P49

The diagnostic tools for species determination of mycobacteria have evolved, as has the accuracy of interpretation. In Denmark, routine species determination of non-tuberculous mycobacteria has been identified with line probe assays and additional sequencing of the 16S rRNA gene and later ITS. In recent years, awareness of M. chimaera has increased, mainly due to contamination cases with M. chimaera in heater-cooler units (HCU) used during thoracic surgery.

As new molecular tools have improved since the samples first were analysed, we re-evaluated all the M. intracellulare group species identifications from 2012 to 2020. In addition, we wanted to develop a PCR for detection of the native 13 Kb plasmid (p13) present in all M. chimaera strains and the 32 Kb plasmid (p32) present only in the subtypes contaminating HCUs and which potentially can have infected patients during thoracic surgery.

All isolates between 2012 through March 2020 assigned to M. avium complex, M. intracellulare group, M. intracellulare, or M. chimaera were selected for this study, in total of 328 isolates.

During the studied period, 107 M. chimaera patient isolates were examined. The 103 were positive for p13, and two were also positive for p32. The two p32 positive samples came from patients who had undergone thoracic surgery.

This study clearly shows that the vast majority of the M. intracellulare group is M. chimaera. Furthermore, by using the p32 PCR, we could precisely identify the M. chimaera from the HCUs used during thoracic surgery.