A 54-year-old man comes to the hospital due to 4 days of progressive nasal congestion, facial pain, swelling, and fever.  The patient has taken over-the-counter decongestants, which provided no relief.  He has a history of uncontrolled diabetes mellitus due to dietary and medication noncompliance.  The patient’s temperature is 38.3 C (101 F).  Examination shows right facial swelling and purulent nasal discharge with necrotic destruction of the nasal mucosa and turbinates.  The diagnosis of invasive mucormycosis is made, and surgical debridement is performed.  He is started on an antifungal agent that binds to ergosterol and alters cell membrane permeability.  Considering the adverse effects of this medication, which of the following should be routinely monitored in this patient?

A 78-year-old woman comes to the office due to fever, headache, sore throat, cough, and severe myalgias for 24 hours.  Her medical problems include hypertension and Alzheimer dementia.  Her family came to visit over the weekend, and her grandson had symptoms of a cold.  The patient’s temperature is 38.9 C (102 F).  Lung examination is unremarkable.  A nasal specimen swab is positive for influenza.  The patient is started on oseltamivir.  Which of the following is most likely impaired in the patient’s infected cells as a result of the treatment?

A 77-year-old woman is brought to the emergency department due to fever and confusion.  The patient has a history of Alzheimer dementia and lives in a nursing home.  Temperature is 38.4 C (101.1 F), blood pressure is 104/74 mm Hg, pulse is 110/min, and respirations are 18/min.  Suprapubic tenderness is present on physical examination.  Urinalysis shows numerous bacteria and leukocytes, and urine culture grows Pseudomonas aeruginosa.  Further analysis reveals that the isolated organism produces an enzyme that is located on the cytoplasmic surface of the cell membrane and that catalyzes the transfer of acetyl groups to exogenous substances.  The bacteria are most likely resistant to which of the following antibiotics?

A 43-year-old woman comes to the emergency department due to low-grade fevers and malaise.  She has a history of lung transplantation due to cystic fibrosis and had 2 episodes of cytomegalovirus (CMV) viremia over the past few months, which were treated with ganciclovir.  Temperature is 37.6 C (99.7 F).  Physical examination is unrevealing.  Chest x-ray and urinalysis are negative for infection.  Polymerase chain reaction testing for CMV in blood shows elevated CMV levels consistent with CMV viremia.  Given the recurrent episodes of viremia, genotype analysis is performed and demonstrates ganciclovir-resistant CMV.  The patient is started on an alternate intravenous antiviral agent.  She develops hypocalcemia and hypomagnesemia.  Which of the following agents is the most likely cause of these side effects?

A 23-year-old man is hospitalized for fever, headache, and confusion.  He does not use tobacco or illicit drugs and is monogamous with his wife.  The patient’s cerebrospinal fluid analysis reveals lymphocytic pleocytosis, and a PCR is positive for herpesvirus.  The patient is treated with intravenous high-dose acyclovir.  Fever and mental status gradually improve, but on the third day of hospitalization the patient’s serum creatinine level increases to 3.4 mg/dL from a baseline of 0.9 mg/dL at admission.  The observed finding could have been prevented by which of the following?

A 5-year-old girl is brought to the physician by her parents due to intense perianal itching, especially during the night.  The patient is otherwise healthy and her development has been normal.  Physical examination shows perianal excoriation.  Cellulose adhesive tape is applied to the perianal area shortly after she wakes in the morning.  Microscopic analysis of the tape reveals the presence of eggs that are asymmetrically flattened on one side.  Which of the following is the most appropriate treatment for this patient’s condition?

A 31-year-old man comes to the emergency department due to 2 weeks of fever, night sweats, and productive cough.  He has also had a 5-kg (11-lb) weight loss.  He has no other medical problems.  The patient is a software engineer who moved to the United States from Uzbekistan 15 years ago.  He takes no medications and has no known drug allergies.  Temperature is 38.3 C (101 F), blood pressure is 110/80 mm Hg, pulse is 94/min, and respirations are 18/min.  He weighs 60 kg (132.3 lb).  Pulse oximetry shows 94% on room air.  Chest-x ray reveals a cavitary lesion in the right lung.  Sputum culture is obtained.  Following exposure to drug A, the cultured pathogen stops proliferating and loses color when exposed to an acid-alcohol decolorizing agent.  Drug A is most likely to be which of the following medications?

