ID Self Assessment UPDT

9. L.G. is a 49-year-old woman with a history of mitral valve prolapse. She presents to her physician's office with malaise and a low-grade fever. Her physician notes that her murmur is louder than normal and orders blood cultures and an echocardiogram. A large vegetation is observed on L.G.'s mitral valve, and her blood cultures are growing Enterococcus faecalis (susceptible to all antibiotics). Which is the best therapy for L.G.? A. Penicillin G plus gentamicin for 2 weeks. B. Vancomycin plus gentamicin for 2 weeks. C. Ampicillin plus gentamicin for 4-6 weeks. D. Cefazolin plus gentamicin for 4-6 weeks

9. Answer: C Enterococcal endocarditis should be treated for 4-6 weeks. The 2-week treatment regimen is indicated only for streptococcal endocarditis. There is also no indication that the patient is penicillin allergic; thus, vancomycin should not be used as first-line treatment. Ampicillin plus gentamicin for 4-6 weeks is the regimen of choice for penicillin-susceptible enterococcal endocarditis. Cephalosporins have no activity against Enterococcus; therefore, the regimen with cefazolin is inappropriate.

1. P.E. is a 56-year-old man who comes to the clinic with a 3-day history of fever, chills, pleuritic chest pain, malaise, and cough productive of sputum. In the clinic, his temperature is 102.1ºF (38.9ºC) (all other vital signs are normal). His chest radiograph shows consolidation in the right lower lobe. His white blood cell count (WBC) is 14,400/mm3, but all other laboratory values are normal. He is given a diagnosis of community-acquired pneumonia (CAP). He has not received any antibiotics in 5 years and has no chronic disease states. Which is the best empiric therapy for P.E.? A. Doxycycline 100 mg orally two times/day. B. Cefuroxime axetil 250 mg orally two times/ day. C. Levofloxacin 750 mg/day orally. D. Trimethoprim/sulfamethoxazole (TMP/SMZ) double strength orally two times/day.

1. Answer: A The patient has CAP that does not require hospitalization (CURB-65 score is 1 at most [no mention of mental status]). Because he has not received any antibiotics in the past 3 months and has no comorbidities, he is at low risk of DRSP. Therefore, the drug of choice is either a macrolide or doxycycline. Cefuroxime is not recommended for treatment of CAP. Fluoroquinolones are only recommended if the patient has had recent antibiotics or has comorbidities. Trimethoprim/sulfamethoxazole is not used for CAP.

10. N.L. is a 28-year-old woman with no significant medical history. She reports to the emergency department with fever and severe right lower quadrant pain. She has had a dull pain for the past few days, but it suddenly became severe during the past 8 hours. Her temperature is 103.5°F (39.7°C), and she has rebound tenderness on abdominal examination. She is taken to surgery immediately, where a perforated appendix is diagnosed and repaired. Which is the best follow-up antibiotic regimen? A. Vancomycin 1000 mg intravenously every 12 hours plus metronidazole 500 mg intravenously every 8 hours. B. Ceftriaxone 1 g/day intravenously plus ciprofloxacin 400 mg intravenously every 12 hours. C. Ertapenem 1 g/day intravenously. D. No antibiotics needed after surgical repair of a perforated appendix.

10. Answer: C A perforated appendix requires antibiotics after surgery for an intra-abdominal infection. The combination of vancomycin and metronidazole does not have adequate activity against aerobic, gram-negative organisms (e.g., E. coli). The combination of ceftriaxone and ciprofloxacin does not have adequate activity against anaerobic organisms (e.g., B. fragilis group). Ertapenem is a good choice for intra-abdominal infections, although it has limited activity against Enterococcus.

2. H.W. is a 38-year-old woman who presents with high temperature, malaise, dry cough, nasal congestion, and severe headaches. Her symptoms began suddenly 3 days ago, and she has been in bed since then. She reports no other illness in her family, but several people have recently called in sick at work. Which is best for H.W.? A. Azithromycin 500 mg, followed by 250 mg/ day orally, for 4 more days. B. Amoxicillin/clavulanic acid 875 mg orally two times/day. C. Oseltamivir 75 mg two times/day orally for 5 days. D. Symptomatic treatment only.

