Group B streptococcal disease — MCQs

An 18-month-old boy presents to the emergency department for malaise. The boy’s parents report worsening fatigue for 3 days with associated irritability and anorexia. The patient’s newborn screening revealed a point mutation in the beta-globin gene but the patient has otherwise been healthy since birth. On physical exam, his temperature is 102.4°F (39.1°C), blood pressure is 78/42 mmHg, pulse is 124/min, and respirations are 32/min. The child is tired-appearing and difficult to soothe. Laboratory testing is performed and reveals the following: Serum: Na+: 137 mEq/L Cl-: 100 mEq/L K+: 4.4 mEq/L HCO3-: 24 mEq/L Urea nitrogen: 16 mg/dL Creatinine: 0.9 mg/dL Glucose: 96 mg/dL Leukocyte count: 19,300/mm^3 with normal differential Hemoglobin: 7.8 g/dL Hematocrit: 21% Mean corpuscular volume: 82 um^3 Platelet count: 324,000/mm^3 Reticulocyte index: 3.6% Which of the following is the most likely causative organism for this patient's presentation?

A 3100-g (6.9-lb) male newborn is brought to the emergency department by his mother because of fever and irritability. The newborn was delivered at home 15 hours ago. He was born at 39 weeks' gestation. The mother's last prenatal visit was at the beginning of the first trimester. She received all standard immunizations upon immigrating from Mexico two years ago. Seven weeks ago, she experienced an episode of painful, itching genital vesicles, which resolved spontaneously. Four hours before going into labor she noticed a gush of blood-tinged fluid from her vagina. The newborn is ill-appearing and lethargic. His temperature is 39.9°C (103.8°F), pulse is 170/min, respirations are 60/min, and blood pressure is 70/45 mm Hg. His skin is mildly icteric. Expiratory grunting is heard on auscultation. Skin turgor and muscle tone are decreased. Laboratory studies show: Hemoglobin 15 g/dL Leukocyte count 33,800/mm3 Platelet count 100,000/mm3 Serum glucose 55 mg/dL Which of the following is the most likely causal organism?

A 7-year-old boy is brought to the physician for the evaluation of sore throat for the past 2 days. During this period, he has had intermittent nausea and has vomited once. The patient has no cough, hoarseness, or rhinorrhea. He had similar symptoms at the age of 5 years that resolved spontaneously. He is otherwise healthy. His temperature is 37.9°C (100.2°F), pulse is 85/min, and blood pressure is 108/70 mm Hg. Head and neck examination shows an erythematous pharynx with grayish exudates overlying the palatine tonsils. There is no lymphadenopathy. Rapid antigen detection test for group A streptococci is negative. Which of the following is most appropriate next step in the management of this patient?

You are treating a neonate with meningitis using ampicillin and a second antibiotic, X, that is known to cause ototoxicity. What is the mechanism of antibiotic X?

A 63-year-old man with aortic valve disease is admitted to the hospital for a 3-week history of progressively worsening fatigue, fever, and night sweats. He does not smoke, drink alcohol, or use illicit drugs. Temperature is 38.2°C (100.8°F). Physical examination shows a systolic murmur and tender, erythematous nodules on the finger pads. Blood cultures show alpha-hemolytic, gram-positive cocci that are catalase-negative and optochin-resistant. Which of the following is the most likely causal organism?

A 62-year-old woman presents to the emergency department for evaluation of a spreading skin infection that began from an ulcer on her foot. The patient has type 2 diabetes mellitus that is poorly controlled. On examination, there is redness and erythema to the lower limb with skin breakdown along an extensive portion of the leg. The patient’s tissues separate readily from the fascial plane, prompting a diagnosis of necrotizing fasciitis. What is the exotoxin most likely associated with this patient’s presentation?

An 82-year-old man presents with painless swelling of the neck for the past week. He reports no recent fever, night sweats, or weight loss. He has no significant medical history, and his only medication is daily aspirin. His temperature is 36.8℃ (98.2℉). On physical examination, there are several non-tender lymph nodes, each averaging 2 cm in diameter, which are palpable in the right anterior cervical triangle. No other palpable lymphadenopathy is noted. The remainder of the physical exam is unremarkable. Laboratory studies show the following: Hemoglobin 10 g/dL Leukocyte count 8000/mm3 with a normal differential Platelet count 250,000/mm3 Erythrocyte sedimentation rate 30 mm/h An excisional biopsy of a cervical lymph node reveals the presence of Reed-Sternberg (RS) cells. Computed tomography (CT) scans and positron emission tomography (PET) scans reveal no mediastinal mass or signs of additional disease. Which of the following aspects most strongly indicates a good prognosis for this patient?

A 5-year-old child is brought to a pediatric clinic by his mother for a rash that started a few days ago. The mother adds that her son has also had a fever and sore throat since last week. His immunizations are up to date. On examination, a rash is present over the trunk and upper extremities and feels like sandpaper to touch. An oropharyngeal examination is suggestive of exudative pharyngitis with a white coat over the tongue. The physician swabs the throat and uses the swab in a rapid antigen detection test kit. He also sends the sample for microbiological culture. The physician then recommends empiric antibiotic therapy and tells the mother that if the boy is left untreated, the likelihood of developing a complication later in life is very high. Which of the following best explains the mechanism underlying the development of the complication the physician is talking about?

A 10-year-old boy is brought to the emergency department by his parents because of a dull persistent headache beginning that morning. He has nausea and has vomited twice. During the past four days, the patient has had left-sided ear pain and fever, but his parents did not seek medical attention. He is from Thailand and is visiting his relatives in the United States for the summer. There is no personal or family history of serious illness. He is at the 45th percentile for height and 40th percentile for weight. He appears irritable. His temperature is 38.5°C (101.3°F), pulse is 110/min, and blood pressure is 98/58 mm Hg. The pupils are equal and reactive to light. Lateral gaze of the left eye is limited. The left tympanic membrane is erythematous with purulent discharge. There is no nuchal rigidity. Which of the following is the most appropriate next step in management?

A 10-year-old girl with a rash is brought to the clinic by her mother. The patient’s mother says that the onset of the rash occurred 2 days ago. The rash was itchy, red, and initially localized to the cheeks with circumoral pallor, and it gradually spread to the arms and trunk. The patient’s mother also says her daughter had been reporting a high fever of 39.4°C (102.9°F), headaches, myalgia, and flu-like symptoms about a week ago, which resolved in 2 days with acetaminophen. The patient has no significant past medical history. Her vital signs include: temperature 37.0°C (98.6°F), pulse 90/min, blood pressure 125/85 mm Hg, respiratory rate 20/min. Physical examination shows a symmetric erythematous maculopapular rash on both cheeks with circumoral pallor, which extends to the patient’s trunk, arms, and buttocks. The remainder of the exam is unremarkable. Laboratory findings are significant for a leukocyte count of 7,100/mm3 and platelet count of 325,000/mm3. Which of the following is the next best step in the management of this patient?