Environmental reservoirs in healthcare settings — MCQs

The surgical equipment used during a craniectomy is sterilized using pressurized steam at 121°C for 15 minutes. Reuse of these instruments can cause transmission of which of the following pathogens?

A 50-year-old male presents to the emergency room complaining of fever, shortness of breath, and diarrhea. He returned from a spa in the Rocky Mountains five days prior. He reports that over the past two days, he developed a fever, cough, dyspnea, and multiple watery stools. His past medical history is notable for major depressive disorder and peptic ulcer disease. He takes omeprazole and paroxetine. He does not smoke and drinks alcohol on social occasions. His temperature is 102.8°F (39.3°C), blood pressure is 120/70 mmHg, pulse is 65/min, and respirations are 20/min. Physical examination reveals dry mucus membranes, delayed capillary refill, and rales at the bilateral lung bases. A basic metabolic panel is shown below: Serum: Na+: 126 mEq/L Cl-: 100 mEq/L K+: 4.1 mEq/L HCO3-: 23 mEq/L Ca2+: 10.1 mg/dL Mg2+: 2.0 mEq/L Urea nitrogen: 14 mg/dL Glucose: 90 mg/dL Creatinine: 1.1 mg/dL Which of the following is the most appropriate growth medium to culture the pathogen responsible for this patient’s condition?

A patient is hospitalized for pneumonia. Gram-positive cocci in clusters are seen on sputum gram stain. Which of the following clinical scenarios is most commonly associated with this form of pneumonia?

A 57-year-old HIV-positive male with a history of intravenous drug abuse presents to the emergency room complaining of arm swelling. He reports that he developed progressively worsening swelling and tenderness over the right antecubital fossa three days prior. He recently returned from a trip to Nicaragua. His past medical history is notable for an anaphylactoid reaction to vancomycin. His temperature is 101.4°F (38.6°C), blood pressure is 140/70 mmHg, pulse is 110/min, and respirations are 20/min. Physical examination reveals an erythematous, fluctuant, and tender mass overlying the right antecubital fossa. Multiple injection marks are noted across both upper extremities. He undergoes incision and drainage and is started on an antibiotic that targets the 50S ribosome. He is discharged with plans to follow up in one week. However, five days later he presents to the same emergency room complaining of abdominal cramps and watery diarrhea. Which of the following classes of pathogens is most likely responsible for this patient’s current symptoms?

A 67-year-old man is brought to the emergency department because of severe dyspnea and orthopnea for 6 hours. He has a history of congestive heart disease and an ejection fraction of 40%. The medical history is otherwise unremarkable. He appears confused. At the hospital, his blood pressure is 165/110 mm Hg, the pulse is 135/min, the respirations are 48/min, and the temperature is 36.2°C (97.2°F). Crackles are heard at both lung bases. There is pitting edema from the midtibia to the ankle bilaterally. The patient is intubated and admitted to the critical care unit for mechanical ventilation and treatment. Intravenous morphine, diuretics, and nitroglycerine are initiated. Which of the following is the most effective method to prevent nosocomial infection in this patient?

A 69-year-old man is brought to the emergency department by his wife because of fever, cough, diarrhea, and confusion for 2 days. He recently returned from a cruise to the Caribbean. He has a history of chronic obstructive pulmonary disease. He has smoked one pack of cigarettes daily for 40 years. His temperature is 39.1°C (102.4°F), pulse is 83/min, and blood pressure is 111/65 mm Hg. He is confused and oriented only to person. Physical examination shows coarse crackles throughout both lung fields. His serum sodium concentration is 125 mEq/L. Culture of the most likely causal organism would require which of the following mediums?

A 32-year-old woman presents to your office with abdominal pain and bloating over the last month. She also complains of intermittent, copious, non-bloody diarrhea over the same time. Last month, she had a cough that has since improved but has not completely resolved. She has no sick contacts and has not left the country recently. She denies any myalgias, itching, or rashes. Physical and laboratory evaluations are unremarkable. Examination of her stool reveals the causative organism. This organism is most likely transmitted to the human host through which of the following routes?

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?

A 42-year-old man presents with unremitting diarrhea that has lasted for 2 weeks. He describes his bowel movements as watery, non-bloody, foul-smelling, and greasy. He also has cramping abdominal pain associated with the diarrhea. He says that his symptoms started right after he returned from a father-son camping trip to the mountains. His son has similar symptoms. His vital signs include: pulse 78/min, respiratory rate 15/min, temperature 37.2°C (99.0°F), and blood pressure 120/70 mm Hg. A stool sample is obtained and microscopic analysis is significant for the findings shown in the image below. Which of the following pathogens is most likely responsible for this patient’s condition?

A surgical ICU has implemented multiple interventions over 18 months: chlorhexidine bathing, antibiotic stewardship, contact precautions for MRSA, and environmental cleaning protocols. Despite these efforts, MRSA surgical site infection rates remain unchanged at 8 per 1000 surgical procedures. Universal MRSA screening shows 15% of admitted patients are colonized. Evaluate the most effective evidence-based strategy to reduce MRSA SSI rates further.