Infectious Diseases

Notes created on October 18, 2024 at 10:14 AM by Minutes AI

Non-Infectious Diseases (00:00 - 09:57)

• Diseases that cannot be transmitted to others.

• Often caused by genetic problems or environmental factors.

• Example:

• A person lacking an immune system may become ill from non-pathogenic vibrio

Infectious Diseases
• Caused by pathogens, which may include microbes or worms.

• Can be communicable or contagious.

• Communicable: Transmissible between individuals, but not guaranteed.

• Contagious: Highly infectious, almost guaranteed transmission upon contact.

Nosocomial Diseases
• Infections acquired in a hospital setting.

• Common in ICUs and among immunocompromised patients.

• Often arise from healthcare personnel.

• Example: A patient may develop a multidrug-resistant infection unrelated to their

Natrogenic Diseases
• Result from direct medical procedures.

• Often due to improper sterilization of instruments.

• Less common than nosocomial diseases.

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 • Cases may warrant legal action due to negligence.

Disease Progression
• Incubation Period:

• Initial stage where no symptoms are present.

• Prodomal Period:

• Beginning of symptoms as pathogens multiply.

• Period of Illness:

• Clear signs of infection with active symptoms.

• Period of Decline:

• Immune system begins to reduce pathogen levels.

• Convalescence Period:

• Recovery phase, potential for permanent tissue damage.

Pneumonia and Asthma (10:02 - 20:01)

• Discussion about pneumonia and its effects.

• Mention of kids having pneumonia and the risk of asthma and scar tissue.

• Coughing may persist after recovery due to scar tissue.

Bacterial Growth and Illness

• Bacterial growth follows a logarithmic graph.

• Initial phase (lag phase) shows no growth.

• Log phase shows exponential growth; peak illness occurs during this phase.

• Example of Nurse Timmy and food poisoning.

• Foodborne illness like E. coli requires time to grow before causing symptoms.

Disease Periods and Microbiology

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• Importance of understanding disease periods.

• Infections can have varying symptoms, both bacterial and non-bacterial.

• Reference to Koch's Postulates.

• Method to isolate and identify bacteria causing disease.

Lethal Dose Curve (LD Curve)

• LD curve measures percentage of mortality in experiments.

• Example with mice infected with smooth and rough strains of Staph.

• LD50 indicates the concentration of pathogens required to kill 50% of subjects.

• Application of LD50 in microbiology and toxicology.

• Understanding patient risks based on bacterial growth stages.

Stages of Pathogenesis
• Stages include exposure, adherence, invasion, and transmission.

• Microorganisms aim to survive in a host to transmit to another host.

• Skin as a portal of entry.

• Skin is the largest organ and very porous.

• Keratinocytes repel many pathogens despite porosity.

Skin and Mucous Membranes (20:05 - 30:03)

• Keratinocytes are stacked and rigid, making it hard for pathogens to penetrate.

• Skin is the largest organ, increasing odds of infection.

• Mucous membranes protect critical areas:

• Respiratory tract

• Gastrointestinal tract

• Urinary tract

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 • Conjunctiva (eye membrane)

Parenteral Infections
• Defined as unnatural entry of infections.

• Examples include:

• Tick bites can transmit bacteria like **Borrelia burgdorferi**, causing tick fever.

• Dog bites and needle pricks (e.g., from unclean tattoo needles) are also risks.

• Rare case of a tornado injury leading to infection:

• A woman was struck by a tree branch, allowing mucor spores to enter her

Listeria Monocytogenes
• Listeria poses risks primarily to pregnant individuals.

• Infection can lead to:

• Mild symptoms in non-pregnant individuals.

• Severe consequences for fetuses, including spontaneous abortion.

Microbial Adhesion
• Microbes attach to surfaces using adhesins.

• Example: **E. coli** produces glycopalates to adhere to tissues.

• Biofilms form on catheters:

• Can cause infections if bacteria enter the bloodstream.

• Catheter-related infections are a significant concern.

Invasion Mechanisms
• After adhesion, microbes can invade host tissues.

• Example: **H. pylori** affects stomach cells:

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 • Bacteria release exoenzymes to break down mucin gel.

• This process leads to ulcer formation in the stomach.

H. pylori and Nobel Prize (30:09 - 40:08)

• A man won the Nobel Prize for his self-experimentation with H. pylori.

• He ingested the bacteria and developed stomach ulcers.

• Treated himself with antibiotics, leading to recovery.

• This case highlighted ethical considerations in medical research.

Pathogens and Immune Evasion

• Some pathogens are obligate intracellular pathogens.

• Obligate anaerobes require the absence of oxygen.

• Some viruses are obligate pathogens that must enter cells.

• Example: Cryptococcus neoformans.

• Has a large outer coating that protects it from macrophages.

• It can live inside white blood cells, evading the immune system.

Types of Infections
• Local infections are confined to a small area.

• Example: Infection from a cut on the skin.

• Focal infections spread from a localized area to a secondary site.

• Systemic infections affect the entire body.

• Disseminate throughout the body.

• Primary infections are the initial infections caused by one pathogen.

• Secondary infections arise when the host's defenses are compromised.

Transmission and Portals of Exit

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• Pathogens must transmit from one host to another.

• Common portals of exit: skin and respiratory tract.

• Secretions can act as vehicles for transmission.

• Example: sexually transmitted diseases.

• Skin flakes can also carry pathogens.

• Close contact with infected individuals can lead to transmission.

Virulence Factors
• Virulence factors determine a pathogen's ability to infect and damage tissues.

