Characterization of ESBL-Producing and Isolated from Clinical Samples in a Northern Portuguese Hospital: Predominance of CTX-M-15 and High Genetic Diversity.

BACKGROUND

are major players in the spread of resistance to β-lactam antibiotics through the action of CTX-M β-lactamases. We aimed to analyze the diversity and genetic characteristics of ESBL-producing and isolates from patients in a Northern Portuguese hospital.

METHODS

A total of 62 cefotaxime/ceftazidime-resistant ( = 38) and ( = 24) clinical isolates were studied. Identification was performed by MALDI-TOF MS. Antimicrobial susceptibility testing against 13 antibiotics was performed. Detection of ESBL-encoding genes and other resistance genes, phylogenetic grouping, and molecular typing (for selected isolates) was carried out by PCR/sequencing.

RESULTS

ESBL activity was detected in all 62 and isolates. Most of the ESBL-producing isolates carried a gene (37/38 isolates), being predominant ( = 32), although ( = 1) and ( = 1) were also detected. Two isolates carried the gene. The lineages ST131-B2 and ST410-A were detected among the ESBL-producing blood isolates. Regarding the 24 ESBL-producing isolates, 18 carried a gene (, 16 isolates; , 2 isolates). All isolates carried genes, including ESBL-variants ( and , 14 isolates) or non-ESBL-variants ( and , 10 isolates); ten isolates also carried the gene and showed imipenem-resistance. ESBL-positive isolates were ascribed to the B phylogenetic group (82%), mostly associated with ST131 lineage and, at a lower rate, to ST410/A. Regarding , the three international lineages ST15, ST147, and ST280 were detected among selected isolates.

CONCLUSIONS

Different ESBL variants of CTX-M (especially CTX-M-15) and SHV-type (specially SHV-12) were detected among CTX/CAZ and isolates, in occasions associated with carbapenemase genes ( gene).