Protection from Mycobacterium avium complex disease in human immunodeficiency virus-infected persons with a history of tuberculosis

Attenuated tuberculin skin test responses associated with Mycobacterium intracellulare sputum colonization in an adolescent TB prevalence survey in Western Kenya

INTRODUCTION

Exposure to Non-tuberculous Mycobacteria (NTM) varies regionally and may partly explain the disparate outcomes of BCG vaccination and tuberculosis (TB) susceptibility.

METHODS

We examined NTM sputum colonization, associations with clinical characteristics, and tuberculin skin test (TST) responses in an adolescent TB prevalence survey.

RESULTS

Among 5004 adolescents screened, 2281 (45.5 %) were evaluated further. TB and NTM prevalence rates were 0.3 % and 8.0 %, respectively. Among 418 NTM isolates, 103 were unidentifiable, and 315 (75 %) comprised 15 species, the most frequent being M. intracellulare (MAC) (108, 26 %), M. scrofulaceum (96, 23 %) and M. fortuitum (51, 12 %). "NTM colonized" adolescents had less frequent chronic cough and night sweats (adjusted odds ratio [aOR] 0.62, 95 % confidence interval [CI] 0.44-0.87and aOR 0.61, CI 0.42-0.89 respectively), and lower TST induration (median 11 mm (interquartile range [IQR] 0-16) vs 13 mm (IQR 6-17; p = 0.006)) when compared to "NTM not colonized" participants. MAC, but not M. scrofulaceum or M. fortuitum, was associated with decreased TST induration (median 7.5 mm (IQR 0-15) vs 13 mm (IQR 6-17) among "MAC colonized" vs "not colonized", p = 0.001).

CONCLUSION

We observed high NTM prevalence rates with species-specific associations with TST induration, consistent with a model of species-dependent heterologous immunity among mycobacteria.

Virulence Mechanisms of Mycobacterium abscessus: Current Knowledge and Implications for Vaccine Design

Mycobacterium abscessus is a member of the non-tuberculous mycobacteria (NTM) group, responsible for chronic infections in individuals with cystic fibrosis (CF) or those otherwise immunocompromised. While viewed traditionally as an opportunistic pathogen, increasing research into M. abscessus in recent years has highlighted its continued evolution into a true pathogen. This is demonstrated through an extensive collection of virulence factors (VFs) possessed by this organism which facilitate survival within the host, particularly in the harsh environment of the CF lung. These include VFs resembling those of other Mycobacteria, and non-mycobacterial VFs, both of which make a notable contribution in shaping M. abscessus interaction with the host. Mycobacterium abscessus continued acquisition of VFs is cause for concern and highlights the need for novel vaccination strategies to combat this pathogen. An effective M. abscessus vaccine must be suitably designed for target populations (i.e., individuals with CF) and incorporate current knowledge on immune correlates of protection against M. abscessus infection. Vaccination strategies must also build upon lessons learned from ongoing efforts to develop novel vaccines for other pathogens, particularly Mycobacterium tuberculosis (M. tb); decades of research into M. tb has provided insight into unconventional and innovative vaccine approaches that may be applied to M. abscessus. Continued research into M. abscessus pathogenesis will be critical for the future development of safe and effective vaccines and therapeutics to reduce global incidence of this emerging pathogen.

Recombinant BCG-Prime and DNA-Boost Immunization Confers Mice with Enhanced Protection against Mycobacterium kansasii

The incidence of infections with nontuberculous mycobacteria (NTM) has been increasing worldwide. The emergence of multidrug-resistant NTM is a serious clinical concern, and a vaccine for NTM has not yet been developed. We previously developed a new recombinant Bacillus Calmette–Guérin (rBCG) vaccine encoding the antigen 85B (Ag85B) protein of Mycobacterium kansasii—termed rBCG-Mkan85B—which was used together with a booster immunization with plasmid DNA expressing the same M. kansasii Ag85B gene (DNA-Mkan85B). We reported that rBCG-Mkan85B/DNA-Mkan85B prime–boost immunization elicited various NTM strain-specific CD4⁺ and CD8⁺ T cells and induced Mycobacterium tuberculosis-specific immunity. In this study, to investigate the protective effect against M. kansasii infection, we challenged mice vaccinated with a rBCG-Mkan85B or rBCG-Mkan85B/DNA-Mkan85B prime–boost strategy with virulent M. kansasii. Although BCG and rBCG-Mkan85B immunization each suppressed the growth of M. kansasii in the mouse lungs, the rBCG-Mkan85B/DNA-Mkan85B prime–boost vaccination reduced the bacterial burden more significantly. Moreover, the rBCG-Mkan85B/DNA-Mkan85B prime–boost vaccination induced antigen-specific CD4⁺ and CD8⁺ T cells. Our data suggest that rBCG-Mkan85B/DNA-Mkan85B prime–boost vaccination effectively enhances antigen-specific T cells. Our novel rBCG could be a potential alternative to clinical BCG for preventing various NTM infections.

