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Biomedical subjects

C R Horsburgh

Publications and source records attributed to C R Horsburgh.

At least 37 records · Page 2Linked to original sources
PubMed1997

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.

AIDS-Related Opportunistic Infections↗
PubMed1996

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

Risk of Mycobacterium avium complex disease was examined in human immunodeficiency virus (HIV)-infected patients with and without a history of tuberculosis. Information was obtained by retrospective review of charts of patients in HIV clinics in 10 US cities. Among 1363 patients with <200 CD4 cells/mm3 seen at Grady Memorial Hospital (GMH), 11 (17%) of 66 with a history of a positive purified protein derivative (PPD) skin test acquired M. avium infection, while 29 (16%) of 185 who were PPD-negative (but not anergic) did not (P = .85). Only 4 (8%) of 49 GMH patients with a history of tuberculosis acquired M. avium infection compared with 252 (19%) of 1314 GMH patients without a history of tuberculosis (P = .05). Proportional hazards analysis of risk factors for M. avium infection among 441 persons with and 8702 persons without a history of tuberculosis in 9 other cities confirmed protection from M. avium infection in persons with a history of tuberculosis (relative risk, 0.52; 95% confidence interval, 0.36-0.76; P < .001). Prior tuberculosis provides protection against M. avium infection in HIV-infected persons, possibly by stimulation of antimycobacterial immunity.

Adolescent↗
PubMed1996

Epidemiology of disease caused by nontuberculous mycobacteria.

The clinically important nontuberculous mycobacteria include M. kansasii, M. genavense, M. marinum, M. simiae, M. scrofulaceum and M. szulgai, M. avium, M. haemophilum, M. intracellulare, M. malmoense, M. ulcerans, and M. xenopi, M. abscessus, M. chelonae, M. fortuitum, and (rarely) M. smegmatis. Four clinical syndromes account for nearly all cases: pulmonary disease, lymphadenitis, skin or soft tissue disease, and disseminated disease in AIDS. M. avium and M. intracellulare (known together as M. avium complex), are the most common causes of pulmonary disease, lymphadenitis, and disseminated disease. All four clinical syndromes seem to be increasing in frequency, particularly in immunosuppressed hosts. Nontuberculous mycobacteria are acquired from the environment, but specific reservoirs of these organisms leading to human disease have not been defined.

Humans↗
PubMed1995

Mycobacterium avium complex in water, food, and soil samples collected from the environment of HIV-infected individuals.

As part of an epidemiologic study of Mycobacterium avium complex (MAC) infection in San Francisco, water, food and soil samples were collected from the home environment of 290 persons with human immunodeficiency virus (HIV) infection and cultured for mycobacteria. Isolates recovered from the environment were compared with isolates cultured from study patients. Although mycobacteria were recovered from numerous environmental samples, isolates reactive with MAC-specific DNA probes were recovered from only four of 528 (0.76%) water samples and one of 397 (0.25%) food samples. The species M. avium was recovered from one water (0.19%) and one food sample. In contrast, MAC was recovered from 55% and M. avium from 27% of soil samples taken from potted plants in patients' home. Speciation of 76 MAC isolates from study patients showed all isolates belonged to the species M. avium. With use of serotype and multilocus enzyme electrophoresis analysis, some of the soil isolates were found to be similar to isolates recovered from study patients. The results of this study suggest that soil, rather than water, may be a significant reservoir of organisms causing MAC infection in San Francisco.

Bacteriological Techniques↗
PubMed1995

Preventing disseminated Mycobacterium avium complex disease in patients infected with human immunodeficiency virus.