An infant is evaluated at the office after developing prominent oral thrush, interstitial pneumonia, and severe lymphopenia during the first year of life.  The patient was born full-term to a 25-year-old woman who received no prenatal care and has substance use disorder with intravenous drug use.  She breastfed her son for the first month but then switched to formula feedings.  The mother is currently unwilling to undergo any kind of testing.  She tells the health care provider, “Just take care of my son.”  Which of the following prenatal interventions would have most likely prevented this infant’s condition?

A 43-year-old immigrant from Southern Asia suffers from a cough that has lasted for several months duration.  He comes to the clinic today because of recent onset hemoptysis.  On further evaluation, he reports a 15-lb weight loss over the past four months.  Sputum cultures grow acid-fast bacilli that are susceptible to most antimycobacterial drugs in vitro.  Isoniazid monotherapy in this patient would most likely result in:

A 12-year-old boy is brought to the emergency department by paramedics after being found unresponsive at home.  He had 24 hours of headache, nausea, and fever, which his parents were treating with acetaminophen.  His temperature is 39.6 C (103.4 F).  Physical examination reveals neck stiffness.  Lumbar puncture is performed.  Analysis of cerebrospinal fluid shows marked pleocytosis, and Gram stain shows gram-negative cocci in pairs.  The parents are concerned about their younger son, who shares a bedroom with the patient.  Which of the following is the most appropriate management of this patient’s household contacts?

A 43-year-old man comes to the office due to fatigue and worsening pedal edema over the past several weeks.  The patient was diagnosed with advanced HIV infection and started on antiretroviral therapy 3 months ago.  He also has a history of hypertension.  Physical examination shows bilateral lower extremity pitting edema.  Serum creatinine is elevated and serum phosphorus is decreased compared to test results 3 months ago.  Urinalysis reveals moderate proteinuria and glucosuria.  Renal biopsy shows cytoplasmic vacuolization in the proximal tubules accompanied by loss of brush border and basement membrane denudation.  Intracytoplasmic eosinophilic inclusions are also seen in the proximal tubules.  There are no significant interstitial inflammatory infiltrates, and the glomeruli appear normal.  Which of the following is the most likely diagnosis in this patient?

A 23-year-old man comes to the office due to several days of dysuria.  He has had no fever or hematuria.  The patient has no other medical conditions, takes no medications, and has no known allergies.  Temperature is 37.1 C (98.8 F).  On genitourinary examination, mucopurulent discharge is noted at the urethral meatus.  Microscopy of the discharge shows numerous neutrophils, some of which contain intracellular gram-negative diplococci.  A single intramuscular injection of ceftriaxone is administered.  Which of the following additional medications is recommended at this time?

A 21-year-old man comes to the office due to several days of intense pruritus of the inguinal-genital area.  He has had no fever, dysuria, or skin rash.  He is not using any new soaps, detergents, or lotions.  The patient has had 3 sexual partners in the past year.  He was treated for chlamydial urethritis 6 months ago and since then has been using condoms consistently.  Vital signs are within normal limits.  Genitourinary examination shows no urethral discharge, penile lesions, or inguinal lymphadenopathy.  There are skin excoriation marks in the pubic area and other findings as shown in the exhibit.  Which of the following is the most appropriate pharmacotherapy for this patient’s condition?

A 24-year-old pregnant woman comes to the emergency department in active labor at full term.  The patient has a history of HIV from injection drug use.  She is not adherent with antiretroviral therapy and has had no recent testing of CD4 count or plasma viral load.  Physical examination shows regular uterine contractions, ruptured amniotic membranes, and a fully dilated cervix.  A decision is made to continue with the vaginal delivery due to advanced labor.  Intravenous zidovudine is administered to the patient during the delivery and to the infant immediately after birth.  This medication helps decrease the risk of perinatal transmission by inhibiting which of the following components of viral genome replication?

