MB Exam 5

• 1) Know the causative organism, nature of that organism (bacterial, viral, fungal, protozoal), general symptoms (specific disease processes are covered in later parts of the study guide) and affected tissues/organs/systems of the diseases discussed.


  Viral = common cold and influenza;

  Bacterial = strep, diphtheria, TB, whooping cough, pneumonia;

  Fungal= ciccio myces, blastiodmyces, haplasmodyces;

  Viral : rotavirus and norwalk virus;

  Bacterial :H. pylori, E.coli, Salmonella enterica/typi, cholera, C.diff;

  Protozoal = giardia
• What feature of influenza allows it to rapidly change over time? What two viral

  structures are usually involved with this change? What is the term for this change?

  What animal species are involved in this change?

  The envelope contains two spikes: hemagglutinin (H antigen) and neuraminidase (N antigen). Changes antigenicity by reassortment of segments. Affects humans, birds and pigs
• How do people die from influenza? What was unique about the influenza strain involved in the 1918 pandemic that made it so deadly?

  Robust immune response, co-infection/super infection, already have issues; it was a recombination that had never been seen before, also lots of world travel (WWI). It can lead to secondary infections with viruses or bacteria such as pneumonia. The 1918 influenza directly led to viral pneumonia with asphyxia
• Why can we get colds so many times over the course of our lifetimes? Why does rhinovirus preferentially infect the nose and eyes? What is the most likely explanation as to why rhinovirus infections more common in the winter?

  Because it has a high mutation rate (over 85 different antigens); a result of immune response; it replicates better in colder temps, more compact (people wise), the infection is able to stay suspended in the air longer, damaged/dry mucous membranes
• What are some complications of strep throat?

  Whitish coat on throat, Scarlet fever, Rheumatic fever, Septicemia
• What are the primary symptoms of diphtheria? How is diphtheria treated?

  sore throat, fever, exudative pharyngitis with thick pseudomembrane. There is a vaccine to prevent it and it is treated with antibiotics and antitoxins.
• What population does pneumonia caused by Streptococcus pneumoniae primarily affect? What structure allows these bacteria to cause pneumonia?

  The elderly, The capsule = the virulence factor
• Why do the bacteria that cause tuberculosis remain viable in the lungs for such extended periods of time?

  Because they are engulfed by the macrophages, then are able to multiply here; Once the macrophage dies, the bacteria is released and the infection is rampant
• What cell types are infected by Bordetella pertussis? What is the hallmark symptom of infection by these bacteria?

  Ciliated epithelial cells in the upper respiratory tract and kills them. A horrible cough with a whooping sound in between breaths.
• What sorts of environments are Blastomyces dermatitidis fungi found in? Where are the most blastomycosis cases in the state of Minnesota?

  Ohio and Mississippi valley, also the great lakes region including MN River valleys, Most commonly found in northern MN perhaps St. Louis County
• How are Histoplasma capsulatum and Coccidiodes immitis different in their geographical ranges? In whom are these types of fungi most likely to cause serious disease?

  Histoplasma are found in the soil of wet areas (south east) and Coccidiodes are found in the soil of dry areas (south west). It causes the most serious infection in people with compromised immune systems.
• What does stomach colonization of H. pylori predispose someone to? How are infections treated?

  Patients with H.pylori have a higher chance of stomach cancer and ulcers. Infections are treated with antibiotics, proton pump inhibitors.
• How do H. pylori survive in the low (acidic) pH of the stomach?

  They produce urease (which generates NH3 from urea) and raise the pH to less acidic levels.
• What are some negative consequences of eradication of H. pylori from the stomach?

  There is an increase in gerd (acid reflux) and esophageal cancer.
• How are strains of E. coli categorized?

  Enterotoxigenic E. coli (ETEC):

  - Traveler's diarrhea and infant diarrhea (important in developing countries); Fecal-oral route of transmission; Enterotoxin = Heat labile toxin (LT); Hypersecretion of ions and water = watery diarrhea; Small intestine

  Enterohemorrhagic E. coli (EHEC):

  - Hemorrhagic colitis, EHEC (e.g. 0157:H7) bind to large

  intestine cells, Produce verotoxin - kills intestinal cells, Copious bloody diarrhea (dysentery) without mucosal invasion or inflammation
• How do ETEC and EHEC cause their respective symptoms?

