Introduction to Microbiology Study Guide, Exams of Nursing

Download Introduction to Microbiology Study Guide and more Exams Nursing in PDF only on Docsity! NUR 2100 Exams 1-3 combined study guides 2024 Update Introduction to Microbiology • History of Microbiology (USLO 1.1) o Cell theory – cells are basic unit of life o 3 tenets • Tenet 1 - Living organisms are made up of one or more cells. • Tenet 2 - Living cells arise from pre-existing cells. • Tenet 3 - Cells are the fundamental unit of structure and function of living organisms. o Hooke – First to observe cells (called them little boxes = cells) o Virchow – Popularized Cell Theory by stating that cells give rise to other cells o Van Leeuwenhoek – First to observe bacteria and protozoa (microbes). Called them animalcules. o Spontaneous generation vs. Biogenesis o Spontaneous generation – old idea that life can come from non-living matter (refuted by Redi and Pasteur) o Biogenesis – Life comes from life o Pasteur – Refuted spontaneous generation using the swan neck flask experiment. o Redi – 17th century. Experiment with maggots on meat. Meat in a sealed container that did not come into contact with flies did not generate maggots. Refutes spontaneous generation o Endosymbiotic theory o Symbiosis is a relationship between organisms o The endosymbiotic theory states that mitochondria and chloroplasts arose as a result of prokaryotic cells establishing a symbiotic relationship within a eukaryotic host. (Mitochondria and chloroplasts both have their own genomes And they both have ribosomes that are both 70s, which is the size.) • Relationship between Microbiology and Medicine (USLO 1.2) o Germ theory of disease o The germ theory of disease, states that many diseases may result from microbial infection. The work of several scientists and physicians contributed to the germ theory of disease linking microbes to the spread of disease. o Lister – Proposed that microbes can result in infection, investigated this phenomenon in post-operative care. Introduced the use of disinfectants and antiseptics in surgery. o Semmelweis – Observed that midwives washed hands and maternity wards didn’t have as many infections as wards where non-handwashing medical students were working. He introduced the idea of handwashing to prevent transfer of disease from physicians to patients o Koch’s Postulates o Koch – scientist that established a protocol that connects the causative microbe to an infection (Koch’s postulates). Was studying Bacillus antrhacis (Anthrax) in cows. • Established the idea of one microbe causes one disease. • Koch’s postulates (know these four) 1. The suspected pathogen must be found in every case of disease and not be found in healthy individuals. 2. The suspected pathogen can be isolated and grown in pure culture. 3. A healthy test subject infected with the suspected pathogen must develop the same signs and symptoms of disease as seen in postulate. 4. The pathogen must be re-isolated from the new host and must be identical to the pathogen from postulate 2. o Concept of chemotherapy o Chemotherapy – use of a small molecule that has antimicrobial properties to treat disease • Pathogen – microbe that causes disease • Normal Flora – microbe that resides symbiotically with host. Most likely benefits the host somehow. o Fleming – discovered penicillin by observing the growth of bacteria on plates contaminated with mold. Mold prevented bacterial growth, thus was the source of penicillin. • True antibiotic is a natural antibacterial compound produced by fungi or other bacteria • Semi-synthetic antibiotic is a chemically modified true antibiotic. o Unit conversions (micrometers, nanometers) • 1 micrometer = 1000 nanometer • 1 nanometer = 0.001 micrometer o Microbial Staining techniques o Simple stains – use a single dye to visualize cell shape and arrangement o Differential stains – uses multiple dyes • Gram-stain – differentiate cells based on cell wall • Gram + - thick outer cell wall of peptidoglycan • Gram - - thin cell wall of peptidoglycan covered by outer membrane • Procedure: • Mordant is iodine, which fixes crystal violet to peptidoglycan in cell wall. Mordant doesn’t work in case of Gram – cells. Thus, alcohol decolorization removes outer membrane and any crystal violet • Acid-fast stain - It is able to differentiate two types of gram-positive cells: those with a waxy mycolic acid in their walls (Mycobacteria) and those that do not. • Procedure 1. Stain with Carbolfuchsin (Red) 2. Decolorize non-acid fast bacteria with