ID Self Assessment

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 14.4/mm3, but all other laboratory values are normal. He is given a diagnosis of community-acquired pneumonia. He has not received any antibiotics in 5 years and has no chronic disease states. Which one of the following is the best empiric therapy for P.E.? A. Doxycycline 100 mg orally 2 times/day. B. Cefuroxime axetil 250 mg orally 2 times/day. C. Levofloxacin 750 mg/day orally. D. Trimethoprim/sulfamethoxazole (TMZ/ SMZ) double strength orally 2 times/day.

1. Answer: D Transmission of HIV to a child is decreased if the mother's viral load is decreased. The benefits of therapy far outweigh the risk. A potent combination antiretroviral therapy that includes zidovudine throughout the pregnancy is the most appropriate therapeutic regimen for an asymptomatic patient with HIV who is pregnant (even in the first trimester) and has a low CD4 count and high viral load (although if the woman is on a fully suppressed regimen without zidovudine, that regimen should be continued without changes). Although zidovudine 300 mg 2 times/day orally throughout the pregnancy, followed by zidovudine during labor and to the baby for 6 weeks, was the regimen originally studied to decrease HIV transmission, potent combination antiretroviral therapy is indicated because of the patient's low CD4 count and high viral load; therefore, single-drug therapy is inappropriate. A single dose of nevirapine at the onset of labor will not have the impact on viral load and will not lower the risk of HIV transmission as much as potent combination antiretroviral therapy throughout the pregnancy. Single-dose nevirapine is indicated in women in labor who were not treated during their pregnancy.

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, and a perforated appendix is diagnosed and repaired. Which one of the following is an appropriate 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 Data are continuous and probably normally distributed (given the large population of 350 patients in the study); therefore, a parametric test is indicated. The t-test is the best parametric test for comparing two groups. Although an analysis of variance is a parametric test, it is used to compare more than two groups. A chi-square test is used to compare nominal or categorical data between two groups. The end points in this study are continuous and, therefore, should not be compared using this statistical test. The Wilcoxon rank sum test is a nonparametric analog to the t-test.

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 one of the following 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 2 times/day. C. Oseltamivir 75 mg 2 times/day orally for 5 days. D. Symptomatic treatment only

2. Answer: A The patient should be told that atazanavir can cause hyperbilirubinemia. This patient should be told to talk to a pharmacist about the current combination therapy because there are many drug interactions with antiretroviral agents. However, although atazanavir inhibits CYP3A4, tenofovir does not (it is an NRTI, not a protease inhibitor). In addition, informing the patient to cut the dose in half if there are adverse effects is incorrect because antiretroviral drugs, especially protease inhibitors, should never be used below the recommended dose. Informing the patient that tenofovir and emtricitabine cause additive peripheral neuropathy is incorrect because neither of these drugs is associated with that adverse effect.

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 one of the following study designs is best? A. Case series. B. Case-control study. C. Prospective cohort study. D. Randomized clinical trial

3. Answer: B There are many other reasons to change antiretroviral therapy in addition to clinical deterioration. These include an inability to decrease viral load to undetectable levels, the detection of virus after initial suppression to undetectable levels, a failure to increase the CD4 count by 50-100 cells/mm3 during the first year of therapy, and a failure to increase the CD4 count above 350 cells/mm3 while on therapy. If there is a question of ineffective antiretroviral therapy, single drugs should be changed only with caution (consider changing the entire regimen). Resistance does not occur more commonly with emtricitabine than with other antiretroviral agents.

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 one of the following is the best empiric therapy for N.R.? A. Oral amoxicillin 3 g in a single dose. B. Oral ciprofloxacin 500 mg 2 times/day for 7 days. C. Oral TMP/SMZ double strength 2 times/day for 3 days. D. Oral cephalexin 500 mg 4 times/day for 3 days.

