Gram-positive — MCQs

An 11-year-old boy presents with a sore throat, fever, chills, and difficulty swallowing for the past 3 days. The patient’s mother says that last night he was short of breath and had a headache. Past medical history is unremarkable. The patient has not been vaccinated as his mother thinks it is "unnecessary". His temperature is 38.3°C (101.0°F), blood pressure is 120/70 mm Hg, pulse is 110/min, and respiratory rate is 18/min. On physical examination, the patient is ill-appearing and dehydrated. A grayish-white membrane and pharyngeal erythema are present in the oropharynx. Significant cervical lymphadenopathy is also present. A throat swab is taken and gram staining shows gram-positive club-shaped bacilli along with few neutrophils. Which of the following would most likely be the result of the bacterial culture of the throat swab in this patient?

A 24-hour-old newborn presents to the emergency department after a home birth because of fever, irritability alternating with lethargy, and poor feeding. The patient’s mother says symptoms acutely onset 12 hours ago and have not improved. No significant past medical history. His mother did not receive any prenatal care, and she had rupture of membranes 20 hours prior to delivery. His vital signs include: heart rate 150/min, respiratory rate 65/min, temperature 39.0°C (102.2°F), and blood pressure 60/40 mm Hg. On physical examination, the patient has delayed capillary refill. Laboratory studies show a pleocytosis and a low glucose level in the patient’s cerebrospinal fluid. Which of the following is the most likely causative organism for this patient’s condition?

An 11-year-old boy is brought to the emergency department by his parents for confusion and fever. The patient began complaining of a headache yesterday afternoon that progressively got worse. After waking him up this morning, his mom noticed that “he seemed funny and wasn’t able to carry a conversation fully.” When asked about his past medical history, the dad claims that he’s been healthy except for 2-3 episodes of finger pain and swelling. Physical examination demonstrates a boy in moderate distress, altered mental status, and nuchal rigidity. A CSF culture reveals a gram-positive, diplococci bacteria. What characteristic would you expect in the organism most likely responsible for this patient’s symptoms?

A 3-year-old male is brought to the ER with a sore throat and fever. Examination of the pharynx reveals a dark, inflammatory exudate. Cysteine-tellurite agar culture produces black, iridescent colonies. Microscopic features of the causal organism most likely include which of the following?

A microbiology graduate student was given a swab containing an unknown bacteria that caused an ear infection in a seven-year-old girl. The student identified the bacteria as a gram-positive, catalase-negative cocci showing alpha-hemolysis (greenish discoloration around colonies) when grown on blood agar. Which of the following characteristics is associated with this bacteria?

A 25-year-old woman presents with fever, rash, abdominal pain, and vaginal discharge for the past 3 days. She describes the pain as moderate, cramping in character, and diffusely localized to the suprapubic region. She says the rash is painless and does not itch. She also complains of associated generalized muscle aches and vomiting since last night. The patient denies any recent menstrual irregularities, dysuria, painful urination or similar symptoms in the past. Her past medical history is significant for chronic asthma, managed medically. There is no recent travel or sick contacts. Patient denies any smoking history, alcohol or recreational drug use. She has been sexually active for the past year with a single partner and has been using oral contraceptive pills. Her vital signs include: temperature 38.6°C (101.0°F), blood pressure 90/68 mm Hg, pulse 120/min, and respirations 20/min. Physical examination reveals a diffuse erythematous desquamating maculopapular rash over the lower abdomen and inner thighs. There is moderate tenderness to palpation of the suprapubic and lower right quadrants with no rebound or guarding. Abdomen is non-distended with no hepatosplenomegaly. Pelvic examination reveals a purulent vaginal discharge. Which of the following best describes the organism responsible for this patient’s condition?

A 21-year-old man seeks evaluation at an urgent care clinic because of nausea, vomiting, and abdominal pain that began 2 hours ago. He attended a picnic this afternoon, where he ate a cheese sandwich and potato salad. He says that a number of his friends who were at the picnic have similar symptoms, so he thinks the symptoms are associated with the food that was served. His medical history is significant for celiac disease, which is well-controlled with a gluten-free diet and an appendectomy was performed last year. His vital signs include a temperature of 37.0°C (98.6°F), respiratory rate of 15/min, pulse of 97/min, and blood pressure of 98/78 mmHg. He is started on intravenous fluids. Which of the following is the most probable cause of this patient’s condition?

A 54-year-old man comes to the physician because of persistent right knee pain and swelling for 2 weeks. Six months ago, he had a total knee replacement because of osteoarthritis. His temperature is 38.5°C (101.3°F), pulse is 100/min, and blood pressure is 139/84 mm Hg. Examination shows warmth and erythema of the right knee; range of motion is limited by pain. His leukocyte count is 14,500/mm3, and erythrocyte sedimentation rate is 50 mm/hr. Blood cultures grow gram-positive, catalase-positive cocci. These bacteria grow on mannitol salt agar without color change. Production of which of the following is most important for the organism's virulence?

An 8-day-old male infant presents to the pediatrician with a high-grade fever and poor feeding pattern with regurgitation of milk after each feeding. On examination the infant showed abnormal movements, hypertonia, and exaggerated DTRs. The mother explains that during her pregnancy, she has tried to eat only unprocessed foods and unpasteurized dairy so that her baby would not be exposed to any preservatives or unhealthy chemicals. Which of the following characteristics describes the causative agent that caused this illness in the infant?

A 56-year-old woman comes to the emergency department because of worsening pain and swelling in her right knee for 3 days. She underwent a total knee arthroplasty of her right knee joint 5 months ago. The procedure and immediate aftermath were uneventful. She has hypertension and osteoarthritis. Current medications include glucosamine, amlodipine, and meloxicam. Her temperature is 37.9°C (100.2°F), pulse is 95/min, and blood pressure is 115/70 mm Hg. Examination shows a tender, swollen right knee joint; range of motion is limited by pain. The remainder of the examination shows no abnormalities. Arthrocentesis of the right knee is performed. Analysis of the synovial fluid shows: Appearance Cloudy Viscosity Absent WBC count 78,000/mm3 Segmented neutrophils 94% Lymphocytes 6% Synovial fluid is sent for culture and antibiotic sensitivity. Which of the following is the most likely causal pathogen?