A 22-year-old male patient complains of fever and shortness of breath. There is no pleuritic chest pain or rigors and no sputum production. A chest x-ray shows diffuse perihilar infiltrates. The patient worsens while on azithromycin. A methenamine silver stain shows cystlike structures. Which of the following is correct?
Patients with Pneumocystis jiroveci (formerly carinii) frequently present with shortness of breath and no sputum production. The interstitial pattern of infiltrates on chest x-ray distinguishes the pneumonia from most bacterial infections. Diagnosis is made by review of methenamine silver stain. Serology is not sensitive or specific enough for routine use. The organism does not grow on any media. Cavitation is quite unusual. The history is likely to suggest a risk factor for HIV disease. The disease commonly recurs in patients with CD4 counts below 200/µL unless prophylaxis (usually with trimethoprim-sulfamethoxazole) is employed.
A 40-year-old woman cut her finger while cooking in her kitchen. Two days later she became rapidly ill with fever and shaking chills. Her hand became painful and mildly erythematous. Later that evening her condition deteriorated as the erythema progressed and the hand became a dusky red. Bullae and decreased sensation to touch developed over the involved hand. What is the most important next step in the management of this patient?
The striking features of this infection are its rapid onset and progression to a cellulitis characterized by dusky dark red erythema, bullae formation, and anesthesia over the area. The patient is acutely ill with fever, tachycardia, and other evidence of SIRS (systemic inflammatory response syndrome). These are clues to necrotizing fasciitis, a rapidly spreading deep soft tissue infection. The organism, usually S pyogenes, reaches the deep fascia from the site of penetrating trauma. Prompt surgical exploration down to fascia or muscle may be lifesaving. Necrotic tissue is Gram stained and cultured—streptococci, staphylococci, mixed anaerobic infection, or clostridia are all possible pathogens. Antibiotics to cover these organisms are important but not as important as prompt surgical debridement. Acute osteomyelitis is considered when cellulitis does not respond to antibiotic therapy, but would not present with this rapidity.
A 25-year-old man from East Tennessee had been ill for 5 days with fever, chills, and headache when he noted a rash that developed on his palms and soles. In addition to macular lesions, petechiae are noted on the wrists and ankles. The patient has recently returned from a summer camping trip. Which of the following is the most important aspect of the history?
The rash of Rocky Mountain spotted fever (RMSF) occurs about 5 days into an illness characterized by fever, malaise, and headache. The rash may be macular or petechial, but almost always spreads from the ankles and wrists to the trunk. The rash indicates endothelial infection, which in severe cases can lead to capillary leak and shock. North Carolina and East Tennessee have a relatively high incidence of disease. RMSF is a rickettsial disease with the tick as the vector, and the disease is more common in warm months when ticks are active. About 80% of patients will give a history of tick exposure. Doxycycline is considered the drug of choice, but chloramphenicol is preferred in pregnancy because of the effects of tetracycline on fetal bones and teeth. Overall mortality from the infection is now about 5%.
A 19-year-old man has a history of athlete’s foot but is otherwise healthy when he develops sudden onset of fever and pain in the right foot and leg. On physical examination, the foot and leg are fiery red with a well-defined indurated margin that appears to be rapidly advancing. There is tender inguinal lymphadenopathy. Which organism is the most likely cause of this infection?
Erysipelas, the cellulitis described, is typical of infection caused by S pyogenes (group A β-hemolytic streptococci). There is often a preceding event such as a cut in the skin, dermatitis, or superficial fungal infection that precedes this rapidly spreading cellulitis. Patients are usually febrile and may appear toxic. Staphylococcus epidermidis does not cause rapidly progressive cellulitis. Staphylococcus aureus can cause cellulitis that is difficult to distinguish from erysipelas, but it is usually more focal and likely to produce furuncles, or abscesses. Tinea infections spread slowly and are confined to the epidermis; they would not cause fever, dermal edema, or tender lymphadenopathy. Anaerobic cellulitis is more often associated with underlying diabetes. α-Hemolytic streptococci rarely cause skin and soft tissue infections.
An 18-year-old male patient has been seen in the clinic for urethral discharge. He is treated with ceftriaxone, but the discharge has not resolved and the culture has returned as no growth. Which of the following is the most likely etiologic agent to cause this infection?
About half of all cases of nongonococcal urethritis are caused by C trachomatis. Ureaplasma urealyticum and Trichomonas vaginalis are rarer causes of urethritis. Herpes simplex would present with vesicular lesions and pain, not with a meatal discharge. C psittaci is the etiologic agent in psittacosis. Almost all gonococci are susceptible to ceftriaxone at recommended doses.
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