radiation and noionizing radiation

• Best seen with ultraviolet radiation

• Leads to abnormal bonds with molecules (Thymine Dimmers)