Molecular epidemiology of ESBL-producing and : establishing virulence clusters.

Objective: To genetically characterize clusters of virulence factors (VFs) among extended spectrum β-lactamase (ESBL)-producing and and assess whether these clusters are associated with genetic determinants or clinical outcomes.

Methods: One hundred forty-eight and 82 . clinical isolates were obtained from 213 patients in Paris, France. Isolates underwent ESBL characterization, MultiLocus Sequence Typing (MLST) typing and phylogenetic group identification. Detection of ten and seven . VF-encoding genes were assessed, from which a -medians partition algorithm with Jaccard similarity measure was used to construct clusters.

Results: CTX-M was the predominant ESBL and susceptibility to trimethoprim-sulfamethoxazole (32%), ciprofloxacin (22%) and aminoglycosides (32%) was low. In , there were five identified clusters, with significantly different distributions of ESBL-sequence type (<0.001), ST131 (<0.001) and phylogenetic group (=0.001) between clusters. "Siderophore exclusive", "siderophore exclusive with " and "adhesin sfa/papGIII-rich" clusters had higher 12-month mortality rates compared to others (49% vs 22%, respectively, =0.02). In , three different clusters, with significantly different distributions of aminoglycoside-sensitivity (<0.004), MLST-type (<0.001) and relaxase plasmids (=0.001) were described.

Conclusion: Distinct clusters of and VFs are observed within ESBL-producing isolates and are strongly associated with several genetic determinants. Their association with overall morbidity and mortality requires further evidence.