Prevalence of mycobacterium avium complex infection in AIDS patients

Increasing nontuberculous mycobacteria reporting rates and species diversity identified in clinical laboratory reports

Background

Nontuberculous Mycobacteria (NTM) are environmental microorganisms that can affect human health. A 2009–2010 occurrence survey of NTM in potable tap water samples indicated an increased recovery rate for many clinically significant species such as M. avium (30%) and M. abscessus (12%). To determine if these trends by species were mirrored in human infections, isolation rates of NTM species identified in clinical laboratory reports from four states were evaluated.

Method

Clinical laboratory reports from the Mississippi, Missouri, Ohio, and Wisconsin Health Departments were used to investigate the species of NTM isolated from human specimens in 2014. The NTM positive specimen reports were tabulated for each species and complex/group. The number of reports by month were used to investigate seasonal trends. The 2014 isolation rates were compared to historic values to examine longitudinal trends.

Results

The positive rate of NTM specimens increased from 8.2 per 100,000 persons in 1994 to 16 per 100,000 persons in 2014 (or 13.3 per 100,000 after excluding Mycobacterium gordonae). Changes in NTM diversity were observed in complex/groups known to be clinically significant. Between 1994 and 2014 the rate implicating M. abscesses-chelonae group and M. avium complex increased by 322 and 149%, respectively.

Conclusions

Based on public health data supplied by the four State’s Health Departments and the 2014 U.S. population, 50,976 positive NTM specimen reports per year were projected for the nation; serving as an indicator for the national potential disease burden that year.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3043-7) contains supplementary material, which is available to authorized users.

Validation of endogenous reference genes for expression profiling of RAW264.7 cells infected with Mycobacterium avium subsp. paratuberculosis by quantitative PCR

Reference genes are frequently used to normalize between different biological samples the levels of mRNA measured using quantitative PCR (qPCR). The expression level of many commonly used reference genes has been shown to vary between tissues or cells, or following exposure to various treatments including infection with microbes. The selection of an appropriate reference gene for an individual experiment is therefore a crucial step in the process of accurately determining changes in gene expression. For this purpose, we analyzed the expression of nine commonly used reference genes in a murine macrophage cell line, RAW264.7, for their potential use in the analysis of differential gene expression by quantitative polymerase chain reaction (qPCR) following experimental infection with Mycobacterium avium subsp. paratuberculosis. Only one of nine putative reference genes tested, casc3a, was found to be suitable, and combinations of two or more reference genes were disadvantageous. Based on data from the study, we recommend an approach for selection of reference genes, conducting assays with technical replicates in duplicate rather than triplicate, determining decision-limit quality control criteria for technical replicates and assessing the significance of gene expression fold differences using DeltaDeltaC(t) based on knowledge of the variation in the reference gene.

High rates of disseminated infection due to non-tuberculous mycobacteria among AIDS patients in Finland

OBJECTIVE

to determine the rate of disseminated infection due to non-tuberculous mycobacteria (NTM) among Finnish AIDS patients, and to analyse the epidemiology of these infections.

METHODS

in a prospective cohort study HIV-infected patients with CD4 counts < 200 x 10(6)/l were interviewed, and had mycobacterial blood cultures performed at baseline and at 6 months, then subsequently for clinical indications; autopsies were performed on patients who died. The cohort was followed at least for 24 months or to death. Water samples were collected from the homes of patients and from the environment and cultured for organisms of the Myobacterium avium complex (MAC). Environmental and clinical isolates were compared using pulsed field gel electrophoresis (PFGE).

RESULTS

NTM infection occurred in 22 (43%) of 51, 19 isolates were Mycobacterium avium, two M. genavense and one M. intracellulare. Multivariate analysis identified urban residence (P=0.04) and eating raw fish (P=0.04) as independent risk factors. Molecular analysis revealed two clusters of related isolates (three M. avium, two M. genavense) among urban residents.

CONCLUSION

AIDS patients in Finland have high rates of disseminated infection due to NTM. Clusters of identical organisms and association with urban residence suggests that these are newly acquired infections in advanced AIDS.

Prospective 7-year monitoring of MAC bacteremia in HIV-positive Swedish patients

OBJECTIVE: To record the cumulative incidence of Mycobacterium avium complex (MAC) bacteremia among HIV-infected patients and to study colonization in relation to symptoms of infection. METHODS: In a prospective study, 61 patients with a CD4 count less-than-or-eq, slant200x106/L were followed by cultures from sputum, feces and blood every 3--6 months and for development of MAC bacteremia and clinical symptoms. The main end-points were MAC bacteremia and death. RESULTS: From the start in November 1989 to January 1997 about 34% had developed MAC bacteremia with a median follow-up of 22 months. At the time of positive blood cultures, all but one patient had symptoms consistent with disseminated MAC infection. Positive cultures from respiratory and gastrointestinal tract were recorded before MAC bacteremia in only four patients. All but one had symptoms at the time of positive blood culture. CONCLUSIONS: The incidence of MAC bacteremia was similar to figures in other studies. The presence of symptoms in close relation to positive blood cultures supports late colonization and late infection in HIV disease. Screening patients with samples from the respiratory and gastrointestinal tracts is not useful