A Rare Form of Pott's Disease With Multifaceted Pathological Complications

While tuberculosis is globally very prevalent, especially in the developing world, tuberculosis of the central nervous system (CNS) (including Pott's `disease) is an extremely rare occurrence for neurology/neurosurgery departments in the modern era. It is normally treated via rifampin, isoniazid, pyrazinamide, and ethambutol (RIPE) therapy with the need for surgical intervention deemed by the presence of neurological deficiency or abscess, spinal instability, or significant kyphosis. Here we describe a case of an elderly woman with Pott's disease and a history of HIV presenting with neurologic deficiencies in both legs and an infected mass causing mid-thoracic compression and kyphotic deformity. The presence of a compromised immune system greatly complicates treatment and worsens outcomes. The patient underwent trans-thoracic corpectomy for decompression and mass removal. Spinal realignment was accomplished with an anterior graft, using the patient's rib, preceding posterior stabilization with instrumentation. Postoperatively, the patient received RIPE therapy. Despite a compromised immune system, the full neurologic function of both legs was restored in four months.

Looking beyond Typical Treatments for Atypical Mycobacteria

The genus Mycobacterium comprises not only the deadliest of bacterial pathogens, Mycobacterium tuberculosis, but several other pathogenic species, including M. avium and M. abscessus. The incidence of infections caused by atypical or nontuberculous mycobacteria (NTM) has been steadily increasing, and is associated with a panoply of diseases, including pulmonary, soft-tissue, or disseminated infections. The treatment for NTM disease is particularly challenging, due to its long duration, to variability in bacterial susceptibility profiles, and to the lack of evidence-based guidelines. Treatment usually consists of a combination of at least three drugs taken from months to years, often leading to severe secondary effects and a high chance of relapse. Therefore, new treatment approaches are clearly needed. In this review, we identify the main limitations of current treatments and discuss different alternatives that have been put forward in recent years, with an emphasis on less conventional therapeutics, such as antimicrobial peptides, bacteriophages, iron chelators, or host-directed therapies. We also review new forms of the use of old drugs, including the repurposing of non-antibacterial molecules and the incorporation of antimicrobials into ionic liquids. We aim to stimulate advancements in testing these therapies in relevant models, in order to provide clinicians and patients with useful new tools with which to treat these devastating diseases.

BCG Vaccination Induces M. avium and M. abscessus Cross-Protective Immunity

Pulmonary non-tuberculous mycobacterial (NTM) infections particularly caused by Mycobacterium avium complex (MAC) and Mycobacterium abscessus (MAB) are becoming major health problems in the U.S. New therapies or vaccines which will help prevent the disease, shorten treatment duration and/or increase treatment success rates are urgently needed. This study was conducted with the objective of testing the hypothesis that Bacillus Calmette Guerin (BCG), a vaccine used for prevention of serious forms of tuberculosis (TB) in children and adolescents in tuberculosis hyperendemic countries, induces cross-protective T cell immunity against Mycobacterium avium (MAV) and MAB. Human TB and NTM cross-protective T cells were quantified using flow cytometric assays. The ability of BCG expanded T cells to inhibit the intracellular growth of MAV and MAB was assessed in co-cultures with infected autologous macrophages. In both BCG-vaccinated and M. tuberculosis (Mtb)-infected mice, NTM cross-reactive immunity was measured using IFN-γ ELISPOT assays. Our results demonstrate the following key findings: (i) peripheral blood mononuclear cells from TB skin test-positive individuals contain MAV and MAB cross-reactive T cells, (ii) both BCG vaccination and Mtb infection of mice induce MAV and MAB cross-reactive splenic cells, (iii) BCG-expanded T cells inhibit intracellular MAV and MAB, (iv) CD4, CD8, and γδ T cells play important roles in inhibition of intracellular MAV and MAB and (v) BCG vaccination of healthy volunteers induces TB and NTM cross-reactive T cells. In conclusion, BCG-vaccination induces NTM cross-reactive immunity, and has the potential for use as a vaccine or immunotherapy to prevent and/or treat pulmonary NTM disease.