alcohol 3. Counterstain with the Kinyoun stain (Blue) • Capsule stain – stains capsule if present • Difficult to perform because capsule doesn’t readily absorb dyes. Must use mordant (positive stain) or stain background (negative stain). • “Stained” capsule appears as halo around bacterial cell • Endospore staining – detects endospores which allow for survival in adverse conditions. • Malachite green is applied to stain spores after heat treatment to allow dye to penetrate cell • After washing, a counterstain of Safranin is applied to stain cell red/pink around endospore • Flagella staining • It is a tedious process of using mordant and carbolfuschsin to build the diameter of the flagellum until it is visible. Cellular Structure • Prokaryotic cellular structures and functions (USLO 2.1) o External structures (definitions • Glycocalyx - includes capsules and biofilms • Flagella - a whip-like structure used for movement • Fimbriae - short projections used for attachment • Pili - longer projections used for motility and conjugation • Cell Wall – Variable between different groups of bacteria but most common is made of peptidoglycan. Can prevent lysis in hypotonic environments; can’t prevent plasmolysis (shriveling) in hypertonic environments o Internal structures • Cytoplasm – Thick solution containing water, proteins (enzymes), and nutrients • Ribosome – Cell structure that synthesizes proteins. Prokaryotic ribosomes are 70S in size. • DNA – Genetic information in the form of a circular chromosome in the cytoplasm • Endospore – Protects genome during unfavorable environmental conditions. Endospores are resistant to a variety of disinfecting and sterilizing techniques. • Plasmid – Circular piece of DNA that can transfer information to other cells • Plasma membrane – Just beneath Cell Wall; phospholipid bilayer. o Bacterial cell shape and arrangement • Shape (know shapes and arrangements) • Coccus - round sphere • Bacillus - rod • Vibrio - curved rod • Coccobacillus - short rod • Spirochete - long helical spiral • Arrangement • Diplococcus - pair of cocci • Tetrad - a group of 4 cells arranged in a square • Streptococcus - chain of cocci • Staphylococcus - cluster of cocci • Streptobacillus - chain of rods • Eukaryotic cellular structures and functions o Organelles • Nucleus – Defining characteristic of eukaryotic cells; double membrane organelle that contains DNA • DNA – genetic material; composed in stick shaped chromosomes in nucleus • Plasma membrane – Phospholipid bilayer • Cell Wall – Present in some cells and differs in composition based on group (fungal cells have a cell wall made of chitin or beta glycan) • Mitochondria – Site that produces large amounts of ATP during cellular respiration. Has its own genome and ribosomes are 70S (prokaryotic-like) • Ribosomes – in the cytoplasm, different from prokaryotics, 80S in size • E.R. – Two types: Rough – organelle covered in ribosomes, used in protein production; Smooth – performs lipid biosynthesis • Golgi Apparatus – Exports proteins o Compared to prokaryotic cells • Be sure that you can differentiate prokaryotic and eukaryotic cells • Cell wall structures (USLO 2.2) o Gram-positive and Gram-negative cell walls o Gram Positive Cells (Stains Purple from Gram Stain) o Thick cell wall on the outside made of peptidoglycan o Cell wall is reinforced with Teichoic Acids o Susceptible to penicillin, which inhibits synthesis of cell o Gram Negative Cells (Stains Red from Gram Stain) • An outer and inner membrane. In between the membranes is a thin cell wall made of peptidoglycan • Outer membrane contains lipopolysaccharide (LPS), an important molecule to the pathogenicity and immune reactions to gram negative bacteria. o LPS is made of two components: ▪ Lipid A ▪ O Antigen • Resistant to antibiotics (like penicillin) that inhibit synthesis of peptidoglycan • Hydrophobic tails (Fatty acids) • Sterols • Small ring shaped lipids • Examples: • Cholesterol in humans • Ergosterol in fungi • Carbohydrates • Primarily used for quick energy, but also used for structure • Three types: • Monosaccharides • Simple building blocks of larger carbohydrates • Types • Pentoses. Ex: • Deoxyribose • Ribose • Hexose • Glucose • Lactose • Fructose • Disaccharides • Two monosaccharides linked together by a condensation reaction (also called dehydration synthesis) • Examples: • Sucrose • Maltose • Polysaccharides • Three of more monosaccharides linked together by a condensation reaction • Examples: • Glycogen – animal energy storage • Starch – plant