Since around 2000 - earlier in Poland and Spain and later in France and the UK - dramatic shifts have occurred in the prevalence and types of extended-spectrum beta-lactamases (ESBLs) in Europe. Before this watershed, most producers were nosocomial isolates, often Klebsiella spp. or Enterobacter spp. from specialist care units, and had mutant TEM or SHV ESBLs. Subsequently, CTX-M ESBLs have become dominant, with much greater penetration into Escherichia coli, and with many infections in 'complicated community' patients, usually with underlying disease, recent antibiotic usage, or healthcare contact. The degree of clonality among producers varies with the country, as does the enzyme type produced, with group 9 (CTX-M-9 and -14) enzymes dominant in Spain and group 1 enzymes (particularly CTX-M-3 and -15) dominant elsewhere. Irrespective of the particular enzyme, most producers are multiresistant. These changing patterns present major therapeutic and infection control challenges, with the public health intervention points unclear.

This work further confirmed the predominant role of ISEcp1 in the mobilization of bla(CTX-M) genes of the CTX-M-1 cluster and the presence of In35, of an integron similar to In60 and a novel complex Class 1 integron.

We have developed a PCR-based assay that easily identifies a clone with high likelihood of producing ESBLs, including CTX-M-15.

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Kluyvera ascorbata produces a ␤-lactamase that results in an atypical susceptibility pattern, including lowlevel 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 ␤-lactamases. Finally, mobilization of bla KLUA on a plasmid was found to be mediated probably by a genetic mobile element like ISEcp1.

The CTX-M-15-producing E. coli diffusing clone is associated with a high level of antibiotic resistance and with high virulence, showing that, under certain selective pressures, the previously observed trade-off between resistance and virulence may not apply.

Pantoea agglomerans and other Pantoea species cause infections in humans and are also pathogenic to plants, but the diversity of Pantoea strains and their possible association with hosts and disease remain poorly known, and identification of Pantoea species is difficult. We characterized 36 Pantoea strains, including 28 strains of diverse origins initially identified as P. agglomerans, by multilocus gene sequencing based on six protein-coding genes, by biochemical tests, and by antimicrobial susceptibility testing. Phylogenetic analysis and comparison with other species of Enterobacteriaceae revealed that the genus Pantoea is highly diverse. Most strains initially identified as P. agglomerans by use of API 20E strips belonged to a compact sequence cluster together with the type strain, but other strains belonged to diverse phylogenetic branches corresponding to other species of Pantoea or Enterobacteriaceae and to probable novel species. Biochemical characteristics such as fosfomycin resistance and utilization of D-tartrate could differentiate P. agglomerans from other Pantoea species. All 20 strains of P. agglomerans could be distinguished by multilocus sequence typing, revealing the very high discrimination power of this method for strain typing and population structure in this species, which is subdivided into two phylogenetic groups. PCR detection of the repA gene, associated with pathogenicity in plants, was positive in all clinical strains of P. agglomerans, suggesting that clinical and plant-associated strains do not form distinct populations. We provide a multilocus gene sequencing method that is a powerful tool for Pantoea species delineation and identification and for strain tracking.The genus Pantoea includes several species that are generally associated with plants, either as epiphytes or as pathogens, and some species can cause disease in humans. Pantoea agglomerans, the Pantoea species most commonly isolated from humans, is widely distributed in nature and has been isolated from numerous ecological niches, including plants, water, soil, humans, and animals. It is frequently associated with plants as an epiphyte or an endophyte, and some isolates have been reported to be tumorogenic pathogens (20, 51). As an opportunistic human pathogen, P. agglomerans can occur sporadically or in outbreaks. At the beginning of the 1970s, P. agglomerans (then called Enterobacter agglomerans) was implicated in a large U.S. and Canadian outbreak of septicemia caused by contaminated closures on bottles of infusion fluids; 25 hospitals were involved, with 378 cases (34). Since then, P. agglomerans bacteremia has also been described in association with the contamination of intravenous fluid, parenteral nutrition, the anesthetic agent propofol, blood products, and transference tubes used for intravenous hydration (2-4, 22, 36). P. agglomerans has been recovered from joint fluids of patients with arthritis, synovitis, or osteomyelitis (7). Infection often occurs after injuries with plant thorns, wood slivers, or wooden spl...

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