No abstract

Background: Multidrug resistance Gram-negative pathogens are a serious problem worldwide. In Japan, the prevalence of fluoroquinolone (FQ) resistant Escherichia coli and Proteus mirabilis increased annually from 1994 to 2007. However FQs retained activity against Klebsiella pneumoniae, Serratia marcescens and Acinetobacter species during this period. The nationwide surveillance data for the above 5 pathogens causing urinary tract infections (UTI) are presented herein.Methods: A total of 19,684 isolates belonging to 5 species were collected from 92 participating centers in the Levofloxacin Surveillance Group in Japan from 1994 to 2010. Antimicrobial susceptibility was tested by broth microdilution methods following the Clinical and Laboratory Standards Institute guidelines (CLSI). ESBL phenotypic confirmatory testing for E. coli, K. pneumonia and P. mirabilis was performed by the disk diffusion method in accordance with the CLSI guideline. The type of ESBL was specified by PCR analysis.Results: The percentage of levofloxacin susceptible isolates for E. coli decreased from 97.9% (1994) to 70.7% (2010). The susceptibility of P. mirabilis isolates also decreased from 97.9% (1994) to 85.1% (2010). In contrast, levofloxacin susceptible K. pneumoniae isolates decreased slightly from 99.7% (1994) to 97.5% (2010). Acinetobacter spp. susceptibility remained constant at levels of approximately 90%. Interestingly, the percentage of susceptibility to levofloxacin in S. marcescens increased dramatically from 86.5% (1994) to 95.8% (2010). Only 3.3% of E. coli isolates produced ESBL in 2004 whereas 9.9% of E. coli produced ESBL in 2010. The frequencies of the CTX-M-1 group and CTX-M-9 in E. coli were 31.5% (23 isolates) and 71.2% (52 isolates), respectively. Moreover, 82.2% of ESBL producing isolates showed resistance to levofloxacin. The percentage of levofloxacin resistance in ESBL producing E. coli was higher than non-ESBL producing E. coli (21.1%). Conclusion:The percent susceptibility of levofloxacin against Gram-negative organisms from UTI was maintained at 70% to 98%. Levofloxacin still retains activity for K. pneumoniae, S. marcescens and Acinetobacter spp. However, the isolation frequency of ESBL producing E. coli is increasing in Japan and the predominant type of ESBL was the CTX-M-type including the CTX-M-9 and CTX-M-1 groups.