Module 3 Infection And Immunity

Question 1

You are asked to see a 19 year old girl who became intoxicated at a party and had unprotected sex with a man she did not know. She is concerned about contracting a sexually transmitted disease especially HIV. Which one of the following changes in her blood will occur if she has contracted HIV?

Answer 1

Decrease in CD4+ T helper cells

Question 2

During a rotation at a wound care clinic, one of your patients is interested in learning more about the healing process. He is recovering from a severe leg laceration sustained in an ATV accident. He has been reading on the Internet about healing and asks you about the role of macrophages. He understands that they have a primary role in the initial response to infections but can’t remember how the body develops macrophages. You tell him that they originate from which of the following cells?

Answer 2

Monocytes

Macrophages are formed through the differentiation of monocytes, one of the major groups of white blood cells of the immune system. When there is tissue damage or infection, the monocytes leave the bloodstream and enter the affected tissue or organ and undergo a series of changes to become macrophages

Question 3

During your endocrinology rotation, you are asked to see a patient recently diagnosed with rheumatoid arthritis. As you are heading in to see her, you recall that rheumatoid arthritis involves the formation of immune complexes and represents which one of the following types of hypersensitivity reactions?

Answer 3

Type III hypersensitivity reaction

Type III hypersensitivity occurs when there is an accumulation of immune complexes (an excess of antigen-antibody complexes) that have not been adequately cleared by innate immune cells, giving rise to an inflammatory response and attraction of leukocytes. Such reactions may progress to immune complex diseases

Question 4

A 38-year-old male presents to your clinic, with persistent abdominal pain. This pain has a burning quality, is located in his epigastric area, and worsens approximately 15-30 minutes after eating. He has had the pain on and off for over three months. Antacids do not help. He works as an accountant and has been under considerable stress recently. You suspect peptic ulcer disease and test him for Helicobacter pylori. The test comes back positive. Which one of the following toxins is associated with H. pylori?

Answer 4

Urease

The ulcer-causing gastric pathogen Helicobacter pylori is the only bacterium known to colonize the harsh acidic environment of the human stomach. H. pylori survives in acidic conditions by producing urease, which catalyzes hydrolysis of urea to yield ammonia thus elevating the pH of its environment.

Question 5

During your immunology rotation, you see a patient who was recently diagnosed with chronic granulomatous disease. You realize that this condition can lead to immunodeficiency through which one of the following processes?

Answer 5

Neutropenia (low number of neutrophils in the blood)

Chronic granulomatous disease (CGD) is a rare inherited primary immune deficiency disorder that affects certain white blood cells (neutrophils, monocytes, macrophages, eosinophils). The disorder is characterized by an inability to resist infections caused by certain types of bacteria and fungal species and a tendency to develop chronic inflammation

Question 6

During a talk you are giving to high school students on allergic reactions, you explain that there are a number of types of hypersensitivity reactions. The most commonly known, immediate allergic reaction, where free antigens cross link the IgE on mast cells and basophils, is which one of the reactions?

Answer 6

Type I hypersensitivity reaction (an allergic reaction)

In type 1 hypersensitivity, B-cells are stimulated (by CD4+TH2 cells) to produce IgE antibodies specific to an antigen. The difference between a normal infectious immune response and a type 1 hypersensitivity response is that in type 1 hypersensitivity, the antibody is IgE instead of IgA, IgG, or IgM.

Question 7

While vacationing in a tropical country, you develop diarrhea, which is accompanied by nausea and vomiting. You suspect you ingested an organism from the drinking water. What is the most likely organism causing your illness?

Answer 7

Escherichia Coli

Question 8

You have just finished assessing a patient who presented to the ER; the patient has a high fever, cough, and shortness of breath. You suspect a bacterial pneumonia and have sent him for blood work and a chest X-ray. If you are correct, you are expecting to see an elevation in his white blood cell count. This elevation would be primarily due to an elevation of which one of the following?

Answer 8

Neutrophils

Question 9

During a case discussion with your peers on autoimmune disorders, you are told about a patient with a chronic inflammatory disorder that is characterized by a butterfly rash on the cheeks and nose, arthralgias and polyarthritis, and glomerulonephritis. Before you are told about some of the other ailments that can be associated with this condition, you recognize it as a case of:

Answer 9

Systemic lupus erythematosus

Question 10

A 23-year-old female presents to your clinic, with a three-day history of fever, chills, malaise, and generalized body aches. Initially, she had a slight runny nose and was coughing, but her symptoms have since rapidly progressed to involve fever and chills. On examination, her temperature is 102.3° F (39° C), and she is tachycardic. Her oral pharynx is slightly erythematous and without exudate. Her lungs are clear to auscultation. Her periphery is cool, but pulses and capillary refill are adequate. What is the most likely diagnosis in this case?