energy storage • Cellulose – Plant Cell Wall • Peptidoglycan – Bacteria Cell Wall • Beta glucan – Fungal Cell Wall • Chitin – Fungal Cell Wall • Nucleic acids • Made of nucleotides. Nucleotides are made of: • Pentose sugar • Phosphate • Nitrogenous Base • DNA • Deoxyribose • Double Stranded helix • Bases: A, G, C, T • RNA • Ribose • Single Stranded • Bases: A, G, C, U o The function of enzymes in metabolism (USLO 3.2) o Enzyme function • Enzymes are proteins that speed up chemical reactions. • Enzyme structure • Holoenzyme is term for complex that contains: • Apoenzyme – Actual enzyme (protein) • Co-enzyme – organic molecules that couples with apoenzyme to activate it • Co-factor- inorganic molecule that couples with apoenzyme to complete structure/allow for activity • Enzyme active site is where substrate binds o Enzyme inhibition • Competitive inhibition – Molecule blocks the active site of the enzyme • Non-competitive inhibition – Molecule binds to a second site (allosteric site) which changes shape of active site. This prevents substrate from binding to enzyme. o Anabolic reactions (USLO 3.3) • Assembling larger molecules from building blocks. This can require energy • Many are classified as endergonic reactions – consume energy • Example: A dehydration synthesis where amino acids are covalently linked together to make a protein o Catabolic reactions (USLO 3.3) • Breaking down larger molecules into smaller ones. This can release energy into the surrounding environment • Many are classified as exergonic reactions – release energy • Example: A hydrolysis reaction where polysaccharides are broken down into monosaccharides. o Types of phosphorylation (USLO 3.4) • Oxidative phosphorylation – transferring a phosphate to ADP to make ATP using energy from the passing or movement of electrons (example: Electron Transport Chain) • Substrate Level Phosphorylation – transferring a phosphate to ADP to make ATP using a phosphorylated donor molecule (example: ATP produced in glycolysis or the Kreb’s Cycle) o Pathways of carbohydrate catabolism (USLO 3.4) • Glycolysis • Occurs in the cytoplasm of both eukaryotic cells and prokaryotic cells • Reactants needed: 1 Glucose, 2 ATP • Products produced: 2 Pyruvates, 2 NADH (an electron carrier), 2 ATP • Transition Reaction • Occurs in the matrix of the mitochondria in eukaryotes and in the cytoplasm of prokaryotes • Reactants needed: 2 pyruvates 1. Tonicity of the environment can affect bacteria’s growth • Isotonic environment – no loss or gain of fluid • Hypertonic environment – water moves out of the cell and cell shrinks within cell wall. This is called plasmolysis shriving and shrinking o Oxygen • Hypotonic environment – Water moves into the cell but the cell wall counteracts the swelling and prevents lysis 1. Obligate aerobe – requires oxygen for growth 2. Obligate anaerobe – can’t use oxygen and will be harmed by its presence 3. Facultative anaerobe – Bacteria that can grow in the presence of oxygen or without it. 4. Aerotolerant anaerobe – bacteria that aren’t harmed by oxygen, but they don’t use it for growth 5. Microaerophile – aerobic, but require depressed oxygen environments. o Nutrient requirements 1. Carbon 2. Ammonia 3. Oxygen 4. Phosphate • Microbial growth patterns (USLO 4.2) o Growth curve o Log phase is where you have the highest level of metabolic activity, a large amount of binary fission occurring, and this is where antibiotics (antimicrobials) are most effective because this is where they are stopping things like DNA replication. Highest metabolic activity o Generation time 1. The time it takes for a bacterial population to double through one round of binary fission (bacterial cell division) o Calculate microbial population size 1. Direct methods • Direct Counting - Direct cell counting can be done manually with the aid of a microscope, a special microscope slide called a hemocytometer and a special dye. ( The fastest way to get a count and you get a dead and live percentage because live will be clear.) • Plate Method - Plating a known volume of a sample can also be used to count the number of microbes in a sample. The original sample, however, must be diluted before plating, using one of two methods can be used to count the total number of viable cells. • Pour Plate - The pour plate method a method used to count the number of colony-forming units or microbes in a liquid sample. A fixed amount of inoculum is mixed with warm, liquid agar and added to a sterile plate. After incubating at the appropriate temperature