[Environmental mycobacterial diseases in patients with and without HIV infection: epidemiology and clinical course]

Epidemiological profile and follow-up of patients with pulmonary disease by non-tuberculous mycobacteria in Baixada Santista area, São Paulo

Objective

To present the frequency and species diversity of non-tuberculous mycobacteria, estimate the prevalence of non-tuberculous mycobacterial pulmonary disease, describe the epidemiological profile, and determine the follow-up of patients with non-tuberculous mycobacterial pulmonary disease living in a region with a high burden of tuberculosis.

Methods

This a retrospective cohort observational study using data records obtained from the Instituto Adolfo Lutz - Santos and from the São Paulo Sistema de Vigilância de Tuberculose do Estado de São Paulo in the period between 2000 and 2009. The studied variables were: socio-demographic characteristics, current and past history of tuberculosis, aspects related to diagnosis, and treatment and associated diseases.

Results

We included 319 non-tuberculous mycobacteria isolates in the study, corresponding to 257 patients. The species Mycobacterium kansasii (28.5%) and Mycobacterium fortuitum (16.6%) presented the higher occurrence. In 10.9% (24) of the patients, there was a criterion for confirming a case of pulmonary disease due to non-tuberculous mycobacteria. In relation to gender and age, male and individuals over 50 years old were the most frequent. Considering the confirmed cases, 47.8% had a past history of tuberculosis.

Conclusion

The lack of information about the cases is evident, since pulmonary disease due to non-tuberculous mycobacteria is not mandatory. The therapeutic regimen according to the identified species is fundamental for success in combating the infections caused by non-tuberculous mycobacteria. Besides that, information about the regional epidemiology of pulmonary disease caused by non-tuberculous mycobacteria and the search for associations with other comorbidities are important to establish the correct treatment. In order to improve surveillance of pulmonary diseases by non-tuberculous mycobacteria, we suggest the implantation of a sentinel surveillance and of population-based studies.

Clinical Significance of Environmental Mycobacteria Isolated From Respiratory Specimens of Patients With and Without Silicosis

OBJECTIVE

To describe the clinical, functional and radiographic differences of respiratory disease caused by environmental mycobacteria (EM) in patients with and without silicosis.

METHOD

Retrospective, observational study in patients with nontuberculous mycobacteria isolated in the Hospital Meixoeiro (University Hospital of Vigo) microbiology laboratory between January 2007 and December 2013. Patients were grouped according to the presence or absence of silicosis and mycobacterial lung disease, using American Thoracic Society criteria.

RESULTS

In 156 cases, at least one species of EM had been isolated from the respiratory culture. A total of 71% were identified in men, 40 (25.6%) of whom had silicosis. Sixty patients (38.5%) met American Thoracic Society microbiological criteria: 62.5% of the silicosis group and 30.2% of the non-silicosis group. The most common species were Mycobacterium avium complex, Mycobacterium genavense and Mycobacterium chelonae. American Thoracic Society criteria for environmental mycobacterial disease were met in 34 (22.7%) patients: 14 in the silicosis group and 20 in the non-silicosis group. Treatment was administered in 24 cases, with better bacteriological eradication levels in the non-silicosis group.

CONCLUSIONS

In our series, a history of silicosis was related with a higher incidence of environmental mycobacterial disease. The causative species in the majority of cases in our setting was Mycobacterium avium complex, followed by Mycobacterium genavense. Patients with silicosis showed lower cure rates after treatment.

Inhibition of maturation of human monocyte-derived dendritic cells in a patient with Mycobacterium avium infection

Mycobacterium avium complex is a facultative intracellular pathogen that can cause pulmonary disease in immunocompromised individuals. Dendritic cells (DCs) play a central role in protective immunity against mycobacteria. Mycobacterium avium complex infects DCs but does not impair in vitro infected monocytes differentiation into DCs. A 54-year old woman affected by chronic graft-versus-host-disease (cGVHD) was referred to our Division of Dermatology. Immature DCs were generated from her monocytes. One week later she was hospitalized due to a lung infection with Mycobacterium avium complex. Monocyte-derived DCs during Mycobacterium avium infection expressed low levels of CD1a and CD80 as determined by flow cytometry. They also expressed high levels of CD83 and CD86, and when stimulated with LPS for 24 hrs they slightly up-regulated CD83 and did not produce IL12. When monocyte-derived DCs were obtained from the patient after having recovered from the Mycobacterium avium complex infection, they expressed normal levels of CD1a and CD80 and were negative both for CD83 and for CD86. IL12 production in response to LPS was restored. Inhibition of DC maturation by the in vivo infection with Mycobacterium avium may be an immune-evasion mechanism used by the pathogen because incompletely matured DCs may not activate effector T cells efficiently in vivo.

