86 Molecular typing of rapidly growing mycobacteria (RGM) in patients with cystic fibrosis (CF)

Objectives To perform molecular typing of clinical strains of RGM isolated from the lower respiratory tract of CF patients with persistent, transient and intermittent infections. Secondary, to assess whether chronic infections are sustained by the same bacterial species, over time. Methods Twenty-three patients, out of the 793 followed at the Regional Reference Centre for Cystic Fibrosis of Milan, have a persistent RGM infection, and 19 show an intermittent infection. From October 2013 to October 2014, 65 strains were isolated and typed by gene sequencing of the rpo B gene. The gene sequences obtained were compared to those already present in the GenBank database to discriminate subspecies of RGM. Results Molecular typing of 46 strains (at two different follow-up times: T1, T2), isolated from 23 patients with chronic RGM colonization, reveals that chronic infection are sustained, in 100% of cases, by MAC (61% M. abscessus sensu stricto, 26% M. bolletii and 13% M. massiliense ), and species identified at T1 is the same identified at T2. In 19 patients, the intermittent infection is sustained by different species of RGM: 37% M. chelonae, 26% M. abscessus sensu stricto, 26% M. bolletii, 5.5% M. fortuitum and 5.5% M. massiliense. Conclusion The chronic infections are sustained by MAC, with a higher prevalence of M. abscessus sensu stricto, and that species acquired at T1 persists over time. Intermittent infections are sustained by M. chelonae, M. fortuitum and MAC. Further correlation studies between the clinical course of the pulmonary disease and the presence of MAC different subspecies are recommended in order to create appropriate therapeutic schemes.