Ceftriaxone-resistant Salmonella enterica serovar Hadar: evidence for interspecies transfer of blaCMY-2 in a Taiwanese university hospital.

The emergence of resistance 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 beta-lactamase. To our knowledge, this is the first report of S. hadar harboring blaCMY-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 blaCMY-2 in both the Salmonella isolate and one E. coli isolate, suggesting the possibility 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.