Human immunodeficiency virus-related gastrointestinal pathology: a southern Africa perspective with review of the literature (part 1: infections)

CONTEXT

Human immunodeficiency virus infection is rife in sub-Saharan Africa and in southern Africa in particular. Despite the increasing availability of antiretroviral therapy in this region, opportunistic infections remain common and frequently involve the gastrointestinal tract.

OBJECTIVE

To review the histopathologic findings and distinguishing features of human immunodeficiency virus-associated gastrointestinal infections in southern Africa and relate those findings to the documented international literature.

DATA SOURCES

The available literature on this topic was reviewed and supplemented with personal experience in a private histopathology practice in South Africa.

CONCLUSIONS

In southern Africa, the range of gastrointestinal, opportunistic infectious pathology in human immunodeficiency virus afflicted patients is diverse and includes viral, bacterial, fungal, and parasitic infections. This infectious pathology is sometimes a manifestation of systemic disease. In profoundly immunocompromised patients, unusual histologic features, involvement of uncommon gastrointestinal tract sites, and more than one pathogen may be seen.

Prevalence of nontuberculous mycobacterial lung disease in U.S. Medicare beneficiaries

RATIONALE

Pulmonary nontuberculous mycobacteria (PNTM) are an important cause of morbidity among older adults in the United States, but national prevalence estimates are lacking.

OBJECTIVES

To describe the prevalence and trends of PNTM disease among adults aged 65 years or older throughout the United States.

METHODS

A nationally representative 5% sample of Medicare Part B beneficiaries was analyzed from 1997 to 2007. Demographic and medical claims data were compiled and prevalence estimates for PNTM and selected comorbidities were calculated and trends over time evaluated. Logistic regression was used to identify demographic and geographic factors associated with PNTM.

MEASUREMENTS AND MAIN RESULTS

From 1997 to 2007, the annual prevalence significantly increased from 20 to 47 cases/100,000 persons, or 8.2% per year. The period prevalence was 112 cases/100,000 persons, although prevalence was twofold higher among Asians/Pacific Islanders than among whites (228 vs. 116 cases/100,000 persons). Western states had the highest period prevalence at 149 cases/100,000 persons, with Hawaii having the highest prevalence at 396 cases/100,000 persons, followed by southeastern states, which had a period prevalence of 131 cases/100,000 persons. PNTM cases had more comorbid conditions than noncases and were 40% more likely to die than noncases. Women were 1.4 times more likely to be a PNTM case than men. Relative to whites, Asians/Pacific Islanders were twice as likely to be a case, whereas blacks were half as likely.

CONCLUSIONS

The prevalence of PNTM is increasing across all regions of the United States and among both men and women. Significant racial/ethnic and geographic differences suggest important gene-environment interactions.

Environmental risk factors for infection with Mycobacterium avium complex

Infection with Mycobacterium avium complex is acquired from the environment, but risk factors for M. avium complex infection and disease are poorly understood. To identify risk factors for infection, the authors performed a 1998-2000 cross-sectional study in western Palm Beach County, Florida, using a population-based random household survey. M. avium complex infection was identified by use of the M. avium sensitin skin test. Of 447 participants, 147 (32.9%) had a positive test reaction, 186 (41.6%) had a negative test reaction, and, for 114 (25.5%), test results were indeterminate. Among the 333 participants with positive or negative M. avium sensitin skin tests, age-adjusted independent predictors of M. avium complex infection in a multivariate model included Black race (odds ratio = 3.8, 95% confidence interval: 2.2, 6.6), birth outside the United States (odds ratio = 2.1, 95% confidence interval: 1.1, 3.9), and more than 6 years' cumulative occupational exposure to soil (odds ratio = 2.7, 95% confidence interval: 1.3, 6.0). Exposure to water, food, or pets was not associated with infection. Results indicate that soil is a reservoir for M. avium complex associated with human infection and that persons whose occupations involve prolonged soil exposure are at increased risk of M. avium complex infection.

