Rapid identification of Mycobacterium genavense with a new commercially available molecular test, INNO-LiPA MYCOBACTERIA v2

Mycobacterium genavense as a cause of subacute pneumonia in patients with severe cellular immunodeficiency

BACKGROUND

Mycobacterium genavense is a rare nontuberculous mycobacteria (NTM). Human infections are mostly disseminated in the setting of the AIDS epidemic or the use of aggressive immunosuppressive treatments. M. genavense culture is fastidious, requiring supplemented media. Pulmonary involvement rarely occurs as a primary localization.

CASES PRESENTATION

We report here two patients with pneumonia as the predominant manifestation of M. genavense infection: one kidney transplanted patient and one HIV-infected patient. Both patients were initially treated with anti-tuberculous drugs before the identification of M. genavense on sputum or broncho-alveolar lavage fluid culture. A four-drug regimen including clarithromycin and rifabutin was started. Gamma interferon has been helpful in addition to antimycobacterial treatment for one patient.

CONCLUSION

Clinicians should be aware that M. genavense could be the etiologic agent of sub-acute pneumonia mimicking tuberculosis in patients with cellular immunodeficiency status.

Tuberculosis in Birds: Insights into the Mycobacterium avium Infections

Tuberculosis, a List B disease of World Organization for Animal Health, caused by M. avium or M. genavense predominantly affects poultry and pet or captive birds. Clinical manifestations in birds include emaciation, depression and diarrhea along with marked atrophy of breast muscle. Unlike tuberculosis in animals and man, lesions in lungs are rare. Tubercular nodules can be seen in liver, spleen, intestine and bone marrow. Granulomatous lesion without calcification is a prominent feature. The disease is a rarity in organized poultry sector due to improved farm practices, but occurs in zoo aviaries. Molecular techniques like polymerase chain reaction combined with restriction fragment length polymorphism and gene probes aid in rapid identification and characterization of mycobacteria subspecies, and overcome disadvantages of conventional methods which are slow, labour intensive and may at times fail to produce precise results. M. avium subsp. avium with genotype IS901+ and IS1245+ causes infections in animals and human beings too. The bacterium causes sensitivity in cattle to the tuberculin test. The paper discusses in brief the M. avium infection in birds, its importance in a zoonotic perspective, and outlines conventional and novel strategies for its diagnosis, prevention and eradication in domestic/pet birds and humans alike.

Mycobacterium genavense infections: a retrospective multicenter study in France, 1996-2007

Mycobacterium genavense, a nontuberculous mycobacterium, led to devastating infections in patients with acquired immunodeficiency syndrome (AIDS) before highly active antiretroviral therapy (HAART) was available, as well as in other immunocompromised patients. We conducted the current study to describe the features of this infection in patients infected with human immunodeficiency virus (HIV) in the HAART era and in non HIV-infected patients.We conducted a retrospective cohort survey in France. All patients with M. genavense infection diagnosed from 1996 to 2007 at the National Reference Center, Institut Pasteur, Paris, were identified and their clinical, laboratory, and microbiologic data were centralized in a single database. Twenty-five cases of M. genavense infection originating from 19 centers were identified. Twenty patients had AIDS, 3 had solid organ transplantation, and 2 had sarcoidosis. Sixty-four percent (n = 16) were male, mean age was 42 years, and median CD4 count was 13/mm (range, 0-148/mm) in patients with AIDS. Twenty-four patients had disseminated infection with fever (75%, n = 18), weight loss (79%, n = 19), abdominal pain (71%, n = 17), diarrhea (62.5%, n = 15), splenomegaly (71%, n = 17), hepatomegaly (62.5%, n = 15), or abdominal adenopathy (62.5%, n = 15). M. genavense was isolated from the lymph node (n = 13), intestinal biopsy (n = 9), blood (n = 6), sputum (n = 3), stool (n = 3), and bone marrow (n = 5). Eleven patients (44%) died, 8 (32%) were considered cured with no residual symptoms, and 6 (24%) had chronic symptoms. The 1-year survival rate was 72%.The prognosis of M. genavense infection in HIV-infected patients has dramatically improved with HAART. Clinical presentations in HIV and non-HIV immunocompromised patients were similar.

[Utility of molecular biology in the microbiological diagnosis of mycobacterial infections]

Species within the Mycobacterium genus are of major medical interest, since, together with environmental and opportunistic species, there are two species (Mycobacterium tuberculosis and Mycobacterium leprae) that remain an important public health challenge. Despite efforts to control tuberculosis (TB), this disease remains one of the most prominent health problems worldwide. In the last few years, mycobacteriology has experienced major technological advances. Nevertheless, the early diagnosis of mycobacterial infection and, especially of TB, is still based on microscopic examination of properly stained samples. At present, this procedure is still the simplest, fastest and most cost-effective method for preliminary diagnostic guidance. Effective control of TB is based on rapid detection of M. tuberculosis, followed by immediate implementation of the appropriate antituberculosis therapy. Because of the emergence of multidrug resistant strains, the development of rapid diagnostic methods, both for identification of M. tuberculosis and susceptibility testing, has become a pressing need. The availability of molecular epidemiology methods that are easy to implement and standardized and that would allow identification of related cases is of key importance to identify epidemic outbreaks and control the spread of TB. Despite the evident progress in the molecular diagnosis of mycobacterial infections, the available techniques are still inadequate. In this review, we describe the state of the art of the main molecular techniques for direct detection of mycobacteria in clinical samples, their identification, detection of resistance to the most important antituberculosis agents, and molecular epidemiology. In each case, we describe the advantages and limitations of current techniques. In the near future, clinical mycobacteriology will probably evolve to the universal use of genetic techniques for direct diagnosis and detection of resistance. The molecular epidemiology of TB will be performed, in its various applications, by faster and more automated techniques than those currently available.

Evaluation of the invader assay with the BACTEC MGIT 960 system for prompt isolation and identification of mycobacterial species from clinical specimens

Rapid and accurate identification of mycobacterial species is essential for patient management. We describe the use of the Invader assay in conjunction with the BACTEC MGIT 960 system that together provide an efficient procedure for clinical use. This assay discriminates single-base differences (e.g., genotyping single-nucleotide polymorphisms) under homogeneous and isothermal conditions and can measure directly on genomic DNA without prior target DNA amplification. To identify a wide variety of mycobacterial species, 20 Invader probes were designed to target the 16S rRNA gene and the 16S-23S rRNA gene internal transcribed spacer 1 (ITS-1) region. To validate the Invader probes, we used 78 ATCC strains, and 607 clinical mycobacterial strains, which were identified by DNA sequencing of the 16S rRNA gene and ITS-1. The Invader assay could accurately identify and differentiate these strains according to target sequences. Moreover, it could detect and identify 116 (95.1%) of 122 positive liquid cultures from the BACTEC MGIT 960 system and did not react to 83 contaminated MGIT cultures. Species identification takes 6.5 h by the Invader assay: 2.0 h for DNA extraction, 0.5 h for handling, and up to 4 h for the Invader reaction. The Invader assay has the speed, ease of use, and accuracy to be an effective procedure for the bacteriological diagnosis of mycobacterial infections.

Hyperammonemia in generalized Mycobacterium genavense infection after renal transplantation

After solid organ transplantation, patients are susceptible to infection caused by uncommon pathogens due the immunosuppressive drug therapy. Here, we report the first case of disseminated Mycobacterium genavense infection in a HIV seronegative renal transplant patient. The most striking clinical feature was a decreased consciousness. Blood results revealed hyperammonemia with otherwise normal liver function. Occurrence of hyperammonemia and massive M. genavense infection has not been reported before.