HONOLULU – The diversity of species in the sputum of patients undergoing therapy for nontuberculosis mycobacterial pulmonary disease (NTM-PD) could be a marker for treatment efficacy, authors of a small prospective study suggest.
Neil Osterweil/MDedge
Dr. Noeul Kang
Among 14 patients treated for NTM-PD, 7 of whom had treatment-refractory disease and 7 of whom had microbiological cures after antibiotic therapy, the diversity of the microbiome in sputum was greater for those patients who were cured, indicating that , said Noeul Kang, MD, PhD, from Samsung Medical Center in Seoul, South Korea.
“What we found was that in NTM-PD patients, the sputum of the patients who remained in long-time stabilization without recurrence exhibited higher microbiome diversity than that of treatment-refractory patients, and several genera were identified in the samples of the cured group. We hope to do more research on this, and we are planning to compare the patients who have never been treated with those who respond to treatment,” she said at the annual meeting of the American College of Chest Physicians (CHEST).
NTM-PD on the rise
The incidence and prevalence of NTM-PD in both South Korea and the United States have been rising steadily since 2007, with the highest incidence occurring among those 65 and older.
“NTM-PD is becoming a global burden,” Dr. Kang said.
Across the world the most commonly occurring organisms in NTM-PD patients are Mycobacterium avium complex (MAC), with other mycobacteria species varying in frequency by region.
Outcomes of treatment differ according to the etiologic organism, with M. avium complex infections being successfully treated in about 60% of patients, compared with 70% of patients’ infections with the M. abscessus massiliense, and 30%-40% of infections yielding to antibiotics in patients with M. abscessus abscessus, Dr. Kang said.
To compare the characteristics of the sputum microbiota of NTM-PD patients based on their treatment outcomes, Dr. Kang and colleagues looked at sputum from all patients with NTM-PD who agreed to provide samples at their center from 2018 through 2022.
After excluding those who did not receive antibiotics, those who were on treatment but did not have refractory disease, and those who were lost to follow-up or whose samples did not pass quality control, they identified seven patients who had microbiological cures, and seven whose disease remained refractory to treatment.
They defined culture conversion at three or more consecutive negative sputum cultures after treatment, collected at least 4 weeks apart, and microbiological cures at maintenance of multiple consecutive negative cultures without any positive cultures of the causative species from respiratory samples.
Infections were deemed to be refractory if there were sustained positive cultures from respiratory samples of causative NTM species after at least 1 year of antibiotic therapy.
Diversity analysis
Samples from 8 of the 14 participants had M. abscessus-PD, with the proportion higher among those who had a sustained microbiological cure (71.4% vs. 42.9%).
At baseline, patients with refractory disease were found to have significantly lower alpha diversity, a measure of microbial diversity within a single sample, compared with those whose infections were cured (P = .025).
In addition, samples at 6-month follow-up from those with baseline refractory infections had differences in the species level of beta-diversity (that is, differences among samples), compared with both baseline and follow-up samples from the cured group (P = .022 and .024, respectively).
The investigators also used linear discriminant analysis to look at taxonomic biomarkers, and observed that several species were more abundant in samples from the microbiological cure group than from the refractory disease group (P < .05) These species included organisms in the Streptococcus pneumoniae group, Prevotella melaninogenica, and Haemophilus parahaemolyticus group.