Detection of the Klebsiella pneumoniae carbapenemase type 2 Carbapenem-hydrolyzing enzyme in clinical isolates of Citrobacter freundii and K. oxytoca carrying a common plasmid.

The Klebsiella pneumoniae carbapenemase (KPC) was detected in carbapenem-resistant isolates of Citrobacter freundii and Klebsiella oxytoca recovered from different patients in a Michigan hospital. Restriction analysis and hybridization with a KPC-specific probe showed the bla(KPC-2) genes of these two genera of the family Enterobacteriaceae are carried on a common plasmid.

Carbapenem resistance in Klebsiella pneumoniae not detected by automated susceptibility testing.

Detecting beta-lactamase-mediated carbapenem resistance among Klebsiella pneumoniae isolates and other Enterobacteriaceae is an emerging problem. In this study, 15 blaKPC-positive Klebsiella pneumoniae that showed discrepant results for imipenem and meropenem from 4 New York City hospitals were characterized by isoelectric focusing; broth microdilution (BMD); disk diffusion (DD); and MicroScan, Phoenix, Sensititre, VITEK, and VITEK 2 automated systems. All 15 isolates were either intermediate or resistant to imipenem and meropenem by BMD; 1 was susceptible to imipenem by DD.

Experimental prediction of the evolution of ceftazidime resistance in the CTX-M-2 extended-spectrum beta-lactamase.

We applied in vitro evolution to an Escherichia coli strain containing bla(CTX-M-2) and obtained 10 independent mutant bla(CTX-M-2) alleles that confer elevated resistance to ceftazidime (MIC > or = 32 microg/ml) but lost the ability to confer resistance to cefepime. All alleles had a Pro-to-Ser substitution at position 167.

Utility of NCCLS guidelines for identifying extended-spectrum beta-lactamases in non-Escherichia coli and Non-Klebsiella spp. of Enterobacteriaceae.

NCCLS screening and confirmation methods for detecting extended-spectrum beta-lactamases (ESBLs) apply only to Escherichia coli and Klebsiella spp., yet ESBLs have been found in other members of the family Enterobacteriaceae. We evaluated the effectiveness of NCCLS methods for detecting ESBLs in 690 gram-negative isolates of Enterobacteriaceae that excluded E.

Carbapenem-resistant strain of Klebsiella oxytoca harboring carbapenem-hydrolyzing beta-lactamase KPC-2.

We investigated a Klebsiella oxytoca isolate demonstrating resistance to imipenem, meropenem, extended-spectrum cephalosporins, and aztreonam. The MICs of both imipenem and meropenem were 32 microg/ml. The beta-lactamase activity against imipenem and meropenem was inhibited in the presence of clavulanic acid.

Evaluation of the NCCLS extended-spectrum beta-lactamase confirmation methods for Escherichia coli with isolates collected during Project ICARE.

To determine whether confirmatory tests for extended-spectrum beta-lactamase (ESBL) production in Escherichia coli are necessary, we selected 131 E. coli isolates that met the National Committee for Clinical Laboratory Standards (NCCLS) screening criteria for potential ESBL production from the Project ICARE (Intensive Care Antimicrobial Resistance Epidemiology) strain collection. For all 131 isolates, the broth microdilution (BMD) MIC of at least one extended-spectrum cephalosporin was >/=2 micro g/ml.

Carbapenem resistance in a clinical isolate of Enterobacter aerogenes is associated with decreased expression of OmpF and OmpC porin analogs.

We investigated the mechanism of imipenem resistance in Enterobacter aerogenes strain 810, a clinical isolate from the United States for which the imipenem MIC was 16 micro g/ml and the meropenem MIC was 8 micro g/ml. An imipenem-susceptible revertant, strain 810-REV, was obtained after multiple passages of the strain on nonselective media. For the revertant, the imipenem MIC was View Article and Find Full Text PDF

TEM-71, a novel plasmid-encoded, extended-spectrum beta-lactamase produced by a clinical isolate of Klebsiella pneumoniae.

TEM-71, a novel extended-spectrum beta-lactamase from a Klebsiella pneumoniae clinical isolate, had an isoelectric point of 6.0 and a substrate profile showing preferential hydrolysis of cefotaxime over ceftazidime. It differed from TEM-1 by two substitutions, Gly238Ser and Glu240Lys, and was under the control of the strong P4 promoter.