A novel discrete mobile DNA element from Tn2l from the plasmid R100.1 is described, and its mobilization function was confirmed experimentally. In addition, the element behaves as a recombinase-active locus (tnpl) which facilitates insertions of antibiotic resistance genes as modules or cassettes at defined hot spots or integration sites. A similar tnpl sequence was detected by DNA hybridization in a series of P-lactamase transposons and plasmids and localized on their physical maps. The genetic function of the locus cloned from Tn2l into pACYC184 was tested for conduction and integration into the plasmids R388 and pOX38Km, and the results suggested recombinase-integrase activity and recA independence. DNA sequence analysis of the tnpl locus revealed no inverted or direct terminal repeats or transposition features of class I and class II transposons. The coding capacity revealed three putative open reading frames encoding 131, 134, and 337 amino acids. Orf3 encoded a putative polypeptide product of 337 amino acids that shared highly significant identity with the carboxyl region of integrase proteins. A comparison and an alignment of the tnpl locus from Tn2l and its flanking sequences identified similar sequences in plasmids and in transposons. The alignment revealed discrete nucleotide changes in these tnpl-like loci and a conserved 3' and 5' GTTA/G hot spot as a duplicated target site. Our data confirm the remarkable ubiquity of tnpl associated with antibiotic resistance genes. We present a model of transposon modular evolution into more complex multiresistant units via tnpl and site-specific insertions, deletions, and DNA rearrangements at this locus.Plasmid-mediated P-lactamases in gram-negative bacteria constitute a family of related but biochemically distinct enzymes, now numbering more than 40, that determine resistance to penicillins, cephalosporins, and other 1-lactam

A series of intragenic DNA probes, encoding the major part of the transposase resolvase and inverted repeats of transposons Tn3, Tn2l, and Tn25O1, were used in hybridization assays for homologous DNA sequences in 18 transposons studied. The tnpA and tnpR probes detected extensive homology with Tn3-like and Tn21-like elements for 11 transposons. This high degree of homology was confirmed with the 38-and 48-base-pair inverted-repeat oligonucleotide probes of Tn3, Tn2l, and Tn2S01. The Southern-type gel hybridization experiments localized the tnpA-homologous sequences on the physical DNA maps constructed. The genetic and physical maps of the transposons were compared, as were their nucleic acid sequence homologies. These comparisons suggested a subfamily of mobile elements distinct from but related to the Tn2l group. Based on these results, an evolutionary model is proposed and a pedigree is presented for the genesis of multiresistance ,-lactamase transposons.More than 30 biochemically distinct P-lactamases are known to be plasmid encoded in gram-negative bacteria (21,24,25,28).

We performed a molecular and epidemiologic study of a healthcare-associated rhinovirus outbreak to better understand transmission in neonatal intensive care settings. Sequencing of the 7 outbreak strains revealed 4 distinct clades, indicating multiple sources. A single clade infected 3 patients in adjacent rooms, suggesting horizontal transmission. We observed 1 rhinovirus-associated death.