<i>bla</i> _CTX-M-1/9/1 Hybrid Genes May Have Been Generated from <i>bla</i> _CTX-M-15 on an IncI2 Plasmid

<jats:title>ABSTRACT</jats:title> <jats:p> Three hybrid CTX-M β-lactamases, CTX-M-64, CTX-M-123, and CTX-M-132, with N and C termini matching CTX-M-1 group enzymes and centers matching CTX-M-9 group enzymes, have been identified. The hybrid gene sequences suggested recombination between <jats:italic>bla</jats:italic> <jats:sub>CTX-M-15</jats:sub> and <jats:italic>bla</jats:italic> <jats:sub>CTX-M-14</jats:sub> , the two most common <jats:italic>bla</jats:italic> <jats:sub>CTX-M</jats:sub> variants worldwide. However, <jats:italic>bla</jats:italic> <jats:sub>CTX-M-64</jats:sub> and <jats:italic>bla</jats:italic> <jats:sub>CTX-M-123</jats:sub> are found in an IS <jats:italic>Ecp1-bla</jats:italic> <jats:sub>CTX-M</jats:sub> transposition unit with a 45-bp “spacer,” rather than the 48 bp usually associated with <jats:italic>bla</jats:italic> <jats:sub>CTX-M-15</jats:sub> , and 112 bp of IncA/C plasmid backbone. This is closer to the context of <jats:italic>bla</jats:italic> <jats:sub>CTX-M-55</jats:sub> , which has one nucleotide difference from <jats:italic>bla</jats:italic> <jats:sub>CTX-M-15</jats:sub> , on IncI2 plasmid pHN1122-1. Here, we characterized an IncI2 plasmid carrying <jats:italic>bla</jats:italic> <jats:sub>CTX-M-15</jats:sub> with a 45-bp spacer (pHNY2-1) by complete sequencing and also sequenced IncI2 plasmids carrying <jats:italic>bla</jats:italic> <jats:sub>CTX-M-64</jats:sub> (pHNAH46-1) or <jats:italic>bla</jats:italic> <jats:sub>CTX-M-132</jats:sub> (pHNLDH19) and an IncI1 plasmid carrying <jats:italic>bla</jats:italic> <jats:sub>CTX-M-123</jats:sub> (pHNAH4-1). pHNY2-1 has the same IS <jats:italic>Ecp1-bla</jats:italic> <jats:sub>CTX-M</jats:sub> -IncA/C insertion as pHN1122-1, pHNAH46-1, and pHNLDH19, and all four plasmid backbones are almost identical. pHNAH4-1 (IncI1 sequence type 108 [ST108]) carries a transposition unit that includes a 2,720-bp fragment of the IncI2 backbone, suggesting IS <jats:italic>Ecp1</jats:italic> -mediated transfer of <jats:italic>bla</jats:italic> <jats:sub>CTX-M</jats:sub> -IncA/C-IncI2 to an IncI1 plasmid. All three hybrid <jats:italic>bla</jats:italic> <jats:sub>CTX-M</jats:sub> genes may have resulted from recombination between <jats:italic>bla</jats:italic> <jats:sub>CTX-M-14</jats:sub> and <jats:italic>bla</jats:italic> <jats:sub>CTX-M-15</jats:sub> with a 45-bp spacer on an IncI2 plasmid. Five additional <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Escherichia coli</jats:named-content> isolates of different sequence types from different provinces, farms, and/or animals had <jats:italic>bla</jats:italic> <jats:sub>CTX-M-64</jats:sub> on a pHNAH46-1-like IncI2 plasmid and 9 had <jats:italic>bla</jats:italic> <jats:sub>CTX-M-123</jats:sub> on a pHNAH4-1-like IncI1 ST108 plasmid. Thus, epidemic IncI plasmids may be responsible for the spread of <jats:italic>bla</jats:italic> <jats:sub>CTX-M-64</jats:sub> and <jats:italic>bla</jats:italic> <jats:sub>CTX-M-123</jats:sub> between different animals and different locations in China. </jats:p>