In vitro susceptibility of commonly used antibiotics on community-acquired uncomplicated urinary tract infection pathogens in Beijing

Abstract

Objective To investigate the distribution and susceptibility patterns of common uropathogens causing community-acquired urinary tract infection (UTI) in Beijing. Methods A total of 300non-duplicate isolates were randomly collected from 3 hospitals in Beijing between Jan,1 2010 and Mar,312011.Minimal inhibitory concentrations (MICs) were determined by the broth microdilution methods,which were performed and interpreted according to the guidelines established by the Clinical and Laboratory Standards Institute (CLSI).A panel of 8 antimicrobial agents were tested:amikacin,cefaclor,cefepime,cefoperazone/sulbactam,ciprofloxacin,levofloxacin,gentamicin and nitrofurantoin. Fosfomycin trometamol MICs were determined by the agar-dilution method in cation-adjusted MH agar supplemented with glucose 6-phosphate at a concentration of 25 mg/L as detailed in the guidelines issued by 2010 CLSI. All the Escherichia coli,Klebsiella pneumoniae and Proteus mirabilis strains were screened and confirmed by double-disk synergy test for extended-spectrum β-lactamase (ESBLs). Results Among the organisms cultured,E.coli was the predominant pathogen (65.0％ ), followed by Enterococcus (11.7％ ),Staphylococcus ( 6.3％ ), Klebsiella pneumoniae ( 5. 3％ ), Proteus mirabilis ( 4. 7％ ), and Pseudomonas aeruginosa (3.0％).Lower susceptibility rates to ciprofloxacin and levofloxacin (31.4％ -47.4％ ) were observed among all the stains.Amikacin,cefoperazone/sulbactam,nitrofurantoin and fosfomycin trometamol were the most active drugs (92.1％,92.1％,88.4％ and 87.9％ susceptible strains,respectively) among the Gram-negative strains.Isolates of Staphylococcus were highly sensitive to amikacin ( 100.0％ ),cefoperazone/sulbactam (94.7％),nitrofurantoin ( 100.0％ ).Higher susceptibility rates to nitrofurantoin (91.4％) and fosfomycin trometamol (90.0％) were observed in Enterococcus.ESBLs-producing strains accounted for 52.3％ (102/195) in E.coli,43.8％ (7/16) in K.pneumoniae and 14.3％(2/14) in P.mirabilis,respectively. Conclusions Resistance is most common to ciprofloxacin and levofloxacin of all the stains.Currently,the most appropriate agents for the empirical management of uncomplicated UTI seems to be amikacin,cefoperazone/sulbactam,nitrofurantoin and fosfomycin trometamol. Key words: Urinary tract infections; Community-acquired infections; Anti-bacterial agents; Pathogens; In vitro