title: Antimicrobial susceptibility to parenteral and oral agents in a largely polyclonal collection of CTX-M-14 and CTX-M-15-producing Escherichia coli and Klebsiella pneumoniae.
abstract: Activity of oral and parenteral antimicrobials against consecutively isolated extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (n = 149) and Klebsiella pneumoniae (n = 20) was determined, and susceptibility test methods were compared for parenteral β-lactams. Polymerase chain reaction (PCR) targeting bla(CTX-M), bla(SHV) and bla(TEM), and DNA sequencing and epidemiological typing with pulsed-field gel electrophoresis were performed. PCR targeting pabB was screened for E. coli O25b-ST131. Minimum inhibitory concentrations (MICs) were determined using Etest and broth microdilution. Disc diffusion was performed according to European Committee on Antimicrobial Susceptibility Testing (EUCAST). Dominating genotypes were bla(CTX-M-15) (75%) and bla(CTX-M-14) (23%). Four E. coli clusters (7-18 isolates) were found. Forty-two per cent of E. coli belonged to O25b-ST131. Ciprofloxacin resistance was 72%, trimethoprim resistance was 70%. Among E. coli, resistance to mecillinam (13%), nitrofurantoin (7%) and fosfomycin (3%) was low, although resistance was high in K. pneumoniae (25%, 60%, 85%). Susceptibility to ertapenem was 99%, piperacillin-tazobactam 91%, tigecycline 96% and temocillin 76%. Susceptibility rates obtained with broth microdilution and Etest were in agreement for cefotaxime (2 vs 1%) and ceftazidime (9 vs 11%), but not for piperacillin-tazobactam (59 vs 91%). With disc diffusion major errors occurred with piperacillin-tazobactam (18/169). Several therapeutic alternatives exist for ESBL-producing E. coli, but few exist for K. pneumoniae. Disc diffusion and Etest can accurately predict susceptibility to cefotaxime and ceftazidime, but not to piperacillin-tazobactam with the present breakpoints.
authors.affiliation: Division of Medicine, Department of Infectious Diseases, Karolinska University Hospital, Huddinge, Stockholm, Sweden. emilia.titelman@karolinska.se
authors.forename: Emilia
authors.initials: E
authors.lastname: Titelman
authors.forename: Aina
authors.initials: A
authors.lastname: Iversen
authors.forename: Gunnar
authors.initials: G
authors.lastname: Kahlmeter
authors.forename: Christian G
authors.initials: CG
authors.lastname: Giske
mesh_terms: D000284:Administration, Oral; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects*; D007267:Injections; D007711:Klebsiella pneumoniae / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D001618:beta-Lactamases / Q000096:biosynthesis*
chemical_list: D000900:Anti-Bacterial Agents; C456080:beta-lactamase CTX-M-14; C473109:beta-lactamase CTX-M-15; D001618:beta-Lactamases