Frequency and epidemiology of extended-spectrum β-lactamase-producing Enterobacteriaceae isolates susceptible to third-generation cephalosporins or to aztreonam

Abstract

Objective: We evaluated among 400 strains of extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBLE) the rate of strains categorized as intermediate or resistant to 3rd generation cephalosporins or aztreonam according to the 2011 guidelines of the French Society of Microbiology Antibiogram Committee.

Material and methods: MICs of cefotaxime, ceftazidime, cefepime or aztreonam were determined by the E-test method for isolates with susceptible zones to these antibiotics.

Results: Overall, 109/400 (27.3%) isolates were susceptible to at least one of these 4 agents. Notably, 21.8% of Escherichia coli isolates were susceptible to ceftazidime, and 21.1% of Klebsiella pneumoniae isolates were susceptible to cefepime. Discrepancies between categorization by disk diffusion and MIC determination were observed for aztreonam and cefepime.

Conclusion: These results indicate alternatives to carbapenems for treating infections caused by ESBLE.

Keywords: Aztreonam; Aztréonam; Céphalosporines de 3(e) génération; Enterobacteriaceae; Entérobactéries; Extended-spectrum β-lactamase; Third-generation cephalosporins; β-lactamase à spectre étendu.