Outer membrane protein change combined with co-existing TEM-1 and SHV-1 beta-lactamases lead to false identification of ESBL-producing Klebsiella pneumoniae

Abstract

Nine isolates of Klebsiella pneumoniae, obtained from one colonized and eight bacteraemic patients on a paediatric ward, were shown to be identical by PFGE, indicating an outbreak. Screening for extended-spectrum beta-lactamase (ESBL) production using the double-disc synergy test, Etest for ESBLs and agar diffusion tests indicated ESBL production. The isolates showed reduced susceptibility to cefotaxime but not to other third-generation cephalosporins. Molecular studies revealed production of TEM-1 and SHV-1 but no ESBLs were identified. Deficiency in expression of an outer membrane protein (OmpK35) was also observed. These observations led us to postulate that the extremely low level of OmpK35 expression and the co-existence of TEM-1 and SHV-1 resulted in an increased MIC of cefotaxime and the false designation of the isolates as ESBL producers. All the infected infants were treated with either third-generation cephalosporins alone or multiple antibiotics including a third-generation cephalosporin, and recovered and were discharged without sequelae.

Rapid molecular detection of extended-spectrum β-lactamase gene variants with a novel ligation-mediated real-time PCR

“…Wu et al (2001) found that decreased outermembrane permeability, due to loss of outer-membrane protein K35 (OmpK35), and the hydrolytic effect of TEM-1 can increase the MIC of cefotaxim slightly. The addition of clavulanic acid inhibits TEM-1 b-lactamase production and reduces the MIC, causing augmentation of the inhibition zone diameter, resulting in a false-positive ESBL test result (Beceiro et al, 2011;Robberts et al, 2009).…”

Antibacterial activity of the aqueous extract of <I>Thonningia sanguinea</i> against Extended-Spectrum-b-Lactamases (ESBL) producing <i>Escherichia coli</i> and <i>Klebsiella pneumoniae</i> strains

“…All discs were purchased from Biorad (France). The procedures and interpretation of the double-disc synergy test were described previously 12 .…”

“…Of the four clinical isolates of K. pneumoniae and E. coli, two were confirmed to be ESBL producing isolates by the double disc synergy test according to Wu et al 12 . Double-disc tests showed synergy for co-amoxiclav with cefotaxime, aztreonam and cefepime against both E. coli (no.…”

Higher CTX-M, Tem, and SHV Extended-Spectrum Beta-Lactamase Plasmid Gene Combination Frequency in Esbl Producing Klebsiella Pneumoniae Compared With Esbl Producing Escherichia Coli

“…plasmid Mini Kit I (Omega Bio-Tek, USA). The presence of plasmid extended-spectrum betalactamase genes was confirmed by polymerase chain reaction (PCR), using gene specific primers as described in the literature (Edelstein, Pimkin, Palagin, Edelstein, & Stratchounski, 2003;Wu et al, 2001). These PCR products were analyzed using 2% agarose gel.…”