Bacteria — MCQs

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?

A 67-year-old man presents to the physician with profuse watery diarrhea along with fever and crampy abdominal pain. He has been taking an antibiotic course of cefixime for about a week to treat a respiratory tract infection. At the doctor’s office, his pulse is 112/min, the blood pressure is 100/66 mm Hg, the respirations are 22/min, and the temperature is 38.9°C (102.0°F). His oral mucosa appears dry and his abdomen is soft with vague diffuse tenderness. A digital rectal examination is normal. Laboratory studies show: Hemoglobin 11.1 g/dL Hematocrit 33% Total leucocyte count 16,000/mm3 Serum lactate 0.9 mmol/L Serum creatinine 1.1 mg/dL What is most likely to confirm the diagnosis?

A 2-year-old boy is brought to the emergency department by his parents after they found him to be lethargic and febrile. His current symptoms started 1 week ago and initially consisted of a sore throat and a runny nose. He subsequently developed a fever and productive cough that has become worse over time. Notably, this patient has previously presented with pneumonia and gastroenteritis 8 times since he was born. On presentation, the patient's temperature is 103°F (39.4°C), blood pressure is 90/50 mmHg, pulse is 152/min, and respirations are 38/min. Based on clinical suspicion, an antibody panel is obtained and the results show low levels of IgG and IgA relative to the level of IgM. The expression of which of the following genes is most likely abnormal in this patient?

A 4-year-old boy is brought to the emergency department by his parents. He is lethargic and confused and has a severe headache, vomiting, and a high-grade fever since earlier that day. His mother reports that the child was doing well until 2 days ago when he developed a fever and green nasal discharge. The patient has a history of neonatal sepsis, meningococcemia at 18 months of age, and pneumococcal pneumonia at 2 and 3 years of age. His scheduled vaccinations are up to date. His blood pressure is 70/50 mm Hg, heart rate is 120/min, respiratory rate is 22/min, and temperature is 39.3°C (102.4°F). On examination, the child is lethargic and his skin is pale, with several petechiae over his buttocks. There is a purulent nasal discharge from both nostrils. The lungs are clear to auscultation bilaterally. Heart sounds are normal. There is marked neck rigidity. Cerebrospinal fluid analysis shows the following results: Opening pressure 100 mm H2O Appearance cloudy Protein 500 mg/dL (5 g/L) White blood cells 2500/μL (polymorphonuclear predominance) Glucose 31 mg/dL (1.7 mmol/L) Culture positive for N. meningitidis Which of the following immunological processes is most likely to be impaired in this child?

A 6-year-old male who recently immigrated to the United States from Asia is admitted to the hospital with dyspnea. Physical exam reveals a gray pseudomembrane in the patient's oropharynx along with lymphadenopathy. The patient develops myocarditis and expires on hospital day 5. Which of the following would have prevented this patient's presentation and decline?