Appearance of Salmonella enterica isolates producing plasmid-mediated AmpC beta-lactamase, CMY-2, in South Korea.

Of 176 Salmonella isolates isolated from 2000 to 2003 in a Korean university hospital, 2 cefoxitin-resistant isolates of Salmonella enterica serovar Rissen were found in 2002. Both isolates were resistant to multiple beta-lactam antibiotics, including ampicillin, amoxicillin-clavulanate, cefoxitin, cefotaxime, and ceftazidime. Cell sonicates of the both clinical isolates and their transconjugants had beta-lactamase band of approximate isoelectric point of >8.6. The resistance to cefoxitin was transferred by conjugation to the recipient Escherichia coli J53. The resistance determinant was on conjugative plasmids that encoded a CMY-2, a plasmid-mediated AmpC beta-lactamase. To our knowledge, these are the first description of S. enterica serovar Rissen harboring CMY-2 in South Korea.