LAUSR

AIM The ulcerative phase of oral mucositis following radiotherapy/chemotherapy for oral cancer colonizes bacteria, fungi and viruses. The role of a microbiota, specifically bacterial colonization in oral mucositis, is still unclear, and there is no existing data that correlates the shift in the bacterial colonization with mucositis severity. The aim of this study was to assess the bacterial colonization and study the MCR-1 (mobilized colistin resistance), VIM2 (β-lactam resistance), TET(K) (tetracycline resistance) and blaKPC (carbapenem resistance) genes' expression in isolated facultative anaerobes at 3 time points in oral mucositis patients undergoing radiotherapy and concomitant radiochemotherapy. METHODS A total of 24 oral cancer patients were divided into 2 groups: A (N = 12) undergoing radiotherapy; and B (N = 12) undergoing radiochemotherapy. Saliva was collected from all patients at 3 time intervals during the treatment. The isolated bacterial colonies were subjected to gene expression and analysis. RESULTS Staphylococcus aureus (22%), Staphylococcus epidermidis (29%), Pseudomonas aeruginosa (28%), Escherichia coli (25%) and Klebsiella pneumoniae (26%) are the facultative anaerobes isolated from saliva. The bacterial isolates obtained during and at the end of therapy appeared to express a higher level of antibiotic-resistance genes (VIM2, MCR-1, TET[K], blaKPC ) than those isolated at the onset of therapy. CONCLUSION Bacterial colonization and gene expression varied during different stages of mucositis.