Sitafloxacin/sulbactam combination for the treatment of extensively-drug resistant Acinetobacter baumannii infections

19 December, 2018

The combination of sitafloxacin and sulbactam was found to have synergistic effect and enhanced in vitro antimicrobial activity against extensively drug-resistant (XDR) Acinetobacter baumannii.

Multidrug-resistant (MDR) A. baumannii refers to strains that are resistant to at least three different classes of the following antimicrobial agents: aminoglycosides, antipseudomonal penicillins, carbapenems, cephalosporins, and quinolones; XDR includes resistance to tigecycline and polymyxins – in addition to the mentioned antimicrobials.1 The emergence of XDR-A. baumannii has resulted in limited treatment options in clinical practice.

The current study conducted by a team of researchers from Shandong University aimed to identify the antimicrobial activity of a sitafloxacin/sulbactam combination against XDR-A. baumannii. Previously, sitafloxacin has been demonstrated to have acceptable antimicrobial activity against carbapenem-resistant A. baumannii despite their resistance to other fluoroquinolones.2 Sulbactam, on the other hand, has been shown to have synergistic effects with other antimicrobials and is used for A. baumannii infections.2

A total of 50 XDR-A. baumannii strains were isolated from sputum, lavages, blood, skin wounds, cerebrospinal fluid, and urine specimens.2 The minimum inhibitory concentration (MIC) for sulbactam and sitafloxacin was determined using broth microdilution assay; the in vitro antimicrobial activity was determined using the microdilution checkerboard method; and time-kill study was conducted for four strains of XDR-A. baumannii with different susceptibilities to determine the bactericidal activities of sitafloxacin and sulbactam.2

The sitafloxacin/sulbactam combination had an increased inhibitory effect on XDR-A. baumannii strains compared to the use of sitafloxacin or sulbactam alone. A susceptibility rate of 96% was reported with the sitafloxacin/sulbactam combination.2 The combination also induced a synergistic or partial synergistic effect on the majority of the 50 strains; none of the strains exhibited antagonistic effects.2 Time-kill studies of the combination of sitafloxacin/sulbactam showed bactericidal activity and synergistic effect against all four selected XDR-A. baumannii isolates.2

The researchers concluded that the sitafloxacin/sulbactam combination could be an alternative treatment of XDR-A. baumannii infections – which are on the rise particularly in hospitals and other care facilities.


Sulbactam enhances the in vitro activity of sitafloxacin against extensively-drug resistant Acinetobacter baumannii.

PMID: 30233699

DOI: 10.3892/etm.2018.6630



  1. Lee K, et al. Yonsei Med J 2011;52:879-891.
  2. Xu N, et al. Exp Ther Med 2018;16:3485-3491.