and time, the number of colonies is counted on plates with 30 - 300 colonies. • Spread Plate - The spread plate method technique is also used to plate samples from a liquid for the purpose of isolating or counting the bacteria present in a sample. The technique is commonly used in food safety but can be employed in other conditions too. A set volume of the liquid sample from each dilution, usually 100 microliters, is placed on a sterile, nutrient agar and spread evenly. After incubating at the appropriate temperature and time, the number of colonies is counted on plates with 30 - 300 colonies. (Good for isolating a single colony, colonies are usually genetic clones of eachother) 2. Indirect methods • Metabolic Activity - Metabolic activity is an indirect way to estimate bacterial numbers. The method assumes the amount of a selected metabolic product (CO2 for example) is in direct proportion to the number of bacteria present. (quick but not as quick as direct counting. Looking for a metabolic byproduct) • Dry Weight - Dry weight can also be used to estimate bacterial count. It is useful for filamentous microorganisms. In this procedure, the sample is concentrated by filtration or centrifugation and then dried in a desiccator. It is then weighed. (connect dry weight, filamentous, and indirect method) • Microbial culture methods (USLO 4.3) o Aseptic technique 1. Biosafety levels • BSL-1 – Organisms usually don’t cause disease. PPE = lab coat, gloves, eye and face protection • BSL-2 – Organisms that are commonly encountered in the community and present moderate health hazard. PPE is basically same as BSL-1. • BSL-3 – Organisms of local or exotic origin with respiratory transmission. Serious or lethal diseases. PPE= BSL-1 plus respiratory protection • BSL-4 – Organisms have potential for lethal infection through inhalation of aerosols or droplets. PPE – positive pressure one-piece body suit with life support system o Isolation of pure cultures 1. Samples usually contain organism of interest AND normal microbiota. These steps all for isolation of organism of interest (know these steps in order) • Culture sample in specialized media 1. Filtration (this is a mechanical method) • Removes bacteria by passing contaminated fluid through mesh that catches bacteria but not fluid • Factors that influence the effectiveness of microbial growth control techniques (USLO 4.5) o Contact Time 1. Antimicrobial agent’s effectiveness increases with increased time of contact with microbes. • D value –(how we measure it’s effectiveness) how long it would take to reduce number of bacteria by 90% or one log10 o Concentration of antimicrobial agent 1. Antimicrobial agent’s effectiveness increases with increased concentration of the agent o Population Size 1. Antimicrobial agent’s effectiveness decreases with increased size of bacterial population (more bacteria on surface = longer contact time and/or concentration of agent) (need to consider how contaminated this item is that they are trying to sterilize.) o Type of Microbe (c-diff takes special applications) 1. Different microbial structures and types of microbial cells have different levels of resistance to antimicrobial agents used to eliminate them. Unit 5 • DNA Replication (USLO 5.1) o Enzymes o Helicase – Enzyme that separates the strands of the template DNA molecules o Gyrase - This enzyme relieves strain on the DNA strand. o Primase – This enzyme creates and RNA primer for DNA polymerase to use as a starting point o DNA polymerase - This enzyme reads the DNA strand and adds the complementary nucleotide to the growing DNA strand. o Ligase - This enzyme glues DNA fragment strands (Okazaki Fragments) together o Template o Template strands are separated. Each will combine with a new strand to make two DNA molecules o End product o Two new DNA molecules each has one new strand and one template strand o Semiconservative mode of replication ( it gets split from one to two DNA molecules) • Gene Expression (USLO 5.2) o Transcription (using DNA as a template to make RNA, DNA is not consumed in this process it is a template ) (remember RNA is single stranded and has a U instead of a T) o Enzymes • Helicase and Gyrase are used again to separate template DNA strands (temporarily) • RNA polymerase synthesizes a strand of mRNA that is complementary to the DNA template strand. o Template • Promoter – special sequence on the DNA molecule that marks the beginning of a gene (this is what the RNA polymerase will bind to) • Gene – Sequence of DNA that codes