PHM 507 Exam 1 | Complete Solutions (Verified Answers)

PHM 507 Exam 1 | Complete Solutions (Verified Answers) What is microbiology? The study of microorganisms What types of organisms does microbiology focus on? Single cells, cell clusters, viruses (not cellular), acellular microbes, and cellular Microorganisms What are the two major classifications of microorganisms? Acellular microbes and cellular microorganisms What are the two categories of acellular microbes? Viruses and prions How would you describe a virus? -Not considered true cells -Composed of nucleic acid (DNA or RNA) -Has a protein coat (capsid) -May have a lipid envelope -Cannot reproduce independently What are prions? -Infectious misfolded proteins -Causes chronic neurodegenerative diseases What are the two categories of cellular microorganisms? Prokaryotes and eukaryotes What are the categories of prokaryotes? -Bacteria -Archaebacteria (Archaea) What are the characteristics of prokaryotes? -No true nucleus -Haploid (single set of chromosomes) What are the categories of eukaryotes? -Algae -Protozoa -Fungi -Slime molds What are the characteristics of eukaryotes? -True nucleus -Diploid (two sets of chromosomes) How does microbiology contribute to health? It identifies pathogens, aids in vaccine and antibiotic development, enables accurate diagnoses, monitors antimicrobial resistance, and guides infection control in hospitals What role do microbes play in environmental health? Microbes help clean up waste and recycle nutrients in nature How is microbiology used in industry? Microbes are used to produce food products like yogurt and cheese, and to create other useful goods What is the significance of microbiology in farming? Microbes support plant growth and protect crops from pests How does microbiology advance scientific research? Microbes are used to study life processes and develop technologies like CRISPR What is normal flora? Microbes that naturally live on or in the body, such as on the skin, mouth, gut, respiratory tract, and urogenital tract What are the benefits of normal flora? They defend against pathogens, aid digestion, and support the immune system What are opportunistic pathogens? Normal flora that cause disease when immunity is low or when they enter parts of the body where they don't belong Name body sites that are normally sterile. Blood, cerebrospinal fluid (CSF), internal organs (heart, liver, kidneys), muscles, bones, and urine in the bladder What does the presence of microbes in sterile body sites usually indicate? Infection Are all microorganisms harmful? No; many are harmless or beneficial; only some cause disease and are called pathogens What is a pathogen? A microorganism (bacteria, virus, fungus, or parasite) that can cause disease in a host What is pathogenicity? The ability of a microorganism to cause disease What is virulence? The degree of harm or severity of the disease caused by a pathogen What is an opportunistic pathogen? A normally harmless microbe that causes disease when the host's immunity is weakened or it enters an unusual body site What is an obligate pathogen? A microbe that always causes disease when it infects a host What is an accidental pathogen? A microorganism that doesn't usually infect humans but can cause disease if it accidentally enters the body What is epidemiology? The study of disease occurrence and transmission in populations What does epidemiology focus on? The distribution and determinants of health problems in populations What tools does epidemiology use to track diseases? Research methods and statistical measures How does the public health approach differ from clinical medicine? It focuses on populations rather than individuals How are diseases categorized in epidemiology? By time, place, and person to detect trends and outbreaks What are the main modes of disease transmission? -Direct contact (person-to-person) -Indirect contact (contaminated surfaces/objects) -Airborne droplets (coughing/sneezing) -Vectors (e.g., mosquitoes) -Common sources (contaminated food/water) What defines a disease outbreak? When disease cases rise above expected levels in a population What are virulence factors? Traits that help microbes infect and damage the host What do adhesins do? Help microbes attach to host cells How do microbes invade tissues? Using enzymes and toxins What helps microbes resist immune defenses? Capsules and antigen variation What facilitates damage to host cells? Exotoxins and endotoxins What are common entry points for microbes? Skin, respiratory tract, digestive