Colonization with Mycobacterium avium complex--an outdated concept

Nontuberculous mycobacterial lung diseases

Nontuberculous mycobacteria (NTM) are generally hardy, ubiquitous environmental bacteria that vary in geographic distribution and pulmonary pathogenicity. Relatively few of the more than 115 species of NTM have been associated with lung disease. Diagnosis of disease due to NTM relies on a combination of clinical, imaging, and microbiologic data. Because NTM may present as acid-fast bacilli in respiratory secretions of patients with clinical and radiologic features that mimic tuberculosis, laboratory discrimination of NTM from Mycobacterium tuberculosis is a priority. This discrimination is now often rapidly achievable using molecular techniques, although some tests have limited sensitivity. NTM species have different antibiotic response patterns, and success with medical treatment alone varies. Macrolides are an essential component of therapy for many species but must be combined with other drugs.

When and how to treat pulmonary non-tuberculous mycobacterial diseases

Non-tuberculous mycobacteria are ubiquitous environmental organisms that have been recognized as a cause of pulmonary infection for over 50 years. Traditionally patients have had underlying risk factors for development of disease; however, the proportion of apparently immunocompetent patients involved appears to be rising. Not all patients culture-positive for mycobacteria will have progressive disease, making the diagnosis difficult, though criteria to aid in this process are available. The two main forms of disease are cavitary disease (usually involving the upper lobes) and fibronodular bronchiectasis (predominantly middle and lingular lobes). For patients with disease, combination antibiotic therapy for 12-24 months is generally required for successful treatment, and this may be accompanied by drug intolerances and side-effects. Published success rates range from 30% to 82%. As the progression of disease is variable, for some patients, attention to pulmonary hygiene and underlying diseases without immediate antimycobacterial therapy may be more appropriate. Surgery can be a useful adjunct, though is associated with risks. Randomized controlled trials in well-described patients would provide stronger evidence-based data to guide therapy of non-tuberculous mycobacteria lung diseases, and thus are much needed.

Sputum bacteriology in patients hospitalized with acute exacerbations of chronic obstructive pulmonary disease and concomitant pneumonia in Hong Kong

AIM

To study the sputum microbiology of patients admitted to a teaching hospital with acute exacerbations of chronic obstructive pulmonary disease (AECOPD) with concomitant pneumonia.

METHODS

This was a retrospective study in a tertiary university hospital in Hong Kong. All episodes of AECOPD with pneumonia, patient demographics, length of stay, sputum culture and radiological results admitted in the first half of the year 2000 were retrieved from hospital records.

RESULTS

There were 118 patients (91 male) with 150 episodes of AECOPD with concomitant pneumonia. The age of the patients was 74.8 +/- 10.0 years. Positive routine sputum culture was detected in 45.6% of the patients. Among these hospital admissions, 8.7, 4.0 and 12.0%, respectively, required intensive care unit admissions, mechanical ventilation and non-invasive positive pressure ventilation. Haemophilus influenzae was the commonest organism found in sputum (26.0%), followed by Pseudomonas aeruginosa (5.5%), Streptococcus pneumoniae (3.4%), and Moraxella catarrhalis (3.4%). Mycobacterium tuberculosis was found in 1.5% of the admissions. The presence of P. aeruginosa in sputum was associated with a longer hospital length of stay (9.1 +/- 3.1 vs. 7.1 +/- 4.2 days, P = 0.03).

CONCLUSION

In contrast to most other studies reporting S. pneumoniae as the most likely bacterial pathogen, H. influenzae was the commonest bacterium isolated in sputum in our patients with AECOPD and concomitant pneumonia.

Sputum bacteriology in patients with acute exacerbations of COPD in Hong Kong

STUDY OBJECTIVE

To study the demographics and sputum microbiology of patients admitted to a teaching hospital with acute exacerbations of chronic obstructive pulmonary disease (AECOPD).

DESIGN

A retrospective study.

SETTING

A tertiary university hospital in Hong Kong.

PATIENTS

All episodes of AECOPD, patient demographics, length of stay, sputum culture and radiological results admitted in the first half of the year 2000 were retrieved from hospital records.

RESULTS

There were 329 patients with 418 episodes of AECOPD without concomitant pneumonia. The age of the patients was 74.4+/-8.3 years. The acute hospital length of stay for an episode of AECOPD was 7.3+/-6.5 days. Haemophilus influenzae was the commonest organism found in sputum (23.1%), followed by Pseudomonas aeruginosa (6.3%) and Streptococcus pneumoniae (4.0%). Mycobacterium tuberculosis was found in 1.1% of the admissions. Presence of organisms in sputum had no association with the hospital length of stay and intensive care unit admissions. In patients whose FEV1 was >50% of predicted values, there was a higher chance of positive sputum growth of H. influenzae than those with FEV1 <50% (16/44 vs. 31/162 episodes, respectively, P=0.02).

CONCLUSIONS

H. influenzae was the commonest bacterium isolated in sputum in patients with AECOPD. In areas endemic of tuberculosis, it is advisable to use fluoroquinolones for AECOPD with caution.

Nontuberculous mycobacteria in women, young and old

Lady Windermere syndrome is a unique entity within the spectrum of pulmonary NTM diseases. There are differences in several clinical aspects between Lady Windermere syndrome and the classic pulmonary NTM disease, including manifestations, pathogenesis, and natural history. Recently, emerging pieces of information provide a more scientific explanation of why women are more susceptible to this form of infection and how they develop clinical disease. As the result, these patients probably require quite different diagnostic and therapeutic approaches compared with those with the classic presentation. Studies exclusive to LWS are lacking and are absolutely necessary as they will enhance our understanding of, and hence successful management strategies for, this increasingly recognized disease.

Diffuse pulmonary disease caused by nontuberculous mycobacteria in immunocompetent people (hot tub lung)

The clinicopathologic spectrum of infections due to nontuberculous mycobacteria (NTM) includes cavitary disease, opportunistic infection, and nodular disease associated with bronchiectasis. We report a less well-described manifestation of NTM infection: 10 immunocompetent patients without preexisting bronchiectasis had radiographic evidence of diffuse infiltrative lung disease. The most common symptoms were dyspnea, cough, hypoxia, and fever. All 10 patients had used a hot tub. Histologic examination revealed exuberant nonnecrotizing, frequently bronchiolocentric, granulomatous inflammation in all cases. In 1 case, necrotizing granulomas were also noted. The inflammation often was associated with patchy chronic interstitial pneumonia and organization. Cultures revealed NTM in all cases (Mycobacterium avium complex in all but 1 case), but staining for acid-fast bacilli was positive in only 1 case. Four patients received corticosteroids alone for presumed hypersensitivity pneumonia, 4 were treated with antimycobacterial therapy, and 2 received both. All patients demonstrated significant improvement at the time of follow-up. These findings suggest that disease due to NTM may manifest as diffuse infiltrates in immunocompetent adults and that hot tub use may be an important risk factor for this disease pattern.