Plasmid-Mediated Imipenem-Hydrolyzing Enzyme KPC-2 among Multiple Carbapenem-Resistant Escherichia coli Clones in Israel

Abstract

Carbapenem resistance in Escherichia coli is rare. We report four genetically unrelated carbapenem-resistant E. coli isolates cultured from four patients hospitalized in Tel Aviv Medical Center. PCR, sequencing, and Southern blot analysis identified KPC-2 as the imipenem-hydrolyzing enzyme in all four strains, carried on different plasmids with a possible common origin. This is the first discovery of KPC-2 in E. coli and the first report of this enzyme originating outside the United States.Carbapenem resistance in Escherichia coli does not occur naturally, and acquired resistance is rare in this species (15). Few cases of carbapenem-resistant E. coli strains have been reported. The first reported case in 1999 described the occurrence of outer-membrane protein deficiency coupled with the plasmid-mediated class C ␤-lactamase CMY (17). Carbapenemhydrolyzing, plasmid-mediated metallo-␤-lactamases in clinical E. coli strains from various parts of the world have been reported (6,11,16,19), but class A carbapenemases in E. coli have been described in only one case, involving KPC-3 acquisition in a patient in the United States during imipenem therapy (7).A high prevalence of extended-spectrum-␤-lactamase-producing E. coli clinical isolates has been observed and studied in our institution (5), but carbapenem resistance in this species has never been observed. In February 2005, an imipenemresistant E. coli strain (MIC, 32 g/ml) was isolated from a urine culture from a 75-year-old woman with multiple chronic illnesses hospitalized at Tel Aviv Medical Center due to syncope. During September and October 2005, three additional carbapenem-resistant E. coli isolates were isolated at our hospital. We examined the epidemiological and genetic relatedness and the clinical scenario as well as the enzymatic mechanism leading to this resistance. MATERIALS AND METHODSSetting, bacterial strains, and antibiotic susceptibility testing. Tel Aviv Medical Center is a 1,200-bed tertiary care teaching hospital, with 70,000 admissions annually. Four clinical isolates of Escherichia coli were isolated from four patients hospitalized during 2005 in our institution. The patients' relevant clinical data were collected from their medical records. Antibiotic susceptibilities were determined by Vitek-2 (BioMerieux Inc., Marcy, France). MICs of all carbapenems (imipenem, meropenem, and ertapenem) were determined by Etest (AB Biodisk, Solna, Sweden).PFGE. The genetic relatedness of the four E. coli isolates was analyzed by pulsed-field gel electrophoresis (PFGE). Bacterial DNA was prepared and cleaved with 20U SpeI endonuclease (New England Biolabs, Boston, MA) as previously described (5), and DNA macrorestriction patterns were visually compared and interpreted according to the criteria established by Tenover et al. (18).Carbapenemase analysis and IEF of ␤-lactamases. Visualization of imipenem-hydrolyzing ␤-lactamase activity by the E. coli clinical isolates was performed by an imipenem inactivation bioassay (21) performed on Mueller-Hinton agar plates ...

bla KPC RNA Expression Correlates with Two Transcriptional Start Sites but Not Always with Gene Copy Number in Four Genera of Gram-Negative Pathogens

“…Little is known about the role gene expression plays in KPC-mediated resistance or how the level of expression may affect susceptibility testing. Hydrolysis of carbapenems by KPCs has been demonstrated in vitro (1,21,22); however, multiple studies have reported variability in susceptibility testing of KPC-producing clinical isolates (2,3,13,22). Although variation in KPC enzyme production could contribute to the variability seen during susceptibility testing, it is difficult to assess the influence of the KPC ␤-lactamase on susceptibility testing using clinical isolates which may harbor multiple ␤-lactamases and may have alterations in outer membrane proteins (4,7,9,10,21,24).…”

Validation of a High-Throughput Screening Assay for Identification of Adjunctive and Directly Acting Antimicrobials Targeting Carbapenem-Resistant Enterobacteriaceae

“…13 Furthermore, transfer of carbapenemase-containing plasmids into E. coli K-12 is associated with a substantially lower MIC in the recipient. 14 These observations suggest that attributes of the host strain contribute substantially to the phenotypic expression of carbapenem resistance. We therefore hypothesized that CRE strains could be modulated using small molecules to lower the carbapenem MIC into the susceptible range and thereby restore carbapenem therapeutic efficacy.…”

Avaliação fenotípica da enzima Klebsiella pneumoniae carbapenemase (KPC) em Enterobacteriaceae de ambiente hospitalar

“…Outro aspecto importante reportado no trabalho foi que vários isolados se apresentaram sensíveis ao imipenem (5) . (11) .…”