Prolonged fever due to Mycobacterium avium complex (MAC) disease in advanced HIV infection: a public health concern

From March 1997 to June 1998, infectious etiologies of prolonged fever was prospectively investigated in 104 advanced human immunodeficiency virus (HIV) infected patients admitted to Siriraj Hospital. The etiology could be identified in 91 cases (87.5%). Of these, blood cultures from 68 patients yielded mycobacteria and fungi. Mycobacterium avium complex was the most common blood isolate in 24 per cent of the patients; followed by Mycobacterium tuberculosis in 20.2 per cent, Cryptococcus neoformans in 5.8 per cent, Penicillium marneffei in 5.8 per cent. During the course of febrile illness, 79 of the 91 patients (86.8%) exhibited focal lesions. Weight loss, elevated serum alkaline phosphatase were often found to be significantly more associated with MAC bacteremia (P < 0.05). Pulmonary involvement significantly correlated more with M. tuberculosis bacteremia than MAC bacteremia (P < 0.05). No cause could be identified in 13 cases. Mycobacterium blood culture alone established the etiologies in 68 cases (65.4%). Of the 25 patients with disseminated MAC (DMAC) infection, nine patients died during hospitalization. Another three cases died within a few months of appropriate anti-MAC chemotherapy. We concluded that the risk of DMAC infection in advanced AIDS patients in Thailand is high when low CD4 lymphocyte count is established. The prolonged fever resulted from DMAC in advanced HIV infection is warrant to be public health concern. Mycobacterium blood culture is a most valuable tool contributing to the diagnosis of infectious agents in this condition. The guidelines of 1997 USPHS/IDSA should be followed to give chemoprophylaxis against DMAC disease in patients with advanced HIV infection and a CD4 count less than 50 cells/mm3.     

Nontuberculous mycobacterial infections

The acquired immunodeficiency syndrome (AIDS) pandemic has led to greater understanding and respect for the pathogenic potential of non-tuberculous mycobacteria. Mycobacterium avium complex (MAC) has emerged as the most common systemic bacterial infection in AIDS, causing debilitating disseminated disease in late-stage HIV-infected patients. With the release of the macrolide antibiotics, clarithromycin and azithromycin, effective and well-tolerated therapeutic regimens for MAC have been developed which prolong survival and increase quality of life. The macrolides and rifabutin are also effective as preventive therapy for MAC in patients with AIDS. Mycobacterium kansasii, which causes pulmonary disease similar to tuberculosis as well as disseminated disease in AIDS, is treatable with isoniazid, rifampin and ethambutol. Clinical syndromes and therapeutic options for other non-tuberculous mycobacteria in AIDS are also reviewed.     

The roles of muscarinic receptor subtypes in modulation of nasal ciliary action

OBJECTIVE: Clinicopathological features of mycobacteriosis were studied by means of microscopical examination of 34 autopsy cases in patients with acquired immunodeficiency syndrome (AIDS) and the diagnostic methods were evaluated. METHODS: All cases were anatomized, sampled, fixed and embedded routinely and stained with hematoxylin-eosin. Acid fast stain was applied to identify the mycobacteria. The pathological sections and files were reviewed systemically and retrospectively. RESULTS: Thirty-four cases of mycobacteriosis, including Mycobacterium avium-intracellular complex (MAI) infection (20 cases) and Mycobacterium tuberculosis (10 cases) and mixed infection of both pathogens (4 cases) were found out of 151 autopsy AIDS patients. MAI infection involved mostly the lymph nodes (21 cases) and followed by spleen, liver and lung, etc. The infection were often disseminated and characterized by proliferation of histocytes with foamy or vacuolar cytoplasm containing acid fast bacilli and formation of granulomatous nodules. Tuberculosis often involved the lung (10 cases) and lymph node (8 cases), the typical manifestations of which were caseous necrosis and tuberculation. Other opportunistic infections and neoplasmas occurred with mycobacteriosis in 25 cases. CONCLUSIONS: Mycobacteriosis, especially the tuberculosis and MAI infection are common in patients with AIDS, which are often disseminated and involved the lung and lymph node. The diagnosis can be made according to the specific pathological appearances and positive acid fast stain.     

