Impact of changes in CLSI and EUCAST breakpoints for susceptibility in bloodstream infections due to extended-spectrum β-lactamase-producing Escherichia coli.

The impact of recent changes in and discrepancies between the breakpoints for cephalosporins and other antimicrobials, as determined by CLSI and European Committee on Antimicrobial Susceptibility Testing (EUCAST), was analysed in patients with bloodstream infections caused by extended-spectrum β-lactamase (ESBL) producing Escherichia coli in Spain, was analysed. We studied a cohort of 191 episodes of bloodstream infection caused by ESBL-producing E. coli in 13 Spanish hospitals; the susceptibility of isolates to different antimicrobials was investigated by microdilution and interpreted according to recommendations established in 2009 and 2010 by CLSI, and in 2011 by EUCAST. Overall, 58.6% and 14.7% of isolates were susceptible to ceftazidime, and 35.1% and 14.7% to cefepime using the CLSI-2010 and EUCAST-2009/2011 recommendations, respectively (all isolates would have been considered resistant using the previous guidelines). Discrepancies between the CLSI-2010 and the EUCAST-2011 recommendations were statistically significant for other antimicrobials only in the case of amikacin (98.4% versus 75.9% of susceptible isolates; p <0.01). The results varied depending on the ESBL produced. No significant differences were found in the percentage of patients classified as receiving appropriate therapy, following the different recommendations. Four out of 11 patients treated with active cephalosporins according to CLSI-2010 guidelines died (all had severe sepsis or shock); these cases would have been considered resistant according to EUCAST-2011. In conclusion, by using current breakpoints, extended-spectrum cephalosporins would be regarded as active agents for treating a significant proportion of patients with bloodstream infections caused by ESBL-producing E. coli.

Rodríguez-Baño J ，Picón E ，Navarro MD ，López-Cerero L ，Pascual A ，ESBL-REIPI Group ... -  《-》

Laboratory identification, risk factors, and clinical outcomes of patients with bacteremia due to Escherichia coli and Klebsiella pneumoniae producing extended-spectrum and AmpC type β-lactamases.

Extended-spectrum β-lactamase (ESBL)-producing bacteria coexpressing AmpC type β-lactamase (ACBL) are associated with the laboratory issue of false susceptibility to third-generation cephalosporins. This study was to evaluate laboratory tests and clinical significance of bacteremic isolates of Escherichia coli and Klebsiella pneumoniae with both ESBL and ACBL [dual-type lactamases (DTL)]. From 2006 to 2009, 78 E coli and 12 pneumoniae bacteremic isolates with reduced susceptibility to cefotaxime (CTX) or ceftazidime (CAZ) were identified and relevant patients' data were collected for analysis. Phenotypic and genotypic characterizations of these selected isolates were determined by inhibitor-based assays and polymerase chain reaction-based genetic analyses, respectively. Among the 90 isolates, 47 had DTL production. There was an increasing annual prevalence from 29% in 2006 to 56% in 2009 (p=0.02). Phenotypic assays had a sensitivity and specificity of 57% (43/76) and 93% (13/14) for ESBL detection and 95% (58/61) and 34% (10/29) for ACBL, respectively. Among the DTL-producing isolates, phenotypic assays yielded a higher false negative rate of ESBL detection than that of ACBL detection (70% versus 6%), while all false negative ESBL results were associated with ESBL genes other than bla(CTx-M). The majority of the DTL-producing isolates were in the category of resistance to CTX (47/47, 100%) and CAZ (44/47, 94%) by the Clinical and Laboratory Standards Institute (CLSI) 2010 interpretive criteria, of which many were considered intermediate or fully susceptible to CTX (25/47, 53%) and CAZ (15/47, 32%) by the previous ones (CLSI-2009). The DTL-producing isolates exhibited a lower susceptibility rate to fluoroquinolones, aztreonam, and β-lactam/lactamase inhibitors than those with either ESBL or ACBL alone. The use of indwelling catheters or nasogastric tubes was associated with bacteremia due to the DTL isolates, but the mortality rates were not different among those due to isolates with ESBL, ACBL, or both. By multivariate analysis, Pittsburg bacteremia score and Charlson comorbidity index were the significant predictors for all-cause mortalities. Bacteremic episodes due to DTL-producing E coli and K pneumoniae became increasingly prevalent and were often associated with coresistance to antibiotics other than β-lactams, but they were not associated with a worse prognosis than those due to ESBL- or ACBL-producing bacteria.

Tsui K ，Wong SS ，Lin LC ，Tsai CR ，Chen LC ，Huang CH ... -  《-》

[Fosfomycin susceptibility of urinary Escherichia coli isolates producing extended-spectrum beta-lactamase according to CLSI and EUCAST recommendations].

Cağan Aktaş S ，Gençer S ，Batırel A ，Hacıseyitoğlu D ，Ozer S ... -  《MIKROBIYOLOJI BULTENI》

Evaluation of MicroScan WalkAway and Vitek 2 for determination of the susceptibility of extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae isolates to cefepime, cefotaxime and ceftazidime.

Jang W ，Park YJ ，Park KG ，Yu J ... -  《-》

Comparison of European Committee on Antimicrobial Susceptibility Testing (EUCAST) and CLSI screening parameters for the detection of extended-spectrum β-lactamase production in clinical Enterobacteriaceae isolates.

Polsfuss S ，Bloemberg GV ，Giger J ，Meyer V ，Hombach M ... -  《-》