Spectrum of clinical disease in a series of 135 hospitalised HIV-infected patients from north India

BACKGROUND

Literature on the spectrum of opportunistic disease in human immunodeficiency virus (HIV)-infected patients from developing countries is sparse. The objective of this study was to document the spectrum and determine the frequency of various opportunistic infections (OIs) and non-infectious opportunistic diseases, in hospitalised HIV-infected patients from north India.

METHODS

One hundred and thirty five consecutive, HIV-infected patients (age 34 +/- 10 years, females 17%) admitted to a tertiary care hospital in north India, for the evaluation and management of an OI or HIV-related disorder between January 2000 and July 2003, were studied.

RESULTS

Fever (71%) and weight loss (65%) were the commonest presenting symptoms. Heterosexual transmission was the commonest mode of HIV-acquisition. Tuberculosis (TB) was the commonest OI (71%) followed by candidiasis (39.3%), Pneumocystis jiroveci pneumonia (PCP) (7.4%), cryptococcal meningitis and cerebral toxoplasmosis (3.7% each). Most of the cases of TB were disseminated (64%). Apart from other well-recognised OIs, two patients had visceral leishmaniasis. Two cases of HIV-associated lymphoma were encountered. CD4+ cell counts were done in 109 patients. Majority of the patients (82.6%) had CD4+ counts <200 cells/microL. Fifty patients (46%) had CD4+ counts <50 cells/microL. Only 50 patients (37%) received antiretroviral therapy. Twenty one patients (16%) died during hospital stay. All but one deaths were due to TB (16 patients; 76%) and PCP (4 patients; 19%).

CONCLUSIONS

A wide spectrum of disease, including both OIs and non-infectious opportunistic diseases, is seen in hospitalised HIV-infected patients from north India. Tuberculosis remains the most common OI and is the commonest cause of death in these patients.

Incidence of acquired immunodeficiency syndrome-associated opportunistic diseases and the effect of treatment on a cohort of 1115 patients infected with human immunodeficiency virus, 1989-1997

Temporal trends in the incidence of opportunistic diseases (ODs) related to acquired immunodeficiency syndrome (AIDS) were studied during 1989-1997 in 1115 outpatients infected with human immunodeficiency virus (331 of whom had AIDS) in a hospital in Madrid, Spain. We analyzed the effect of adherence to antiretroviral therapy and Pneumocystis carinii pneumonia (PCP) prophylaxis on the incidence of OD. Diseases that showed a significant decreasing trend were esophageal candidiasis, pulmonary and extrapulmonary tuberculosis, and cerebral toxoplasmosis. Patients who adhered to antiretroviral therapy had a smaller risk of OD. Patients who adhered to PCP prophylaxis had a reduced risk of cerebral toxoplasmosis and PCP. A reduction in the incidence of AIDS-related ODs was observed, mainly in patients who underwent prophylaxis. Adherence to antiretroviral treatment and PCP prophylaxis was associated with a reduction in the risk of disease.

Sources of disseminated Mycobacterium avium infection in AIDS

OBJECTIVES

To identify the sources of disseminated Mycobacterium avium complex (MAC) infection in AIDS.

METHODS

HIV positive subjects with CD4 counts <100/mm(3) in Atlanta, Boston, New Hampshire and Finland were entered in a prospective cohort study. Subjects were interviewed about potential MAC exposures, had phlebotomy performed for determination of antibody to mycobacterial lipoarabinomannin and for culture. Patient-directed water samples were collected from places of residence, work and recreation. Patients were followed for the development of disseminated MAC. Univariate and multivariate risk factors for MAC were analyzed.

RESULTS

Disseminated MAC was identified in 31 (9%) subjects. Significant risks in univariate analysis included prior Pneumocystis carinii pneumonia (PCP) (hazard ratio 1.821), consumption of spring water (4.909), consumption of raw seafood (34.3), gastrointestinal endoscopy (2.894), and showering outside the home (0.388). PCP, showering and endoscopy remained significant in a Cox proportional hazards model. There was no association between M. avium colonization of home water and risk of MAC. In patients with CD4<25, median OD antibody levels to lipoarabinomannin at baseline were 0.054 among patients who did not develop MAC and 0.021 among patients who did develop MAC (P=0.077).

CONCLUSIONS

MAC infection results from diverse and likely undetectable environmental and nosocomial exposures. Mycobacterial infection before HIV infection may confer protection against disseminated MAC in advanced AIDS.