2. Answer: D The symptoms of this patient (high temperature, malaise, dry cough, nasal congestion, and severe headaches) are most consistent with influenza; therefore, an antibacterial agent would not affect recovery. Oseltamivir should be initiated within 48 hours of symptom onset, so because this patient is more than 3 days out from symptom onset, oseltamivir will not affect recovery. Because of the viral etiology and time since symptom onset, symptomatic treatment is all that is indicated.

3. A study is designed to assess the risk of pneumococcal pneumonia in elderly patients 10 years or more after their pneumococcal vaccination, compared with elderly patients who have never received the vaccination. Which study design is best? A. Case series. B. Case-control study. C. Prospective cohort study. D. Randomized clinical trial.

3. Answer: B A case-control study would be the most appropriate study design because it is the most ethical, cost-effective, timely methodology. A stronger study design—for instance, a prospective cohort study or a randomized controlled trial—has many disadvantages if used to Answer: this question. In a prospective cohort study, too many patients would need to be observed because of the relatively low incidence of confirmed pneumococcal pneumonia. This study would therefore be too costly and take too long to complete. Randomized controlled trials also have many disadvantages in this situation. First, patients would need to be vaccinated and then observed for at least 10 years. Second, too many patients would need to be observed because of the relatively low incidence of confirmed pneumococcal pneumonia. Third, it would be unethical to randomize half of the patients to no vaccination. This study would therefore be too costly, unethical, and time-consuming. A case series would evaluate only a few patients given a diagnosis of pneumococcal pneumonia 10 or more years after vaccination. It would not provide comparative data, nor would it provide a strong study design.

4. N.R. is a 28-year-old woman who presents to the clinic with a 2-day history of dysuria, frequency, and urgency. She has no significant medical history, and the only drug she takes is oral contraceptives. Which is the best empiric therapy for N.R.? A. Oral nitrofurantoin extended release (ER) 100 mg two times/day for 3 days. B. Oral ciprofloxacin 500 mg two times/day for 7 days. C. Oral TMP/SMZ double strength two times/ day for 3 days. D. Oral cephalexin 500 mg four times/day for 3 days

4. Answer: C Although nitrofurantoin is a recommended first-line agent, the therapy duration is too short for its use. Because this patient has no contraindications to the use of TMP/SMZ or nitrofurantoin, and TMP/SMZ resistance rates are not mentioned as being high, fluoroquinolones would not be considered appropriate as first-line therapy in this particular case. In addition, 7 days of therapy is not necessary. The best choice for this patient is TMP/SMZ double strength twice daily orally for 3 days. The patient should be counseled about the potential interaction between antibiotics and oral contraceptives. β-Lactams are not as effective as TMP/SMZ, and data are limited on their use for 3 days.

5. B.Y. is an 85-year-old woman who is bedridden and lives in a nursing home. She is chronically catheterized, and her urinary catheter was last changed 3 weeks ago. Today, her urine is cloudy, and a urinalysis shows many bacteria. B.Y. is not noticing any symptoms. A urine culture is obtained. Which option is best for B.Y.? A. No therapy because she is chronically catheterized and has no symptoms. B. No antibiotic therapy, but the catheter should be changed. C. Oral ciprofloxacin 500 mg two times/day for 7 days and a new catheter. D. Oral ciprofloxacin 500 mg two times/day for 14-21 days without a change in catheter.

5. Answer: A For the asymptomatic patient who is bedridden and chronically catheterized, with cloudy urine and bacteria shown by urinalysis, no therapy is indicated. All patients with chronic urinary catheters will be bacteriuric. Because this patient is asymptomatic, the catheter does not need to be replaced. If she were symptomatic, catheter replacement might be indicated. Antibiotics are not indicated; however, a 7-day course would be appropriate if treatment were instituted. A long course of treatment only increases the risk of acquiring resistant organisms.

