Dataset Information

International spread and persistence of TEM-24 is caused by the confluence of highly penetrating enterobacteriaceae clones and an IncA/C2 plasmid containing Tn1696::Tn1 and IS5075-Tn21.

ABSTRACT: TEM-24 remains one of the most widespread TEM-type extended-spectrum beta-lactamases (ESBLs) among Enterobacteriaceae. To analyze the reasons influencing its spread and persistence, a multilevel population genetics study was carried out on 28 representative TEM-24 producers from Belgium, France, Portugal, and Spain (13 Enterobacter aerogenes isolates, 6 Escherichia coli isolates, 6 Klebsiella pneumoniae isolates, 2 Proteus mirabilis isolates, and 1 Klebsiella oxytoca isolate, from 1998 to 2004). Clonal relatedness (XbaI pulsed-field gel electrophoresis [PFGE] and E. coli phylogroups) and antibiotic susceptibility were determined by standard procedures. Plasmid analysis included determination of the incompatibility group (by PCR, hybridization, and/or sequencing) and comparison of restriction fragment length polymorphism (RFLP) patterns. Characterization of genetic elements conferring antibiotic resistance included integrons (classes 1, 2, and 3) and transposons (Tn3, Tn21, and Tn402). Similar PFGE patterns were identified among E. aerogenes, K. pneumoniae, and P. mirabilis isolates, while E. coli strains were diverse (phylogenetic groups A, B2, and D). Highly related 180-kb IncA/C2 plasmids conferring resistance to kanamycin, tobramycin, chloramphenicol, trimethoprim, and sulfonamides were identified. Each plasmid contained defective In0-Tn402 (dfrA1-aadA1, aacA4, or aacA4-aacC1-orfE-aadA2-cmlA1) and In4-Tn402 (aacA4 or dfrA1-aadA1) variants. These integrons were located within Tn21, Tn1696, or hybrids of these transposons, with IS5075 interrupting their IRtnp and IRmer. In all cases, blaTEM-24 was part of an IS5075-DeltaTn1 transposon within tnp1696, mimicking other genetic elements containing blaTEM-2 and blaTEM-3 variants. The international dissemination of TEM-24 is fuelled by an IncA/C2 plasmid acquired by different enterobacterial clones which seem to evolve by gaining diverse genetic elements. This work highlights the risks of a confluence between highly penetrating clones and highly promiscuous plasmids in the spread of antibiotic resistance, and it contributes to the elucidation of the origin and evolution of TEM-2 ESBL derivatives.

SUBMITTER: Novais A

PROVIDER: S-EPMC2812134 | biostudies-literature | 2010 Feb

REPOSITORIES: biostudies-literature

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International spread and persistence of TEM-24 is caused by the confluence of highly penetrating enterobacteriaceae clones and an IncA/C2 plasmid containing Tn1696::Tn1 and IS5075-Tn21.

Novais Angela A Baquero Fernando F Machado Elisabete E Cantón Rafael R Peixe Luísa L Coque Teresa M TM

Antimicrobial agents and chemotherapy 20091207 2

TEM-24 remains one of the most widespread TEM-type extended-spectrum beta-lactamases (ESBLs) among Enterobacteriaceae. To analyze the reasons influencing its spread and persistence, a multilevel population genetics study was carried out on 28 representative TEM-24 producers from Belgium, France, Portugal, and Spain (13 Enterobacter aerogenes isolates, 6 Escherichia coli isolates, 6 Klebsiella pneumoniae isolates, 2 Proteus mirabilis isolates, and 1 Klebsiella oxytoca isolate, from 1998 to 2004). ...[more]

PMID: 19995930

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Project description:The transposon Tn21 and a group of closely related transposons (the Tn21 family) are involved in the global dissemination of antibiotic resistance determinants in gram-negative facultative bacteria. The molecular basis for their involvement is carriage by the Tn21 family of a mobile DNA element (the integron) encoding a site-specific system for the acquisition of multiple antibiotic resistance genes. The paradigm example, Tn21, also carries genes for its own transposition and a mercury resistance (mer) operon. We have compiled the entire 19,671-bp sequence of Tn21 and assessed the possible origins and functions of the genes it contains. Our assessment adds molecular detail to previous models of the evolution of Tn21 and is consistent with the insertion of the integron In2 into an ancestral Tn501-like mer transposon. Codon usage analysis indicates distinct host origins for the ancestral mer operon, the integron, and the gene cassette and two insertion sequences which lie within the integron. The sole gene of unknown function in the integron, orf5, resembles a puromycin-modifying enzyme from an antibiotic producing bacterium. A possible seventh gene in the mer operon (merE), perhaps with a role in Hg(II) transport, lies in the junction between the integron and the mer operon. Analysis of the region interrupted by insertion of the integron suggests that the putative transposition regulator, tnpM, is the C-terminal vestige of a tyrosine kinase sensor present in the ancestral mer transposon. The extensive dissemination of the Tn21 family may have resulted from the fortuitous association of a genetic element for accumulating multiple antibiotic resistances (the integron) with one conferring resistance to a toxic metal at a time when clinical, agricultural, and industrial practices were rapidly increasing the exposure to both types of selective agents. The compendium offered here will provide a reference point for ongoing observations of related elements in multiply resistant strains emerging worldwide.

Dataset Information

International spread and persistence of TEM-24 is caused by the confluence of highly penetrating enterobacteriaceae clones and an IncA/C2 plasmid containing Tn1696::Tn1 and IS5075-Tn21.

Publications

International spread and persistence of TEM-24 is caused by the confluence of highly penetrating enterobacteriaceae clones and an IncA/C2 plasmid containing Tn1696::Tn1 and IS5075-Tn21.

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