Microbiota Core in Central Lung Cancer with Streptococcal Enrichment as a Possible Diagnostic Marker

Abstract

Background: Dysbiosis has been scarcely explored in the respiratory tract with cancer. We aimed to define the bacterial and fungal microbiota of the bronchi in cancer versus a healthy state, also defining the microbiota core, and their correlation with that in saliva and feces; and to detect markers for the early diagnosis of central lung cancer. For this purpose, twenty-five patients with central lung cancer and sixteen healthy controls without antimicrobial intake during the previous month were recruited. Bacterial and fungi distribution was determined by massive sequencing in bronchial biopsies. Complex computational analysis was performed to define for the first time the lung microbiota core.Results: A greater abundance of Streptococcus, Rothia, Gemella and Lactobacillus distinguish the saliva of patients. Affected and contralateral bronchi of these patients have almost identical microbiota dominated by Streptococcus, whereas Pseudomonas was the major genera in controls. Oral and pulmonary ecosystems were significantly more similar in patients, probably due to microaspirations. Streptococcal bronchial abundance differentiates patients from controls by an ROC curve (90.9% sensitivity, 83.3% specificity, AUC=0.897). The mycobiome of controls (Candida) was significantly different from that of patients (Malassezia), with the cancer-affected bronchi similar to their saliva, but different from their contralateral bronchi. Conclusions: Central lung cancer is highly enriched with Streptococcus, and shows significantly differences in their composition from healthy subjects. Alterations are not restricted to the tumor tissue, and seem to be the consequence of microaspirations from the oral cavity. These findings could be useful in the screening and even diagnosis of this pathology.