Bacteria — MCQs

Fluorescein is an artificial dark orange colored organic molecule used in the diagnosis of corneal ulcers and herpetic corneal infections. It is observed that, in experimental animals, the fluorescein binds to receptors on certain B cells, but it does not stimulate them to produce fluorescein specific antibodies unless it is first attached to a larger molecule such as albumin. Which of the following terms best describes fluorescein?

A 24-year-old college student consumed a container of canned vegetables for dinner. Fourteen hours later, he presents to the E.R. complaining of difficulty swallowing and double-vision. The bacterium leading to these symptoms is:

A 25-year-old professional surfer presents to the emergency room with leg pain and a headache. He recently returned from a surf competition in Hawaii and has been feeling unwell for several days. He regularly smokes marijuana and drinks 6-7 beers during the weekend. He is otherwise healthy and does not take any medications. His temperature is 102.2°F (39°C), blood pressure is 121/78 mmHg, pulse is 120/min, and respirations are 18/min saturating 99% on room air. He is sitting in a dim room as the lights bother his eyes and you notice scleral icterus on physical exam. Cardiopulmonary exam is unremarkable. Which of the following findings would most likely be seen in this patient?

A 17-year-old girl is brought to the emergency department by her father with fever, chills, and a body rash. Her father reports that 3 days ago, his daughter underwent surgery for a deviated nasal septum. Since then, she has been "sleepy" and in moderate pain. When the patient’s father came home from work today, he found the patient on the couch, shivering and complaining of muscle aches. He also noticed a rash all over her body. The patient says she feels “hot and cold” and also complains of lightheadedness. The patient has no other past medical history. She has been taking oxycodone for the post-surgical pain. She denies any recent travel. The father reports the patient’s brother had a minor “cold” last week. The patient’s mother has major depressive disorder. The patient denies tobacco or illicit drug use. She says she has tried beer before at parties. Her temperature is 103.2°F (39.6°C), blood pressure is 84/53, pulse is 115/min, respirations are 12/min, and oxygen saturation is 99% on room air. The patient is awake and oriented but slow to respond. There is no focal weakness or nuchal rigidity. Physical examination reveals nasal packing in both nostrils, tachycardia, and a diffuse, pink, macular rash that is also present on the palms and soles. Initial labs show a neutrophil-dominant elevation in leukocytes, a creatinine of 2.1 mg/dL, an aspartate aminotransferase of 82 U/L, and an alanine aminotransferase of 89 U/L. Which of the following is the most likely cause of the patient’s symptoms?

A 45-year-old man comes to the emergency department because of chills and numerous skin lesions for 1 week. He has also had watery diarrhea, nausea, and abdominal pain for the past 2 weeks. The skin lesions are nonpruritic and painless. He was diagnosed with HIV infection approximately 20 years ago. He has not taken any medications for over 5 years. He sleeps in homeless shelters and parks. Vital signs are within normal limits. Examination shows several bright red, friable nodules on his face, trunk, extremities. The liver is palpated 3 cm below the right costal margin. His CD4+ T-lymphocyte count is 180/mm3 (N ≥ 500). A rapid plasma reagin test is negative. Abdominal ultrasonography shows hepatomegaly and a single intrahepatic 1.0 x 1.2-cm hypodense lesion. Biopsy of a skin lesion shows vascular proliferation and abundant neutrophils. Which of the following is the most likely causal organism?

Two days after hospital admission and surgical treatment for a cut on his right thigh from a sickle, a 35-year-old man has fever, chills, and intense pain. The wound is swollen. He had a similar injury 4 months ago that resolved following treatment with bacitracin ointment and daily dressings. He works on a farm on the outskirts of the city. He appears anxious. His temperature is 38.5°C (101.3°F), pulse is 103/min, and blood pressure is 114/76 mm Hg. Examination shows a 6-cm edematous deep, foul-smelling wound on the medial surface of the right thigh. The skin over the thigh appears darker than the skin on the lower leg. There are multiple blisters around the wound. Light palpation around the wound causes severe pain; crepitus is present. Which of the following is the most likely causal organism?

A 10-year-old boy from Sri Lanka suffers from an autosomal dominant condition, the hallmark of which is hyperimmunoglobulinemia E and eosinophilia. He suffers from recurrent infections and takes antibiotic chemoprophylaxis. A STAT3 mutation analysis has been performed to confirm the diagnosis of Job syndrome. I. Eosinophilia II. Eczema III. Hay fever IV. Atopic dermatitis V. Recurrent skin and lung infections VI. Bronchial asthma What combination of symptoms above is characteristic of this condition?

A 33-year-old woman presents to the urgent care center with 4 days of abdominal pain and increasingly frequent bloody diarrhea. She states that she is currently having 6 episodes of moderate volume diarrhea per day with streaks of blood mixed in. Her vital signs include: blood pressure 121/81 mm Hg, heart rate 77/min, and respiratory rate 15/min. Physical examination is largely negative. Given the following options, which is the most likely pathogen responsible for her presentation?

An investigator studying mechanisms of acquired antibiotic resistance in bacteria conducts a study using isolated strains of Escherichia coli and Staphylococcus aureus. The E. coli strain harbors plasmid pRK212.1, which conveys resistance to kanamycin. The S. aureus strain is susceptible to kanamycin. Both bacterial strains are mixed in a liquid growth medium containing deoxyribonuclease. After incubation for 2 days and subsequent transfer to a solid medium, the S. aureus colonies show no lysis in response to the application of kanamycin. Analysis of chromosomal DNA from the kanamycin-resistant S. aureus strain does not reveal the kanamycin-resistance gene. Which of the following mechanisms is most likely responsible for this finding?

A 55-year-old homeless man is presented to the emergency department by a group of volunteers after they found him coughing up blood during 1 of the beneficiary dinners they offer every week. His medical history is unknown as he recently immigrated from Bangladesh. He says that he has been coughing constantly for the past 3 months with occasional blood in his sputum. He also sweats a lot at nights and for the past 2 days, he has been thirsty with increased frequency of urination and feeling hungrier than usual. The respiratory rate is 30/min and the temperature is 38.6°C (101.5°F). He looks emaciated and has a fruity smell to his breath. The breath sounds are reduced over the apex of the right lung. The remainder of the physical exam is unremarkable. Biochemical tests are ordered, including a hemoglobin A1c (HbA1c) (8.5%) and chest radiography reveals cavitations in the apical region of the right lung. Which of the following immune cells is most critical in orchestrating the formation and maintenance of the granulomatous structure that led to these cavitations?