Skin test reactivity and cellular immune responses to Mycobacterium avium sensitin in AIDS patients at risk for disseminated M. avium infection

Skin tests and lymphocyte proliferation assays (LPA) were performed with Mycobacterium avium sensitin on patients with AIDS. Among 139 subjects, 13% had positive skin test results and 32% had positive LPA results. The LPA may be a more sensitive indicator of prior M. avium infection in this population.

Mycobacteriosis in the compromised host

The studies of rare genetic defects, the preliminary results of population-based studies, being validated by the experimental immunocompromised animal models and the current observations accumulated in immunocompromised patients with mycobacterial diseases provide us with insights into the importance of the macrophage activation pathway in controlling human infection with pathogenic and non pathogenic intracellular multiplying mycobacteria. Initial cytokine production by infected macrophages and/or dendritic cells could be crucial in the overall regulation of self cure, acquired protection or immunopathological sequelae expressing the disease. Knowledge of molecular and genetic cross-talks between phagocytic and specialized antigen presenting cells and different mycobacterial products associated with persistence or replication of the intracellular bacteria, could provide further informations on the global immune regulation of the early host responses to infection and the following events. It seems likely that the development of mycobacterial infections in humans will turn out to be as much dependent on the genetic make up of the host as or the virulence of the bacteria.

Nontuberculous mycobacterial disease in northern Australia: a case series and review of the literature

We performed a retrospective/prospective review of all cases of disease due to nontuberculous mycobacteria (NTM) reported in the Northern Territory, Australia, during the period 1989-1997. Fifty-eight cases were reported, with an average yearly incidence of 3.9 cases per 100,000 persons. The number increased significantly for the second half of the study period (39 vs. 19 cases; P<.02). The yearly incidence of pulmonary Mycobacterium avium/Mycobacterium intracellulare complex (MAC) disease not associated with human immunodeficiency virus (HIV) infection was 2.1 cases per 100,000 population. MAC was the most common isolate (78%) and pulmonary disease the most frequent clinical presentation (62%). Disease due to NTM or MAC was not found more commonly in rural areas. Significant risks for non-HIV-associated pulmonary MAC disease included male sex (odds ratio [OR], 2.1; 95% confidence interval [CI], 1.0-4.5) and age >50 years (OR, 26.5; 95% CI, 10.9-67.3), but aboriginal people appeared underrepresented (OR, 0.77; 95% CI, 0.30-1.87). Mycobacterium tuberculosis was almost 5 times more likely than NTM to be the cause of non-HIV-associated mycobacterial pulmonary disease (153 vs. 32 cases; OR, 4.79; 95% CI, 3.22-7.14). Mycobacterial lymphadenitis in aboriginal children was more likely to be tuberculous than nontuberculous (OR, 6.5; 95% CI, 1.4-41.7), but not in nonaboriginal children (OR, 1.0). With treatment, 66% of the cases of non-HIV-associated pulmonary MAC disease had favorable outcomes, and 7% of patients had progressive fatal disease. Outcomes of therapy for lymphadenitis and skin/soft-tissue disease were excellent, but those of HIV-associated disseminated MAC disease were poor.

Infections with Mycobacterium tuberculosis and Mycobacterium avium among HIV-infected patients after the introduction of highly active antiretroviral therapy. EuroSIDA Study Group JD

The impact of highly active antiretroviral therapy (HAART) among human immunodeficiency virus (HIV)-infected patients on the incidences of mycobacterial infections has not been studied in detail. We assessed incidences of mycobacterial diseases among HIV- infected patients following the introduction of HAART, using data from the EuroSIDA study, a European, multicenter observational cohort of more than 7,000 patients. Overall incidences of Mycobacterium tuberculosis (TB) and Mycobacterium avium complex (MAC) were 0.8 and 1.4 cases/100 person-years of follow-up (PYF), decreasing from 1.8 (TB) and 3.5 cases/100 PYF (MAC) before September 1995 to 0.3 and 0.2 cases/100 PYF after March 1997. After adjustment for changes in CD4 cell count and use of antiretroviral treatment in Cox proportional hazards models, the risk of MAC decreased with increasing calendar time (hazard ratio per calendar year; HR = 0.58 [95% confidence intervals: 0.45-0.74], whereas this was not the case for TB; 0.95 [0.74-1.22]). In conclusion, we documented marked decreases in the incidence of TB and to an even larger extent of MAC among HIV-infected patients from 1994 to 1999. The decrease in TB was associated with the introduction of HAART and changes in CD4 cell count. These factors could also explain some of the decrease in MAC over time, though there remained a significantly lower risk of MAC than expected.