tract, urogenital tract, and mucous membranes What happens during colonization? Microbes adhere and multiply at the entry site What is microbial invasion? Penetration and spread of microbes through tissues What are components of innate immunity? Physical barriers, phagocytes, and inflammation What are components of adaptive immunity? Antibodies and T-cells targeting specific microbes What are the possible outcomes of infection? -Microbe eliminated → health restored -Microbe evades defenses → disease develops How is infection diagnosed? Based on symptoms and lab tests How are pathogens removed or killed? Using antimicrobials like antibiotics, antivirals, and antifungals How can the immune system be supported? Through vaccination and supportive care How is disease spread prevented? Hygiene, isolation, and vaccination Why is monitoring important during treatment? To detect resistance and complications What is metabolism in microorganisms? All biochemical reactions that support life What is catabolism? Breakdown of molecules to release energy What is anabolism? Building of cellular components using energy What does metabolism enable microorganisms to do? -Grow -Reproduce -Adapt to environments Why do microorganisms need energy? To perform essential cellular functions like growth, reproduction, and adaptation What are common sources of energy for microorganisms? -Organic compounds (e.g., sugars) -Inorganic compounds (e.g., sulfur, ammonia) -Light (in photosynthetic microbes) What molecule stores energy in microorganisms? ATP (adenosine triphosphate), the universal energy currency What are redox reactions? Chemical reactions involving the simultaneous processes of oxidation and reduction Define OILRIG -Oxidation is loss of electrons -Reduction is gain of electrons Why are redox reactions important in microbial metabolism? They help generate energy by transferring electrons through metabolic pathways What are key electron carriers in redox reactions? NAD⁺/NADH and FAD/FADH₂ What are the three main mechanisms microorganisms use to generate ATP? -Substrate-level phosphorylation -Oxidative phosphorylation -Photophosphorylation What is substrate-level phosphorylation? Direct transfer of a phosphate group to ADP to form ATP When does substrate-level phosphorylation occur? During glycolysis and fermentation Does substrate-level phosphorylation require an electron transport chain? No, it does not What does oxidative phosphorylation involve? An electron transport chain (ETC) and the creation of a proton gradient In which types of respiration is oxidative phosphorylation used? Aerobic and anaerobic respiration Where does photophosphorylation occur? In photosynthetic microbes What drives ATP production in photophosphorylation? Light energy drives electron flow through a photosynthetic ETC How is photophosphorylation similar to oxidative phosphorylation? Both use an electron transport chain to generate a proton gradient for ATP synthesis What is respiration in microorganisms? A process of energy generation that uses an electron transport chain (ETC) What happens during electron transport in respiration? Electrons move through the ETC, creating a proton gradient across the membrane What does the proton gradient do? It drives ATP synthesis What are the two main types of respiration? -Aerobic respiration: uses oxygen (O₂) as the final electron acceptor -Anaerobic respiration: uses other inorganic molecules (e.g., nitrate, sulfate, carbon dioxide) Which respiration type is more energy-efficient? Aerobic respiration typically yields more ATP than anaerobic respiration What types of microbes use aerobic respiration? Aerobic bacteria, yeasts, and some protozoa What is the terminal electron acceptor in aerobic respiration? Oxygen (O₂) What are the three main stages of aerobic respiration? -Glycolysis: Glucose is broken down into pyruvate -Krebs cycle (TCA cycle): Generates electron carriers (NADH, FADH₂) -Electron Transport Chain (ETC): Electrons flow to oxygen, driving ATP synthesis What is the energy yield of aerobic respiration per glucose molecule? Approximately 36-38 ATP When does anaerobic respiration occur? In the absence of oxygen (O₂) What types of microbes carry out anaerobic respiration? Anaerobic bacteria and Archaea What are some alternative terminal electron acceptors used in anaerobic respiration? -Nitrate (NO₃⁻) -Sulfate (SO₄²⁻) -Carbon dioxide (CO₂) How does the ATP yield of anaerobic respiration compare to other processes? It produces a moderate amount of ATP—less than aerobic