VBS 2032 EXAM 3 QUESTIONS WITH CORRECT ANSWERS LATEST UPDATE 2026

VBS 2032 EXAM 3 QUESTIONS WITH CORRECT ANSWERS LATEST UPDATE 2026 Active immunity - Answers when body produces its own immune response and memory cells (long lasting, slower) Passive immunity - Answers when antibodies are received from another source (short term, fast, no memory) Variolation - Answers early method of immunization using live smallpox virus from infected individuals to induce a mild infection and immunity How does variolation differ from smallpox vaccination? - Answers variolation uses the actual smallpox virus and is risky, while vaccination uses a safer related virus (cowpox) to provide immunity without causing severe disease Who discovered the smallpox vaccine? - Answers Edward Jenner Attenuated vaccine - Answers vaccine composed of a weakened form of the pathogen that is unable to cause disease Example of a combination attenuated vaccine - Answers MMR vaccine (measles, mumps, rubella) rVSV-ZEBOV Ebola vaccine - Answers recombinant vaccine that uses vesicular stomatitis virus engineered to express an Ebola virus protein, triggering an immune response without causing Ebola Toxoid vaccine - Answers vaccine made from an inactivated toxin that stimulates immunity against the toxin rather than the pathogen itself Example of toxoid vaccine - Answers tetanus Inactivated polio vaccine (IPO) - Answers injected, contains killed virus, and is very safe but provides less gut immunity Oral polio vaccine (OPV) - Answers taken orally, contains live attenuated virus, and provides strong intestinal immunity When wild poliovirus is circulating, which vaccine is preferred? - Answers OPV, because it provides strong intestinal immunity and helps stop transmission What is a risk of the oral polio vaccine (OPV)? - Answers it can rarely mutate back to a virulent form and cause vaccine-derived polio Why can't immunocompromised individuals receive attenuated vaccines? - Answers their immune systems may not control even the weakened pathogen, leading to disease Can pregnant women receive attenuated vaccines? - Answers no, because of potential risk to the fetus Why are boosters necessary for subunit vaccines? - Answers subunit vaccines produce a weaker immune response, so boosters are needed to maintain immunity and memory Why are adjuvants sometimes necessary in vaccines? - Answers they enhance the immune response, making the vaccine more effective Why does the conjugate Hib vaccine work better than a polysaccharide-only vaccine? - Answers conjugation to a protein allows T-cell involvement, leading to stronger and longer-lasting immunity, especially in children How does an RNA vaccine work? - Answers it delivers mRNA into cells, which then produce a viral protein that triggers an immune response and memory formation What are advantages of RNA vaccines? - Answers rapid development, no live virus needed, strong immune response, and safe for immunocompromised individuals What types of COVID-19 vaccines have been developed? - Answers mRNA vaccines, viral vector (adenovirus-based) vaccines, protein subunit vaccines, and inactivated virus vaccines How do clinical trial phases differ? - Answers phase 1 tests safety (small group), phase 2 tests effectiveness and dosing (hundreds), phase 3 tests large-scale efficacy and safety (thousands) Why are preclinical trials necessary? - Answers to test safety and immune response in cells and animals before human trials How do RNA COVID-19 vaccines stimulate immunity? - Answers mRNA enters cells, cells produce viral proteins, immune system responds, and memory cells form How do adenovirus-based COVID-19 vaccines stimulate immunity? - Answers a modified virus delivers DNA for a viral protein into cells, which produce the protein and trigger an immune response with memory How are antibiotics administered to livestock like chickens and turkeys? - Answers they are commonly given through feed or drinking water, and less commonly by injection How can antibiotics given to people, pets, or livestock circulate in the environment? - Answers through waste (urine/feces), runoff into water systems, contamination of soil, improper disposal of medications, and spread via food products How can antibiotic resistance spread within a healthcare system? - Answers through contaminated surfaces, medical equipment, healthcare workers, and patient-to-patient transmission How can antibiotic resistance spread between people? - Answers through direct contact, respiratory droplets, poor hygiene, and shared environments How can antibiotic resistance spread between bacteria? - Answers through horizontal gene transfer (conjugation, transformation, transduction), often via plasmids How did the Veterinary