Genetic relatedness between human and animal polymorphic blaTEM genes strengthens zoonotic potential among uropathogenic Escherichia coli strains

AGGAATCCCATG-30 and CTX-M-R2, 50-GCCGTCTAAGGCGATAAAC-30, were used to amplify the entire allele (876 bp) for sequencing. This revealed that S. enterica serovar Senftenberg strain 9-4 produced CTX-M-3, which was first identified in Poland. Southern hybridization using the whole blaCTX-M gene as a probe showed that the gene was located on a plasmid of < 38 kb in size. Attempts to transfer this plasmid to E. coli HB101 were unsuccessful. The blaCTX-M gene was cloned into pBluescript II SK(–) and expressed in E. coli XL1-Blue cells. The MICs for both S. enterica serovar Senftenberg 9-4 and E. coli XL1-Blue transformants are shown in Table 1. Detection of CTX-M-3 in S. enterica serovar Senftenberg may have public health implications. Previously, the ESBL SHV-5 was detected in clinical isolates of this serovar causing an outbreak in burn wounds in a hospital in Delhi, India. Our results show that non-clinical isolates can constitute a reservoir for blaCTX-M alleles, and can facilitate the spread of cefotaximases to clinical isolates. In support of this hypothesis, the metallo-b-lactamase Sfh-I was recently detected in bacteria not of clinical origin. Therefore, researchers working on ESBLs especially in endemic areas should also direct their attention to non-clinical isolates found in these regions.