AIDS-associated renal tuberculosis

In order to study the prevalence and the clinical features of renal tuberculosis associated with AIDS, we studied the renal tissue of the necropsies made in 46 AIDS patients under light microscopy. We found renal tuberculous granuloma in 11 (23%) patients (in 3 without previous diagnosis of renal or extrarenal tuberculosis) and only 4 of them presented moderate hematuria or pyuria sterile. As subclinical renal tuberculosis was frequent in this group of AIDS patients, the urine culture for Mycobacterium tuberculosis may be useful for diagnosing tuberculosis in AIDS patients.     

Rapid diagnosis of Mycobacterium tuberculosis bacteremia by PCR

A method based on DNA amplification and hybridization has been used for the rapid detection of Mycobacterium tuberculosis in blood samples from 38 hospitalized patients (15 human immunodeficiency virus [HIV] positive and 23 HIV negative) in whom localized or disseminated forms of tuberculosis were suspected. In 32 of these patients, the diagnosis of tuberculosis was eventually confirmed by conventional bacteriological or histological procedures. M. tuberculosis DNA was detected with the PCR technique in the peripheral blood mononuclear cells from 9 of 11 (82%) HIV-infected patients and in 7 of 21 (33%) HIV-negative patients (P < 0.01), while M. tuberculosis blood cultures were positive in 1 of 8 (12.5%) and 1 of 18 (5.5%) patients, respectively. PCR was positive in all cases with disseminated disease in both HIV-negative and HIV-positive patients and also in the HIV-positive patients with extrapulmonary tuberculosis. Seven samples from patients with documented illness other than tuberculosis and 12 specimens from healthy volunteers, including seven volunteers with a recent positive purified protein derivative test, were used as controls and had a negative PCR. These results suggest that detection of M. tuberculosis DNA in peripheral blood mononuclear cells may be a useful tool for rapid diagnosis of disseminated and extrapulmonary forms of tuberculosis, especially in an HIV-positive population.     

Correspondence and personal contact between donor families and organ recipients: one OPO''s procedure and experience

OBJECTIVE: To determine the frequency of disseminated Mycobacterium avium-complex infections (MAC) and the impact of MAC disease on overall survival in patients with HIV disease and AIDS. METHODS: Prospective study of HIV infected patients with a CD4 lymphocyte count < 150/microliter or patients with AIDS over a 7-year period. Blood cultures of all patients presenting symptoms and signs suggestive of disseminated MAC infection were grown. Only patients who deceased at our clinic (n = 427) were included in the final analysis in order to calculate MAC disease-free survival and overall survival after first CD4 lymphocyte count < 100/microliter. RESULTS: 101 out of 427 patients (24%) developed disseminated MAC disease: The median time between first CD4 lymphocyte count < 100/microliter and MAC disease was 441 days (range 16 to 1560). The actuarial risk of MAC disease for the entire patient population was 12%, 28%, and 42% after 1, 2, and 3 years, respectively. When comparing overall survival after first CD4 lymphocyte count < 100/microliter, there was no statistically significant difference between patients who subsequently developed disseminated MAC infection and those who did not. CONCLUSION: MAC disease is a very frequent opportunistic infection in advanced AIDS, mostly in patients with less than 50 CD4 cells/microliter. In contrast to reports from the US, only 24% of our patients developed MAC disease. Survival time between patients with and without MAC infection did not differ.     

Clinical features of tuberculosis associated with HIV infection in Taiwan

To understand the clinical characteristics and outcome of tuberculosis (TB) in patients with acquired immunodeficiency syndrome (AIDS) in Taiwan, we reviewed the medical records of 118 adult AIDS patients who were hospitalized at National Taiwan University Hospital between January 1988 and September 1995. Among them, 29 (24.6%) had TB. The mean age of the AIDS patients with TB was 37 years (range, 25-66 yr). Most patients were in the advanced stages of AIDS when human immunodeficiency virus (HIV) infection and/or TB were first diagnosed. The mean CD4+ lymphocyte count was 0.037 x 10(9)/L (range, 0-0.152 x 10(9)/L) at the time TB was diagnosed. There was no statistically significant difference in the mean CD4+ lymphocyte count between patients with isolated pulmonary TB and those with extrapulmonary involvement. Twenty-two patients (75.8%) had extrapulmonary TB with the most common site being the lymph nodes (72.7%). Clinical symptoms were nonspecific, and the chest physical examination was not helpful in the diagnosis. Acid-fast bacilli were detected in sputum smears from eight patients (36.4%). A primary tuberculosis pattern (hilar adenopathy, pleural effusion, middle or lower lobe infiltrates) in the chest radiographs was the most common radiologic finding (36.4%) in patients with pulmonary TB. The reactivation pattern (predominant upper-lobe infiltrates with or without cavitation) could only be found in cases of pulmonary TB without extrapulmonary involvement. Atypical patterns (diffuse interstitial infiltrates mimicking Pneumocystis carinii pneumonia or other patterns) and normal chest radiographs were noted in nearly one-third of the patients with pulmonary TB. A good response to antituberculosis drugs and a favorable outcome were demonstrated in the patients, except for two with drug-resistant Mycobacterium tuberculosis infection. Early identification of TB in HIV-infected patients requires clinical awareness of the unusual clinical presentations, especially among patients in the advanced stages of AIDS.     