respiration but more than fermentation What is fermentation? An anaerobic pathway that does not use an electron transport chain (ETC) What acts as the terminal electron acceptor in fermentation? An organic molecule, such as pyruvate What is the primary purpose of fermentation? To regenerate NAD⁺ from NADH so glycolysis can continue What are common end products of fermentation? -Lactic acid (by lactic acid bacteria) -Ethanol (by yeasts) -Acids and gases (by various anaerobes) How much energy does fermentation yield per glucose molecule? Only 2 ATP What are the two major types of organisms based on cell structure? -Prokaryotes: No nucleus (e.g., Bacteria, Archaea) -Eukaryotes: Nucleus present (e.g., Fungi, Protozoa) What system is used to name microorganisms? Binomial nomenclature How is a microorganism's name written in binomial nomenclature? -Genus name: Capitalized -Species name: Lowercase -Both italicized when written Give an example of binomial nomenclature Clostridium tetani -Clostridium = Genus -tetani = Species Can a genus include multiple species? Yes; example: -Clostridium tetani -Clostridium botulinum What is the typical size range of bacteria? 0.2-10.0 micrometers (μm) What are cocci? Round or spherical-shaped bacteria What are bacilli? Rod-shaped bacteria What are spirilla? Spiral or corkscrew-shaped bacteria What does "diplo-" indicate in bacterial arrangement? Bacteria arranged in pairs What does "strepto-" indicate in bacterial arrangement? Bacteria arranged in chains What does "staphylo-" indicate in bacterial arrangement? Bacteria arranged in clusters What is the purpose of Gram staining? To differentiate bacteria based on their cell wall structure What is the cell wall structure of Gram-positive bacteria? Thick peptidoglycan layer and no outer membrane What stain do Gram-positive bacteria retain? Crystal violet What color do Gram-positive bacteria appear under the microscope? Purple What is the cell wall structure of Gram-negative bacteria? Thin peptidoglycan layer and an outer membrane Do Gram-negative bacteria retain crystal violet? No What stain do Gram-negative bacteria take up? Safranin What color do Gram-negative bacteria appear under the microscope? Pink What is a bacterial capsule? An antiphagocytic layer that helps bacteria evade the immune system What staining method is used to detect capsules? Nigrosin or India ink How does capsule staining work? The background is stained, and the capsule appears as a clear halo around the cell What does the presence of a halo indicate in capsule staining? The organism has a capsule What does the absence of a halo indicate? No capsule is detected Name two pathogens commonly identified using capsule staining. Klebsiella pneumoniae and Cryptococcus neoformans What are flagella? Thin, hair-like organelles used for bacterial motility Why can't flagella be seen under a regular bright field microscope? They are too thin and require special staining methods to be visible What is the purpose of flagella staining? To detect the presence and arrangement of flagella What does "monotrichous" mean? A single flagellum on one end of the cell What does "peritrichous" mean? Flagella distributed all over the surface of the cell What is a key use of flagella staining? Identification of motile bacterial species What is the purpose of the Ziehl-Neelsen acid-fast stain? To identify bacteria with waxy cell walls containing mycolic acids What happens to acid-fast bacteria during staining? They retain the pink stain even after the acid-alcohol decolorizing step What happens to non-acid-fast bacteria during staining? They are decolorized and do not retain the pink stain What is a key organism identified by acid-fast staining? Mycobacterium tuberculosis How does Mycobacterium tuberculosis appear under the microscope? Pink, beaded, and slightly curved What is the clinical use of the Ziehl-Neelsen stain? It is essential for diagnosing mycobacterial infections such as tuberculosis (TB) What is an endospore? A bacterial survival capsule—latent, highly resistant to extreme conditions When are endospores formed? Under stress, such as heat, starvation, or chemical exposure How long can endospores survive? Hundreds to thousands of years What triggers sporulation? Poor environmental conditions What is germination in the endospore life cycle? The return of endospores to vegetative cells when conditions improve What are the staining results in an endospore stain? -Spores = Green -Vegetative cells = Pink/Red Which genera are commonly identified using endospore