Abstract
We analyzed the prevalence of resistance to extended-spectrum cephalosporins (ESCs) among clinical strains of Salmonella enterica collected by the Laboratory of Clinical Microbiology in the University Clinical Hospital Lozano Blesa in the region of Aragón (Spain), for which very few epidemiological information exists. A total of 2,092 strains of S. enterica were identified in stool samples from patients with gastroenteritis. Five isolates showed an extended-spectrum beta-lactamase (ESBL) phenotype: four isolates of S. enterica serotype Virchow harbored the ESBL-encoding bla(CTX-M-9) gene and an isolate of serotype Enteritidis carried a bla(CTX-M-1) gene, which, to the best of our knowledge, is described here for the first time in this serotype of S. enterica. The five ESC-resistant isolates were also resistant to spectinomycin, streptomycin, kanamycin, sulfonamides, tetracycline, and trimethoprim as well as to nalidixic acid. The ESBL isolate of serotype Enteritidis, however, remained susceptible to kanamycin and nalidixic acid. A class 1 integron of 1.5 kb was detected for the four serotype Virchow isolates with the gene cassette dfrA16-aadA2. The bla(CTX-M-9) gene was carried by an ∼300-kb IncHI2 conjugative plasmid in the case of the S. enterica serotype Virchow isolates. The bla(CTX-M-1) gene was carried by an ∼100-kb IncI1-N conjugative plasmid for the serotype Enteritidis ESC-resistant isolate. All the four ESC-resistant strains of S. enterica serotype Virchow clustered together in a XbaI pulsed-field gel electrophoresis, which also revealed a strong similarity between them and some pulsotypes of S. enterica serotype Virchow from France.
Highlights
Nontyphoidal salmonellosis is one of the most prevalent food borne bacterial infections in Europe and in North America
Since the first blaCTX-M genes were described in the early 1990s, S. enterica has been one of the first species of Enterobacteriaceae to be identified harbouring this kind 178 of resistances 1
CTX-M-9 was first reported in Spain in 1996, produced by an E. coli human isolate and S. enterica serotype Virchow carrying a blaCTX-M-9 appeared just a 180 few years later 34
Summary
Appropriate drugs for Salmonella infections include ampicillin, extended-spectrum cephalosporins (ESC), fluoroquinolones, and trimethoprimsulfamethoxazole. Rising rates of resistance to ampicillin and trimethoprimsulfamethoxazole have significantly reduced their efficacy and fluoroquinolones are not approved for the use in children. ESC have become the current drugs of 14 choice for the treatment for invasive infections in children 4. The number of cases of salmonellosis caused by isolates resistant to these ESC is in continuous increase since 16 the very first case was detected in the early 1980s 1. They are still rare over 17 the total of Salmonella foodborne infections, just reaching a 0.2 % in Europe in 2004 25
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