Tuberculosis cutis miliaris disseminata due to multidrug-resistant Mycobacterium tuberculosis in AIDS patients

Two patients with AIDS and disseminated tuberculosis characterized by cutaneous involvement are reported. They developed a maculopapular skin eruption, from which a multidrug-resistant Mycobacterium tuberculosis strain was isolated. In both cases the clinical course was rapidly fatal. Tuberculosis cutis miliaris disseminata should be differentiated from the skin lesions frequently seen in HIV-infected patients, especially from folliculitis. In patients with tuberculosis, the appearance of cutaneous lesions may be due to the haematogenous dissemination of mycobacteria. Therefore, early identification of the causative organism by use of optimal microbiological methods is fundamental.     

Clinical features and outcome in disseminated mycobacterial diseases in AIDS patients in Taiwan

OBJECTIVE: To describe and compare the clinical features and outcome of disseminated tuberculosis (TB) and Mycobacterium avium complex (MAC) disease in AIDS patients. DESIGN: Prospective cohort study. SETTING: A 1800-bed university teaching hospital, the largest centre for HIV/AIDS patients in Taiwan. METHODS: From July 1994 through June 1997, a standardized protocol was used to record the demographic and clinical features in all hospitalized HIV-infected patients, and to perform routine studies and invasive procedures for diagnosis of disseminated mycobacterial diseases. To compare the survival, control patients were selected from the HIV-infected patients hospitalized in the same hospital during the same study period, and had similar age, sex, CD4+ cell counts and antiretroviral therapy regimens. RESULTS: A total of 22 cases of disseminated TB and 15 cases of disseminated MAC were identified. Disseminated TB and MAC occurred in patients with similarly low CD4+ cell counts (median, 23 versus 5 x 10(6)/l; P = 0.08). The clinical features favouring disseminated TB included night sweats, peripheral lymphadenopathy, acid-fast bacilli in sputum smears, chest radiographic findings of hilar enlargement, and lack of prior AIDS-defining illnesses. Hepatosplenomegaly, elevated serum alkaline phosphatase (more than twice the upper limit of normal), elevated serum gamma-glutamyl transpeptidase (more than three times the upper limit of normal), and leukopenia favoured disseminated MAC. The patients with disseminated TB survived much longer than patients with disseminated MAC (mean survival, 96 versus 22 weeks, P = 0.008) but had a similar outcome to control patients (P = 0.60). CONCLUSION: Disseminated TB and MAC are distinguishable by clinical features in AIDS patients with similar immunocompromised states. Those features may facilitate diagnosis and selection of specific therapeutic regimens. Disseminated TB was not associated with a shortened survival period in AIDS patients when they completed anti-TB treatment. In contrast, disseminated DMAC was associated with shortened survival despite treatment with potent regimens. These results may emphasize the importance of prophylaxis for MAC in this population.     

Disseminated Mycobacterium genavense infection: clinical and microbiological features and response to therapy

OBJECTIVE: Mycobacterium genavense is a newly described pathogen that causes disseminated infection in AIDS. It is difficult to detect and identify due to its slow growth and fastidious nature. There is little information available about therapy for this new pathogen. We describe clinical and laboratory features and response to therapy in four patients with advanced AIDS complicated by disseminated M. genavense infection from Denver, Colorado, USA. DESIGN AND METHODS: Retrospective analysis of four cases identified in an AIDS clinic affiliated with a municipal hospital in Denver, Colorado. Clinical samples were inoculated onto BACTEC 12B, Lowenstein-Jensen, and Middlebrook 7H11 media. RESULTS: The clinical features mimicked those of disseminated M. avium complex infection, with invasion of liver, spleen and lymph nodes with acid-fast bacilli (AFB). Acid-fast smears of blood and lymph nodes were positive; there was a modest increase in the growth index in BACTEC broth and tiny colonies appeared on Middlebrook agar. Patients were treated with combinations of antimycobacterial agents. Blood smears and cultures reverted to negative in treated patients. The best clinical response was associated with clarithromycin therapy. CONCLUSIONS: Disseminated disease due to M. genavense should be suspected among patients with the clinical presentation of disseminated M. avium complex infection and low growth index on BACTEC cultures for AFB. The diagnosis of M. genavense may be facilitated by performing acid-fast stains of samples from BACTEC bottles in such individuals. Clarithromycin therapy is associated with clinical improvement and clearance of bacteremia.     

