Functional characterization of IS1999, an IS4 family element involved in mobilization and expression of beta-lactam resistance genes.

IS1999 and a point mutant derivative, IS1999.2, have been described inserted upstream of emerging antibiotic resistance genes bla(VEB-1) and bla(OXA-48). 5' Rapid amplification of cDNA ends experiments revealed that expression of these beta-lactamase genes was driven by the outward-directed promoter, P(out), located in the IS1999 elements.

Characterization of the naturally occurring oxacillinase of Acinetobacter baumannii.

A chromosomally encoded oxacillinase, OXA-69, was characterized from Acinetobacter baumannii AYE. beta-Lactamase OXA-69 shared 97% amino acid identity with the recently described OXA-51 enzyme of A. baumannii and 62 and 56% amino acid identity with the carbapenem-hydrolyzing oxacillinases OXA-24 and OXA-23, respectively.

Regional occurrence of plasmid-mediated carbapenem-hydrolyzing oxacillinase OXA-58 in Acinetobacter spp. in Europe.

The spread of the plasmid-mediated carbapenem-hydrolyzing oxacillinase OXA-58 was detected in Acinetobacter sp. clinical isolates from southern Europe, the Balkans, and central Turkey. It may contribute significantly to the emergence of carbapenem resistance in Acinetobacter spp.

Contribution of acquired carbapenem-hydrolyzing oxacillinases to carbapenem resistance in Acinetobacter baumannii.

Carbapenem-hydrolyzing oxacillinases are reported increasingly in Acinetobacter baumannii. Since they hydrolyze carbapenems at low levels, the roles of carbapenem-hydrolyzing oxacillinases OXA-23, OXA-40, and OXA-58 in A. baumannii were determined.

Genetic and biochemical characterization of the chromosome-encoded class B beta-lactamases from Shewanella livingstonensis (SLB-1) and Shewanella frigidimarina (SFB-1).

Objectives: To determine the beta-lactamase gene content of beta-lactam-susceptible psychrophilic gram-negative bacilli, Shewanella frigidimarina and Shewanella livingstonensis, isolated from a marine environment.

Methods: Beta-lactamase genes were cloned, sequenced and expressed in Escherichia coli. Kinetic parameters were determined using purified enzymes.

OXA-58, a novel class D {beta}-lactamase involved in resistance to carbapenems in Acinetobacter baumannii.

A carbapenem-resistant Acinetobacter baumannii strain was isolated in Toulouse, France, in 2003. Cloning and expression in Escherichia coli identified the carbapenem-hydrolyzing beta-lactamase OXA-58, which is weakly related (less than 50% amino acid identity) to other oxacillinases. It hydrolyzed penicillins, oxacillin, and imipenem but not expanded-spectrum cephalosporins.

A nosocomial outbreak of Acinetobacter baumannii isolates expressing the carbapenem-hydrolysing oxacillinase OXA-58.

Objective: The aim of this study was to analyse the spread of the bla(OXA-58) gene as a source of carbapenem resistance in Acinetobacter baumannii in the burns unit of a university hospital in Toulouse in 2003-2004.

Methods: Six carbapenem-resistant A. baumannii isolates from six patients, and a carbapenem-resistant environmental A.

In vivo acquisition of high-level resistance to imipenem in Escherichia coli.

Four clonally related Escherichia coli strains were isolated successively from bile duct of a girl suffering from sclerosing cholangitis. One of them, selected after an imipenem-containing regimen, was resistant to carbapenems and to broad-spectrum cephalosporins due to a plasmid-mediated cephalosporinase, CMY-2, and the lack of outer membrane proteins OmpF and OmpC.

Genetic and biochemical characterization of a chromosome-encoded carbapenem-hydrolyzing ambler class D beta-lactamase from Shewanella algae.

A chromosome-encoded beta-lactamase gene from Shewanella algae clinical isolate KB-1 was cloned and expressed in Escherichia coli. It encoded the Ambler class D enzyme OXA-55, sharing less than 55% identity with any other oxacillinases. Although conferring a narrow-spectrum beta-lactam resistance phenotype, OXA-55 had carbapenem-hydrolyzing activity that mirrored the reduced susceptibility to imipenem observed in S.

Chromosome-encoded ambler class D beta-lactamase of Shewanella oneidensis as a progenitor of carbapenem-hydrolyzing oxacillinase.

A chromosome-encoded beta-lactamase gene from a Shewanella oneidensis reference strain was cloned and expressed in Escherichia coli. It encoded a carbapenem-hydrolyzing Ambler class D beta-lactamase, OXA-54, that shared 92% amino acid identity with the plasmid-encoded carbapenem-hydrolyzing oxacillinase OXA-48 from Klebsiella pneumoniae. This work suggests that Shewanella spp.

Emergence of oxacillinase-mediated resistance to imipenem in Klebsiella pneumoniae.

Klebsiella pneumoniae strain 11978 was isolated in Turkey in 2001 and was found to be resistant to all beta-lactams, including carbapenems. Cloning and expression in Escherichia coli identified five beta-lactamases, including two novel oxacillinases. The beta-lactamase OXA-48 hydrolyzed imipenem at a high level and was remotely related (less than 46% amino acid identity) to the other oxacillinases.

Emergence in Klebsiella pneumoniae of a chromosome-encoded SHV beta-lactamase that compromises the efficacy of imipenem.

A Klebsiella pneumoniae isolate was identified that had reduced susceptibility to several expanded-spectrum cephalosporins and imipenem. That isolate produced a chromosome-encoded SHV-type beta-lactamase, SHV-38, that had an alanine to valine substitution in position Ambler 146 compared to beta-lactamase SHV-1. The kinetic parameters for purified beta-lactamases SHV-38 and SHV-1 showed that the hydrolytic spectrum of SHV-38 included only ceftazidime and imipenem.

Genetic and functional analysis of the chromosome-encoded carbapenem-hydrolyzing oxacillinase OXA-40 of Acinetobacter baumannii.

Clinical isolate Acinetobacter baumannii CLA-1 was resistant to a series of antibiotic molecules, including carbapenems. Cloning and expression of the beta-lactamase gene content of this isolate in Escherichia coli DH10B identified a chromosome-encoded oxacillinase, OXA-40, that differed by one or two amino acid changes from OXA-24, -25, and -26 and an AmpC-type cephalosporinase. The OXA-40 beta-lactamase had a mainly narrow-spectrum hydrolytic profile, but it included ceftazidime and imipenem.