• Example: COVID-19 virus has spike proteins that facilitate infection.

• These factors are often small molecules encoded in the pathogen's genome.

• Understanding virulence factors is important for research and treatment.

Horizontal Gene Transfer and COVID Variants (40:14 - 50:13)

• Horizontal gene transfer can occur, allowing pathogens to acquire traits.

• Variants like the Delta variant can emerge due to this process.

• Vaccines developed against spike proteins may become ineffective as variants arise.

• Antibodies from vaccinated individuals may not recognize new variants.

Virulence Factors
• Adhesion proteins are crucial for infection.

• Type one fimbriae help bacteria adhere to host cells.

• Enterotoxigenic E. coli (ETEC) utilizes fimbriae to attach to intestinal linings.

• Causes symptoms such as diarrhea as toxins irritate intestinal cells.

Exoenzymes and Infections

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• Exoenzymes assist pathogens in invading host tissues.

• H. pylori secretes exoenzymes to degrade host tissues.

• Bacteremia and septicemia refer to bacteria and microbes in the bloodstream.

• Toxemia refers to toxins in the blood, which can be fatal.

Shock and Septic Shock

• Septic shock can occur when bacteria multiply in the blood.

• Results in organs failing due to lack of oxygen delivery.

• The body enters shock when overwhelmed by bacterial presence.

• Septic shock is a worst-case scenario in untreated infections.

Hyaluronidase S and Staphylococcus aureus

• Hyaluronidase S breaks down hyaluronic acid, compromising tissue integrity.

• Staphylococcus aureus can grow on salty skin, making it a common pathogen.

• Exoenzymes from Staphylococcus aureus can lead to tissue degradation.

• Infections can result in accumulation of debris if not properly cleaned.

Exoenzymes and Their Role (50:16 - 00:16)

• Staph aureus coats itself with DNA.

• Stops the spreading of organisms by trapping them in DNA.

• "They literally get trapped in the DNA. They can't go anywhere."

• C. pyrrhaginous degrades collagen between epithelial cells.

• Creates openings for bacteria to enter the bloodstream.

• Exoenzymes act like "little pickaxes" to chip away at cells.

Toxins: Endotoxins and Exotoxins

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• Endotoxins are part of gram-negative bacteria.

• Lipid A component is toxic and makes us feel uncomfortable.

• Exotoxins are secreted by gram-positive and some gram-negative bacteria.

• Example: Staph aureus secretes exotoxins.

• Grouped into three categories: Intrasonitor toxins, membrane-disordering toxins,

Intrasonitor Exotoxins
• A-B toxin structure.

• A subunit causes disease; B subunit attaches to the cell.

• "Once it slots in there, it's like flipping a switch."

• A component enters the cell before the vacuole seals.

• Effectively causes cell damage.

Botulinum Toxin
• Potent neurotoxin used in Botox.

• "This is one of the most toxic things you can get your hands on."

• B subunit anchors in neurons; A subunit interferes with acetylcholine.

• Prevents muscle contractions, leading to paralysis.

• Medical uses include treating overactive bladders.

Superantigens and Immune Response

• Superantigens can over-activate the immune system.

• "It tells your immune systems you need to extra work hard."

• COVID-19 example of superantigens causing cytokine storms.

• Results in high fevers and decreased blood pressure.

• Immunosuppressants were considered to control the overactive immune response.

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Immune System and COVID (00:16 - 10:15)
• Immune system slowing mechanism

• "It tries to slow down your immune system not enough to where you can get sick

• COVID evolution over time

• COVID was a massive issue four years ago; now it can be treated quickly.

• Vaccination is recommended: "You should go get vaccinated if you can, if you're

Endotoxins and Exotoxins

• Comparison of endotoxins and exotoxins

• Endotoxins are heat stable; heating does not break them down.

• Example of food poisoning

• Quick onset may indicate endotoxins; long-term symptoms suggest an actual

Pathogen Avoidance Mechanisms

• Immunovation strategies

• Pathogens avoid immune system through various methods.

• Production of capsules

• Capsules prevent immune cells from consuming bacteria.

• Secretion of enzymes

• Enzymes neutralize harmful environments and degrade antibodies.

Antigenic Variation
• Types of antigenic variation

• Antigenic drift involves mutations over time (e.g., COVID spike protein changes).

• Antigenic shift occurs when different strains interact and share genetic

• Importance of vaccination

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 • Vaccination helps prevent the emergence of new strains through herd immunity.

Virulence Factors
• Mechanisms in eukaryotic and bacterial organisms

• Eukaryotic organisms can secrete toxins and enzymes.

• Example of mucor fungi

• Mucor fungi interact with hosts and produce exoenzymes that contribute to

Mold and Spores (10:17 - 13:19)

• Moldy smell indicates presence of spores in the air.

• Spores enter the nose and bind to epithelial tissue.

• Binding is compared to Velcro.

Immune Response and Infection

• Healthy individuals can handle initial exposure.

• Immune cells typically manage the spores effectively.

• In individuals without an immune system, spores can invade.

• Spores can rupture epithelial cells and enter the bloodstream.

Rhizopus and Mucor Infections

• Rhizopus thrives on iron and sugar present in blood.

• Infection can lead to loss of blood flow to tissue.

• Consequences of infection include severe disfigurement.

• Surgical debridement is often required for treatment.

Protozoa and Helminths

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• Protozoa and helminths mimic host cells to avoid immune detection.

• Some worms can disguise themselves by taking host cell fragments.

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