JAC Advance Access first published online on October 8, 2009
This version published online on October 13, 2009
Journal of Antimicrobial Chemotherapy, doi:10.1093/jac/dkp361
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Original research |
Emergence of extended-spectrum β-lactamases and AmpC-type β-lactamases in human Salmonella isolated in Spain from 2001 to 2005
Instituto de Salud Carlos III, Centro Nacional de Microbiología, Majadahonda, Madrid, Spain
Received 10 May 2009; returned 16 July 2009; revised 5 September 2009; accepted 12 September 2009
* Corresponding author. Tel: +34-918223699; Fax: +34-915097966; E-mail: ruben.gs{at}isciii.es
Objectives: To study the resistance to third-generation cephalosporins in Salmonella strains isolated from humans in a 5 year period in Spain, and to identify the responsible genes and their dissemination.
Methods: Twenty-seven isolates were analysed by PCR and sequencing to identify the genes responsible for the β-lactamase resistance phenotypes. The transferability of the phenotypes was tested by conjugation to Escherichia coli K12J53, plasmid detection with S1-PFGE, hybridization and PCRs of the transconjugants. The genetic relationship was determined by PFGE.
Results: We found blaCTX-M-9 and blaCTX-M-10 in Salmonella Virchow PT19. blaCTX-M-14 was detected in Salmonella (IV) 44:z4,z23:-, Salmonella Enteritidis PT6a, Salmonella Typhimurium DT193 and Salmonella Typhimurium DT104B. blaCTX-M-1 was found in Salmonella Litchfield. blaCTX-M-15 and blaCTX-M-32 were found in Salmonella Enteritidis PT1. blaSHV-12 was found in Salmonella Blockley, Salmonella Hadar PT2, Salmonella Enteritidis PT21, Salmonella Enteritidis PT1 and Salmonella Bredeney. blaSHV-2 was found in Salmonella Livingstone. blaCMY-2 was detected in Salmonella Bredeney, Salmonella Newport, Salmonella Enteritidis PT5b and Salmonella Heidelberg. blaDHA-1 was detected for the first time in Spain in Salmonella Newport. One strain of Salmonella Senftenberg harboured two extended-spectrum β-lactamases, blaSHV-12 and blaCTX-M-9. We have found a large variety of β-lactamase families as well as several members of major relevance, such as CTX-M-15, CTX-M-32, CMY-2 and DHA-1. XbaI-PFGE, conjugation assays and S1-PFGE hybridization showed that all these β-lactamases were mediated by plasmids.
Conclusions: This study demonstrates the emergence of a public health risk related to resistance to β-lactams in Salmonella. The resistance trends need to be monitored carefully.
Key Words: resistance mechanisms , Enterobacteriaceae , molecular identification , ESBLs
The original version was incorrect. On page 2, in the PFGE types paragraph, there are updates to lines 2, 4, 5 and 6.