for a protein o End product • New strand of mRNA (specific to gene expression) • Template DNA is left intact ( it can be used repeatedly ) o Translation o Components of protein synthesis • mRNA – Template (to make a protein) • Codons – group of 3 nucleotides that code for an amino acid (this is on the mRNA) • Start Codon – First codon, marks the beginning of translation (DOES CODE FOR AN AMINO ACID) • Stop Codon – Marks end of translation (DO NOT CODE FOR AN AMINO ACID) • Ribosome – links amino acids together (machine that is performing translation interacting and polymerizing the amino acids) • tRNA – shuttle amino acids to ribosome (the cross over from the growing peptide chain) o Codon Table (Amino Acid Sequencing Chart) – shows the relationship of codons to amino acids (Example Codon UGC codes for a Cysteine (CYS). • Mutations (USLO 5.3) o Beneficial versus harmful – some mutations produce a benefit by creating a functional protein that performs a new function for the cell. Other mutations can harmful, where a pre-existing functional protein has lost its function. o Types of mutations • Silent - change in the DNA that codes for the same amino acid o Transposons - unique DNA sequences that independently excise themselves out of DNA and "jump" and integrate into another location on the DNA (sort of like DNA transfer but it happens in the same molecule) • Significance of horizontal gene transfer (USLO 5.5) o Horizontal gene transfer can result in the transfer of • Genes for virulence factors • Toxins • Antibiotic Resistance (through conjugation) Unit 6 Characteristics of Microorganisms (USLO6.1) • Protozoans o Common infections • Malaria - caused by Plasmodium species • Trichomoniasis - caused by Trichomonas vaginalis • Giardiasis - caused by the protozoan Giardia lamblia o Classified by mobility (organs of mobility in protozoa) • Cilia - hair like appendages for locomotion • Pseudopods - lobe like pseudopodia used for movement • Flagellum - whip-like structure to propel the organism forward o Complex life cycle moving from trophozoites to cysts to survive harsh conditions. • Schizogony – asexual reproduction by multiple fissions • Can reproduce sexually and asexually • Host • Definitive hosts – host where parasite is sexually reproducing • Intermediate host – host where parasite is maturing through asexual stages • Helminths o Two main groups • Roundworms (Nematodes) • Flatworms (Platyhelminthes) o Example organisms • Tapeworms • Roundworms • Hookworms o Have rudimentary digestive and nervous systems. Most complex system is reproductive systems • Fungi o Characteristics • Chitin or Beta Glucans in cell wall • Ergosterol in plasma membrane • Decomposers ( irritate the body by decomposing the tissue around it) o Hypha (filament or basic tissue) • Septate hypha – strands of cells with cell walls separating adjacent cells • Nonseptate hypha – strands of fungal cells without separation between the adjacent cells o Life Cycles • Sporangium produce spores • Asexual spores germinate into mycelium(the main body) (groups of hypha) • Sexual spores germinate in structures that produce gametes • Plasmogamy – fusion of cell membranes of gametes or reproductive structures • Karyogamy – fusion of nuclei, occurs after plasmogamy, leads to formation of a zygote. • Algae o Can perform photosynthesis o Can be single cellular or multicellular o Not pathogenic, but some members can produce toxins (ex. Dinoflagellates are responsible for red tides and produce neurotoxins) Life Cycles of Select Eukaryotic Microorganisms (USLO 6.2) • Protozoans (See notes above) • Helminths (See notes above) • Fungi (See notes above) Viral Structure, Function, and Diseases • Structure of acellular agents (USLO 6.3) o Viruses (virion) • Made of nucleic acids and protein (called the capsid). • Virion – Similar term to virus. Contain Nucleic Acids and protein. • Envelope – Some viruses will also have a phospholipid bilayer surrounding the virion. This structure is called the envelope. o Viroids – Infectious RNA (no protein) o Prions – Infection proteins • Viral replication cycles (USLO 6.4) o Stages 1. Attachment – Virus binds to membrane proteins 2. Penetration – Animal viruses will be endocytosed into the cell, bacteriophages insert their DNA through the membrane • Inflammation – Basophils and Mast Cells release histamine, which leads to vasodilation and localized increase in blood flow/temperature. Leads to activation of phagocytes. • Interferons – signaling molecules produced by infected cells that “interfere” with the propagation of viruses in adjacent cells. Create a localized anti- viral state. • Complement proteins – system of blood proteins that creates pores in microbial membranes and can promote inflammation • Fever – pyrogens from microbes can “trick” hypothalamus into initiating body warming response even though temperature is normal. Prostaglandins are molecules produced by the body (including the hypothalamus) during an inflammatory response that provide same affect. Pyrogens come from pathogens, prostaglandins come from you. o Third Line of Defense • Adaptive Immune System (T and B cells) • Cell mediated arm • Kills cells infected with intracellular pathogens (pathogens inside cells) • Relies on Cytotoxic T cells • Humoral arm • Relies on B cells that differentiate to plasma cells • Plasma cells secrete antibodies • Role of Microbiota in immunity (USLO 7.2) o Locations of the normal microbiota • Conjunctiva • Oral Cavity • Skin – staphylococcal, propioibacteria, corneobacteria are common residents. • GI tract – lower GI houses the Microbiome, a diverse set of microbes that assist in digestion and have varied affects. Coliform bacteria are common. • Vagina – Lactobacillus produce acidic environment. • These areas should be sterile • Brain and CNS • Kidney and Urinary tract • Blood • Bacteria from the skin can produce • Bacteremia – bacteria in the blood • Septicemia – actively growing bacteria in the blood. o Microbial antagonism • Growth of normal microbiota prevents attachment of pathogens to surfaces • Microbiota produce bacteriocins that can limit damage pathogenic bacteria o Symbiosis • Mutualism – two organism that mutually benefit each other • Commensalism – relationship where one organism benefits and the other is unaffected • Parasitism – relationship where one organism benefits at the detriment to the other. • Cell mediated vs Humoral Response (USLO 7.3) o Both arms respond to antigens (proteins or glycoproteins that are unique to pathogens) • Bacterial antigens • Peptidoglycan • Flagellin • Fimbriae • Viral antigens • Capsid proteins – spike proteins are very common • Envelope proteins • Epitopes – specific areas of antigen that antibodies bind to. • Hapten – small antigen that combines with a larger carrier molecule to induce an adaptive response. o Adaptive immune response • Antigen Presentation • Antigen Presentation ( can perform on Macrophages and Dendritic cells also B cells ): • Class 1 MHC present antigens to CD8 cells (results in death of antigen presenting cell) • Class 2 MHC present antigens to CD4 cells (activates helper T cells) • Cell mediated arm • Cells: • Cytotoxic T cells – also called CD8 cells, directly attack and kill infected cells by inducing apoptosis and attacking membrane with perforin • Makes Memory Cells • Regulatory T cells – Respond at end of immune response to decrease the number of activated cells • Humoral Arm • B lymphocytes -produce antibodies • Sensitized B cell has had an antigen bind to surface antibody. • Helper T cell leads sensitized B cell to differentiate into plasma cell (plasma cells secrete antibodies) • Plasma cell end stage for B cyte, this cell secretes antibodies • Memory cells can be formed. When they are activated they produce a secondary response • Antibodies • Structure: light chain, heavy chain, variable and constant region. • Functions: • Neutralization – Block pathogen from binding to host cell • Agglutination – linking pathogens together preventing further spread • Opsonization – Marking pathogen for macrophages • Complement activation – Recruit Complement proteins • ADCC – Activate Natural Killer Cells • Immunoglobulins: • IgG – Secreted in low amounts in primary response, main antibody of secondary response o Portals of entry – organ/system that is affected is usually the portal of entry (example: Port. Of Entry for STD is Urogenital tract for respiratory is upper resp. tract) o Attachment – Multiple phenomena can assist in pathogen attachment: Fimbriae, Pili, Capsule, Biofilms o Invasion – Pathogen gaining access to susceptible tissues o Evading the immune system – Theses can help with evasion Capsule prevents phagocytosis, Antigenic Variation changes antigens, IgA proteases destroy secreted IgAs o Infection • Focal Infection- a localized infection that spreads • Local Infection – infection in single location in the body • Systemic Infection – spreads through body • Primary Infection – infection from a singular pathogen • Secondary Infection – second pathogen (infection) that occurs