[Recent evolution and characterization of extended-spectrum beta-lactamase producing enterobacteria in the CHU of...

ESBL producing enterobacteria (E-ESBL+) are always a public health concern, mainly due to increase of CTX-M beta-lactamase. So, 542 new strains were isolated in the CHU de Nice during the 2005-2007 period. The aim of this work was to characterize the ESBL and to type isolates suspected to be implicated in outbreaks.

Every first E-ESBL+ was studied, the antibiotype was defined by the agar diffusion technique. Type of ESBL was determined by PCR, followed by sequencing for CTX-M and SHV enzymes. Typing was performed when several strains of one species had same antibiotype and beta-lactamase.

CTX-M type ESBL are predominant (45% of all E-ESBL+), mainly in Escherichia coli (34.5%). The TEM24 ESBL was the second predominant type (34.5%), mainly in Enterobacter aerogenes (18.6%) and Klebsiella pneumoniae (9.4%). SHV5/12 ESBL was found mainly in Enterobacter cloacae (7.5%). Several epidemic situations were identified, with CTX-M15 in Escherichia coli (2005/2006: 27 patients), SHV5/12 in Enterobacter cloacae (2006: 10 patients) and TEM in Proteus mirabilis (2007: nine patients). Enterobacter aerogenes is still endemic (101 patients) while an epidemic clone of TEM24 producing K. pneumoniae persists especially in an intensive care unit (26 patients during the three years).

Caracterization of E-ESBL+ is essential to better understand their mode of dissemination, monitor the emergence of new enzymes and adapt the efforts against BMR cross transmission.