staining? Bacillus and Clostridium Name diseases associated with endospore-forming bacteria. Anthrax, botulism, and tetanus What makes up the bacterial cell envelope? Cytoplasmic membrane + cell wall ± capsule What is the function of the nucleoid in bacteria? It contains the bacterial DNA and controls genetic functions What do ribosomes do in bacterial cells? They synthesize proteins What is the role of flagella? They provide motility, allowing the bacterium to move What is the function of pili? They help bacteria attach to surfaces and other cells What are spores in bacteria? Highly resistant structures that allow survival under harsh conditions What are obligate aerobes? Bacteria that require oxygen for energy production and growth Example: Mycobacterium tuberculosis What are obligate anaerobes? Bacteria for which oxygen is toxic; they grow only in oxygen-free environments Example: Clostridium botulinum What are facultative anaerobes? Bacteria that prefer oxygen but can grow without it by switching to fermentation or anaerobic respiration Example: Escherichia coli What are microaerophiles? Bacteria that need oxygen but only in low concentrations; high levels are harmful Example: Helicobacter pylori What are aerotolerant anaerobes? Bacteria that do not use oxygen but can tolerate its presence; they rely on fermentation for energy Example: Lactobacillus What is the purpose of the glucose fermentation test? To assess a bacterium's ability to ferment specific carbohydrates and differentiate bacteria based on fermentation patterns Why do bacteria show different fermentation results? They differ in enzyme systems and sugar utilization What are possible fermentation products? Acid, gas, or alcohol What are common carbohydrates tested in fermentation assays? Glucose, lactose, sucrose, mannitol, maltose, etc. What indicates a positive fermentation reaction? Acid production causes a pH drop, leading to a color change in the medium What is the purpose of the catalase test? To detect the presence of the catalase enzyme, which breaks down hydrogen peroxide (H₂O₂) into water and oxygen What indicates a positive catalase test? Bubbling due to oxygen release What does a positive catalase test suggest about the bacterium? It produces catalase and can protect itself from oxidative damage Why is catalase associated with pathogenicity? It helps bacteria survive the oxidative burst from host immune cells How does the catalase test help in bacterial identification? -Staphylococci are catalase-positive -Streptococci are catalase-negative Name catalase-positive organisms relevant to clinical infections. Staphylococcus aureus, Serratia, Pseudomonas What is CGD? A genetic disorder where phagocytes cannot produce reactive oxygen species due to a defect in the NADPH oxidase complex What happens to phagocytes in CGD? They can ingest microbes but cannot kill them, leading to chronic infections and inflammation Why are catalase-positive organisms problematic in CGD? They degrade hydrogen peroxide, depriving phagocytes of the reactive oxygen needed to kill them What is the purpose of the coagulase test? To differentiate coagulase-positive Staphylococcus aureus from coagulase-negative species Which species are coagulase-negative? Staphylococcus epidermidis and Staphylococcus saprophyticus What reaction occurs in a positive coagulase test? The coagulase enzyme converts fibrinogen into fibrin, forming a clot What does clot formation indicate? A positive test—presence of the coagulase enzyme What does no clot formation indicate? A negative test—absence of coagulase enzyme What is used in the coagulase test to detect clotting? Plasma, which contains fibrinogen Why is the coagulase test clinically important? It confirms the presence of S. aureus in infections such as skin infections, abscesses, and sepsis What is the purpose of the hemolysis test? To differentiate Streptococcus and Enterococcus species based on their ability to lyse red blood cells (RBCs) What is β-hemolysis? Complete destruction of RBCs; appears as a clear zone around colonies Example: Streptococcus pyogenes What is α-hemolysis? Partial destruction of RBCs; produces a greenish discoloration around colonies Example: Streptococcus pneumoniae What is γ-hemolysis? No hemolysis; no change in the agar Example: Enterococcus faecalis What is a biofilm? A structured community of microorganisms attached to a surface and embedded in a self-produced slimy matrix What is the biofilm matrix composed of? Bacteria, polysaccharides, proteins, and DNA What functions