• Vol. 45 No. 6
  • 15 June 2016

In Vitro Efficacy of Six Alternative Antibiotics against Multidrug Resistant Escherichia Coli and Klebsiella Pneumoniae from Urinary Tract Infections



Increasing resistance in Escherichia coli and Klebsiella pneumoniae to fi rstline antibiotics makes therapeutic options for urinary tract infections (UTIs) challenging. This study investigated the in vitro effi cacies of 6 antibiotics against multidrug resistant (MDR) uropathogens. Materials and Methods: Minimum inhibitory concentrations to ceftibuten, cefpodoxime, fosfomycin, mecillinam, temocillin, and trimethoprim were determined against 155 MDR-isolates of E. coli and K. pneumoniae. The presence of extended-spectrum betalactamases (ESBL) and plasmid-borne AmpC enzymes was determined by phenotypic testing with genotyping performed by multiplex polymerase chain reaction. Results: Temocillin demonstrated highest susceptibility rates for both E. coli (95%) and K. pneumoniae (95%) when breakpoints for uncomplicated UTIs were applied; however, temocillin susceptibility was substantially lower when “systemic infection” breakpoints were used. Fosfomycin demonstrated the best in vitro effi cacy of the orally available agents, with 78% and 69% of E. coli and K. pneumoniae isolates susceptible, respectively. The next most effective antibiotics were ceftibuten (45%) and mecillinam (32%). ESBL and ampC genes were present in 47 (30%) and 59 (38%) isolates. Conclusion: This study demonstrated few oral therapeutic options for MDR-uropathogens, with fosfomycin demonstrating the best in vitro activity.

Urinary tract infections (UTIs) are one of the most common bacterial infections worldwide. Enteric Gramnegative organisms account for more than 90% of UTIs, of which Escherichia coli remains the predominant uropathogen. UTIs also remain as one of the most common
indications for antimicrobial prescription.

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