Objective: To determine comparative in vitro activity of sitafloxacin against clinical isolates of bacteria from Thai patients with urinary tract infection and those with lower respiratory tract infection.
Material and Method: 1,255 clinical isolates of Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Acinetobacter baumannii, Enterococcus spp, Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae and Moraxella catarrhalis isolated from different Thai patients with urinary tract infection and those with lower respiratory tract infection in 2010 were included. The minimum inhibitory concentrations (MICs) of sitafloxacin, ciprofloxacin, levofloxacin, moxifloxacin, imipenem, amikacin, ampicillin, ceftazidime, ceftriaxone, penicillin, piperacillin/tazobactam, vancomycin, azithromycin and trimethoprim/sulfamethoxazole were determined by standard agar dilution method.
Results: The MIC50 and MIC90 values of sitafloxacin against all tested bacteria were lowest when compared with those of levofloxacin, ciprofloxacin and moxifloxacin. Sitafloxacin was active against 51% of methicillin-resistant S. aureus (MRSA) isolates. The activity of sitafloxacin against multidrug-resistant (MDR) Gram-negative bacteria, such as, extended spectrum beta-lactamase (ESBL)-producing E. coli and K. pneumomiae, P. aeruginosa and A. baumannii was comparable to or more than that of some beta-lactam/beta-lactamase inhibitors, cephalosporins or carbapenems.
Conclusion: Sitafloxacin is more active than levofloxacin, ciprofloxacin and moxifloxacin against isolated bacteria from Thai patients with urinary tract and lower respiratory infections including antibiotic resistant bacteria, such as MRSA, ESBLproducing Gram-negatives, carbapenem-resistant A. baumannii.

Keywords: In vitro activity, Sitafloxacin, Floroquinolone