Molecular characterization of Mycobacterium kansasii isolates in the State of São Paulo between 1995-1998

Mycobacterium kansasii is the most common cause of pulmonary nontuberculous mycobacteria infection and classical identification of this pathogen needs a time consuming phenotypic tests. Polymerase chain reaction-restriction fragment length polymorphism analysis (PRA) of the gene enconding for the 65 kDa heat shock (hsp65) protein offers an easy, rapid, and inexpensive procedure to identify and subtype M. kansasii isolates. In the present study, we performed a retrospective analysis of patients who had mycobacteria identified on the basis of phenotypic tests by means of a review of database at Mycobacteria Laboratory of the Instituto Adolfo Lutz in the period 1995-1998. A total of 9381 clinical isolates were analyzed of which 7777 (82.9%) were identified as M. tuberculosis complex and 1604 (17.1%) as nontuberculous mycobacteria. Of the 296 M. kansasii isolates, 189 (63.8%) isolates obtained from 119 patients were viable and were analyzed by PRA-hsp65. Hundred eight two (98.9%) were classified as M. kansasii type I. Two isolates were classified as type II and III and five isolates were characterized as other Mycobacterium species. Clinical isolates of M. kansasii in the state of Sao Paulo was almost exclusively subtype I regardless of HIV status.

Differential gene expression in mononuclear phagocytes infected with pathogenic and non-pathogenic mycobacteria

The pathogenic mycobacteria are an insidious group of bacterial pathogens that cause the deaths of millions of people every year. One of the reasons these pathogens are so successful is that they are able to invade and replicate within host macrophages, one of the first lines of defence against intruding pathogens. In contrast, non-pathogenic mycobacteria, such as Mycobacterium smegmatis are killed rapidly by macrophages. In order to understand better the series of events that allow pathogenic mycobacteria to survive and replicate within macrophages, while the non-pathogenic mycobacteria are killed rapidly, we inoculated the human monocytic cell line U937 with pathogenic (M. tuberculosis and M. avium) and non-pathogenic (M. smegmatis) mycobacteria and monitored the expression of over 3500 genes at 4, 12 and 24 h post-inoculation using a commercially available gene array system. We observed multiple differences in the gene expression patterns of monocytes infected with pathogenic and non-pathogenic mycobacteria including genes involved in cytokine, lymphokine and chemokine production, adhesion, apoptosis, signal transduction, transcription, protein cleavage, actin polymerization and growth. We also observed differences in gene expression profiles in monocytes infected with M. tuberculosis or M. avium, indicating that there are differences in the host pathogen interactions of mononuclear phagocytes infected with different pathogenic mycobacterial species. These results increase the understanding of the mechanisms used by pathogenic mycobacteria to cause disease, the host response to these organisms, and provide new insights for antimycobacterial intervention strategies.

Mycobacterium avium infection and modulation of human macrophage gene expression

Mycobacterium avium is a facultative intracellular pathogen cleared rapidly via intact host defense mechanisms. In the absence of adequate T cell function, as occurs in HIV-1-induced immunodeficiency, M. avium becomes an opportunistic infection with uncontrolled replication and reinfection of macrophage hosts. How M. avium infects, survives, and replicates in macrophages without signaling an effective microbicidal counterattack is unresolved. To address whether M. avium signals the expression of molecules, which influence mycobacterial survival or clearance, human monocyte-derived macrophage cultures were exposed to M. avium. Within minutes, M. avium, or its cell wall lipoarabinomannan, binds to the adherent macrophages and induces a spectrum of gene expression. In this innate response, the most abundant genes detected within 2 h by cDNA expression array involved proinflammatory chemokines, cytokines including TNF-alpha and IL-1, and adhesion molecules. Associated with this rapid initial up-regulation of recruitment and amplification molecules was enhanced expression of transcription factors and signaling molecules. By 24 h, this proinflammatory response subsided, and after 4 days, when some bacteria were being degraded, others escaped destruction to replicate within intracellular vacuoles. Under these conditions, inducible NO synthase was not up-regulated and increased transferrin receptors may facilitate iron-dependent mycobacterial growth. Sustained adhesion molecule and chemokine expression along with the formation of multinucleated giant cells appeared consistent with in vivo events. Thus, in the absence of T lymphocyte mediators, macrophages are insufficiently microbicidal and provide a nonhostile environment in which mycobacteria not only survive and replicate, but continue to promote recruitment of new macrophages to perpetuate the infection.