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Analysis of 15 European clinical Enterobacteriaceae isolates showed that differences in the genetic context of blaCMY-2-like genes reflected the replicon type, usually IncA/C or IncI1. These blaCMY-2 loci may originate from the same ISEcp1-mediated mobilization from the Citrobacter freundii chromosome as structures described in earlier studies.

We studied the genetic organization of bla(ACC-1) in 14 isolates of Enterobacteriaceae from France, Tunisia, and Germany. In a common ancestor, ISEcp1 was likely involved in the mobilization of this gene from the Hafnia alvei chromosome to a plasmid. Other genetic events involving insertion sequences (particularly IS26), transposons (particularly Tn1696), or sulI-type integrons have occurred, leading to complex genetic environments.

Klebsiella pneumoniae clinical isolates resistant to carbapenems were recovered from 11 patients in the hospital of Sfax, Tunisia. The isolates were closely related as shown by pulsed-field gel electrophoresis, and they produced VIM-4 metallo-enzyme, CTX-M-15 extended-spectrum beta-lactamase, and CMY-4 AmpC enzyme. The bla(VIM-4) gene is part of a class 1 integron.

One hundred twenty CTX-M-15-producing Escherichia coli strains isolated in 10 different hospitals from Paris (France), in the Hospital Charles Nicolle in Tunis (Tunisia), and in the Pasteur Institute in Bangui, Central African Republic (CAR), between 2000 and 2004 were studied. Eighty isolates, recovered from the three countries, were clonally related by repetitive extragenic palindromic PCR and pulsed-field gel electrophoresis. Various resistance profiles were identified among these clonal strains. After conjugation or electroporation of plasmids from E. coli strains representative of each profile and each geographic region, we observed seven resistance profiles in the recipient strains. Incompatibility typing showed that all the plasmids transferred from the clonal strains studied, except one, belonged to the incompatibility group FII. They all shared a multidrug resistance region (MDR) resembling the MDR region located in pC15-1a, a plasmid associated with an outbreak of a CTX-M-15-producing E. coli strain in Canada. They also shared the common backbone of an apparent mosaic plasmid, including several features present in pC15-1a and in pRSB107, a plasmid isolated from a sewage treatment plant. This study suggests that although the plasmid-borne blaCTX-M-15 gene could be transferred horizontally, its dissemination between France, Tunisia, and CAR was due primarily to its residence in an E. coli clone with a strong propensity for dissemination.

Eleven Klebsiella pneumoniae clinical isolates and one Klebsiella oxytoca clinical isolate showing various pulsed-field gel electrophoresis types and producing an inducible DHA-1 class C beta-lactamase were isolated in the Parisian region between 1998 and 2003. The aim of this study was to compare the genetic organization of the bla(DHA-1) genes in this collection of clinical isolates. In four isolates, the Morganella morganii-derived genomic region containing bla(DHA-1) was inserted in an entire complex sul1-type integron, including a region common to In6-In7 (CR1), as previously described in a bla(DHA-1)-producing Salmonella enterica serovar Enteritidis KF92 isolate from Saudi Arabia in 1992. Different gene cassette arrays were characterized in each of these integrons. In two of them, an additional 10-kb fragment was inserted between the CR1 and the M. morganii-derived region and was similar to the sap (ABC transporter family) and psp (phage shock protein) operons originated from Salmonella enterica serovar Typhimurium. The length of the M. morganii region was variable, suggesting that several independent recombination events have occurred and that open reading frame orf513 encodes a recombinase involved in the mobilization of the resistance genes. The genetic organization of bla(DHA-1) was identical in the eight other isolates. This structure is likely derived from a complex integron following the insertion of IS26, leading to the deletion of the first part of integron. The horizontal transfer of one plasmid carrying that truncated integron was shown for seven of these isolates.

We describe in vivo selection of a Klebsiella pneumoniae strain with diminished imipenem susceptibility attributable to plasmid-encoded ACC-1 beta-lactamase production and loss of a 36-kDa major outer membrane protein, together with transfer of this plasmid from K. pneumoniae to Escherichia coli in a Tunisian infant.

We analyzed 19 clinical isolates of the family Enterobacteriaceae (16 Escherichia coli isolates and 3 Klebsiella pneumoniae isolates) collected from four different hospitals in Paris, France, from 2000 to 2002. These strains had a particular extended-spectrum cephalosporin resistance profile characterized by a higher level of resistance to cefotaxime and aztreonam than to ceftazidime. The bla(CTX-M) genes encoding these beta-lactamases were involved in this resistance, with a predominance of bla(CTX-M-15). Ten of the 19 isolates produced both TEM-1- and CTX-M-type enzymes. One strain (E. coli TN13) expressed CMY-2, TEM-1, and CTX-M-14. bla(CTX-M) genes were found on large plasmids. In 15 cases the same insertion sequence, ISEcp1, was located upstream of the 5' end of the bla(CTX-M) gene. In one case we identified an insertion sequence designated IS26. Examination of the other three bla(CTX-M) genes by cloning, sequencing, and PCR analysis revealed the presence of a complex sul1-type integron that includes open reading frame ORF513, which carries the bla gene and the surrounding DNA. Five isolates had the same plasmid DNA fingerprint, suggesting clonal dissemination of CTX-M-15-producing strains in the Paris area.

Escherichia hermannii showed a low level of resistance to amoxicillin and ticarcillin, reversed by clavulanate, and a moderate susceptibility to piperacillin but was susceptible to all cephalosporins. A bla gene was cloned and encoded a typical class A beta-lactamase (HER-1, pI 7.5), which shares 45, 44, 41, and 40% amino acid identity with other beta-lactamases, AER-1 from Aeromonas hydrophila, MAL-1/Cko-1 from Citrobacter koseri, and TEM-1 and LEN-1, respectively. No ampR gene was detected. Only penicillins were efficiently hydrolyzed, and no hydrolysis was observed for cefuroxime and broad-spectrum cephalosporins. Sequencing of the bla gene in 12 other strains showed 98 to 100% identity with bla(HER-1).

Kluyvera ascorbata produces a beta-lactamase that results in an atypical susceptibility pattern, including low-level resistance to penicillins, cephalothin, and cefuroxime, but this resistance is reversed by clavulanate. Ten nucleotide sequences of the corresponding gene, bla(KLUA), were obtained and were found to have minor variations (96 to 100%). Otherwise, bla(KLUA) was found to be similar (95 to 100%) to some plasmid-encoded CTX-M-type beta-lactamases. Finally, mobilization of bla(KLUA) on a plasmid was found to be mediated probably by a genetic mobile element like ISEcp1.