do biofilms serve for microbes? -Enable adherence to surfaces -Provide protection against antibiotics and disinfectants Where are biofilms commonly found? -Medical devices (e.g., catheters, implants) -Teeth (dental plaque) -Lungs (Pseudomonas in cystic fibrosis) -Chronic wounds Why are biofilms clinically significant? -They lead to chronic, persistent infections -They are resistant to removal and standard treatments What is virulence? The capacity of a microorganism to cause disease in a host What are common routes of entry into the host? Respiratory, gastrointestinal, urogenital tracts, or broken skin What strategies do pathogens use to evade host defenses? -Capsules -Antigenic variation -Enzymes and toxins -Inhibition of immune responses How do pathogens adapt to the host environment? By growing and surviving in host tissues under specific conditions like temperature and pH How do pathogens utilize host resources? -For replication -To cause tissue damage and spread infection How can microbes enter through the skin? Via cuts, burns, wounds, or insect bites Example: Staphylococcus aureus What is vector-borne transmission through the skin? Pathogens are injected by insects Example: Plasmodium (malaria) How do microbes enter via the respiratory tract? Inhaled droplets bypass mucus if cilia are damaged Examples: Influenza, Mycobacterium tuberculosis How do microbes enter via the gastrointestinal tract? Through contaminated food or water; some survive stomach acid Examples: Salmonella, Norovirus How do microbes enter via the urogenital tract? Through sexual contact, micro-abrasions, or contaminated medical devices Examples: HIV, Neisseria gonorrhoeae What is vertical transmission? The passage of pathogens from mother to baby How can pathogens cross the placenta? Through maternal blood Examples: Rubella, Zika virus How can pathogens be transmitted during birth? Through exposure to infected vaginal secretions or blood Examples: Herpes simplex virus, HIV What causes cilia damage in the respiratory tract? Smoking or viral infections What condition leads to thick mucus that impairs microbial clearance? Cystic fibrosis What is the goal of microbial evasion strategies? To avoid multiple host defenses, especially phagocytosis How do bacterial capsules inhibit phagocytosis? By masking surface antigens and hiding the bacterial surface from immune cells What do bacterial cell wall proteins do? They interfere with opsonization, preventing immune cells from marking and binding bacteria for destruction What is the role of Protein A in Staphylococcus aureus? It binds antibodies, blocking effective opsonization What does M Protein do in Streptococcus pyogenes? -Inhibits opsonization -Blocks phagocytosis -Promotes adhesion to host cells What is mycolic acid and where is it found? A waxy cell wall component found in Mycobacterium tuberculosis How does mycolic acid help bacteria evade host defenses? -Resists digestion by phagocytes -Provides resistance to many antibiotics What is an opsonin? An immune substance (e.g., antibody or complement protein) that binds to foreign particles and marks them for destruction by phagocytes What role do opsonins play in immunity? They enhance phagocytosis by helping immune cells recognize and "eat" pathogens more efficiently What are passive microbial defenses? Structural components and heat-stable toxins that help microbes resist destruction by host defenses What is Lipid A and where is it found? A heat-stable toxin that is part of lipopolysaccharide (LPS) in Gram-negative bacteria How does Lipid A contribute to microbial defense? It resists immune destruction and can trigger strong inflammatory responses What are active defense enzymes? Enzymes that directly damage host tissues or immune cells to aid bacterial survival and spread What do leukocidins do? Kill white blood cells (e.g., neutrophils), weakening the immune response What is the function of hemolysins? Destroy red and white blood cells, release nutrients like iron, and damage host tissue How does coagulase (produced by Staphylococcus aureus) help bacteria evade immunity? Forms clots around bacteria to shield them from immune cells What do kinases do? Break down clots, allowing bacteria to spread to new tissues What is the role of hyaluronidase and collagenase? Break down connective tissue and collagen, facilitating invasion into deeper tissues and organs What are exotoxins? Secreted proteins produced by bacteria that directly damage host cells Which types of bacteria produce exotoxins? Mostly Gram-positive, but