Molecular characterization of CTX-M-15-producing clinical isolates of Escherichia coli reveals the spread of multidrug-resistant ST131 (O25:H4) and ST964 (O102:H6) strains in Norway

• Published in: APMIS : acta pathologica, microbiologica et immunologica Scandinavica microbiologica et immunologica Scandinavica, 2009-07, Vol.117 (7), p.526-536
• Main Authors: NASEER, UMAER, HALDORSEN, BJØRG, TOFTELAND, STÅLE, HEGSTAD, KRISTIN, SCHEUTZ, FLEMMING, SIMONSEN, GUNNAR SKOV, SUNDSFJORD, ARNFINN
• Format: Article
• Language: English
• Subjects: Bacteriology; beta-Lactamases - biosynthesis; beta-Lactamases - genetics; beta-Lactamases - immunology; Biological and medical sciences; Cluster Analysis; CTX-M-15; DNA, Bacterial - chemistry; DNA, Bacterial - genetics; Drug Resistance, Multiple, Bacterial; Electrophoresis, Gel, Two-Dimensional; ESBL; Escherichia coli; Escherichia coli - enzymology; Escherichia coli - genetics; Escherichia coli - isolation & purification; Escherichia coli Infections - epidemiology; Escherichia coli Infections - microbiology; Fundamental and applied biological sciences. Psychology; Humans; Infectious diseases; MDR; Medical sciences; Microbial Sensitivity Tests; Microbiology; Miscellaneous; Norway - epidemiology; O Antigens - biosynthesis; O Antigens - genetics; PBRT; Phylogeny; Plasmids - genetics; Polymerase Chain Reaction; Prevalence; Prospective Studies; Serotyping; ST131
• ISSN: 0903-4641; 1600-0463
• DOI: 10.1111/j.1600-0463.2009.02465.x

Nationwide, CTX‐M‐producing clinical Escherichia coli isolates from the Norwegian ESBL study in 2003 (n=45) were characterized on strain and plasmid levels. BlaCTX‐M allele typing, characterization of the genetic environment, phylogenetic groups, pulsed field gel electrophoresis (PFGE), serotyping and multilocus sequence typing were performed. Plasmid analysis included S1‐nuclease‐PFGE, polymerase chain reaction‐based replicon typing, plasmid transfer and multidrug resistance profiling. BlaCTX‐M‐15 (n=23; 51%) and blaCTX‐M‐14 (n=11; 24%) were the major alleles of which 18 (78%) and 6 (55%), respectively, were linked to ISEcp1. Thirty‐two isolates were of phylogenetic groups B2 and D. Isolates were of 29 different XbaI‐PFGE‐types including six regional clusters. Twenty‐three different O:H serotypes were found, dominated by O25:H4 (n=9, 20%) and O102:H6 (n=9, 20%). Nineteen different STs were identified, where ST131 (n=9, 20%) and ST964 (n=7, 16%) were dominant. BlaCTX‐M was found on ≥100 kb plasmids (39/45) of 10 different replicons dominated by IncFII (n=39, 87%), FIB (n=20, 44%) and FIA (n=19, 42%). Thirty‐nine isolates (87%) displayed co‐resistance to other classes of antibiotics. A transferable CTX‐M phenotype was observed in 9/14 isolates. This study reveals that the majority of CTX‐M‐15‐expressing strains in Norway are part of the global spread of multidrug‐resistant ST131 and ST‐complex 405, associated with ISEcp1 on transferrable IncFII plasmids.