New study advances the understanding of the resistance mechanisms of ‘Haemophilus parainfluenzae’

A study carried out in the Microbiology Service of the Bellvitge University Hospital and the IDIBELL Bacterial Infections Research Group has detected for the first time the acquisition of an extended spectrum beta-lactamase (ESBL) CTX-M-15 in multidrug-resistant strains of Haemophilus parainfluenzae isolated from urogenital samples. This finding, published in the International Journal of Antimicrobial Agents, highlights the possibility that this resistance mechanism could spread to other sexually transmitted pathogens.

The opportunistic pathogen H. parainfluenzae colonizes the human respiratory and urogenital tracts. The genetic material of this bacterium has high plasticity, which allows it to act as a possible reservoir of resistance genes. The increase in the prevalence of multidrug-resistant strains detected in recent years, combined with the increase in urogenital infections associated with this microorganism, highlights the need to thoroughly understand its mechanisms of acquisition and spread of antibiotic resistance.

This work describes the molecular mechanisms of resistance associated with four multidrug-resistant strains of H. parainfluenzae isolated in patients with urethritis. The strains were resistant to six families of antibiotics, including beta-lactams, fluoroquinolones, macrolides, tetracycline, chloramphenicol and cotrimoxazole. Furthermore, they had a resistance profile compatible with the presence of the ESBL enzyme, something that had not been previously described in this species. Through sequencing, a beta-lactamase blaCTX-M-15 integrated into the genome was identified due to the transposition of new mobile genetic elements that conferred high levels of resistance to cephalosporins.

This was the first time that this beta-lactamase was detected in H. parainfluenzae. The potential of this pathogen to accumulate antibiotic resistance determinants, together with the possibility of transmitting these elements to other pathogens associated with sexually transmitted infections, is a cause of concern for public health.