Feed Directive (2017) change antibiotic use in livestock in the US? - Answers it required veterinary oversight and eliminated the use of medically important antibiotics for growth promotion Does reducing antibiotic usage always reduce antibiotic resistance? Why or why not? - Answers no, because resistance genes can persist in bacteria, spread through horizontal gene transfer, and be maintained even without antibiotic pressure What is a non-medically important antibiotic? - Answers an antibiotic not used in human medicine What is a medically important antibiotic? - Answers an antibiotic used to treat human infections What is a critically important antibiotic? - Answers a medically important antibiotic that is essential for treating serious or life-threatening human infections Why did virginiamycin use decline while bambermycin increased in turkey production ()? - Answers virginiamycin is medically important to humans, so its use was restricted; bambermycin is not medically important, so it became a substitute What is co-selection involving bacterial plasmids? - Answers when one selective pressure (like disinfectant) selects for plasmids carrying multiple resistance genes, maintaining resistance to both disinfectants and antibiotics When one selective pressure (like disinfectant) selects for plasmids carrying multiple resistance genes, maintaining resistance to both disinfectants and antibiotics. - Answers because resistance genes for disinfectants and antibiotics can be linked on the same plasmid, so selecting for one also selects for the other What does APEC stand for? - Answers Avian Pathogenic Escherichia coli What does ExPEC stand for? - Answers Extraintestinal Pathogenic Escherichia coli What does FUTI stand for? - Answers Foodborne Urinary Tract Infection What are COPs? - Answers coliforms of poultry origin (E. coli strains originating from poultry) How can a foodborne E. coli cause a UTI? - Answers by being ingested, colonizing the gut, then spreading to the urinary tract (often via the fecal-urethral route) What is the evidence that some UTIs are caused by E. coli from food? - Answers genetic similarities between E. coli strains from retail meat and human UTI infections suggest a shared source How do recent Salmonella Reading strains differ from older strains? - Answers newer strains often have increased virulence and antibiotic resistance, making them more likely to cause serious disease in humans Acute infection - Answers comes on rapidly, with severe but short-lived effects Chronic infection - Answers develops slowly and lasts for months or years Colonization - Answers establishment and growth of a microorganism on a surface Endotoxin - Answers a toxin that is present inside a bacterial cell and is released when the cell disintegrates Exotoxin - Answers toxic protein produced by a microorganism (simply called toxin) Immunocompromised - Answers having an impaired immune system Infection - Answers invasion by a pathogen on or within the body Infectious disease - Answers infection that prevent body from functioning normally Latent infection - Answers infection in which the infectious agent is present but not causing symptoms Microbiome - Answers the microorganisms in a particular environment Normal microbiota - Answers group of microorganisms that routinely colonize the body of a healthy individual Opportunistic pathogen - Answers disease in immunocompromised individuals (ex. wound) Primary pathogen - Answers disease in healthy individuals Virulence factors - Answers traits that allow pathogens to cause disease and increase their ability to infect and damage the host Times pathogenic microoganisms don't cause disease - Answers - no portal of entry - physical and chemical barriers (ex. lysozyme) - protection by normal microbiota - host receptor not present - innate immunity - acquired immunity Symptom - Answers change in body function that is felt by a patient as a result of disease (ex. pain) Sign - Answers objective evidence of disease (ex. fever) Primary infection - Answers initial infection in a host caused directly by a pathogen (ex. the flu) Secondary infection - Answers infection that occurs after primary, because immune system is weakened or normal defenses are disrupted (ex. developing bacterial pneumonia after the flu) Dysbiosis - Answers microbial imbalance Examples of virulence factors - Answers - toxins - adhesins - bacterial fimbriae (pili) - extracellular enzymes - capsule or slime layer - flagella - conversion to intracellular pathogens - avoidance of immune system Antigenic variation - Answers changes in surface antigens that occur in a microbial population (ex. HIV, influenza) Leukocidins - Answers destroy white blood cells IgA proteases - Answers destroy IgA antibodies Elastase - Answers inactivates complement proteins Long polysaccharide chains in LPS - Answers prevent MAC insertion into membrane 4 phases of infectious disease - Answers 1. incubation period 2. prodromal period 3. period of illness (symptomatic) 4. convalescent period (non diseased) (disability or death) Why isn't Lyme disease contagious? - Answers because it requires transmission through a vector (tick bite) and cannot spread directly from person to person Example of a non-contagious disease - Answers tetanus (caused by bacteria in the environment, not spread between people) What factors influence host immunity? - Answers age, genetics, nutrition, stress, underlying diseases, medications, and overall health How does Mycobacterium tuberculosis evade the immune system? - Answers by surviving inside macrophages and preventing destruction after phagocytosis How do some bacteria evade the complement system? - Answers by having capsules, producing proteins that inactivate complement, or preventing complement activation How does the prodromal period differ from the symptomatic period? - Answers prodromal period has mild, nonspecific symptoms, while the symptomatic period has clear, severe disease symptoms Can someone with a latent infection transmit the disease? - Answers usually no, but some latent infections can reactivate and become transmissible How does normal microbiota protect us from disease? - Answers by competing for nutrients/space, producing antimicrobial substances, and stimulating the immune system Koch's postulates - Answers set of rules for proving that a microorganism causes a specific disease Epidemiological triad - Answers host, agent, environment Epidemiology - Answers study of the distribution and causes of disease in populations Microbial intoxication - Answers toxin is ingested (ex. food poisoning) Microbial infection - Answers the bacterium multiplies in the body (ex. skin infection) Chain of infection - Answers infectious agent, reservoir, portal of exit, mode of transmission, portal of entry, susceptible host Direct transmission - Answers sneeze, cough, handshake, sexual contact Indirect transmission - Answers airborne, food, water Biological vector - Answers actively participates in a pathogen's life cycle Mechanical vector - Answers not important and just carries pathogen Herd immunity - Answers immunity in most of a population Endemic - Answers constantly present in a population (ex. a cold in MN) Incidence - Answers number of new cases in a given population (ex. 375 cases/100,000 people in MN) Basic reproductive number (R0) - Answers the average number of secondary cases that develop from a single case Effective reproductive number (R) - Answers how many cases an infected person will cause in a population with some immunity What types of virulence factors help pathogens spread, evade immunity, or cause damage? - Answers adhesins (attach to cells), enzymes (spread through tissues), capsules (avoid phagocytosis), toxins (damage host cells), antigenic variation (evade immune detection) If you only stay home during the symptomatic phase, will you avoid infecting others? - Answers no, because many infections are contagious during the incubation or prodromal period before symptoms appear What is the difference between an asymptomatic carrier and a latent infection? - Answers an asymptomatic carrier has an active infection without symptoms and can transmit it; a latent infection is inactive/dormant and typically not transmissible Fomite - Answers an inanimate object that can transmit pathogens (ex. doorknobs, phones) When can Koch's postulates not be satisfied? - Answers when pathogens cannot be cultured, cause disease only in humans, require specific conditions, or involve multiple pathogens (e.g., viruses, asymptomatic carriers) How did Zimbler et al. show that a mutated pla increased virulence in Yersinia pestis? - Answers by comparing strains with and without the mutation and showing the mutated version caused more severe disease in experimental models What virulence factor allows Yersinia pestis to live in fleas and how does it affect transmission? - Answers biofilm formation blocks the flea's gut, causing it to regurgitate bacteria into the host during feeding, increasing transmission What factors influence R0 and R? - Answers transmission rate, contact rate, duration of infectiousness, immunity levels, and public health measures How does R₀ influence vaccination strategies? - Answers higher R0 requires a higher percentage of the population to be vaccinated to achieve herd immunity Outbreak - Answers sudden rise in the incidence of a disease What category of food is the most common source of foodborne