The antiviral activity of a guanosine derivative is tested by examining cells infected with different viruses for characteristic abnormal changes in cell morphology due to the viruses.  These changes are known as the cytopathic effect (CPE).  In the presence of significant antiviral activity, CPE will be inhibited.  The following results are obtained from the study:

A difference in which of the following best explains the variation in susceptibility of the various viruses to this specific antiviral agent?

A 32-year-old woman comes to the physician for a health maintenance examination.  She has been well and has no specific complaints.  She eats a well-balanced diet and exercises on a stationary bicycle 3 days a week.  She works as a nursing assistant at a local hospital.  Review of her records shows that she is due for her annual influenza vaccination.  Prior to administration of the vaccine, her skin is disinfected with 70% isopropanol.  Which of the following mechanisms is most likely responsible for the antiseptic properties of isopropanol?

A 33-year-old homeless man is hospitalized due to recent weight loss, odynophagia, and progressive cough.  He is found to be HIV-positive and his CD4 count is 45/mm³.  The patient’s condition improves on a newly instituted treatment, but 4 weeks later at outpatient follow-up he is found to have significantly elevated fasting blood glucose.  Which of the following medications is most likely responsible for his hyperglycemia?

An 84-year-old woman is sent to the hospital from a nursing home due to 3 days of fever, abdominal pain, and progressive lethargy.  The patient has a history of recurrent hospitalizations with multiple antibiotic courses for urinary tract infection, infected decubitus ulcer, and pneumonia.  Her temperature is 38.2 C (101 F), blood pressure is 100/60 mm Hg, and pulse is 110/min.  She has mild suprapubic and right costovertebral angle tenderness.  Urine and blood cultures are obtained, and the patient is started on intravenous fluids and empiric ceftriaxone.  Her urine culture shows extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli.  Which of the following features is most likely to be found in this organism?

A 34-year-old man comes to the emergency department due to recurrent fever, chills, and excessive sweating.  The symptoms began a few days ago and seem to recur every 48 hours.  The patient recently returned from a trip to Latin America.  Temperature is 38.6 C (101.5 F).  Physical examination is otherwise normal.  Laboratory studies are notable for anemia and thrombocytopenia.  A blood smear with Giemsa staining demonstrates red blood cell inclusions.  Chloroquine and primaquine are prescribed.  The addition of primaquine to the treatment regimen is most likely to have which of the following effects?

A 21-year-old woman comes to the office due to burning on urination and increased urinary frequency for the past 2 days.  She has no hematuria, vaginal discharge, or irritation.  The patient has no other medical problems.  Her temperature is 37 C (98.6 F).  Physical examination reveals mild suprapubic tenderness on deep palpation; there is no costovertebral angle tenderness.  Urine dipstick is positive for leukocyte esterase and nitrites.  The patient is started on trimethoprim, which leads to rapid resolution of her symptoms.  Which of the following medications has the same intracellular target as the drug used to treat this patient?

A 65-year-old man comes to the emergency department due to fevers, chills, and confusion.  He has a history of poorly controlled diabetes mellitus with a nonhealing ulcer of the left foot.  His temperature is 38.3 C (101 F), blood pressure is 90/60 mm Hg, pulse is 112/min, and respirations are 22/min.  On examination, there is slight erythema surrounding his left foot ulcer with foul-smelling discharge.  No heart murmur is auscultated, the lungs are clear, and the abdomen is soft and nontender.  Blood cultures are obtained, and he is started on broad-spectrum antibiotics.  Twenty-four hours later, blood cultures grow β-lactamase-producing Bacteroides species.  Which of the following is most likely to provide appropriate antimicrobial coverage for this patient?

