Detection of clonally related Escherichia coli isolates producing different CMY β-lactamases from a cystic fibrosis patient.

OBJECTIVES

This study reports details on Escherichia coli isolates recovered from a cystic fibrosis (CF) patient in order to understand how this pathogen adapts to and resists broad-spectrum antipseudomonal therapy in this context.

METHODS

Five E. coli isolates were obtained from various clinical samples (airways, urine or dialysis catheter) over a 7 month period covering a double-lung transplantation. All isolates were analysed in terms of clonality [enterobacterial repetitive intergenic consensus (ERIC)-PCR and multilocus sequence typing], virulence profiles (phylogroup and search for 15 virulence genes), growth patterns (morphotype, biofilm-forming ability and growth rate), hypermutability and antimicrobial susceptibility, with molecular characterization of β-lactamases and porins.

RESULTS

The five isolates shared similar ERIC-PCR profiles and sequence types (ST1193) and exhibited the same virulence profile. The respiratory isolates were strong mutators, exhibited mucoid or small-colony morphotypes, exhibited strong biofilm-forming ability and grew slowly compared with the others. All isolates were highly resistant to ceftazidime. The respiratory isolates showed reduced susceptibility to cefepime and high resistance to aztreonam. The patient had received a 31 day course of ceftazidime/aztreonam until transplantation. All isolates harboured the same wild-type chromosomal AmpC. A CMY-2 enzyme was detected in the non-respiratory isolates. The respiratory isolates harboured L293S and V211A/L293S new CMY-2 variants, which were designated CMY-94 and CMY-95, respectively. OmpF porin loss was observed in the non-respiratory isolates.

CONCLUSIONS

Our study shows that, similarly to Pseudomonas aeruginosa, E. coli can undergo phenotypic and genomic changes in the CF context. For the first time, we identified an in vivo expanded-spectrum evolution of the CMY-2 β-lactamase, during bacterial persistence in the CF lung.