SRA

Objectives. To study the macrolide resistance levels and the resistance mechanisms among all the isolates of Haemophilus inlfuenzae and Haemophilus parainfluenzae during 2018-2021. Methods. Antimicrobial susceptibility was tested by microdilution. 67 H. influenzae and 52 H. parainfluenzae were selected to perform WGS. The sequences were analyzed to identify macrolide-resistance mechanisms and mobile genetic structures carrying macrolide resistance genes. Results. Macrolide resistance was found in 67 H. influenzae and 52 H. parainfluenzae strains. Macrolide resistance was associated to resistance to other antimicrobials like co-trimoxazole, chloramphenicol and tetracyclines. Acquired resistance genes were found in 67.3% of H. parainfluenzae and in 16.4% of H. influenzae. Mutations and modifications were more common among H. influenzae (82%) than H. parainfluenzae (32.7%). Changes in L22 were found in H. influenzae (32.8%) but not in H. parainfluenzae, while modifications in L4 were found in both species (23,8% and 7.7% respectively). Alterations in AcrB/acrR were also observed for both H. influenzae (34.3%) and H. parainfluenzae(30.8%). Finally, mutations in the 23S rRNA were only observed in H. influenzae (29.8%). 35 strains of H. parainfluenzae had the MEGA element, in 5 cases integrated in an ICE. 11 H. influenzae had MEGA element integrated in ICEs in all the cases. A new ICE called ICEHpaHUB6 was described for the first time for H. parainfluenzae. Conclusions. Macrolide resistance was higher in H. parainfluenzae than in H. influenzae. Differences in the resistance mechanisms were also observed among the two species. When acquiring resistance genes, the integration of MEGA element in ICEs was more frequent in H. influenzae. The description of a new mobile genetic element in H. parainfluenzae that confers an XDR phenotype is a cause of concern.