Disseminated Mycobacterium avium complex (MAC) infection is an important late-stage complication of infection with the human immunodeficiency virus. Since MAC is widely dispersed in the environment, the source of infection for patients with disseminated MAC generally cannot be determined. Therefore, specific recommendations for avoiding exposure are not supported at this time. Routine screening of stools and sputum to detect MAC colonization as a means of targeting prophylaxis for disseminated disease is also not recommended at present. Two randomized, placebo-controlled trials have demonstrated that prophylactic use of rifabutin in persons with low CD4 lymphocyte counts results in a 50% decrease in MAC bacteremia as well as a reduction in some signs, symptoms, and laboratory abnormalities associated with MAC disease. Thus a prophylactic daily dose of rifabutin (300 mg) should be considered for adults who have had a previous AIDS-defining opportunistic illness and who have a CD4 lymphocyte count of < 75/microL. Many experts would consider prophylaxis appropriate only when the CD4 lymphocyte count is < 50/microL, particularly when there has not been a previous AIDS-defining opportunistic infection. Clinicians should be aware of drug interactions and potential adverse effects associated with the use of rifabutin. Preliminary reports of randomized, placebo-controlled trials suggest that chemoprophylaxis with clarithromycin is also effective in the prevention of disseminated MAC disease, and evaluation of other agents is under way. Prophylaxis for disseminated MAC infection in children has not been evaluated but is presumed to be as effective as that in adults. Decisions regarding initiation of MAC chemoprophylaxis should be individualized.

AIDS-Related Opportunistic Infections↗
PubMed1995

Accelerated course of human immunodeficiency virus infection after tuberculosis.

To determine the effect of active tuberculosis on survival and the incidence of opportunistic infections in HIV-infected patients, we performed a retrospective cohort study at four U.S. medical centers to compare the survival and incidence rate of opportunistic infections in 106 HIV-infected patients with active tuberculosis (cases) with that of 106 HIV-infected patients without tuberculosis (control subjects) but with a similar level of immunosuppression (measured by the absolute CD4+ lymphocyte count) as the cases. Cases and control subjects were similar with regard to age, sex, race, previous opportunistic infection, and use of antiretroviral therapy, but they were more likely than control subjects to have a history of intravenous drug use (49 versus 19%). The mean CD4+ counts were similar for cases and control subjects (154 versus 153 cells/microliters, respectively). The incidence rate of new AIDS-defining opportunistic infections in cases was 4.0 infections per 100 person-months compared with 2.8 infections per 100 person-months in control subjects for an incidence rate ratio (RR) of 1.42 (95% confidence interval: 0.94-2.11). Cases also had a shorter overall survival than did controls subjects (p = 0.001). Active tuberculosis was associated with an increased risk for death (odds ratio = 2.17), even when controlling for age, intravenous drug use, previous opportunistic infection, baseline CD4+ count, and antiretroviral therapy. Although active tuberculosis may be an independent marker of advanced immunosuppression in HIV-infected patients, it may also act as a cofactor to accelerate the clinical course of HIV infection.

AIDS-Related Opportunistic Infections↗
PubMed1995

Emergence of Buruli ulcer disease in the Daloa region of Cote d'Ivoire.

Recent reports have suggested increases in Buruli ulcer (BU), an infection caused by Mycobacterium ulcerans in west Africa. In 1991, we conducted surveillance for BU in a rural area of Cote d'Ivoire and identified 312 cases of active or healed ulceration. A case-control study was then performed to investigate risk factors for this infection. The rate of illness did not appear to differ between males and females (5.2% versus 7.5%; P = 0.11). The highest rate of illness was seen in the 10-14-year-old age group (143 cases per 1,000 population). New cases increased more than three-fold between 1987 and 1991, and local prevalence of BU was as high as 16.3%. Twenty-six percent of persons with healed ulcers had chronic functional disability. Participation in farming activities near the main river in the region was identified in the case-control study as a risk factor for infection (odds ratio [OR] for each 10-min decrease in walking distance between the fields and the river = 1.52, 95% confidence interval [CI] 1.01, 2.28, P = 0.046). Wearing long pants was protective (OR 0.20, 95% CI 0.06, 0.62, P < 0.005). We conclude that the incidence of BU is increasing rapidly in Cote d'Ivoire. Specific causes of this increase were not identified, but wearing protective clothing appeared to decrease the risk of disease.

