JAC Advance Access originally published online on January 22, 2007
Journal of Antimicrobial Chemotherapy 2007 59(3):579-582; doi:10.1093/jac/dkl506
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Correspondence |
Extended-spectrum-ß-lactamase-producing Salmonella enterica strains isolated from humans in Hungary, 2000 to 2004
1 Department of Bacteriology, National Center for Epidemiology, H-1097, Gyáli u. 2-6, Budapest, Hungary 2 Department of Phage-typing and Molecular Epidemiology, National Center for Epidemiology, H-1097, Gyáli u. 2-6, Budapest, Hungary 3 Veterinary Medical Research Institute of the Hungarian Academy of Sciences, H-1143, Hungária krt. 21, Budapest, Hungary
* Corresponding author. Tel: +36-1-476-1265; Fax: +36-1-476-1234; E-mail: nogradyn{at}oek.antsz.hu
Keywords: ESBLs , CTX-M-5 , CTX-M-15 , SHV-5
Use of expanded-spectrum cephalosporins for the treatment of salmonellosis has resulted in outbreaks and cases of infections caused by Salmonella enterica that are resistant to oxyimino-cephalosporins since the early 1990s worldwide. For the Eastern and Central European regions Tassios et al.1 reported the occurrence of a blaCTX-M-producing human Salmonella Typhimurium clone in Russia, Hungary and Greece. Vahaboglu et al.2 reported two clonally distinct Salmonella Typhimurium strains producing a TEM-52-type extended-spectrum ß-lactamase (ESBL) isolated in Hungary. Nevertheless, there are no other reports on ESBL-producing salmonellae in Hungary. Therefore, to assess the occurrence of resistance to third-generation cephalosporins, we screened the non-typhoid Salmonella collection of our laboratory for ESBL-producing isolates.
The study included 13 962 isolates from the collection of the Reference Laboratory of Phage-typing of Enteric Bacteria, National Center for Epidemiology, from the period 2000–2004. The serotype of all strains was confirmed by standard tests; the Colindale phage typing systems were used for Salmonella Typhimurium and Salmonella Enteritidis. On receipt, all isolates were routinely screened for resistance to ampicillin, chloramphenicol, gentamicin, kanamycin, streptomycin, trimethoprim/sulfamethoxazole, tetracycline, nalidixic acid, ciprofloxacin and cefotaxime by the disc diffusion method. For ESBL screening, besides the cefotaxime-resistant isolates, all ampicillin-resistant isolates (n = 1690) were selected and tested for cefotaxime and ceftazidime resistance on Mueller–Hinton agar containing 2 mg/L antibiotics. The inocula were prepared by the direct colony suspension method and transferred to the surface of the agar plates by using inoculum replicators. The phenotypic confirmation of ESBL production of the suspicious isolates was performed by double disc approximation tests and ESBL Etests; MICs of cefotaxime and ceftazidime were determined with Etest strips. All ESBL-producing isolates were tested for the presence of the blaTEM2, blaCTX-M3 and blaSHV4 genes by PCR. Purified PCR amplicons were sequenced. Sequences obtained were BLAST-analysed at http://www.ncbi.nlm.nih.gov and compared with those registered in GenBank.
Of the 13 962 non-typhoid Salmonella isolates tested, 14 Salmonella Typhimurium isolates and 1 Salmonella Enteritidis isolate were found to be ESBL-producing and were subjected to the PCRs. There were no ESBL-producing isolates found among the other serotypes tested (Salmonella Infantis, Salmonella Hadar, Salmonella Saintpaul, Salmonella Blockley and Salmonella Panama). Besides two isolates which originated from urine and haemoculture, all other isolates originated from stool samples. The date of isolation, serotype and phage type, resistances to the antimicrobials tested, MICs of cefotaxime and ceftazidime, type of the ESBL genes identified and the country of origin of the isolates are summarized in Table 1.
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The single Salmonella Enteritidis isolate harboured a blaSHV-5 ß-lactamase gene. Emergence of an ESBL-producing Salmonella Enteritidis in Hungary is novel. Of the 14 Salmonella Typhimurium isolates, 3 possessed a blaSHV-5 ß-lactamase gene. These isolates also had a blaTEM-1 gene. The remaining 11 Salmonella Typhimurium isolates possessed blaCTX-M, of which 8 carried blaCTX-M-5. Three isolates were proven to be blaCTX-M-15-positive by sequencing, two of which also had a blaTEM-1 gene.
Two Salmonella Typhimurium isolates were related to the treatment of Romanian patients in Hungary. Interestingly, a Salmonella Typhimurium isolate reported by Miriagou et al.5 and designated as ST5, isolated in 2000 from a Romanian patient, produced ß-lactamase genes of the same type (blaSHV-5 and blaTEM-1) as our two Romanian isolates from 2001. Whether these isolates show a clonal relationship requires further testing. All of the 11 blaCTX-M carrier Salmonella Typhimurium isolates originated from either Ukraine or a Hungarian county located neighbouring the Ukrainian border. The three Ukrainian isolates and five Hungarian isolates harboured a blaCTX-M-5 ESBL gene. As Salmonella Typhimurium strains with blaCTX-M-5 were reported from Latvia by Bradford et al.6 and also from Russia and Belarus by Edelstein et al.,7 it is suggestive that the same blaCTX-M-5-producer Salmonella Typhimurium clone may have spread to Hungary as well. For the years 2003 and 2004, a relatively newly identified version of the blaCTX-M genes, blaCTX-M-15, has appeared in Hungary. Investigations concerning the genetic diversity of the ESBL-producing isolates as well as the location and transferability of the identified resistance genes are in progress.
Our study provides further evidence for the dissemination of ESBL-producing salmonellae in Europe. The emergence of the blaCTX-M-5, blaCTX-M-15 and blaSHV-5 genes in Salmonella Typhimurium and blaSHV-5 in Salmonella Enteritidis in Hungary are reported for the first time. A National ESBL Survey was initiated in 2002 by the National Center for Epidemiology to help the monitoring of the prevalence of salmonellae resistant to expanded-spectrum cephalosporins in Hungary.
None to declare.
Acknowledgements
Part of this work was presented at the 16th ECCMID, Nice, France, 2006 (poster no. P1409). The excellent technical assistance of Mrs Margit Király, Mrs Vera Koppány, Mrs Judit Orbán, Ms Andrea Torma, Ms Judit Berta and Mrs Jánosné Topf is acknowledged. We are grateful to Mrs Gabriella Hajbel-Vékony for performing the sequencing. N. Nógrády is the holder of a Bolyai János stipend from the Hungarian Academy of Sciences.
References
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