Disseminated Mycobacterium avium complex disease in the Swiss HIV Cohort Study: increasing incidence, unchanged prognosis

OBJECTIVES

Disseminated disease due to Mycobacterium avium complex (MAC) bacteria is thought to occur less frequently in Europe than in the USA. This study investigated time trends in the occurrence of, and survival with, disseminated MAC disease in the Swiss HIV Cohort Study (SHCS).

DESIGN, SETTING AND PARTICIPANTS

The SHCS participants who were free of disseminated MAC disease at registration were stratified by calendar period (1987-1989, 1990-1992, 1993-1995) in which the first recorded CD4 count was 0-49, 50-99, or 100-199 x 10(6)/l. Kaplan-Meier estimates of the probability of developing and surviving disseminated MAC disease were calculated for these nine independent groups. Multivariate analyses were performed using Cox proportional hazards regression.

RESULTS

The analysis was based on 6052 participants enrolled between January 1987 and December 1995 and 202 incident episodes of disseminated MAC disease recorded during a mean follow-up time of 3.5 years. The cumulative probability of MAC disease at 2 years in individuals with CD4 counts of 0-49 x 10(6)/l in 1987-1989 was 9.8% [95% confidence interval (CI) 4.4-15.2%], increasing to 29.8% (95% CI, 20.8-38.8%) in 1993-1995. Amongst those with CD4 counts from 50-99 x 10(6)/l these probabilities were 11.9% (95% CI, 5.9-17.8%), and 21.6% (95% CI, 13.9-29.2%), respectively. After adjusting for CD4 count the relative hazard of developing disseminated MAC disease in 1993-1995, compared with 1987-1989, was 1.37 (95% CI, 0.92-2.04). Median survival following diagnosis was 7.9 months with no improvement over time.

CONCLUSIONS

The incidence of disseminated MAC disease among SHCS participants has increased over time. More profound levels of immunosuppression amongst recent study entrants were found to explain this. When compared with US cohorts studied over the same calendar period the incidence of disseminated MAC disease in the SHCS appears to be lower. These findings are consistent with a secular effect of a more mature HIV epidemic in the US but direct comparison between the SHCS and a similar prospective cohort in the US should be undertaken to clarify this issue.

Isolation of Mycobacterium avium complex from water in the United States, Finland, Zaire, and Kenya

Disseminated infection with organisms of the Mycobacterium avium complex (MAC) is a common complication of AIDS in the United States and other developing countries, but it is rare or absent in sub-Saharan Africa. To assess the comparative likelihood of exposure to MAC in these geographic areas, we used a standard protocol to culture 91 water samples from environmental sites and piped water supply systems in the United States, Finland, Zaire, and Kenya. MAC was isolated from all geographic areas and from 22 of 91 (24%) samples. Isolation rates were 13 of 47 (28%) for environmental samples and 9 of 44 (20%) for water supply samples. Overall isolation rates were 18 of 52 (35%) samples in the United States and Finland, whereas they were 4 of 39 (10%) samples in Zaire and Kenya (P = 0.015). MAC isolation rates from water supply systems were 8 of 25 (32%) samples in the United States and Finland and 1 of 19 (5%) samples in Zaire and Kenya (P = 0.056). MAC was isolated from hospital water in the United States and Finland but not in hospital water in Zaire and Kenya. Serovar determinations showed that six of eight isolates from the United States were serovar 4 or 8. One MAC isolate from Zaire was identified as an "X" mycobacterium. These data suggest that exposure to MAC in water is likely in diverse areas of the world, but that the likelihood of human exposure to the organism in water may be slightly less in sub-Saharan Africa than in developed countries in the Northern Hemisphere.

Disseminated Mycobacterium malmoense infection in a patient with chronic granulocytic leukaemia

Mycobacterium malmoense is an atypical mycobacterium previously isolated from lymph nodes in children and from adults with pulmonary disease. Disseminated infection is extremely rare and bone marrow involvement has never previously been described. We report a patient with chronic granulocytic leukaemia and persistent fever with granuloma in the bone marrow due to disseminated M. malmoense infection. The patient initially received treatment with isoniazid, ethambutol and rifampicin with clearance of mycobacteria in the bone marrow and clinical improvement. Sensitivity in vitro was established for streptomycin, amikacin, ethambutol and rifabutin. The patient eventually expired as a result of progressive respiratory failure from other opportunistic infections. At autopsy staining of samples from lung parenchyma revealed fungal hyphi but staining for Pneumocystis carinii and myobacteria were negative.