Answer 10

Influenza

Question 11

A 23-year-old female presents to your clinic, with a three-day history of fever, chills, malaise, and generalized body aches. Initially, she had a slight runny nose and was coughing, but her symptoms have since rapidly progressed to involve fever and chills. On examination, her temperature is 102.3° F (39° C), and she is tachycardic. Her oral pharynx is slightly erythematous and without exudate. Her lungs are clear to auscultation. Her periphery is cool, but her pulse and capillary refill are adequate. You suspect influenza. The best method for confirming this diagnosis is:

Answer 11

Antigen detection

Question 12

While vacationing in a tropical country, you develop diarrhea, which is accompanied by nausea and vomiting. You suspect that you ingested an organism from the drinking water. You are having three to five loose bowel motions per day and two to three episodes of vomiting your stomach contents per day. You are able to keep small amounts of fluid down. What is the best initial treatment for your condition?

Answer 12

Adequate fluid hydration

Question 13

While on a locum, you are asked to see a man who became sick five days ago after returning home from a week-long hiking trip. He initially developed nausea and vomiting but has now developed a fever, maculopapular rash with some petechiae, and increasing abdominal pain. He reports that he was bitten by a tick while on his hike. You are concerned that he may have Rocky Mountain spotted fever. This is a condition involving which one of the following organisms?

Answer 13

Gram negative bacteria

Rocky Mountain spotted fever (RMSF) is a bacterial disease spread by ticks. It typically begins with a fever and headache, which is followed a few days later with the development of a rash.

Question 14

During a talk about infectious disease that you are giving to a local high school class, a student asks what a nosocomial infection is. Which one of the following is the correct answer?

Answer 14

Infections spread in healthcare facilities

Question 15

A 38-year-old male presents to your clinic, with persistent abdominal pain. This pain has a burning quality, is located in his epigastric area, and worsens approximately 15-30 minutes after eating. He has had the pain on and off for over three months. Antacids do not help. He works as an accountant and has been under considerable stress recently. You suspect peptic ulcer disease and test him for Helicobacter pylori. The test comes back positive. Which of the following is the best treatment for H. pylori?

Answer 15

Omeprazole, amoxicillin and clarithromycin

Question 16

You have applied for a position in a new hospital and are required to take a Mantoux skin test for tuberculosis. You realize that this test, when positive, represents which one of the following types of hypersensitivity reactions?

Answer 16

Type IV hypersensitivity reaction

Type IV hypersensitivity is often called delayed type hypersensitivity as the reaction takes several days to develop.[1] Unlike the other types, it is not antibody-mediated but rather is a type of cell-mediated response. This response involves the interaction of T-cells, monocytes, and macrophages

Question 17

A 23-year-old female presents to your clinic, with a three-day history of fever, chills, malaise, and generalized body aches. Initially, she had a slight runny nose and was coughing initially, but her symptoms have since rapidly progressed to involve fever and chills. On examination, her temperature is 102.3° F (39° C), and she is tachycardic. Her oral pharynx is slightly erythematous and without exudate. Her lungs are clear to auscultation. Her periphery is cool, but her pulse and capillary refill are adequate. You confirm influenza B. The best treatment for this condition is:

Answer 17

Supportive therapy

Question 18

You have just finished assessing a patient who presented to the ER; the patient has a high fever, cough, malaise, and body aches. You suspect that he has the flu, but want to rule out a more serious concern, so you have sent him for blood work and a chest X-ray. If you are correct and this patient has a significant viral infection, you are expecting to see an elevation in his white blood cell count. This elevation would be primarily due to an elevation of which one of the following?

Answer 18

Lymphocytes

Question 19

During grand rounds at the hospital, you hear about an unusual case of Creutzfeldt-Jakob disease. Which one of the following organisms is involved in the initial infection in this condition?

Answer 19

Prion

Creutzfeldt–Jakob disease (CJD), also known as subacute spongiform encephalopathy or neurocognitive disorder due to prion disease, is a fatal degenerative brain disorder.