also some Gram-negative bacteria What are the characteristics of exotoxins? Extremely potent and highly specific in their action What are examples of exotoxins? Tetanus toxin, Diphtheria toxin What are the types of exotoxins and their targets? -Cytotoxins → Kill host cells (Diphtheria toxin) -Neurotoxins → Disrupt nerve function (Botulinum, Tetanus toxin) -Enterotoxins → Target intestinal lining → cause diarrhea, vomiting (Cholera toxin) What is an endotoxin? A component of the outer membrane of Gram-negative bacteria, specifically Lipid A in lipopolysaccharide (LPS) When is endotoxin released? When Gram-negative bacteria die or lyse When is LPS released from bacteria? During bacterial lysis, especially in Gram-negative bacteria How is LPS recognized by the immune system? Through TLR4 (Toll-like receptor 4) on immune cells What does LPS trigger in the immune system? An intense immune response, including a cytokine storm What are key cytokines released during a cytokine storm? TNF-α, IL-1, and IL-6 What are the clinical effects of excessive cytokine release? -High fever -Inflammation -Hypotension (low blood pressure) -Disseminated intravascular coagulation (DIC) -Organ failure (septic shock) How does LPS disrupt immune balance? It overstimulates the immune system, causing tissue damage and immune exhaustion instead of protection What is the paradoxical effect of LPS on host defenses? It doesn't evade the immune system—it overwhelms it, leading to shock and systemic harm What does ID₅₀ (Infectious Dose 50%) measure? The number of organisms required to cause disease in 50% of exposed individuals What does LD₅₀ (Lethal Dose 50%) measure? The number of organisms or amount of toxin needed to kill 50% of a test population What does a lower ID₅₀ or LD₅₀ indicate? Higher virulence—fewer organisms needed to infect or kill, making the pathogen more dangerous Why are ID₅₀ and LD₅₀ important? -They help researchers compare how infectious or deadly different microorganisms are -Guide public health responses and treatment strategies Which pathogen has a very low ID₅₀ and is highly infectious? Shigella Which pathogen requires a high infectious dose to cause disease? Salmonella What is reservoir? The natural environment where the infectious agent lives, grows, and multiples (e.g., humans, animals, environment) How do genetic factors influence susceptibility to infection? Some individuals are naturally more resistant or vulnerable due to genetic traits Example: Certain HLA types protect against chronic hepatitis B virus (HBV) What is specific immunity? Immunity gained through vaccines or past infections Example: Passive immunity from mother protects newborns (e.g., pertussis) What are nonspecific defenses? Physical and chemical barriers like skin, mucosa, stomach acid, and normal flora What happens when nonspecific defenses are disrupted? Increased risk of infection Example: Cirrhosis can lead to infections by Listeria and Vibrio What causes immunosuppression? HIV, chemotherapy, transplant drugs, etc. What is the consequence of immunosuppression? Increased risk of opportunistic and hospital-acquired infections What is meant by "mode of transmission"? The method by which a pathogen is transferred from its reservoir to a host What is direct transmission? Physical contact between individuals or with contaminated environments Examples: Hookworm via soil contact Bordetella pertussis via large respiratory droplets What are the three major types of indirect transmission? Airborne, vector-borne, and vehicle transmission What is airborne transmission? Spread via tiny particles (5 μm) that remain suspended in air Examples: Influenza, Measles What is vector transmission? Spread by living carriers like mosquitoes, ticks, or fleas Examples: Malaria, Lyme disease What is vehicle transmission? Spread through non-living objects or substances Examples: Contaminated food, water, blood products, surgical instruments What is a biological vector? A living organism in which the pathogen undergoes development or multiplication before transmission to the host Why is the biological vector essential? It plays a critical role in the pathogen's life cycle What are examples of diseases spread by biological vectors? -Malaria → Plasmodium matures in Anopheles mosquitoes -Lyme disease → Borrelia burgdorferi spread by ticks What is a mechanical vector? A living carrier that transports pathogens on its body surface without biological involvement in the pathogen's life cycle How do mechanical vectors transmit disease? By