Applying experiences from trials of bacille Calmette-Guérin vaccine

Bacille Calmette-Guérin (BCG) vaccine, a live vaccine developed to prevent tuberculosis (TB), has been given to billions of persons over more than 7 decades. Studies of the efficacy of BCG vaccine have had widely divergent results, underscoring the complexity of the biology and immunology of TB. The long duration of TB infection, the heterogeneity of its clinical expression, and lack of inexpensive, reliable markers of infection and disease have made it difficult to study the impact of a vaccine, especially in resource-poor areas. A meta-analysis of data from trials of BCG vaccine found that studies conducted at sites that are a greater distance from the equator are associated with better vaccine efficacy, a finding that needs fuller study. BCG vaccine trials with higher validity scores showed higher rates of protection. Ongoing changes, including human immunodeficiency virus infection and demographic shifts, should be considered when developing trials of future vaccines. Analyses of past studies of BCG vaccine can identify sources of variation that may guide the design of studies of new vaccines. Rigorous study design and new tools are needed if studies are to provide clear, useful answers about new vaccines.

Observed differences in virulence-associated phenotypes between a human clinical isolate and a veterinary isolate of Mycobacterium avium

Mycobacterium avium, the most common opportunistic pathogen in patients with AIDS, is frequently isolated from a variety of environmental sources, but rarely can these environmental isolates be epidemiologically linked with isolates known to cause human disease. Using a number of in vitro tissue culture assays, we found significant pathogenic differences between a serotype 4 human clinical M. avium isolate and a serotype 2 veterinary isolate. Cell association of the patient strain with a human intestinal cell line was 1.7 times that of the veterinary strain. Growth of this clinical strain in human peripheral blood mononuclear cell-derived macrophages increased from 12-fold higher than that of the veterinary isolate after 2 days to 200-fold higher after 4 days. By the conclusion of each experiment, lysis of all examined host cell types and accumulation of cell debris were observed in infections with the human isolate, but monolayers remained relatively intact in the presence of the animal isolate. The two strains also differed in the ability to stimulate human immunodeficiency virus replication in coinfected host cells, with p24 antigen levels after 6 days threefold higher in the cells coinfected with the clinical strain than in those infected with the veterinary strain. If the genetic differences responsible for the phenotypes observed in these assays can be identified and characterized, it may be possible to determine which M. avium strains in the environment are potential human pathogens.

Randomised trial of intradermal Mycobacterium vaccae or intradermal hepatitis B immunisation in children with HIV infection

This study assessed the safety of inactivated Mycobacterium vaccae as a candidate vaccine to prevent disseminated mycobacterial disease in children with HIV infection. 35 children ages 1-8 with CD4 counts > or =300/mm3 in New Hampshire, Boston and Chicago were randomised in a 2:1 schedule to receive a 3-dose series of intradermal M. vaccae vaccine (MV) or hepatitis B vaccine (HBV) at 2-month intervals. Immunisation was safe and well tolerated; 2-day median vaccine site in duration was 5 mm in MV recipients and 0 mm in HBV recipients (p < 0.001). There were no significantly different changes in viral load or CD4 count between the two vaccine groups. No PPD skin test conversions occurred after immunisation. MV is safe and well tolerated and deserves further evaluation as a vaccine to prevent mycobacterial disease in HIV-infected children.

Mycobacterium tuberculosis infection and disease are not associated with protection against subsequent disseminated M. avium complex disease

OBJECTIVE

To determine the relationship between Mycobacterium tuberculosis infection and disease and subsequent disseminated M. avium complex (MAC) disease in HIV-infected persons.

DESIGN

A prospective observational cohort study.

SETTING

The AIDS Linked to the Intravenous Experience (ALIVE) cohort of injecting drug users and the Johns Hopkins Hospital Adult HIV Clinic (JHHAHC).

PARTICIPANTS

HIV-infected persons aged > 18 years with CD4 lymphocytes < 100 x 10(6)/l were followed between July 1989 and 31 October 1996. There were 182 persons in the ALIVE cohort and 1129 persons in JHHAHC who met these criteria.

