[Surveillance of in vitro susceptibilities to levofloxacin and various antibacterial agents for 11,762 clinical isolates obtained from 69 centers in 2013].

Antimicrobial susceptibility testing has been conducted continuously as postmarketing surveillance of levofloxacin (LVFX) since 1994. The present survey was undertaken to investigate in vitro susceptibilities of bacteria to 33 selected antibacterial agents, focusing on fluoroquinolones (FQs), using 11,762 clinical isolates for 19 species collected from 69 centers during 2013 in Japan. The common respiratory pathogens Streptococcus pyogenes, Streptococcus pneumoniae, Moraxella catarrhalis, and Haemophilus influenzae continue to show a high susceptibility to FQs, while the percentage of macrolide-resistant S. pneumoniae was markedly increased to around 80%. With H. influenzae, the percentage of β-lactamase-negative ampicillin-resistant isolates had been increasing continuously from 2002, but no increase was observed from 2010 to 2013 (25.8% in 2002, 40.0% in 2004, 50.1% in 2007, 57.9% in 2010, and 57.1% in 2013). Most strains of Enterobacteriaceae showed a high susceptibility to FQs, but the isolation frequency of levofloxacin-resistant Escherichia coli including intermediate resistance was 34.4%, showing a continuous increase. Another Enterobacteriaceae member, Klebsiella pneumoniae, showed low resistance to FQs in contrast with E. coli. Regarding methicillin-resistant Staphylococcus aureus (MRSA), the percentage of FQ-susceptible isolates was low at 15.8-18.0%, with the exception of 55.3% susceptibility to sitafloxacin. On the other hand, methicillin-susceptible S. aureus (MSSA) isolates showed high susceptibility to FQs, at 87.0-99.3%. With Enterococcusfaecium, the percentage of FQ-susceptible isolates was 6.8-24.7%. The percentage of FQ-susceptible Pseudomonas aeruginosa was 83.4-89.3% among isolates derived from urinary tract infections (UTIs), while that from respiratory tract infections (RTIs) was 88.1-93.7%. This was summarized as susceptibility to FQs over 80% in both infections. A continuous decrease in FQ-resistant P. aeruginosa was noted, especially among isolates from UTIs. Regarding multidrug-resistant P aeruginosa, the percentage has been decreasing continuously since 2007 and was 1.6% from UTIs and 0% from RTI in this survey. Acinetobacter spp. showed high susceptibility to FQs. The percentage of imipenem-resistant Acinetobacter spp. was 2.7% (14 isolates) and that of multidrug-resistant was 0.2% (1 isolate). In Neisseria gonorrhoeae, ceftriaxone (CTRX) had been showing 100% susceptibility until 2007, but CTRX-resistant strains have been detected in both 2010 and this survey. In conclusion, the resistance of methicillin-resistant staphylococci, E. faecium, N. gonorrhoeae, and E. coli to the FQs, which have been used clinically for over 20 years, was shown to be 30% or more (31.7-87.1%) in the present surveillance regarding susceptibility. These results were similar to those from previous surveillance, and no species that started to show significant resistance to FQs were identified in the present surveillance. Regarding other bacterial species, susceptibility to ciprofloxacin less than 80% was observed in some, while susceptibility to other FQs was maintained at a high level, at 80% or more.