4. Answer: D A change in therapy is indicated for the patient taking potent combination antiretroviral therapy and experiencing hyperglycemia, fat redistribution, and lipid abnormalities. Although adding lipid-lowering agents may be indicated to lower cardiovascular risks, simvastatin should not be used with lopinavir or ritonavir because of the drug interaction (increased simvastatin concentrations lead to increased risk of myalgias). Pravastatin is a better choice (even though it may decrease ritonavir concentrations). Although adding an insulin-sensitizing agent may be indicated, pioglitazone should not be used with lopinavir or ritonavir because of the drug interaction (increased pioglitazone concentrations and potential induction of protease inhibitor metabolism by pioglitazone). Changing agents is a good solution, but NRTIs do not cause endocrine abnormalities, so changing from the nucleoside RTI zidovudine to the nucleotide RTI tenofovir will not improve the symptoms. At this time, changing agents (if possible) to an effective regimen that does not cause endocrine disturbances is the best option. Because protease inhibitors most commonly cause endocrine disturbances, changing to an NNRTI-based regimen is best

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 one of the following therapies should B.Y. receive? 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 2 times/day for 7 days and a new catheter. D. Oral ciprofloxacin 500 mg 2 times/day for 14-21 days without a change in catheter.

5. Answer: D The current recommended regimen for treating cryptococcal meningitis in patients positive for HIV is amphotericin B 0.7 mg/kg/day plus flucytosine 25 mg/ kg every 6 hours for 2 weeks, followed by fluconazole 400 mg/day. Fluconazole alone is recommended only for mild to moderate cryptococcal meningitis, and the dose should be 400 mg/day. Studies have shown that early mortality is greater with fluconazole alone than with amphotericin B alone. When amphotericin B is used alone for cryptococcal meningitis, the dose should be 0.7 mg/kg per day, not 0.3 mg/kg per day. The flucytosine dose of 37.5 mg/kg every 6 hours is high and is especially prone to cause bone marrow suppression in patients who are HIV positive.

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 half-life in this patient is 35 hours, and its volume of distribution is 0.7 L/kg. Which one of the following is correct in determining 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: C The number of patients needed to treat with INH over RIF to prevent one progression to active disease is 200 = 1/(0.008 − 0.003). The only information needed is the absolute risk in both groups, which is provided.

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. He has had a temperature 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 one of the following 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 2 times/ day and warfarin 5 mg/day orally.

7. Answer: D Pyrimethamine plus clindamycin and leucovorin for 6 weeks is the correct choice for the treatment of toxoplasmosis in a patient who is HIV positive, not taking antiretrovirals, and taking dapsone for PCP prophylaxis. Atovaquone is not first-line therapy, although data support its effectiveness in combination with sulfadiazine or pyrimethamine; TMP/SMX is not effective for treatment or secondary prophylaxis of toxoplasmosis. Pyrimethamine and sulfadiazine are the firstline agents for toxoplasmosis; however, leucovorin should always be used with pyrimethamine to prevent myelosuppression.

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 one of the following options describes the best therapy for R.K.? A. This is an 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: B To achieve flucytosine peak concentrations between 50 and 100 mcg/mL (assuming a trough concentration of 25 mcg/mL, every-6-hour dosing, and 100% bioavailability; flucytosine volume of distribution = 0.7 L/ kg; half-life = 3 hours), the concentration needs to be changed by 25 75 mcg/mL. Using the equation ΔCp = dose/Vd, a dose of 12.5 mg/kg would increase the concentration only 17.8 mcg/mL. A dose of 75 mg/kg would increase the concentration by 107 mcg/mL, whereas a dose of 150 mg/kg would increase the concentration by 214 mcg/mL. The correct dose is 37.5 mg/kg because it would increase the concentration by 53.6 mcg/mL.

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 one of the following 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: B Because the patient is symptomatic and her sputum is acid-fast bacillus positive, she should be treated for an active TB infection. Isoniazid, RIF, PZA, and EMB for 2 months, followed by INH and RIF for 4 more months, is the recommended therapy for active TB. Patients should be initiated on at least three antibiotics for the first 2 months. Although fluoroquinolones have some activity against TB, their use as first-line monotherapy is inappropriate.