Impact of New American Thoracic Society Diagnostic Criteria on Management of Nontuberculous Mycobacterial Infection

Application of diagnostic criteria for non-tuberculous mycobacterial disease to a case series of mycobacterial-positive isolates

The American Thoracic Society (ATS) and Infectious Diseases Society of America (IDSA) have provided guidelines to assist in the accurate diagnosis of lung disease caused by nontuberculous mycobacteria (NTM). These microbiologic, radiographic, and clinical criteria are considered equally important and all must be met to make the diagnosis of NTM lung disease. To assess the significance of the three criteria, each was evaluated for its contribution to the diagnosis of NTM lung disease in a case series. Laboratory reports of any specimen positive for NTM isolation were collected between January 1, 2006 and December 31, 2010 at a university medical center. Medical records were reviewed in detail using a standardized form. The total number of patients with a culture from any site positive for NTM was 297 while the number from respiratory specimens during the same period was 232 (78%). Samples from two of these patients also yielded M. tuberculosis complex and were excluded. While 128 of the remaining 230 patients (55.7%) in the cohort met the microbiologic criterion for diagnosis of NTM lung disease, 151 (65.6%) and 189 (78.3%) met the radiologic and clinical criteria respectively. Only 78 patients (33.9%) met all three criteria provided by the ATS/IDSA for diagnosis of NTM lung disease. This evaluation reaffirms that defining NTM lung disease using either one or two of the criteria provided by the 2007 ATS/IDSA guidelines may significantly overestimate the number of cases of NTM lung disease. Based on the experience of defining NTM lung disease in this case series, recommendations for modification of the ATS/IDSA guidelines are provided which include expansion of both radiologic patterns and the list of symptoms associated with NTM lung disease.

Paradigm for diagnosing mycobacterial disease: direct detection and differentiation of Mycobacterium tuberculosis complex and non-tuberculous mycobacteria in clinical specimens using multiplex real-time PCR

AIMS

Mycobacterium tuberculosis and non-tuberculous mycobacteria (NTM) are clinically different, and the rapid detection and differentiation of M. tuberculosis complex (MTBC) and NTM is crucial for patient management and infection control. Given the slow growth of most pathogenic mycobacteria, nucleic acid amplification assays are excellent tools for direct identification of mycobacteria in clinical specimens. Recently, a multiplex real-time PCR assay was developed that can directly detect 20 mycobacterial species in clinical specimens. Here, we evaluated the diagnostic performance of the assay for diagnosing mycobacterial disease under routine laboratory conditions.

METHODS

A total of 3334 specimens collected from 1437 patients suspected of tuberculosis infection were subjected to acid-fast bacilli staining, conventional culture and the multiplex real-time PCR assay. To evaluate the sensitivity and specificity of the assay, the overall diagnosis of tuberculosis was defined by positive culture plus medical history, and the 2007 American Thoracic Society and Infectious Disease Society of America diagnostic criteria for NTM disease were applied.

RESULTS

The sensitivity, specificity, positive predictive value and negative predictive value were 87.5%, 99.6%, 96.1% and 98.5%, respectively, for the detection of MTBC isolates and 53.3%, 99.9%, 95.2%, and 98.9%, respectively, for detecting NTM isolates.

CONCLUSIONS

Thus, the assay can correctly differentiate between MTBC and NTM isolates in clinical specimens and would be a useful tool for the rapid differentiation of tuberculosis and NTM disease, despite its limited sensitivity for the diagnosis of NTM disease.

The impact of the 2007 ATS/IDSA diagnostic criteria for nontuberculous mycobacterial disease on the diagnosis of nontuberculous mycobacterial lung disease

BACKGROUND

In 2007, the American Thoracic Society (ATS) and Infectious Disease Society of America (IDSA) published new diagnostic guidelines for nontuberculous mycobacterial (NTM) disease. Bacteriological criteria have become simpler compared to the 1997 ATS diagnostic criteria.

OBJECTIVE

For assessing the impact of the 2007 ATS/IDSA diagnostic criteria, we compared the diagnosis rate and time to diagnosis of NTM lung disease using the 1997 and 2007 ATS guidelines.

METHODS

Sixty-four patients who had excreted Mycobacterium intracellulare, M. avium, M. abscessus or M. kansasii at least one time in their respiratory specimens at Chonnam National University Hospital were reviewed. The 1997 ATS and 2007 ATS/IDSA guidelines were applied to these patients.

RESULTS

Thirty-seven of 64 patients (57.8%) were diagnosed with NTM lung disease by the 1997 ATS criteria. When the 2007 ATS/IDSA criteria were applied, 6 patients were newly diagnosed with NTM lung disease. The diagnosis rate significantly increased from 57.8 to 67.2% (p < 0.001). The time to diagnosis in the 1997 ATS and 2007 ATS/IDSA guidelines was 46.4 ± 53.0 and 36.2 ± 38.5 days, respectively (p = 0.002).

CONCLUSION

These data suggest that we can shorten the time to diagnose NTM lung disease and diagnose more simply by using the 2007 ATS/IDSA guidelines. Further study will be needed to assess that these changes affect the management of NTM disease.

Clinical relevance of Mycobacterium chelonae-abscessus group isolation in 95 patients

OBJECTIVES

To determine the clinical relevance of Mycobacterium chelonae-abscessus group isolation from clinical samples.

METHODS

We retrospectively reviewed medical files of all patients from whom these mycobacteria were isolated between January 1999 and January 2005 and re-identified the isolates by rpoB sequencing. We applied the American Thoracic Society (ATS) diagnostic criteria to establish clinical relevance.

RESULTS

Ninety-five patients were traced (56 M. chelonae, 25 Mycobacterium abscessus, 8 Mycobacterium massiliense, 6 Mycobacterium bolletii). Most isolates were cultured from pulmonary samples in patients with pre-existing pulmonary disease. Among patients with pulmonary isolates, 27% (20/74) meets ATS criteria; M. abscessus is most relevant (50%; 9/18), followed by M. massiliense (29%; 2/7), M. bolletii (20%; 1/5) and M. chelonae (18%; 8/44). Extrapulmonary disease presented as disseminated skin disease, eye disease specific for M. chelonae and otomastoiditis for M. abscessus. Treatment, especially for pulmonary M. abscessus disease, yielded limited results.

CONCLUSIONS

One-fourth of the patients with pulmonary M. chelonae-abscessus group isolates met the ATS criteria; this percentage differs by species. Species distribution and clinical relevance differ from other regions. M. abscessus isolation in cystic fibrosis patients warrants special attention. Current ATS criteria might be too lenient to diagnose M. chelonae-abscessus group disease.

Guidelines on the diagnosis and treatment of pulmonary non-tuberculous mycobacteria infection

While the prevalence of Mycobacterium tuberculosis continues to decline in the developed world, the same cannot be said for non-tuberculous mycobacteria (NTM). These organisms are increasing in incidence and prevalence throughout the world. This is probably because of a combination of increased exposure, improved diagnostic methods and an increase in the prevalence of risk factors that predispose individuals to infection. Considerable confusion can arise in determining in the wide range of species whether an isolated NTM is in fact a contaminant or a pathogenic organism when isolated in sputum or bronchoalveolar lavage. This confusion combined with increasing requests for advice on the treatment of disease has led to the development of guidelines to assist the clinician in diagnosing and treating infection accurately.