A 43-year-old man comes to the emergency department due to fever, chest pain, and hemoptysis.  He has a history of a hematologic malignancy for which he recently underwent a cycle of chemotherapy.  Laboratory studies show neutropenia due to the chemotherapeutic agents.  A nodule with surrounding hypoattenuation is revealed on chest CT.  Galactomannan and beta-D-glucan assays are elevated.  Sputum cultures grow Aspergillus.  The patient is placed on intravenous amphotericin B.  During the infusion, he develops headaches, rigors, and hypotension.  Over the next few days, there is a decline in renal function attributed to amphotericin.  These toxic effects are likely due to binding of the antifungal agent to which of the following?

A phase II trial is being conducted at an academic medical center to assess the safety and efficacy of a novel antifungal medication that has yielded promising results in preclinical studies.  The medication is known to inhibit fungal colony growth by changing the composition of the fungal cell membrane.  Phase 0 and phase I trials on healthy volunteers have been uneventful.  The current phase II trial includes 175 subjects.  In 168 subjects, the new antifungal agent is found to inhibit liver cytochrome P450-dependent metabolism of several drugs.  Based on these data, the new antifungal agent is most similar to which of the following?

A 45-year-old woman with advanced HIV infection has been receiving antiretroviral therapy for several years.  When treatment was first initiated, the patient’s viral load rapidly decreased to undetectable levels and her CD4+ cell count remained above 200/mm³.  However, recent HIV RNA levels have increased above the detection threshold.  After undergoing drug resistance testing, she is started on an integrase inhibitor, and her viral load decreases precipitously.  Which of the following steps of viral replication is most likely to be inhibited as a result of this patient’s new treatment?

A 47-year-old man comes to the emergency department due to fever and fatigue.  He has a history of HIV and has not been taking his antiretrovirals consistently.  His temperature is 38.3 C (100.9 F), blood pressure is 110/70 mm Hg, pulse is 104/min, and respirations are 20/min.  Physical examination is notable for hepatosplenomegaly and multiple erythematous papules.  Laboratory studies show pancytopenia.  Histoplasma antigen testing is positive.  Intravenous amphotericin B therapy is initiated for disseminated histoplasmosis.  A day later, the patient develops palpitations and weakness.  An ECG reveals frequent premature ventricular beats.  If these new signs and symptoms are caused by drug toxicity, they are most likely related to which of the following?

A 64-year-old man comes to the emergency department due to fever, anorexia, and nausea.  He recently immigrated to the United States from Vietnam to live with his son.  Several weeks ago, the patient was found to have a positive tuberculin skin test after a routine office visit.  He had no respiratory symptoms, and a chest x-ray was unremarkable.  A month ago, he started isoniazid therapy with pyridoxine supplementation.  Today, his temperature is 38.3 C (100.9 F).  On physical examination, there is mild abdominal discomfort.  Laboratory studies are pending.  Which of the following is the most likely cause of this patient’s current symptoms?

A 29-year-old woman comes to the office with malaise, fever, and extremely painful genital lesions.  She has never had such symptoms before.  She is sexually active with a new partner.  On examination, the patient has several tiny, thin-walled vesicles on an erythematous base and exquisitely tender, shallow ulcers on the labia.  Tender inguinal lymphadenopathy is present.  Tzanck smear of the genital lesions shows multinucleated giant cells.  A drug is prescribed that can be used to manage this acute episode and prevent future episodes of this patient’s condition.  This drug most likely works by which of the following mechanisms?

Researchers analyze the HIV viral structure and replication cycle for new drug targets.  They find the virus encodes a large glycoprotein, which gets cleaved into 2 subunits, the surface and transmembrane subunits.  These subunits remain noncovalently bound to each other in the virion.  Upon activation of the surface protein, conformational changes occur in the transmembrane subunit exposing the functional inner core.  A novel drug is developed that selectively binds and prevents normal functioning of the transmembrane subunit, interfering with the normal viral replication cycle.  This agent most likely directly inhibits which of the following viral processes?