CJD is caused by a protein known as a prion. Infectious prions are misfolded proteins that can cause normally folded proteins to become misfolded. About 85% of cases occur for unknown reasons, while about 7.5% of cases are inherited from a person’s parents in an autosomal dominant manner

Question 20

While vacationing in a tropical country, you develop diarrhea, which is accompanied by nausea and vomiting. You suspect that you ingested an organism from the drinking water. For this to have happened, the organism would have had to get past the primary defense in the stomach. Which one of the following is this primary defense?

Answer 20

Hydrochloric acid

Question 21

During your immunology rotation, you meet a 19-year-old male patient who has HIV. He is interested in learning more about the immune system and has been reading on the Internet. He says that the information is confusing, and asks you where T-lymphocytes come from. You explain that they arise from stem cells but differentiate into T-lymphocytes in-which of the following organs?

Answer 21

Thymus

Question 22

During your hematology rotation, you see a patient who was recently diagnosed with sickle cell disease. You realize that this condition can lead to immunodeficiency through which one of the following processes:

Answer 22

Asplenia

Asplenia refers to the absence of normal spleen function and is associated with some serious infection risks.

The most frequent cause of autosplenectomy is sickle cell anemia which causes progressive splenic hypofunction over time. Increased deoxygenation causes sickling of red blood cells, which adhere to the spleen wall and splenic macrophages causing ischemia.

Question 23

While working in a pediatric clinic, you are asked to see a 2-month old infant born at 39 weeks’ gestation to an HIV-positive mother. Serology testing during this visit includes positive test results, using ELISA, Western Blot, and viral culture. Based on these findings, what is the best description of the infant’s HIV status?

Answer 23

HIV positive

Question 24

As you prepare for a medical mission trip to a third-world nation, you review various causes of dysentery. As you read about Entamoeba histolytica, you are reminded that it represents which one of the following types of organisms?

Answer 24

Protozoa

Dysentery: infection of the intestines resulting in severe diarrhea with the presence of blood and mucus in the feces.

Entamoeba histolytica is an anaerobic parasitic amoebozoan, part of the genus Entamoeba. Predominantly infecting humans and other primates causing amoebiasis.

Question 25

During your ICU rotation, you admit a 46-year-old man who has a severe head injury, following a motor vehicle accident. He is placed on a mechanical ventilator to support respiration. On the eighth day post-admission, he develops a fever, his ventilator requirements change, and an X-ray reveals evidence of pneumonia. You get blood and lower respiratory secretion samples for culture and begin empirical antibiotic therapy. Which one of the following is the most likely organism causing the pneumonia?

Answer 25

Klebsiella pneumoniae** I think

Question 26

During a talk you are giving to high school students on allergic reactions, you explain the role of histamine. You explain how histamine is released from which of the following cells?

Answer 26

Mast Cells

Question 27

During a case discussion on autoimmune disorders with your peers, you are told about a 10-year-old patient who, a few weeks after having a sore throat, developed a fever, pain in his hips and knees, and a rash that began on his trunk and disseminated outwards. Before you are told about some of the other ailments that can be associated with this condition, you recognize it as a case of:

Answer 27

Rheumatic fever

Question 28

During your neonatal rotation you notice a whitish material in an infant’s mouth. You gently scrape it with a wooden spatula, but it does not come off. You realize this is most likely an infection of candida albicans. This organism is best described as a:

Answer 28

Fungus

Question 29

A 23-year-old male comes to your clinic, complaining of cough and chest pain. His cough has been intermittent but progressive over the past six days. The chest pain is sharp and associated with coughing. He denies shortness of breath, but thinks he may have a low grade fever. After a thorough history and physical examination, you are concerned he may have atypical (“walking”) pneumonia. The chest x-ray is consistent with right lower lobe pneumonia. Culture reveals small organisms that have no cell wall and are therefore in multiple different shapes. The most likely infecting organism is:

Answer 29

Mycoplasma pneumonia

Most common cause of atypical pneumonia in adults

Question 30

In your clinic, you see a patient whom you diagnosed with walking pneumonia two weeks ago. At that time, you prescribed a 10-day course of antibiotics. The patient reports that he felt much better after two or three days and was back to his normal health by day five, after which he stopped his antibiotics, as they had been nauseating him. He now complains that he has had a fever and worsening cough over the past 36 hours. Of the following, which one has most likely contributed to this patient’s recent worsening symptoms?

Answer 30

Discontinuance of his prescription