illness? - Answers produce (especially leafy greens and fruits) What is the most common cause of foodborne illness? - Answers viruses, especially norovirus What bacteria cause the most serious forms of foodborne illness? - Answers bacteria like E. coli, Salmonella, and Listeria monocytogenes. What kinds of foods does the FDA inspect? - Answers most foods, including produce, seafood, dairy, and packaged foods. What kinds of foods does the USDA-FSIS inspect? - Answers meat, poultry, and processed egg products Outbreak strain - Answers specific genetic variant of a pathogen linked to a particular outbreak How does "outbreak strain" differ from "strain"? - Answers a strain is any genetic variant of a microorganism, while an outbreak strain is specifically associated with a disease outbreak How is a foodborne illness outbreak generally investigated? - Answers by identifying cases, interviewing patients, tracing food sources, testing samples, and comparing pathogen strains using lab methods O antigens - Answers components of the outer membrane (lipopolysaccharide) of Gram-negative bacteria H antigens - Answers flagellar proteins involved in bacterial motility K antigens - Answers capsule polysaccharides that help bacteria evade the immune system Which method has the highest resolution for distinguishing between strains? - Answers whole genome sequencing (WGS) Which method has medium resolution for distinguishing between strains? - Answers pulsed-field gel electrophoresis (PFGE) Which method has the lowest resolution for distinguishing between strains? - Answers antigenic typing What type of selective and differential liquid media was used in the enrichment technique with the chicken drumsticks? What does this media select for? - Answers - selects for Gram-negative enterics - differentiates based on lactose fermentation (pink colonies) What does this media select for? - Answers salmonella What appearance do you predict each bag will have after incubation? - Answers the media may become slightly turbid due to bacterial growth; selective broths often show slight cloudiness but not distinct colonies like on plates What temperature was used for incubation? Why? - Answers around 37°C (human body temperature) because Salmonella grows optimally at this temperature Why won't we be able to calculate the original number of microbes present on our chicken (CFU/ml) after performing an enrichment culture? - Answers because enrichment selectively allows certain bacteria to multiply, which changes their original proportion and number. It amplifies target bacteria rather than preserving the original counts Emerging infectious disease (EID) - Answers a new or changing disease that is increasing or has the potential to increase in incidence in the near future 4 types of EIDs - Answers newly emerging, re-emerging, diseases spreading to new geographic area, diseases evolving new traits Newly emerging diseases - Answers COVID 19: it was previously unknown before 2019 and spread rapidly worldwide Re-emerging diseases - Answers tuberculosis: it existed before but is increasing again due to drug resistance and healthcare gaps Diseases spreading to new geographic areas - Answers zika virus: it spread from Africa/Asia to the Americas Diseases evolving new traits - Answers MRSA: it evolved antibiotic resistance, making it harder to treat What is the most common cause of EIDs? - Answers zoonotic transmission (animal to human) Zoonosis vs EID - Answers zoonosis: disease that spreads from animal to human EID: broader and can be zoonotic or arise in other ways many EIDs are zoonotic but not all Reverse zoonosis - Answers when humans infect animals Why is SARS-CoV-2 considered an "EID of probable animal origin"? - Answers SARS-CoV-2 is considered: - emerging → new disease in humans - probable animal origin → genetically similar to coronaviruses in bats - likely passed through an intermediate animal host before humans What causes "spillover" events? - Answers spillover happens when a pathogen jumps from animals to humans. causes: - increased human-animal contact - habitat destruction - wildlife trade - viral mutations that allow human infection Natural host - Answers - organism where the pathogen normally lives and reproduces - usually doesn't get sick Transmission host - Answers - passes pathogen to humans - may or may not get sick SARS disease - Answers natural host: bats transmission host: civets why EID: newly emerged in humans in 2002 MERS - Answers natural host: bats transmission host: camels why EID: newly emerged in humans in 2012 Why do bats carry many viruses without getting sick - Answers - strong immune systems - unique antiviral defenses - high body temperature during flight (like a fever)