6. A patient with poor renal function is given a diagnosis of methicillin-resistant Staphylococcus aureus (MRSA) endocarditis. An initial 1-g dose of vancomycin is given. The patient has the following characteristics: height 5′10″; weight 72 kg (158 lb); and creatinine 4.2 mg/dL. The vancomycin halflife in this patient is 35 hours, and its volume of distribution is 0.7 L/kg. Which is the best assessment of when the patient will reach a concentration of 10 mcg/L and require another dose? A. About 18 hours from the time of the first dose. B. About 35 hours from the time of the first dose. C. About 70 hours from the time of the first dose. D. Initial dose inadequate to achieve a concentration of 10 mcg/mL.

6. Answer: B Using the equation Cp = dose/Vd, where Vd = volume of distribution, the concentration after the first dose can be calculated. The concentration is 19.8 mcg/mL. Therefore, it will take about 1 half-life to decrease to a concentration of 10 mcg/mL (i.e., 35 hours).

7. V.E. is a 44-year-old man who presents to the emergency department with a warm, erythematous, and painful right lower extremity. There is no raised border at the edge of the infection. Three days ago, he scratched his leg on a barbed wire fence on his property. His temperature has been as high as 101.8°F (38°C) with chills. Doppler studies of his lower extremity are negative. Blood cultures were drawn, and they are negative to date. Which is the best empiric therapy for V.E.? A. Nafcillin 2 g intravenously every 6 hours. The infection may worsen, and necrotizing fasciitis needs to be ruled out. B. Penicillin G, 2 million units intravenously every 4 hours. This is probably erysipelas. C. Piperacillin/tazobactam 3.375 g intravenously every 6 hours. Surgical debridement is vitally important. D. Enoxaparin 80 mg subcutaneously two times/ day and warfarin 5 mg/day orally.

7. Answer: A Because cellulitis (which the patient appears to have) is usually caused by Streptococcus or Staphylococcus, nafcillin is the drug of choice (vancomycin could be initiated empirically if MRSA were a concern in this patient). Necrotizing fasciitis needs to be ruled out because other organisms may be involved, and surgery would be crucial. Although penicillin is the treatment of choice for erysipelas, the patient probably has acute cellulitis (there is no raised border at the edge of the infection, which is indicative of erysipelas). Although piperacillin/tazobactam has activity against both Streptococcus and Staphylococcus, this treatment is too broad spectrum for an acute cellulitis. Because Doppler studies are negative, the likelihood of a deep venous thrombosis is low.

8. R.K. is a 36-year-old woman who presents to the emergency department with a severe headache and neck stiffness. Her temperature is 99.5°F (37.5°C). After a negative computed tomographic scan of the head, a lumbar puncture is performed, showing the following: glucose 54 mg/dL (peripheral, 104), protein 88 mg/dL, and WBC 220/mm3 (100% lymphocytes). The Gram stain shows no organisms. Which option describes the best therapy for R.K.? A. This is aseptic (probably viral) meningitis, and no antibiotics are necessary. B. Administer ceftriaxone 2 g intravenously every 12 hours until the cerebrospinal fluid (CSF) cultures are negative for bacteria. C. Administer ceftriaxone 2 g intravenously every 12 hours and vancomycin 1000 mg intravenously every 12 hours until the CSF cultures are negative for bacteria. D. Administer acyclovir 500 mg intravenously every 8 hours until the CSF culture results are complete.

8. Answer: C Even if a patient is believed to have aseptic meningitis after analysis of the CSF, antibiotics need to be given until CSF cultures are negative. In empiric therapy for bacterial meningitis in adults (i.e., when the CSF Gram stain is negative), ceftriaxone should be used in combination with vancomycin. The vancomycin is required for activity against resistant S. pneumoniae. Although the symptoms and CSF results are similar to what is expected for herpes simplex encephalitis, the use of acyclovir alone in this patient is inappropriate. Antibacterials must be used as well. Viral meningitis is generally caused by coxsackie virus, echovirus, and enterovirus, which are not treated with acyclovir