Differentiation between Mycobacterium tuberculosis and Mycobacterium avium by amplification of the 16S-23S ribosomal DNA spacer

Differentiation between Mycobacterium tuberculosis and M. avium is helpful for the treatment of disseminated mycobacterial infection in AIDS patients. This can traditionally be done by time-consuming biochemical tests or with Accuprobe. Previously, PCR restriction enzyme analysis (PCR-REA) of the 16S-23S rRNA gene spacer was shown to be able to identify a limited number of strains of Mycobacterium. In this study the method was improved by using more specific primers and was tested with 50 clinical isolates of M. tuberculosis and 65 clinical isolates of M. avium complex. Probes specific to the spacers of M. tuberculosis and M. avium were also tested. Both M. tuberculosis and M. avium could be reliably identified either by PCR-REA or by PCR-hybridization, with the results completely agreeing with those obtained by biochemical tests and with the Accuprobe, respectively. The method may therefore be useful as an alternative in-house method for identification of the bacteria.     

Clinical utility of the polymerase chain reaction in the diagnosis of extrapulmonary tuberculosis

This study examines the diagnostic utility of the polymerase chain reaction (PCR) in 156 patients (five human immunodeficiency virus (HIV) seropositive) suspected of extrapulmonary tuberculosis. The results of PCR in 226 samples from 11 different sites were compared with the results of microscopy and culture. Positive culture results were predicted in 86% of samples by PCR but in only 31% by microscopy. Specificity of PCR was 92%. In cases with culture-proven tuberculosis, PCR identified all 11 microscopy positive cases and 19 of 24 (79%) of the microscopy-negative cases. In four patients, PCR excluded the diagnosis of tuberculosis in microscopy-positive samples, which were later shown to contain mycobacteria other than Mycobacterium tuberculosis or laboratory contaminants. In 20 patients (microscopy, PCR and culture negative) a trial of antituberculous drugs was given, but patients showed no improvement and treatment was stopped. In 17 patients, all culture negative (in nine PCR was positive, three of whom also had positive microscopy) the diagnosis was probable tuberculosis based on clinical findings and response to treatment. This polymerase chain reaction has a much higher sensitivity than microscopy and can facilitate therapeutic decisions for those with suspected extrapulmonary tuberculosis.     

Mycobacterium genavense infection presenting as a solitary brain mass in a patient with AIDS: case report and review

Patients with AIDS are prone to developing infections with opportunistic pathogens. Recently, a new mycobacterium, Mycobacterium genavense, has been found to cause infection in patients with AIDS. Previously published reports indicate that patients who are infected with this organism present with the same clinical features as do patients with disseminated infection due to organisms of the Mycobacterium avium complex. We describe an unusual case of a patient with AIDS who presented with grand mal seizures and a mass lesion in his brain, which was found to be caused by infection with M. genavense. No evidence of disseminated infection could be found in this patient. We discuss the microbiology of this organism and review the literature on M. genavense infections. Clinicians should be aware of this organism so that efforts at culture and identification will be made.     

Bone marrow biopsy in the diagnosis of fever of unknown origin in patients with acquired immunodeficiency syndrome