  ETEC: enterotoxin, small intestine, secretory diarrhea; EHEC: p toxin, large intestine, lysed RBC and kidney damage, dysentery
• What medication might make someone more susceptible to Salmonella infection?

  Why?

  Chronic use of antacids because they lower the stomach's acidity.
• What is used to treat Cholera infections? How does this therapy work?

  Oral rehydration therapy works by transporting glucose back into the epithelial cells of the intestine and brings sodium back into the cell by the Na-glucose cotransporter.
• When is Clostridium difficile most likely to cause diarrhea? Why?

  In the hospital; Occurs after antibiotic therapy, a lot of the good bacteria are gone, making room for c diff to grow.
• How does Giardia lamblia cause the characteristic stool composition in its infected host?

  prevents absorption of fats and carbohydrates in the intestines.
• What populations do Rotavirus and Norwalk virus target?

  Rotavirus: primarily infects infants and young children; Norwalk virus: primarily infects older children and adults
• How many coronaviruses are known to infect humans? Describe the spillover process by which MERS-CoV, SARS-CoV, and SARS-CoV-2 likely began infecting humans.

  SARS-CoV-2 first detected in Wuhan, China centered around individuals who had contact with

  seafood market in fall/early winter 2019- SARS-CoV-2 determined to cause COVID-19

  • High degree of sequence similarity to known coronaviruses in horseshoe bats, likely reservoir

  • Most likely spillover event to humans likely required intermediate host, possibly pangolin

  • This has happened before with SARS and MERS. Both outbreaks started with bats that passed virus through an

  intermediate host to humans- SARS: palm civet and MERS: dromedary cam
• Describe the basic structures of coronaviruses (genome, capsid, envelope, etc.)

  • Enveloped with large spike protein

  • Under electron microscopy, the spike proteins look like the

  corona of the sun or a crown (corona is derived from Latin

  word for crown)

  • +ssRNA genome is approximately 30,000 bases in

  length

  • 16 non-structural proteins (RdRp, proofreading protein)

  • 4 structural proteins (spike, nucleocapsid, membrane

  protein, envelope protein)

  • ~10 accessory proteins
• Describe the impact of age and pre-existing conditions on the prognosis for COVID-19.

  Age, Obesity, Type II Diabetes, Heart Disease, Smoking, Pregnancy, Cancer

  • Inequities in housing, education and criminal justice, Access to health care, Occupation, Wealth, education and health care gaps
• What is the difference between the case and infection fatality rates of COVID-19? Why is the infection fatality rate so difficult to determine?

  The main difference between the two rates lies in the denominator used for calculation. CFR uses confirmed cases, while IFR takes into account the total number of infections, including those that were never confirmed or reported. This makes the IFR lower than the CFR because it includes a larger pool of cases, many of which are asymptomatic or mild and therefore don't get counted in confirmed case numbers.
• How is COVID-19 transmitted? Why might asymptomatic infections make containment more difficult?

  Respiratory droplets from coughing, nasal secretions that reach nose, mouth, eyes

  • Aerosols dried respiratory droplets (droplet nuclei) and other small particles from speaking,

  ventilating

  • Fomites (contaminated surfaces)=less important route

  • Asymptomatic and presymptomatic infections play major role in transmission

  • People are likely at their most infectious state 1-2 days before showing symptoms

  • This has been primary issue in controlling spread-not seen with SARS or MERS

  • It's estimated over 70% of US population has been infected, including 80% of children
• How/why do new variants arise?

  New variants of viruses like SARS-CoV-2, the virus that causes COVID-19, arise through a process called mutation. Natural selection, Environmental factors, such as changes in host immunity due to vaccination or previous infection, Immune evasion
• What are case-control studies? When are they used?

  They are used to interview infected and non infected people to see what the common link of the disease is
• What is herd immunity?

  Herd immunity: Prevention of epidemics due to scarcity of susceptible hosts (non-vaccinated/non-immune are protected by those who are vaccinated/immune)