Bacteria — MCQs

A 63-year-old man comes to the physician because of shortness of breath and swollen extremities for 2 weeks. He has had excessive night sweats and a 4-kg (8.8-lb) weight loss over the last 8 weeks. He had an anterior myocardial infarction 3 years ago. He has type 2 diabetes mellitus and hypertension. He immigrated from Indonesia 4 months ago. He works in a shipyard. He has smoked one pack of cigarettes daily for 48 years. Current medications include insulin, aspirin, simvastatin, metoprolol, and ramipril. He is 160 cm (5 ft 3 in) tall and weighs 46.7 kg (103 lb); BMI is 18.2 kg/m2. His temperature is 38.0°C (100.4°F), pulse is 104/min, respirations are 20/min, and blood pressure is 135/95 mm Hg. Examination shows generalized pitting edema. There is jugular venous distention, hepatomegaly, and a paradoxical increase in jugular venous pressure on inspiration. Chest x-ray shows bilateral pleural effusion, patchy infiltrates in the right middle lobe, and pericardial thickening and calcifications. Laboratory studies show: Serum Urea nitrogen 25 mg/dL Creatinine 1.5 mg/dL Urine Blood negative Glucose negative Protein 1+ Which of the following is the most likely explanation for this patient's symptoms?

A 24-year-old woman is brought to the emergency department by friends because of an episode of jerking movements of the whole body that lasted for one minute. She reports a 2-week history of fever, headache, and altered sensorium. Her fever ranges from 38.3°C (101.0°F) to 38.9°C (102.0°F). Her past medical history is significant for toothache and multiple dental caries. The patient denies any history of smoking or alcohol or drug use. She is not currently sexually active. Her vital signs include: blood pressure 110/74 mm Hg, pulse 124/min, respiratory rate 14/min, temperature 38.9°C (102.0°F). On physical examination, the patient is confused and disoriented. She is moving her right side more than her left. A noncontrast CT scan of the head reveals a ring-enhancing lesion in the left frontal lobe consistent with a cerebral abscess. The abscess is evacuated and sent for culture studies. Which of the following microorganisms did the culture most likely grow?

An investigator is studying the effect of different cytokines on the growth and differentiation of B cells. The investigator isolates a population of B cells from the germinal center of a lymph node. After exposure to a particular cytokine, these B cells begin to produce an antibody that prevents attachment of pathogens to mucous membranes but does not fix complement. Which of the following cytokines is most likely responsible for the observed changes in B-cell function?

A father brings his 3-year-old son to the pediatrician because he is concerned about his health. He states that throughout his son's life he has had recurrent infections despite proper treatment and hygiene. Upon reviewing the patient's chart, the pediatrician notices that the child has been infected multiple times with S. aureus, Aspergillus, and E. coli. Which of the following would confirm the most likely cause of this patient's symptoms?

A 3-year-old boy presents to the pediatrics clinic for follow-up. He has a history of severe pyogenic infections since birth. Further workup revealed a condition caused by a defect in CD40 ligand expressed on helper T cells. This congenital immunodeficiency has resulted in an inability to class switch and a poor specific antibody response to immunizations. Which of the following best characterizes this patient's immunoglobulin profile?

A 60-year-old man who recently immigrated from South America schedules an appointment with a physician to complete his pre-employment health clearance form. According to company policy, a skin test for tuberculosis must be administered to all new employees. Thus, he received an intradermal injection of purified protein derivative (PPD) on his left forearm. After 48 hours, a 14-mm oval induration is noticed. The type of cells most likely present and responsible for the indurated area will have which of the following characteristic features?

A 42-year-old man presents with an intermittent low-to-high grade fever, night sweats, weight loss, fatigue, and exercise intolerance. The symptoms have been present for the last 6 months. The patient is a software developer. He smokes one-half pack of cigarettes daily and drinks alcohol occasionally. He denies intravenous drug use. There is no history of cardiovascular, respiratory, or gastrointestinal diseases or malignancies. There is no family history of cancer or cardiovascular diseases. The only condition he reports is a urinary bladder polyp, which was diagnosed and removed endoscopically almost 8 months ago. The patient does not currently take any medications. His blood pressure is 100/80 mm Hg, heart rate is 107/min, respiratory rate is 19/min, and temperature is 38.1°C (100.6°F). The patient is ill-looking and pale. There are several petechial conjunctival hemorrhages and macular lesions on both palms. The cardiac examination reveals heart enlargement to the left side and a holosystolic murmur best heard at the apex of the heart. There is also symmetric edema in both legs up to the knees. Which of the following organisms is most likely to be cultured from the patient’s blood?

Two weeks after undergoing an allogeneic skin graft procedure for extensive full-thickness burns involving his left leg, a 41-year-old man develops redness and swelling over the graft site. He has not had any fevers or chills. His temperature is 36°C (96.8°F). Physical examination of the left lower leg shows well-demarcated erythema and edema around the skin graft site. The graft site is minimally tender and there is no exudate. Which of the following is the most likely underlying mechanism of this patient’s skin condition?

A 38-year-old woman comes to the physician because of a 4-day history of swelling and pain in her left knee. She has had similar episodes of swollen joints over the past 3 weeks. Two months ago, she had a rash on her upper back that subsided after a few days. She lives in Pennsylvania and works as a forest ranger. Her temperature is 37.8°C (100°F). Physical examination shows a tender and warm left knee. Arthrocentesis of the knee joint yields cloudy fluid with a leukocyte count of 65,000/mm3 and 80% neutrophils. A Gram stain of synovial fluid does not show any organisms. Which of the following is the most likely cause of this patient's condition?

A 4-month-old boy is brought to the physician by his parents because of fever for the past 3 days. They also state that he has been less active and has been refusing to eat. The patient has had two episodes of bilateral otitis media since birth. He was born at term and had severe respiratory distress and sepsis shortly after birth that was treated with antibiotics. Umbilical cord separation occurred at the age of 33 days. The patient appears pale. Temperature is 38.5°C (101.3°F), pulse is 170/min, and blood pressure is 60/40 mm Hg. He is at the 25th percentile for height and 15th percentile for weight. Examination shows a capillary refill time of 4 seconds. Oral examination shows white mucosal patches that bleed when they are scraped off. There is bilateral mucoid, nonpurulent ear discharge. Several scaly erythematous skin lesions are seen on the chest. Laboratory studies show a leukocyte count of 38,700/mm3 with 90% neutrophils and a platelet count of 200,000/mm3. Which of the following is the most likely underlying cause of this patient's symptoms?