Salmonella enterica producing extended-spectrum b-lactamases in Zaragoza, Spain, 2001 to 2005

Abstract number: P2085

Pardos M., Seral C., Millan M.I., Arias A., Llaneza M.E., Algarate S., Borras M., Rubio C., Weill F.X., Castillo F.J.

Objective: To study the prevalence of Salmonella enterica producing extended-spectrum betalactamases (ESBL) in the sanitary area of the Hospital "Clinico Universitario Lozano Blesa", Zaragoza, Spain.

Methods: From the cases of gastroenteritis due to Salmonella enterica detected in our area from 2001 to 2005, we selected the isolates with reduced susceptibility to extended spectrum cephalosporins (ESC) using the Wider® semi-automatic system for identification and MIC-determination. Complete serotyping was performed according to the Kauffmann-White scheme. The ESBL phenotype was detected by the double disk synergy test and by E-test. For isolates showing an ESBL phenotype, the genes of CTX-M, SHV and TEM groups were detected by PCR and sequencing. Detection of the gene cassettes of class 1 integrons were also performed by PCR. Transfer of ESC-resistance was performed by conjugation on solid medium using Escherichia coli K12J5 resistant to sodium azide. Plasmid analysis was performed by the S1-nuclease method. Plasmids were typed for their incompatibility group by a PCR-based replicon typing method. The genetic diversity of the S. enterica isolates was assessed by a pulsed field electrophoresis following the PulseNet standardised protocol.

Results: We collected 2170 Salmonella enterica isolates from 2001 to 2005. Only five ESBL-producing isolates were detected (0.23%) in five outpatients. Four serotype Virchow isolates produced CTX-M-9. They showed a reduced susceptibility to ceftriaxone (MIC=32 mg/L) but were susceptible in vitro to ceftazidime (MIC=1 mg/L). They were resistant to aminoglycosides (kanamycin, streptomycin and spectinomycin), tetracycline, trimethoprim and sulfonamides. A single class 1 integron gene cassette was found (dfrA16-aadA2), identical to that of complex integron In60. A 330kb-conjugative plasmid belonging to the incompatibility group Inc HI2 was found in all the tranconjugants, co-transferring all the resistances seen in parental isolates. The fifth isolate belonged to serotype Enteritidis containing a blaCTX-M-1 gene located on a 290kb-conjugative plasmid of Inc I1 group. Two PFGE profiles sharing 90% of identity were seen in the ESC-resistant Virchow isolates.

Conclusion: These are the first cases of ESBL-producing Salmonella in our area and seem to be related with other community-acquired isolates described in Spain and France. The increasing presence of CTX-M genes among Enterobacteriaceae is probably due to the conjugative plasmid location.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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