Bacteria — MCQs

A 51-year-old man presents complaining of decreased vibratory sense in his lower limbs. Physical exam reveals a widened pulse pressure and a decrescendo murmur occurring after the S2 heart sound. After further questioning, he also reports he experienced a maculopapular rash over his trunk, palms and soles many years ago that resolved on its own. In order to evaluate the suspected diagnosis, the physician FIRST tested for which of the following?

A 55-year-old man presents to the physician with complaints of 5 days of watery diarrhea, fever, and bloating. He has not noticed any blood in his stool. He states that his diet has not changed recently, and his family has been spared from diarrhea symptoms despite eating the same foods that he has been cooking at home. He has no history of recent travel outside the United States. His only medication is high-dose omeprazole, which he has been taking daily for the past few months to alleviate his gastroesophageal reflux disease (GERD). Which of the following is the most appropriate initial test to work up this patient’s symptoms?

An 81-year-old man comes to the emergency department with severe left ear pain and drainage for 3 days. He has a history of poorly-controlled type 2 diabetes mellitus. He appears uncomfortable. Physical examination of the ear shows marked periauricular erythema, exquisite tenderness on palpation, and granulation tissue in the external auditory canal. The most likely causal pathogen produces an exotoxin that acts by a mechanism most similar to a toxin produced by which of the following organisms?

A 33-year-old woman comes to the emergency department because of a 3-day history of lower abdominal pain and severe burning with urination. Two years ago, she was diagnosed with cervical cancer and was successfully treated with a combination of radiation and chemotherapy. She has systemic lupus erythematosus and finished a course of cyclophosphamide 3 weeks ago. She is sexually active with multiple male and female partners and uses a diaphragm for contraception. She has smoked two packs of cigarettes daily for 12 years. Current medication includes hydroxychloroquine. Her temperature is 36.6°C (97.9°F), pulse is 84/min, and blood pressure is 136/84 mm Hg. The abdomen is soft and there is tenderness to palpation over the pelvic region. Laboratory studies show: Hemoglobin 13.1 g/dL Leukocyte count 7,400/mm3 Platelet count 210,000/mm3 Urine pH 7 WBC 62/hpf RBC 12/hpf Protein negative Nitrites positive Which of the following is the most likely underlying mechanism of this patient's condition?

An 11-year-old boy is brought to the emergency department by his parents with a 2-day history of fever, malaise, and productive cough. On presentation, he is found to be very weak and is having difficulty breathing. His past medical history is significant for multiple prior infections requiring hospitalization including otitis media, upper respiratory infections, pneumonia, and sinusitis. His family history is also significant for a maternal uncle who died of an infection as a child. Lab findings include decreased levels of IgG, IgM, IgA, and plasma cells with normal levels of CD4 positive cells. The protein that is most likely defective in this patient has which of the following functions?

A 17-year-old boy comes to the emergency department because of a 3-day history of pain in his left wrist. That morning the pain increased and he started to have chills and malaise. Last week he had self-resolving left knee pain. He is otherwise healthy and has not had any trauma to the wrist. He recently returned from a camping trip to Minnesota. He is sexually active with one female partner, who uses a diaphragm for contraception. His temperature is 37.7°C (99.9°F). Examination shows several painless violaceous vesiculopustular lesions on the dorsum of both wrists and hands; two lesions are present on the left palm. There is swelling and erythema of the left wrist with severe tenderness to palpation and passive movement. Which of the following is the most likely diagnosis?

On the 4th day of hospital admission due to pneumonia, a 69-year-old woman develops non-bloody diarrhea and abdominal pain. She is currently treated with ceftriaxone. Despite the resolution of fever after the first 2 days of admission, her temperature is now 38.5°C (101.3°F). On physical examination, she has mild generalized abdominal tenderness without abdominal guarding or rebound tenderness. Laboratory studies show re-elevation of leukocyte counts. Ceftriaxone is discontinued. Given the most likely diagnosis in this patient, which of the following is the most sensitive test?

A 47-year-old man comes to the physician because of abdominal pain and foul-smelling, watery diarrhea for several days. He has not had nausea, vomiting, or blood in the stool. He has a history of alcohol use disorder and recently completed a 7-day course of clindamycin for pneumonia. He has not traveled out of the United States. Which of the following toxins is most likely to be involved in the pathogenesis of this patient's symptoms?

A 58-year-old female, being treated on the medical floor for community-acquired pneumonia with levofloxacin, develops watery diarrhea. She reports at least 9 episodes of diarrhea within the last two days, with lower abdominal discomfort and cramping. Her temperature is 98.6° F (37° C), respiratory rate is 15/min, pulse is 67/min, and blood pressure is 122/98 mm Hg. Her physical examination is unremarkable. Laboratory testing shows: Hb% 13 gm/dL Total count (WBC): 13,400/mm3 Differential count: Neutrophils: 80% Lymphocytes: 15% Monocytes: 5% ESR: 33 mm/hr What is the most likely diagnosis?

A 45-year-old male presents to the emergency room complaining of severe diarrhea. He recently returned from a business trip to Bangladesh. Since returning, he has experienced several loose bloody stools per day that are accompanied by abdominal cramping and occasional nausea and vomiting. His temperature is 101.7°F (38.7°C), blood pressure is 100/60 mmHg, pulse is 120/min, and respirations are 20/min. On examination, he demonstrates mild tenderness to palpation throughout his abdomen, delayed capillary refill, and dry mucus membranes. Results from a stool sample and subsequent stool culture are pending. What is the mechanism of action of the toxin elaborated by the pathogen responsible for this patient’s current condition?