Ceftriaxone-resistant Salmonella enterica serovar hadar: Evidence for interspecies transfer of BLA_CMY-2 in a Taiwanese University Hospital

The emergence of resistence to extended-spectrum cephalosporins in salmonellae is an increasing clinical problem. We report the characteristics of a ceftriaxone-resistant Salmonella enterica serovar Hadar strain collected in 2001 from a patient with a postoperative wound infection in a university hospital in Taiwan. Resistance to extended-spectrum cephalosporins was found to be due to production of the plasmid-mediated CMY-2 AmpC β-lactamase. To our knowledge, this is the first report of S. hadar harboring bla_CMY-2. Seven CMY-2 producing Escherichia coli isolates collected in 2000 were investigated for comparison. Conjugation experiments and plasmid analysis showed an identical plasmid carrying bla_CMY-2 in both the Salmonella isolated and one E. coli isolate, suggesting the posibility that the Salmonella isolate acquired the resistance plasmid from E. coli. These findings suggest that measures are necessary to restrict antibiotic use and so prevent the spread and development of antibiotic resistance in Taiwan.