Lecture%202 - Biology 301 Infectious Disease &...

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Unformatted text preview: Biology 301 Infectious Disease & Society Course Days: Friday Course Time: 1:30pm 4:10pm Instructor: Nathan Dougan Bacteria: Review What are the most important points to remember about bacteria for this class? Basic Structure Single celled organism with no membrane bound organelles Note the various structures from page 3 of the text (i.e. flagella, capsule, etc.) Various Morphologies (see slide from Lecture 1) Bacteria: The basics 1. Morphologies Bacteria: Review Other Basic Properties Gram Positive vs. Gram Negative Bacteria Relationship to oxygen commensal vs. vector borne 2. Cell Wall / Membrane 4. Habitats and unique metabolisms Do bacteria need oxygen? Bacteria classified as aerobic need O2 to live Bacteria classified as anaerobic live in the absence of O2 (O2 will often kill these bacteria) [*Often referred to as obligate anaerobes] Facultative anaerobes prefer the presence of O2 but can continue growing in its absence. Bacteria: Pathogenesis How do bacteria cause disease? There is tremendous variation in how this is accomplished and the goal of this course is to learn most of the fundamental concepts through the presentations of your peers. To help out though, there are a number of common properties among a large number of bacteria. Bacterial Pathogenesis Colonization / Adhesion The bacteria must come in contact with the tissue capable of sustaining its life and attach to that tissue. Invasion Bacteria must "set up shop" in the tissue hey have colonized. The best way to think of this step in pathogenesis is that the bacteria are trying to manipulate the colonized tissue to best suit growth. Invasion Enzymes Hyaluronidase Collagenase Neuraminidase Streptokinase Staphylokinase Lecithinases Phospholipases Hemolysins Leukocidins Streptolysin Phospholipases Lecithinases Hemolysins, Bacterial Pathogenesis Evasion of the host immune response Pathogenic bacteria usually possess structural elements and/or utilize metabolic elements that help them evade host immune responses. Common Mechanisms of Evasion Avoiding Phagocytes is one of the most common tactics that bacteria will utilize in evading host defenses. Avoiding contact Inhibiting engulfment Surviving inside the phagocyte Kill or damage phagocytes Common Mechanisms of Evasion http://www.textbookofbacteriology.net/pathoge This website has great information arranged in a very easy to read format, especially for someone without a microbiology background. Bacteria: Pathogenesis A few critical points to note when you are studying an infectious organism, especially bacteria, is whether the organism is causing disease via: Direct Damage adhesion, competitive exclusion of essential bacteria, inhibition of normal body processes. (Usually minor damage) Some microbiologists include invasion factors in this category which can result in major damage. Bacterial Pathogenesis Immune Reaction (Hypersensitivity) Complement cascade, inflammation, etc. Basically, the host's immune response is so powerful that the colonized (or peripheral) tissues are severly damaged. Local or systemic effects of a toxin usually are the most severe types of damage but immune reactions, and invasion factors can also be very severe. Toxins Bacteria: Pathogenesis How many bacteria does it take to elicit its respective disease? There is quite a bit of variation in this number. The terms you should become familiar with are: ID (Median Infectious Dose) the dose of an 50 infectious organism that will infect 50% of experimental subjects LD (Median Lethal Dose) the dose of an 50 infectious organism/agent that will cause death in Bacteria: Treatment Now that we are becoming familiar with some pathogenic bacteria and how they cause disease, our next logical question is how do we deal with these bacteria? Bacteria: Treatment 1. 2. 3. 4. External Prevention Internal Prevention Treatment of Infection Treatment of Damage External Prevention Control / Elimination of vector borne bacteria. Personal hygiene / healthy practices Comparing Antibacterial Agents Bactericidal Agents that kill bacteria. Bacteriostatic Agents that inhibit the growth of bacteria. Helpful website - http:// www.textbookofbacteriology.net/antimicrobial.html Internal Prevention 1. Oral Antibiotics Dietary / Herbal Supplements designed to boost immune function Exercise Immunology 1. 1. Treatment of Infection Later in the course we will discuss how antibiotics work. The most important things to note at this time are the variety of antibiotics and the significance to the mode of delivery. What is the significance to mode of delivery? Topical Antibiotics Internal Antibiotics 1. 1. Treatment of Damage We will discuss this topic in detail much later in the course. The only connection to make at this point is the varying levels of tissue damage that can occur from bacterial infection based on: The type of damage The type of tissue The duration of damage Outbreak 1 1. 2. 3. What types of laws are used to protect the public from individuals who could potentially spread a serious infection? Do you agree with locking up those who carry MDR TB and who are noncompliant with treatment? How would you stop the outbreak of MDR TB in institutional settings? Outbreak 4 How would you propose to stop the outbreak described? Outbreak 11 How would you prevent this epidemic from spreading? Should the index case individual be located and informed of his status? Should the index case be threatened with legal prosecution if he persists in having unprotected sex with partners (particularly minors)? Outbreak 9 What are your thoughts on the severity of this outbreak? would propose should be done with respect to antibiotics? What Discussion Of the outbreaks you examined in this text so far, which do you feel "closest" to? In other words, which of these outbreaks is most relevant to you? Of these outbreaks, which do you believe has the most severe implications for the American public. Laws regarding infectious disease Immunization ...
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