Adolescent↗
PubMed1994

Predicting Mycobacterium avium complex bacteremia in patients infected with human immunodeficiency virus: a prospectively validated model.

In cases of advanced infection with human immunodeficiency virus, mycobacterial blood cultures are frequently used to diagnose disseminated infection with the Mycobacterium avium complex (MAC). However, no prospectively validated guidelines exist for the use of such cultures. In this study, a two-part model for predicting MAC bacteremia was developed and then validated prospectively. First, a CD4+ cell count of < or = 50/microL was used to predict bacteremia. Then, among patients with < or = 50 CD4+ cells/microL, the documentation of fever on more than 30 days during the preceding 3 months, a hematocrit of < 30%, or a serum albumin concentration of < 3.0 g/dL was used to predict bacteremia. This model had a sensitivity of 89% and positive and negative predictive values of 30% and 98%, respectively, for the identification of patients with bacteremia. Had the model been applied to patients in this study, the number of blood cultures performed would have decreased by 61%, but 11% of the positive cultures would have been missed. In short, this model can predict MAC bacteremia and can potentially guide the use of mycobacterial blood cultures.

AIDS-Related Opportunistic Infections↗
PubMed1994

Mycobacterium avium complex in the respiratory or gastrointestinal tract and the risk of M. avium complex bacteremia in patients with human immunodeficiency virus infection.

Mycobacterium avium complex (MAC) is frequently isolated from the respiratory or gastrointestinal tract of patients with advanced human immunodeficiency virus (HIV) infection. Whether they are at increased risk of MAC bacteremia and whether culture of respiratory tract or stool specimens is useful for predicting bacteremia are unclear. HIV-infected patients with < or = 50 CD4+ cells/microL were prospectively studied. The risk of MAC bacteremia was approximately 60% within 1 year for patients with MAC in either the respiratory or gastrointestinal tract and was greater than for those without MAC in these sites (relative hazards for respiratory and gastrointestinal tract, 2.3 and 6.0; 95% confidence intervals, 1.1-4.6 and 2.5-14.6, respectively). Both respiratory tract specimen and stool culture had poor sensitivities (22% and 20%, respectively) but good positive predictive values (approximately 60%) for bacteremia. Symptomatic HIV-infected patients with MAC in the respiratory or gastrointestinal tract are at a substantial risk for developing MAC bacteremia; culture of these sites has limited usefulness as a screening test.

Adult↗
PubMed1994

Environmental risk factors for acquisition of Mycobacterium avium complex in persons with human immunodeficiency virus infection.

A case-control study was done to determine risk factors for Mycobacterium avium complex (MAC) disease in persons infected with human immunodeficiency virus (HIV) with < 50 CD4+ cells/mm3. In univariate analysis, cases (n = 83) had lower CD4+ cell counts than controls (n = 177) (median, 10 vs. 17/mm3; P < .001) and were more likely to have consumed hard cheese (odds ratio [OR], 5.44; 95% confidence interval [CI], 1.61-18.4) but were less likely to have taken daily showers (OR, 0.55; 95% CI, 0.33-0.94). In multivariate analysis, CD4+ cell count < 25/mm3 (OR, 3.58; 95% CI, 1.71-7.49) and consumption of hard cheese (OR, 5.63; 95% CI, 1.58-20.1) remained associated with disease, while daily showering (OR, 0.58; 95% CI, 0.28-0.88) remained protective. Increased risk for MAC disease in persons with HIV infection and low CD4+ cell counts is not associated with exposure to water or a variety of other environmental sources but may be associated with consumption of hard cheese.

AIDS-Related Opportunistic Infections↗
PubMed1994

Predictors of survival in patients with AIDS and disseminated Mycobacterium avium complex disease.

