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    usmlemate is offline Junior Member
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    Prophylaxis for Mycobacterium avium complex

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    A 42-year-old-man with late stage HIV is failing salvage therapy consisting of zidovudine plus lamivudine plus abacavir (Trizivir) and lopinavir-ritonavir (Kaletra). He is currently taking trimethoprim-sulfamethoxazole (Bactrim, Septra) for Pneumocystis prophylaxis. He has lost 12 pounds during the last two months and is having night sweats. His hematocrit has decreased from 36 to 27 and his absolute CD4 count has decreased from 49 to 19 cells/mm3.

    Which of the following is TRUE regarding prophylaxis for Mycobacterium avium complex (MAC) disease?

    A. The patient's CD4 count is less than 50 cells/mm3 so he should immediately receive prophylaxis for MAC. Recent studies have shown that prophylaxis with rifabutin (Mycobutin) plus clarithromycin (Biaxin) is clearly more effective than clarithromycin alone.

    B. The patient's CD4 count is less than 50 cells/mm3 and this warrants monthly sputum and stool surveillance cultures for MAC. Prophylaxis for MAC should only occur if the patient has a positive stool or urine culture.

    C. Recent guidelines now recommend initiating MAC prophylaxis in a patient with a CD4 cell count less than 100 cells/mm3 if they have concomitant oral candidiasis.

    D. The patient's symptoms of weight loss, night sweats suggest he may possibly have disseminated MAC. Before MAC prophylaxis is started, disseminated MAC infection should be ruled out.

    E. The patient is taking trimethoprim-sulfamethoxazole and that will provide adequate prophylaxis against MAC.

  2. #2
    usmlemate is offline Junior Member
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    Re: Prophylaxis for Mycobacterium avium complex

    Quote Originally Posted by usmlemate
    A 42-year-old-man with late stage HIV is failing salvage therapy consisting of zidovudine plus lamivudine plus abacavir (Trizivir) and lopinavir-ritonavir (Kaletra). He is currently taking trimethoprim-sulfamethoxazole (Bactrim, Septra) for Pneumocystis prophylaxis. He has lost 12 pounds during the last two months and is having night sweats. His hematocrit has decreased from 36 to 27 and his absolute CD4 count has decreased from 49 to 19 cells/mm3.

    Which of the following is TRUE regarding prophylaxis for Mycobacterium avium complex (MAC) disease?

    A. The patient's CD4 count is less than 50 cells/mm3 so he should immediately receive prophylaxis for MAC. Recent studies have shown that prophylaxis with rifabutin (Mycobutin) plus clarithromycin (Biaxin) is clearly more effective than clarithromycin alone.

    B. The patient's CD4 count is less than 50 cells/mm3 and this warrants monthly sputum and stool surveillance cultures for MAC. Prophylaxis for MAC should only occur if the patient has a positive stool or urine culture.

    C. Recent guidelines now recommend initiating MAC prophylaxis in a patient with a CD4 cell count less than 100 cells/mm3 if they have concomitant oral candidiasis.

    D. The patient's symptoms of weight loss, night sweats suggest he may possibly have disseminated MAC. Before MAC prophylaxis is started, disseminated MAC infection should be ruled out.

    E. The patient is taking trimethoprim-sulfamethoxazole and that will provide adequate prophylaxis against MAC.
    The correct answer is D. The patient's constitutional symptoms and anemia suggest that he may have disseminated MAC. Accordingly, studies should be performed to rule out disseminated MAC before prophylaxis is begun, since single drug prophylaxis used in a patient with disseminated MAC could result in drug-resistant MAC. If blood cultures for MAC remain negative after several weeks, it would be reasonable to start MAC prophylaxis at that time.


    Answer A is incorrect. The patient's constitutional symptoms raise concerns about the possibility of disseminated MAC infection and disseminated MAC should be ruled out prior to starting prophylaxis. If the patient had disseminated MAC, the use of a single drug for prophylaxis could result in drug-resistant MAC. Available data suggest that rifabutin plus clarithromycin is no more effective than clarithromycin (Biaxin) alone for MAC prophylaxis and the combination is associated with a higher rate of adverse reactions. In addition, rifabutin could potentially cause significant drug-drug interactions in this patient.

    Answer B is incorrect. There are no recommendations to routinely perform surveillance sputum and stool MAC cultures in HIV-infected patients, regardless of their CD4 cell count. The decision to initiate prophylaxis is based on a CD4 cell count less than 50 cells/mm3, not on evidence of MAC in a stool or sputum culture.

    Answer C is incorrect. Current guidelines for the prevention of opportunistic infections recommend that patients with a CD4 cell count less than 50 cells/mm3 should initiate prophylaxis against disseminated MAC disease. The presence or absence of oral candidiasis is not a factor in deciding whether to initiate MAC prophylaxis.

    Answer E is incorrect. Although trimethoprim-sulfamethoxazole is effective as prophylaxis for Pneumocystis pneumonia and Toxoplasma encephalitis, it does not provide protection against MAC. The preferred prophylactic agents for MAC are azithromycin (Zithromax) or clarithromycin (Biaxin).

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