BACKGROUND: Fever is commonly observed in patients with human immunodeficiency virus (HIV) disease and frequently eludes diagnosis. The role of bone marrow biopsy in the diagnosis of fever of unknown origin in patients infected with HIV remains controversial. PATIENTS AND METHODS: One hundred twenty-three consecutive patients with 137 episodes of fever lasting 10 or more days without diagnosis after 1 week of hospitalization were evaluated by bone marrow biopsy. RESULTS: Overall, a specific diagnosis was achieved in 52 episodes by means of culture and histopathological examination (diagnostic yield, 37.9%). Three types of disease were found: mycobacterial infections (n = 36, 69% of documented episodes), including 18 patients with disseminated tuberculosis and 14 with Mycobacterium avium-intracellulare complex infections; non-Hodgkin lymphomas (n = 12, 23%); and visceral leishmaniasis (n = 4, 8%). Although bone marrow cultures were more sensitive than microscopic examination with special stains for the diagnosis of mycobacterial infections, the pathological examination of bone marrow led to a more rapid diagnosis of disease. In addition, the histopathological examination of bone marrow alone led to the diagnosis of a specific condition in 43 episodes (31.3% of all episodes). CONCLUSIONS: Bone marrow biopsy is a useful procedure for the diagnosis of fever in patients with advanced HIV disease, particularly in areas where tuberculosis and leishmaniasis are prevalent. Involvement of the marrow may be the first indication of the existence of extranodal non-Hodgkin lymphoma. For Mycobacterium avium-intracellulare complex infection, blood cultures were more sensitive than bone marrow biopsy.     

Treatment and prophylaxis of disseminated Mycobacterium avium complex in HIV-infected individuals

OBJECTIVE: To review the pathophysiology, epidemiology, treatment, and prophylaxis of disseminated Mycobacterium avium complex (MAC) infection in HIV-infected individuals. DATA SOURCES: A MEDLINE (January 1966-July 1997) and AIDSLINE (January 1980-July 1997) search of basic science articles pertinent to the MAC infection in HIV-infected patients. STUDY SELECTION AND DATA EXTRACTION: All articles were considered for possible inclusion in the review. Pertinent information, as judged by the authors, was selected for discussion. DATA SYNTHESIS: The organism, epidemiology, and pathophysiology of disseminated MAC are discussed for background. A review of clinical trials for the treatment and prophylaxis of disseminated MAC are presented, along with unresolved issues concerning these topics. CONCLUSIONS: The incidence of disseminated MAC has increased dramatically with the AIDS epidemic. The infection can lead to increased morbidity and mortality in HIV-infected patients. Treatment regimens for patients with a positive culture for MAC from a sterile site should include two or more drugs, including clarithromycin. Prophylaxis against disseminated MAC should be considered for patients with a CD4 cell count of less than 50/mm3.     

Human immunodeficiency virus infection alters antigen-induced cytokine responses in patients with active mycobacterial diseases

Peripheral blood cells from 29 patients with active Mycobacterium avium (MAC) or Mycobacterium tuberculosis diseases were tested for mycobacterial antigen-induced interferon (IFN)-gamma and interleukin (IL)-4 production. Among MAC patients, human immunodeficiency virus (HIV) infection was associated with an 80% decrease in those who produced IFN-gamma, resulting in a predominantly type 2 cytokine profile. HIV infection in patients with tuberculosis correlates with a 37% increase in those producing IL-4 and a type 1 to type 0 profile shift. These qualitative changes were independent of CD4+ or CD8+ cell numbers. The amounts of both IFN-gamma and IL-4 were decreased in the HIV-infected population. Quantitative reduction of IFN-gamma was the result of fewer secreting cells rather than a down-regulation at the single-cell level. Disseminated disease was restricted to 2 of 5 HIV-infected MAC patients with a type 2 cytokine profile and 4 of 5 HIV-infected tuberculosis patients with a type 0 profile. These results demonstrated a shift in mycobacterial antigen-specific cytokine profiles from type 1 to type 0 and to type 2, in parallel with AIDS progression.     

A case of AIDS with disseminated Mycobacterium kansasii infection in which Mycobacterium, avium complex was also detected from his sputum repeatedly

A 43 year-old Japanese male was admitted to our hospital because of productive cough and fever. He was diagnosed as acquired immunodeficiency syndrome (AIDS) in 1994. Laboratory findings were as follows: WBC was 3200/microliter, CD4+ T lymphocyte count was 22/microliter. His chest X-ray film taken on admission showed infiltration with small cavity lesion in middle left lung field. Tuberculin skin reaction was negative. He was treated with isoniazid 0.4 g, rifampicin 0.45 g, and ethambutol 0.75 g each daily. Sputum smear was positive for acid fast bacilli. The cultured isolates were identified as Mycobacterium kansasii (M. kansasii) and Mycobacterium avium complex (MAC). Urine smear was also positive for acid fast bacilli. The cultured isolates were identified as M. kansasii. He was diagnosed as disseminated M. kansasii infection and suspected MAC infection. About one hundred days later, his chest X-ray film showed reticular shadow. His clinical symptoms improved and the sputum smear and culture converted to negative for acid fast bacilli. Based on these findings, his MAC discharge was considered not as MAC infection, but MAC colonization. He returned to the former hospital for AIDS treatment, and he died in August 1996.     