Patients with AIDS and disseminated Mycobacterium avium complex disease (DMAC), as defined by the presence of a positive blood culture for MAC, were studied retrospectively to define the natural history of DMAC. All patients had fevers, severe anemia (hematocrit < 26%), or both. Eighty-seven (76%) had signs, symptoms, or laboratory findings related to the gastrointestinal tract, but no distinct syndrome was identified. Sixty-nine patients received antimycobacterial therapy; assignment to therapy was not randomized. In a proportional hazards analysis, shorter survival was associated with higher initial level of mycobacteremia (relative risk [RR], 1.86; 95% confidence interval [CI], 1.49-2.31; P < .001), while administration of antimycobacterial chemotherapy (RR, 0.42; 95% CI, 0.26-0.70; P < .001) and antiretroviral therapy (RR, 0.40; 95% CI, 0.22-0.73; P < .01) had protective effects. Thus, the initial level of mycobacteremia of patients with DMAC may have prognostic value, and administration of antimycobacterial and antiretroviral agents may be associated with prolonged survival.

AIDS-Related Opportunistic Infections↗
PubMed1994

The impact of Mycobacterium avium complex bacteremia and its treatment on survival of AIDS patients--a prospective study.

It is currently recommended that patients with AIDS and Mycobacterium avium complex (MAC) bacteremia receive antimycobacterial treatment. However, no study has prospectively evaluated the impact of this infection and its treatment on survival. This study prospectively followed a cohort of 367 AIDS patients with < or = 50 CD4+ cells/microL and found that MAC bacteremia was independently associated with an increased risk of death (relative hazard [RH] = 1.8, 95% confidence interval [CI] = 1.3-2.4, P < .001). Patients with MAC bacteremia who were treated had a longer median survival than those who were not (263 vs. 139 days, P < .001); treatment was independently associated with a lower risk of death (RH = 0.45, 95% CI = 0.23-0.89, P < .001). However, 23% of patients with bacteremia died within 28 days of that diagnosis; few were treated. MAC bacteremia contributes to the death of patients with AIDS, and treatment increases survival. However, many patients will not survive long enough to receive treatment. These results underscore the importance of early diagnosis and chemoprophylaxis for MAC bacteremia.

AIDS-Related Opportunistic Infections↗
PubMed1993

Risk of human immunodeficiency virus infection from unprotected receptive anal intercourse increases with decline in immunologic status of infected partners.

To determine whether human immunodeficiency virus (HIV) type 1 infection among unprotected receptive anal partners of HIV type 1-infected men varies by the immunologic status of the HIV type 1-infected index case, 187 sexual partners of 164 HIV type 1-infected index subjects were enrolled at a community health center in Boston, Massachusetts, from 1985-1990. All subjects were interviewed regarding their sexual practices and tested for HIV type 1. Fifty-seven of the 187 sexual partners were infected with HIV type 1. The strongest risk factor for HIV type 1 infection among these partners was unprotected receptive anal intercourse with a known HIV type 1-infected index subject (odds ratio (OR) = 7.2, 95% confidence interval (CI) 3.1-16.3). The risk of unprotected receptive anal intercourse was highest among partners of HIV-infected index subjects who had a T lymphocyte subset ratio of 0.50 or less (OR = 11.4, 95% CI 3.0-43.5) compared with partners of HIV type 1-infected index subjects with a T cell ratio of greater than 0.50 (OR = 5.3, 95% CI 1.9-15.2). After adjustment for confounding, the risk of HIV type 1 infection remained substantially higher among sexual partners who had had unprotected receptive anal intercourse with infected index subjects with a T lymphocyte subset ratio of less than or equal to 0.50 (OR = 7.0, 95% CI 1.8-28.0) compared with partners who had had unprotected receptive anal intercourse with infected index subjects with a T cell ratio of greater than 0.50 (OR = 3.3, 95% CI 1.1-10.0). It would appear that the risk of HIV type 1 infection from unprotected receptive anal intercourse increases as the immunologic status of the HIV type 1-infected insertive anal partner decreases.

Adult↗