The prevalence of ESBL‐producing E. coli and Klebsiella strains in the Copenhagen area of Denmark

The main purpose of the study was to investigate the frequency of ESBL‐producing E. coli and Klebsiella strains in the Greater Copenhagen area. Four collections of strains were investigated: A) 380 consecutive E. coli and Klebsiella isolates primarily from urine, B) 200 gentamicin‐resistant E. coli and Klebsiella isolates primarily from urine, C) 210 consecutive E. coli isolates from blood cultures, and D) 68 cefuroxime‐resistant E. coli and Klebsiella isolates primarily from urine. Only one strain per patient was included. Strains with a zone diameter for cefpodoxime ≤23 mm were tested by a phenotypic confirmatory test for ESBL production and all screening test‐positive strains were examined with PCR and nucleotide sequencing in order to detect the following ESBL genes: ctx‐m, shv, tem and oxa. Strains resistant to cefoxitin were further examined with cefotetan±boronic acid in order to detect AmpC. An ESBL gene was detected in 3/3 confirmatory test‐positive isolates from collection A, in 14/17 from collection B, and in 41/48 from collection D. The distribution of isolates with the ESBL and/or AmpC enzymes was as follows: CTX‐M (n=41), SHV (n=14), AmpC (n=9), CTX‐M and AmpC (n=2), SHV and AmpC (n=1). In conclusion, the frequency of ESBL‐producing E. coli and Klebsiella isolates was low in the Copenhagen area of Denmark (0.8 %). The most common ESBL genes found in our study were ctx‐m and shv genes.