Yersinia pseudotuberculosis O:1 Traced to Raw Carrots, Finland

The ISEcp1 insertion sequence has been described as a fl anking region of several blaCTX-M genes and has been implicated in the expression and mobilization of the genes (5). A recent study by Lartigue et al. showed that a CTX-M-2 progenitor in K. ascorbata could be mobilized and transferred to a conjugative E. coli plasmid by the ISEcp1B element; enhanced mobilization was observed in the presence of ceftazidime, cefotaxime, and piperacillin (10). This Salmonella isolate’s resistance to cefepime and cefquinome, fourth-generation cephalosporins, is troubling. Cefquinome is not approved for use in the United States but has been used in Europe for treating food animals since 1994. ESBLs, including CTX-M enzymes, are more common in Europe than in the United States (1). Further studies are warranted to clarify the extent to which the use of cefquinome has contributed to high CTX-M prevalence in Europe. In conclusion, we report a domestically acquired CTX-M–producing Salmonella isolate in the United States. Because third-generation cephalosporins are important for treating invasive Salmonella infections, continued monitoring of ESBL-producing bacteria is important.