Researchers reported differences in the microbiology and metabolites of the sputum from patients with cystic fibrosis (CF) and nontuberculous mycobacterial (NTM) lung infections vs those with only CF, as published in mSphere. They suggested that these changes may be potential risk factors for developing such infections.

The experimental study conducted by Breen and colleagues analyzed sputum samples from 32 patients with CF and NTM infection and 27 without evidence of NTMs. In general, NTM cases had higher phospholipid metabolism while lower tryptophan-associated molecules and branched-chain amino acids when compared to the control group.

Itaconate, a metabolite produced by macrophages with anti-inflammatory properties, was also decreased in NTM samples. Previous research determined that this compound can inhibit Mycobacterium tuberculosis growth. However, this bacteria also seemed to digest itaconate, making it unclear how it decreases in these patients. Furthermore, 2-methylcitrate/homocitrate and aromatic and branched-chain amino acid levels were also decreased in the NTM group. Both compounds play a role in the metabolism of mycobacterium.

The NTM and control groups showcased different microbiological patterns in each group with a predominance of Veillonella, Atopobium, Haemophilus, Staphylococcus, Streptococcus, unclassified Bacteroidetesand and Prevotella vs unclassified Prevotellaceae bacterium, Alloprevotella, and Oribacterium.

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“While it is not clear at this time how these findings apply to other individuals with CF, or to NTM infections in other lung diseases, the data found in this study mirror what has been observed in previous studies, namely, that certain anaerobic bacteria are overrepresented in patients with NTM infection, and extends these observations to also include differences in sputum metabolites associated with NTM infection,” the authors said.

“Identified differences in these metabolites associated with NTM infection are hypothesis generating for their potential role in susceptibility to NTM infections and will be the subject of future studies.”

Therefore, detecting the microbiota interactions with the host and its response, as well as the intermediaries involved, might lead to identifying potential biomarkers and novel therapeutic strategies. Recalling NTM pulmonary infections account for significant morbidity and mortality in patients with CF, and achieving this goal will greatly impact this population.

“Host risk factors for [NTM] infection in people with cystic fibrosis (CF) are largely unclear. The goal of this study was to help identify potential host and bacterial community risk factors for NTM infection in people with CF, using microbiome and metabolome data from CF sputum samples,” the authors concluded.

Reference

Breen P, Zimbric M, Opron K, Caverly LJ. Sputum metabolites associated with nontuberculous mycobacterial infection in cystic fibrosis. mSphere. Published online April 28, 2022. doi:10.1128/msphere.00104-22