A 25-year-old man comes to the office for follow-up.  He was diagnosed with HIV several weeks ago following a hospitalization for Pneumocystis pneumonia.  He has no other medical problems.  His HIV drug susceptibility report shows no evidence of resistance.  The patient’s treatment regimen includes a drug that is structurally unrelated to nucleosides and is not phosphorylated intracellularly.  The drug acts within the cytoplasm of infected cells to inhibit the synthesis of viral DNA from the RNA template.  Which of the following agents was most likely used in this patient?

A mother brings her 4-year-old son to see you because he has been experiencing decreased appetite, fever, and right-sided ear discharge for the past 24 hours.  His past medical history is significant for three episodes of otitis media over the last year.  You prescribe amoxicillin.  Adding clavulanic acid to this treatment regimen would serve which of the following purposes?

A 42-year-old man comes to the emergency department due to fever, abdominal pain, and explosive diarrhea.  He has a history of HIV but has not been taking any medications.  BMI is 18.2 kg/m².  Abdominal examination is notable for right-sided tenderness to palpation.  Laboratory results show a CD4 cell count of 38/mm³, leukopenia, and thrombocytopenia.  A CT scan of the abdomen reveals colitis.  Colonoscopy reveals areas of erosions and ulcerations; pathology demonstrates cells with viral intranuclear and intracytoplasmic inclusions.  Antiviral therapy is initiated to treat the colitis with an intravenous agent that does not require intracellular activation and is known to bind in vitro with viral-encoded enzymes such as DNA polymerase, RNA polymerase, and reverse transcriptase.  Which of the following agents did this patient most likely receive?

A 50-year-old woman comes to the emergency department due to fever and abdominal pain.  The patient has a history of type 2 diabetes mellitus.  Her temperature is 38.3 C (101 F).  Abdominal examination is notable for right upper quadrant tenderness to palpation that is worsened by deep inspiration.  Laboratory studies show leukocytosis.  An ultrasound of the abdomen reveals multiple gallstones and gallbladder wall thickening with pericholecystic fluid.  Blood cultures are drawn, and surgical consultation is requested.  The patient is initiated on intravenous piperacillin combined with tazobactam.  Which of the following is the most likely reason to use this drug combination in this patient?

A 43-year-old man comes to the office after a recent hospitalization for Pneumocystis pneumonia.  The patient is taking trimethoprim-sulfamethoxazole and says that his pulmonary symptoms are better.  He has a history of HIV and was on highly active antiretroviral therapy until self-discontinuing treatment 2 years ago.  On physical examination, the patient appears to be in no acute distress.  BMI is 20 kg/m².  A few crackles are heard at the lung bases.  His most recent CD4 count is 122/mm³.  After discussing medical compliance and the need to resume antiretroviral therapy, HIV genotyping assay is performed.  Additional testing for HLA-B*57:01 yields positive results.  Which of the following medications is contraindicated in this patient due to the risk of a potentially fatal hypersensitivity reaction?

A 76-year-old hospitalized woman is evaluated for persistent fevers.  Four days ago, she was admitted to the hospital for sepsis, for which she has received broad-spectrum empiric intravenous antibiotic therapy.  Her temperature is 38.9 C (102 F), blood pressure is 110/80 mm Hg, pulse is 98/min, and respirations are 18/min.  Cardiac examination reveals a new diastolic murmur.  Multiple blood cultures drawn at different times grow Enterococcus.  Echocardiogram reveals mitral valve vegetation suggestive of endocarditis.  An intravenous antibiotic is added to the patient’s treatment regimen for synergy.  Several days later, she develops tinnitus and hearing loss attributed to this antibiotic.  The additional antibiotic most directly affects which of the following processes?

Gram-positive bacteria are injected under the skin of experimental animals.  Three days later, the animals are treated with antibiotic therapy.  Aspirates taken from the infection site are plated on nutrient-rich agar.  The isolated bacteria assume a spherical configuration when placed in an isotonic solution and disintegrate rapidly when placed in a hypotonic solution.  Which of the following antibiotics was most likely administered to the animals in this experiment?