Non-tuberculous slow-growing mycobacterial pulmonary infections in non-HIV-infected patients in south London

Abstract

Background: UK data on slow-growing non-tuberculous mycobacterial (NTM) pulmonary infections are sparse and there is little consensus on optimal treatment regimens. Methods: This was a retrospective study of NTM pulmonary infections in a London teaching hospital. Inclusion criteria were culture of slow-growing mycobacteria between 2000 and 2007, age > 18 y, HIV-negative, and meeting American Thoracic Society criteria. Results: Fifty-seven patients were included; 68% were males and the median age was 61 y. Predisposing factors were smoking (70%), alcohol abuse (28%), and chronic obstructive pulmonary disease (37%). Cavitation (56%) and infiltrates (42%) were common radiological findings. The predominant organism was Mycobacterium kansasii (70%). Ninety-three percent of patients with M. kansasii, 63% with Mycobacterium avium intracellulare, 60% with Mycobacterium malmoense, and 25% with Mycobacterium xenopi had clinical disease. Of the 57 patients, 37 were treated and had follow-up data available. Most patients received 3 drugs: rifampicin, ethambutol, and clarithromycin or ciprofloxacin for at least 9 months. Thirty percent experienced drug side effects. M. kansasii treatment had a 100% cure and 10% relapse rate, but 15% died. Conclusions: M. kansasii was the most common NTM and its isolation was predictive of clinical disease. Compared with other studies, treatment with 3 agents had a similar rate of cure and did not appear to reduce the relapse rate of disease, but did increase the risk of side effects.

Keywords::

• Mycobacterial
• pulmonary
• non-tuberculous
• kansasii

Declaration of interest: No competing interests.

Appendix 1

Preparation of samples

Sputa and bronchial washings or bronchoalveolar lavage (BAL) were decontaminated via a modified Petroff's sodium hydroxide procedure for 25 min (equal volumes of sample and 4% sodium hydroxide vortexed for 30 s until homogenized intermittently over the period), then neutralized with potassium dihydrogen orthophosphate (KH₂PO₄) prior to auramine staining and media inoculation. A smear was prepared from tissue samples before decontamination via a sulphuric acid procedure. All respiratory samples were inoculated onto Lowenstein–Jensen slopes and blood agar plates (to check for contamination); liquid media cultures (MB/BacT, bioMérieux) were also set up for smear-positive respiratory samples and tissue specimens. Media were inoculated with 20–30 μl of decontaminated deposit and then incubated at 36°C for a minimum of 8 weeks in the dark. Smear-positive specimens were reincubated for a further 4 weeks if they had failed to grow by 8 weeks. Cultures were examined weekly for growth, and positive mycobacterial cultures were identified in a reference laboratory using standard phenotypic methods and latterly Accuprobe and Hain PCR methods. Sensitivity testing was performed using the radiometric semi-automated method.