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We report a Serratia marcescens and an Escherichia coli isolate simultaneously detected in the same patient. Both isolates showed susceptibility patterns suggestive of harbouring a plasmid-mediated AmpC β-lactamase (pACBL) and a plasmid-encoded quinolone resistance (PMQR). PCR-based replicon, MOB typing, plasmid profile and Southern hybridization analyses revealed that both isolates coharboured blaDHA-1 and qnrB genes on the same IncL/M-MOBP13 plasmid approximately 70 kb in size. Together with the fact that both plasmids were conjugative in the laboratory, these results strongly suggest that a horizontal transfer event could take place in vivo. This is the first report of an isolate of S. marcescens harbouring a pACBL. The only phenotypic method that suggests the presence of a pACBL in an isolate harbouring an inducible chromosomal AmpC enzyme is the observation of scattered colonies near the edge of the inhibition zones of some β-lactams. The presence of both resistance genes on the same plasmid and the reported increase in PMQR could perhaps explain the widespread distribution of blaDHA-1 genes. [ABSTRACT FROM AUTHOR]

A total of 2440 Escherichia coli strains isolated in 2003 at the Hospital de la Santa Creu i Sant Pau were evaluated for the presence of extended-spectrum β-lactamases. Two different nucleotide sequences that encode the same β-lactamase, CTX-M-14, were detected when the blaCTX-M-14-genes of 35 E. coli isolates were analysed. Thirty-two of the 35 had the previously described sequence of the blaCTX-M-14 ( ), named blaCTX-M-14a, and the remaining three isolates showed a nucleotide sequence identical to that of the blaCTX-M-9 gene except for one nucleotide, named blaCTX-M-14b. Characterisation of the regions surrounding the blaCTX-M-14a showed the IS Ecp1 and the IS 903 upstream and downstream, respectively, of the bla gene, whereas the regions surrounding the blaCTX-M-14b contained the genetic environment described for the blaCTX-M-9 gene, the In 60. Characterisation by hybridisation showed that the blaCTX-M-14a was present in IncK plasmids, whereas the blaCTX-M-14b was found in the HI2 Inc group. The CTX-M-14 ESBL in E. coli isolates is the result of the convergence of two different genes. [ABSTRACT FROM AUTHOR]

Escherichia coli and Salmonella enterica isolates carrying the blaCTX-M-9 gene located on plasmids prevailed at the Hospital de la Santa Creu i Sant Pau, Barcelona, Spain in the 1996–1999 period. The blaCTX-M-9-carrying plasmids showed a great variability in size, suggesting the mobilization of the gene among different plasmid scaffolds. The aim of the present work was to identify and better characterize the plasmids involved in the spread of the blaCTX-M-9 gene. Results showed that the majority of these strains carried plasmids belonging to the IncHI2 incompatibility group. The IncHI2 plasmids were further characterized, and found to be related to the reference IncHI2 plasmid R478. [ABSTRACT FROM AUTHOR]

We report a Serratia marcescens and an Escherichia coli isolate simultaneously detected in the same patient. Both isolates showed susceptibility patterns suggestive of harbouring a plasmid-mediated AmpC beta-lactamase (pACBL) and a plasmid-encoded quinolone resistance (PMQR). PCR-based replicon, MOB typing, plasmid profile and Southern hybridization analyses revealed that both isolates coharboured bla(DHA-1) and qnrB genes on the same IncL/M-MOB(P13) plasmid approximately 70 kb in size. Together with the fact that both plasmids were conjugative in the laboratory, these results strongly suggest that a horizontal transfer event could take place in vivo. This is the first report of an isolate of S. marcescens harbouring a pACBL. The only phenotypic method that suggests the presence of a pACBL in an isolate harbouring an inducible chromosomal AmpC enzyme is the observation of scattered colonies near the edge of the inhibition zones of some beta-lactams. The presence of both resistance genes on the same plasmid and the reported increase in PMQR could perhaps explain the widespread distribution of bla(DHA-1) genes.

Escherichia coli and Salmonella enterica isolates carrying the bla(CTX-M-9) gene located on plasmids prevailed at the Hospital de la Santa Creu i Sant Pau, Barcelona, Spain in the 1996-1999 period. The bla(CTX-M-9)-carrying plasmids showed a great variability in size, suggesting the mobilization of the gene among different plasmid scaffolds. The aim of the present work was to identify and better characterize the plasmids involved in the spread of the bla(CTX-M-9) gene. Results showed that the majority of these strains carried plasmids belonging to the IncHI2 incompatibility group. The IncHI2 plasmids were further characterized, and found to be related to the reference IncHI2 plasmid R478.