MAIN OUTCOME MEASURE

The relative risk of disseminated MAC was determined according to a history of prior opportunistic infection, MAC prophylaxis, antiretroviral therapy, M. tuberculosis infection or disease, race, sex, and injecting drug use.

RESULTS

Amongst the 30 patients with active tuberculosis, eight developed disseminated MAC, compared with 208 cases of disseminated MAC amongst 1148 patients without prior M. tuberculosis infection or disease [relative risk (RR), 1.5; 95% confidence interval (CI), 0.8-2.7; P=0.2]. Amongst the 10 patients with extrapulmonary tuberculosis, five developed disseminated MAC (RR, 2.8; 95% CI, 1.5-5.2; P=0.02). Injecting drug use was associated with a decreased risk of disseminated MAC (RR, 0.7; 95% CI, 0.6-0.9; P=0.007). In a logistic regression analysis, disseminated MAC was significantly associated with extrapulmonary tuberculosis and other opportunistic disease, whereas antibiotic prophylaxis and injecting drug use were protective.

CONCLUSIONS

A history of M. tuberculosis infection or disease was not associated with protection against subsequent disseminated MAC disease in HIV-infected persons. However, persons with extrapulmonary tuberculosis were at increased risk for disseminated MAC, particularly at low CD4 cell levels.

Prevention and treatment of disseminated Mycobacterium avium complex infection in human immunodeficiency virus-infected individuals

Disseminated Mycobacterium avium complex (DMAC) infection is a common complication of advanced HIV disease, and is an independent predictor of mortality. The clinical features of DMAC infection are fever, weight loss, abdominal pain, anemia, elevated serum alkaline phosphatase, and elevated serum lactate dehydrogenase. The diagnosis is made by blood cultures; clinical diagnosis is unreliable. Chemoprophylaxis of DMAC infection with azithromycin is recommended when the CD4 lymphocyte count is below 50 cells/mm3. Established DMAC infection is treated with clarithromycin plus ethambutol, unless the isolate is macrolide-resistant, in which case the optimal therapy is uncertain. Highly active antiretroviral therapy is important in both prevention and treatment of DMAC infection.

Geographic and seasonal variation in Mycobacterium avium bacteremia among North American patients with AIDS

Analysis of geographic risk was performed for Mycobacterium avium complex (MAC) bacteremia among North American patients with AIDS. Monthly mycobacterial blood cultures were taken from patients who were placebo recipients in a prospective evaluation of MAC prophylaxis. Of 571 patients, 102 (17.9%) acquired MAC bacteremia during an average follow-up of 256 days. The area with the highest risk for MAC was the South Central region (27.9%; P < 0.02), whereas the area with the lowest risk was Canada (11.3%; P = 0.12). When the southern states were combined and compared with the northern states and Canada, the incidence of MAC bacteremia was higher in the southern states (21.6% versus 14.0%, P < 0.03). Proportional hazards analysis was performed for the difference between the North and South and controlled for baseline CD4 cell count. In this analysis, time to MAC was significantly longer in the North (hazard ratio = 0.587, 95% confidence interval 0.390 to 0.883, P = 0.01). Although overall variation in seasonality was not marked, there was a significant decrease in cases in the North during the summer months (P < 0.01). We conclude that geographic location is a risk factor for MAC bacteremia in patients with advanced AIDS, with decreased risk in northern North America.

Immunization of HIV-infected adults with a three-dose series of inactivated Mycobacterium vaccae

Heat-killed Mycobacterium vaccae vaccine was administered in a 3-dose schedule to 12 HIV-infected adults with CD4 cell counts > or = 300/mm3. Local and systemic side effects were monitored. Delayed-type hypersensitivity to purified protein derivative and Mycobacterium avium sensitin was measured at baseline and after the final dose. Antibody to aralipoarabinomannin, man-lipoarabinomannin, and a short-term culture filtrate of Mycobacterium tuberculosis were also measured. Lymphocyte proliferation responses to M avium sensitin and M vaccae sonicate were determined. Vaccine site induration was maximal at 2 days (median, 6 mm) and no systemic side effects were noted. Purified protein derivative skin test conversions did not occur. Changes in CD4 counts and HIV viral load were not significant. Three (27%) of 11 subjects who completed the trial showed either M avium skin test (n = 1) or short-term culture filtrate antibody (n = 2) responses. A three-dose schedule of M vaccae vaccine is safe and well tolerated in adults with early HIV infection and produces detectable immunologic responses in a subset of these subjects.