Infection control practices — MCQs

A 29-year-old man comes to the physician for a routine health maintenance examination. He feels well. He works as a nurse at a local hospital in the city. Three days ago, he had a needlestick injury from a patient whose serology is positive for hepatitis B. He completed the 3-dose regimen of the hepatitis B vaccine 2 years ago. His other immunizations are up-to-date. He appears healthy. Physical examination shows no abnormalities. He is concerned about his risk of being infected with hepatitis B following his needlestick injury. Serum studies show negative results for hepatitis B surface antigen, hepatitis B surface antibody, and hepatitis C antibody. Which of the following is the most appropriate next step in management?

A medical technician is trying to isolate a pathogen from the sputum sample of a patient. The sample is heat fixed to a slide then covered with carbol fuchsin stain and heated again. After washing off the stain with clean water, the slide is covered with 1% sulfuric acid for decolorization. The sample is rinsed again and stained with methylene blue. Microscopic examination shows numerous red, branching filamentous organisms. Which of the following is the most likely isolated pathogen?

A 57-year-old man comes to the physician because of generalized malaise, yellowish discoloration of the eyes, and pruritus on the back of his hands that worsens when exposed to sunlight for the past several months. He has not seen a physician in 15 years. Physical examination shows scleral icterus and mild jaundice. There is a purpuric rash with several small vesicles and hyperpigmented lesions on the dorsum of both hands. The causal pathogen of this patient's underlying condition was most likely acquired in which of the following ways?

A 28-year-old soldier is brought back to a military treatment facility 45 minutes after sustaining injuries in a building fire from a mortar attack. He was trapped inside the building for around 20 minutes. On arrival, he is confused and appears uncomfortable. He has a Glasgow Coma Score of 13. His pulse is 113/min, respirations are 18/min, and blood pressure is 108/70 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 96%. Examination shows multiple second-degree burns over the chest and bilateral upper extremities and third-degree burns over the face. There are black sediments seen within the nose and mouth. The lungs are clear to auscultation. Cardiac examination shows no abnormalities. The abdomen is soft and nontender. Intravenous fluid resuscitation is begun. Which of the following is the most appropriate next step in management?

The occupational health department at a hospital implements new safety precautions to prevent laboratory-acquired infections. One of the new precautions includes disinfecting the microbiology laboratory benches with 70% ethanol before and after use. This measure is most likely to be effective in preventing the transmission of which of the following viruses?

A scientist is studying the mechanisms by which bacteria become resistant to antibiotics. She begins by obtaining a culture of vancomycin-resistant Enterococcus faecalis and conducts replicate plating experiments. In these experiments, colonies are inoculated onto a membrane and smeared on 2 separate plates, 1 containing vancomycin and the other with no antibiotics. She finds that all of the bacterial colonies are vancomycin resistant because they grow on both plates. She then maintains the bacteria in liquid culture without vancomycin while she performs her other studies. Fifteen generations of bacteria later, she conducts replicate plating experiments again and finds that 20% of the colonies are now sensitive to vancomycin. Which of the following mechanisms is the most likely explanation for why these colonies have become vancomycin sensitive?

A 36-year-old man comes to the physician because of a 2-week history of productive cough, weight loss, and intermittent fever. He recently returned from a 6-month medical deployment to Indonesia. He appears tired. Physical examination shows nontender, enlarged, palpable cervical lymph nodes. An x-ray of the chest shows right-sided hilar lymphadenopathy. A sputum smear shows acid-fast bacilli. A diagnosis of pulmonary tuberculosis is made from PCR testing of the sputum. The patient requests that the physician does not inform anyone of this diagnosis because he is worried about losing his job. Which of the following is the most appropriate initial action by the physician?

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 35-year-old man is brought into the emergency department by emergency medical services with his right hand wrapped in bloody bandages. The patient states that he is a carpenter and was cutting some wood for a home renovation project when he looked away and injured one of his digits with a circular table saw. He states that his index finger was sliced off and is being brought in by his wife. On exam, his vitals are within normal limits and stable, and he is missing part of his second digit on his right hand distal to the proximal interphalangeal joint. How should the digit be transported to the hospital for the best outcome?

A 70-year-old woman comes to the physician for the evaluation of loss of urine for the last several months. She loses small amounts of urine without warning after coughing or sneezing. She also sometimes forgets the names of her relatives. She is retired and lives at an assisted-living facility. She has type 2 diabetes mellitus and hypertension. Her older sister recently received a ventriculoperitoneal shunt. She does not smoke or drink alcohol. Medications include metformin and enalapril. Vital signs are within normal limits. She walks without any problems. Sensation to pinprick and light touch is normal. Which of the following is the most likely underlying cause of this patient's symptoms?