during primary infection • Bacteremia – bacteria in the blood • Septicemia – Bacteria replicating in the blood • Viremia – Virus in the blood • Toxemia – bacterial toxins in the blood o Portals of exit – usually localized to affected organs, example – coughing is portal of exit for respiratory infection • Stages of disease o Incubation – time from moment of exposure, pathogen numbers slowly increasing but may not be detectable, signs and symptoms not present o Prodromal – pathogen numbers increase, early mild sign and symptoms o Illness – typical signs and symptoms present, pathogen number the highest o Decline – slow decrease in pathogens, secondary infections can occur o Convalescence – pathogen numbers decrease to none, sign and symptoms decline • The pattern of infectious disease o Acute – fast increase in pathogen (2 days) and the quick decline in pathogen numbers o Subacute – slow increase of pathogens (slower than two days) and decline is slower. Symptoms are usually less. o Chronic – pathogens present for long periods of times (months/years). Pathogen number slowly increases in this time frame o Latent – pathogen is not detectable until reactivation • Virulence factors of pathogens (USLO 8.2) o Structural Factors these are the strucutal factors • Cell wall – Made of Peptidoglycan, structural virulence factor • Pili/flagella/fimbriae – Structures for attachment to host cell • Capsules – Cell structure that protects from phagocytosis • Endospore – dormant, tough, dessicated structure that is resistant to environmental and chemical agents. Used in transmission of some pathogens like C. diff. o Antigenic variation – variation of surface markers that helps avoid the immune system o Toxins • Endotoxins – LPS • Intracellular toxins – AB toxins, • Membrane disrupting toxins – Hemolysins • Superantigens – over activates the immune system leading to non-effective adaptive responses, helps pathogen avoid detection. o Exoenzymes – enzymes secreted by bacterial pathogens can assist with immune system avoidance and access to deeper tissues examples below • IgA Protease – cleaves IgA’s • Hyaluronidase – cleaves Hyaluronic Acid which is component of Connective and Epithelial tissues. Increases rate of spread through host tissues • Coagualse – cleaves fibrin clots o Adhesins – attachment to host cell • Pathogenic potential (USLO 8.3) o Infectivity and invasiveness go over LD50 in some videos • Infectious Dose – or ID50, dose where 50% of test population is infected • Lethal dose – or LD50, dose where 50% of test population is dead • Pathogenicity – ability of organism to cause disease • Morbidity – condition of showing disease • Mortality – condition of death from disease • Epidemiology Relevance (USLO 8.4) o Transmission, incidence, and frequency of disease. Differentiate • Etiological agent – the causative agent (pathogen) of a disease (group of symptoms) • Mortality – see 8.3 • Morbidity – see 8.3 • Prevalence – the number of people at a given time that have a disease • Incidence – the rate of people contracting a disease o Role of CDC – government agent responsible for tracking existing, new, and emerging diseases. They produce a weekly report on morbidity and mortality for the tracking of diseases. • Epidemiologist – scientist that tracks prevalence, incidence, etc of diseases. • Epidemiological terminology (USLO 8.5) o Sporadic – occurrence of disease due to random events o Endemic – pathogen/disease that is regularly found in a specific area o Epidemic – affects a large number of people in a localized area (community/country) o Pandemic – a disease that spreads between countries/nations o Common Source – a common reservoir of a pathogen that is the sole source of an outbreak o Intermittent source – A reservoir that fluctuates due to external conditions like weather evets o Propagated source – when susceptible host is also a reservoir that can transmit the pathogen to another source o Expected Prevalence – the average number of cases of a disease for an area o Reservoir – source of pathogen • Transmission of infectious diseases (USLO 8.6) o Vertical Transmission – from mother to child o Horizontal Transmission – from individual to individual in same generation/population o Nosocomial – passing of disease in healthcare setting o Direct Contact – spread through contaminated objects, contact with an infected person (skin to skin or with secretions directly from contaminated person) o Indirect Contact • Vehicle Transmission – a non-living object that can transmit a disease