Mycobacterium tuberculosis infection in solid-organ transplant recipients: impact and implications for management

Tuberculosis is a serious opportunistic infection in transplant recipients. On the basis of the compilation of published reports in the literature, the incidence of Mycobacterium tuberculosis infection in organ transplant recipients worldwide ranged from 0.35% to 15%. Nonrenal transplantation (P = .004), rejection within 6 months before the onset of tuberculosis (P = .02) and type of primary immunosuppressive regimen (P = .007) were predictors of M. tuberculosis infection occurring within 12 months after transplantation. Thirty-three percent (155) of 476 transplant patients with tuberculosis had disseminated infection; receipt of OKT3 or anti-T cell antibodies (P = .005) was a significant predictor of disseminated tuberculosis. Overall, the mortality rate among 499 patients was 29%; disseminated infection (P = .0003), prior rejection (P = .006), and receipt of OKT3 or anti-T cell antibodies (P = .0013) were significant predictors of mortality in patients with tuberculosis. Clinically significant hepatotoxicity due to isoniazid occurred in 2.5%, 4.5%, and 41% of renal, heart and lung, and liver transplant recipients, respectively. The diagnosis and effective management of tuberculosis after transplantation warrant recognition of the unique epidemiological and clinical characteristics of tuberculosis in transplant recipients.     

Does AIDS impair the absorption of antituberculosis agents?

SETTING: Case reports of low serum concentrations of antituberculosis drugs, with resultant treatment failure and emergence of drug-resistant organisms in patients with the acquired immune-deficiency syndrome (AIDS), have prompted suggestions that therapeutic drug monitoring (TDM) may be indicated in patients co-infected with the human immunodeficiency virus (HIV) and Mycobacterium tuberculosis. OBJECTIVE: To test whether the bioavailability of antituberculosis drugs is altered in HIV-infected patients with tuberculosis. METHOD: Twenty-seven hospitalized tuberculosis patients (13 with AIDS, 14 HIV-negative) were entered into a pharmacokinetic trial. Following the supervised administration of standardized doses of isoniazid, rifampicin and pyrazinamide, the plasma concentrations of the drugs were measured repeatedly over 12 hours and the following parameters were derived for each agent: maximum measured drug concentration (Cmax), time-to-maximum measured drug concentration (Tmax) and area-under-the-concentration-time curve to 12 hours (AUC). RESULTS: No significant differences emerged between the two groups in Cmax, Tmax, and AUC for isoniazid and pyrazinamide. For rifampicin the AIDS patients showed a greater AUC (P < 0.01) than the controls, but there were no significant differences in Cmax and Tmax. CONCLUSION: There was no evidence that HIV infection reduced the plasma concentrations of antituberculosis drugs.     

Peripheral neuroblastoma in a young Beagle dog

Disseminated Mycobacterium avium complex (MAC) infections are common in patients with acquired immunodeficiency syndrome (AIDS). These patients frequently seek care with fever accompanied by generalized systemic symptoms and undergo bone marrow biopsy. It is our practice to stain all bone marrow trephine biopsy specimens from patients infected with HIV for acid-fast bacilli (AFB). We evaluated this practice by comparing the sensitivity and turnaround time for detection of MAC by biopsy specimen staining, bone marrow aspirate culture, and blood culture. Bone marrow trephine biopsy specimens with corresponding bone marrow aspirate and blood cultures from 86 HIV-positive patients were reviewed. Of the 86 patients, 30 had positive results for disseminated MAC infection, and all 30 of those patients had positive blood cultures. Bone marrow aspirate cultures identified 17 MAC-positive cases, and AFB staining of the biopsy specimen identified 9. The mean times to detection of MAC positivity were 1.1 days for AFB staining of the biopsy specimen, 19 days for bone marrow aspirate culture, and 16 days for blood culture. While AFB staining of biopsy specimens was the least sensitive of the detection methods, it was useful for the rapid diagnosis of disseminated MAC infection, allowing for prompt initiation of antimycobacterial therapy in one third of patients.