physically transferring pathogens from contaminated surfaces (e.g., feces) to food or skin What are examples of mechanical vectors? -Houseflies -Cockroaches -Pathogens: Salmonella, Shigella What are portals of exit? Routes through which pathogens leave the host to infect new individuals How do pathogens exit via the respiratory tract? Through coughing, sneezing, or talking Examples: Tuberculosis, Influenza How do pathogens exit via the gastrointestinal tract? Through feces, saliva, or vomit Examples: Vibrio cholerae, Norovirus How do pathogens exit via the genitourinary tract? Through urine, semen, or vaginal fluids Examples: Neisseria gonorrhoeae, Chlamydia trachomatis How do pathogens exit through skin or wounds? Via open lesions or cuts Example: Staphylococcus infections How do pathogens exit via blood? Through needles, transfusions, or insect bites Examples: HIV, Hepatitis B, Plasmodium (malaria) What are nosocomial infections? Infections acquired during care in a healthcare facility that were not present or incubating at the time of admission When do nosocomial infections typically occur? 48 hours or more after hospital admission What types of healthcare settings are associated with HAIs? Hospitals, ICUs, nursing homes, clinics Who is most at risk for nosocomial infections? Chemotherapy patients Surgical, burn, or transplant patients Premature and newborn infants Elderly individuals Patients with ventilators, catheters, or cannulas Why are these patients more vulnerable? -Weakened immune systems -Disrupted physical barriers -Frequent exposure to hospital flora, including multidrug-resistant organisms (MDROs) What is the most frequent type of nosocomial infection? Catheter-Associated Urinary Tract Infections (CAUTIs) What type of nosocomial infection is linked to central lines? Bloodstream infections What lower respiratory tract infection is commonly associated with ventilators? Ventilator-Associated Pneumonia (VAP) What type of nosocomial infection occurs after surgery? Surgical Site Infections (SSIs) Which gastrointestinal infection is often linked to antibiotic use? Clostridium difficile (C. diff) What are the most common pathogens causing nosocomial infections? Escherichia coli Enterococcus species Staphylococcus aureus Clostridium difficile Pseudomonas aeruginosa What is herd immunity? Population-level immunity that reduces disease spread, achieved through vaccination or natural infection How does herd immunity work? -Infectious agents need susceptible hosts to spread -High immunity interrupts transmission chains -Reduces the number of new infections Why is herd immunity important? -Protects those who cannot be vaccinated (e.g., newborns, immunocompromised) -Prevents outbreaks and epidemics -Critical for highly contagious diseases like measles What are examples of herd immunity in action? -Smallpox eradication via vaccination -Measles requires ~95% immunity to prevent outbreaks -Pertussis protection of newborns by vaccinating older children/adults What factors affect herd immunity? -Vaccination coverage and effectiveness -Population density and social behavior -Infectiousness and transmission mode of the pathogen What's the key takeaway about herd immunity? It protects entire communities and is essential for controlling and preventing infectious diseases What is an infection? An infection occurs when pathogens enter the body and begin to multiply What are the two main types of infections based on spread? -Localized: confined to one area -Systemic: spread throughout the body What defines a local infection? It affects a single organ or tissue and does not spread beyond that site What are typical symptoms of a local infection? -Redness -Swelling -Pain -Heat -Pus What are examples of local infections? -Boil -Infected cut -Strep throat What is a systemic infection? An infection that spreads throughout the body via the bloodstream or lymphatic system, affecting multiple organs or systems Why are systemic infections dangerous? They can become life-threatening if not treated promptly due to widespread inflammation and organ involvement What is sepsis? A life-threatening condition where the body's immune response to infection causes widespread inflammation, leading to tissue damage, organ failure, or death What is septic shock? A severe complication of sepsis involving dangerously low blood pressure and organ failure. It is a medical emergency What are typical symptoms of systemic infection? -Fever -Chills -Fatigue -Muscle aches -Weakness What happens during the incubation period?