# First identification and molecular characterization of CTX-M-15 extended-spectrum β-lactamase and OXA-9 β-lactamase in Haemophilus influenzae in the Iberian Peninsula

## TL;DR

This study reports the first identification of CTX-M-15 and OXA-9 enzymes in Haemophilus influenzae in the Iberian Peninsula, highlighting growing antibiotic resistance.

## Contribution

First report of CTX-M-15 and OXA-9 in H. influenzae in the Iberian Peninsula, with molecular characterization of resistance elements.

## Key findings

- CTX-M-15 was identified in a multidrug-resistant H. influenzae strain from Portugal.
- OXA-9 was found in a β-lactam and aminoglycoside-resistant H. influenzae strain from Spain.
- Both strains carried novel integrative and conjugative elements (ICEs) associated with resistance.

## Abstract

We describe, for the first time, the presence and characterization of CTX-M-15 and OXA-9 in two Haemophilus influenzae strains: PTHi-14525 (CTX-M-15) from Portugal and HUB-HI042681 (OXA-9) from Spain. Multidrug-resistant PTHi-14525 carried blaCTX-M-15 (two copies) and blaTEM-1 in an ICEHpaHUB5-like element. HUB-HI042681, resistant to β-lactams and aminoglycosides, carried a novel ICEHinHUB1. These findings highlight the genomic plasticity and expanded resistome of H. influenzae, raising concerns about treatment and emphasizing the need for continuous genomic surveillance.