Evolution and Spread of a Multidrug-Resistant Proteus mirabilis Clone with Chromosomal AmpC-Type Cephalosporinases in Europe

Abstract

ABSTRACTProteus mirabilisisolates obtained in 1999 to 2008 from three European countries were analyzed; all carried chromosomal AmpC-type cephalosporinaseblaCMYgenes from aCitrobacter freundiiorigin (blaCMY-2-like genes). Isolates from Poland harbored severalblaCMYgenes (blaCMY-4,blaCMY-12,blaCMY-14,blaCMY-15, andblaCMY-38and the new geneblaCMY-45), while isolates from Italy and Greece harboredblaCMY-16only. Earlier isolates withblaCMY-4orblaCMY-12, recovered in France from Greek and Algerian patients, were also studied. All isolates showed striking similarities. TheirblaCMYgenes resided within ISEcp1transposition modules, named Tn6093, characterized by a 110-bp distance between ISEcp1andblaCMY, and identical fragments of bothC. freundiiDNA and a ColE1-type plasmid backbone. Moreover, these modules were inserted into the same chromosomal site, within thepepQgene. Since ColE1 plasmids carrying ISEcp1with similarC. freundiiDNA fragments (Tn6114) had been identified earlier, it is likely that a similar molecule had mediated at some stage this DNA transfer betweenC. freundiiandP. mirabilis. In addition, isolates withblaCMY-12,blaCMY-15, andblaCMY-38genes harbored a secondblaCMYcopy within a shorter ISEcp1module (Tn6113), always inserted downstream of theppiDgene. Sequence analysis of all mobileblaCMY-2-like genes indicated that those integrated in theP. mirabilischromosome form a distinct cluster that may have evolved by the stepwise accumulation of mutations. All of these observations, coupled to strain typing data, suggest that theblaCMYgenes studied here may have originated from a single ISEcp1-mediated mobilization-transfer-integration process, followed by the spread and evolution of aP. mirabilisclone over time and a large geographic area.