Interpretive criteria for susceptibility tests with DU-6859a and FK-037 tested against Haemophilus influenzae and Neisseria gonorrhoeae

Bacterial Infections in the Elderly Patient: Focus on Sitafloxacin

Sitafloxacin (DU-6859a) is a new-generation oral fluoroquinolone with in vitro activity against a broad range of Gram-positive and -negative bacteria, including anaerobic bacteria, as well as against atypical bacterial pathogens. Particularly in Japan this antibiotic was approved in 2008 for treatment of a number of bacterial infections caused by Gram-positive cocci and Gram-negative cocci and rods, including anaerobia atypical bacterial pathogens. As compared to oral levofloxacin sitafloxacin was non-inferior in the treatment of community-acquired pneumonia and non-inferior in the treatment of complicated urinary tract infections, according to the results of randomized, double-blind, multicentre, non-inferiority trials. Non-comparative studies demonstrated the efficacy of oral sitafloxacin in otorhinolaryngological infections, urethritis in men, cervicitis in women and odontogenic infections. Most common adverse reactions were gastrointestinal disorders and laboratory abnormalities in patients receiving oral sitafloxacin; diarrhea and liver enzyme elevations were among the common. In the Japanese population sitafloxacin covers broad spectrum of bacteria as compared to carbapenems, whereas in the Caucasians its use is currently limited due to the potential for ultraviolet A phototoxicity. Sitafloxacin is a promising therapeutic agent which merits further investigation in randomized clinical trials of elderly patients.

In vitro antibacterial activity and pharmacodynamics of new quinolones

This synopsis of published literature summarises data on the in vitro antibacterial activity and pharmacodynamics of fluoroquinolones. Data were compiled for ciprofloxacin, levofloxcin, moxifloxacin, gatifloxacin, grepafloxacin, gemifloxacin, trovafloxacin, sitafloxacin and garenoxacin. All of these quinolones are almost equipotent against gram-negative bacteria but demonstrate improved activity against gram-positive species. The new quinolones are uniformly active against gram-positive species except Streptococcus pneumoniae; against which gemifloxacin, sitafloxacin and garenoxacin are one to two dilution steps more active than moxifloxacin. All of the new quinolones except gemifloxacin demonstrate enhanced activity against anaerobes. Since all the new quinolones show similar activity against the major respiratory tract pathogens except Streptococcus pneumoniae and members of the family Enterobacteriaceae, their pharmacokinetics and pharmacodynamics will be clinically relevant differentiators and determinants of their overall activity and efficacy. In vitro simulations of serum concentrations revealed that (i). gemifloxacin and levofloxacin were significantly and gatifloxacin moderately less active than moxifloxacin against Streptococcus pneumoniae and Staphylococcus aureus, and (ii). resistant subpopulations emerged following exposure to levofloxacin and gatifloxacin (gemifloxacin not yet published) but not to moxifloxacin. The emergence of resistance is a function of drug concentrations achievable in vivo and the susceptibility pattern of the target organisms. Therefore, the use of less potent fluoroquinolones with borderline or even suboptimal pharmacokinetic/pharmacodynamic surrogate parameters will inadvertently foster the development of class resistance. Drugs with the most favourable pharmacokinetic/pharmacodynamic characteristics should be used as first-line agents in order to preserve the potential of this drug class and, most importantly, to provide the patient with an optimally effective regimen.

In vitro activities of sitafloxacin (DU-6859a) and six other fluoroquinolones against 8,796 clinical bacterial isolates

The in vitro activities of sitafloxacin, ciprofloxacin, trovafloxacin, levofloxacin, clinafloxacin, gatifloxacin, and moxifloxacin against 5,046 gram-negative bacteria, 3,344 gram-positive cocci, and 406 anaerobes were determined. Sitafloxacin was the most active agent against gram-positive cocci and anaerobes. Against Enterobacteriaceae and nonfermenters, its activity was either equivalent to or better than that of clinafloxacin.

Activities of three investigational fluoroquinolones (BAY y 3118, DU-6859a, and clinafloxacin) against Neisseria gonorrhoeae isolates with diminished susceptibilities to ciprofloxacin and ofloxacin

Between 1 January 1992 and 31 December 1993, our laboratory, as part of the Gonococcal Isolate Surveillance Project, found that 39 of 673 isolates of Neisseria gonorrhoeae from one local sexually transmitted diseases clinic demonstrated decreased susceptibilities to both ciprofloxacin and ofloxacin. The MICs of BAY y 3118, DU-6859a, and clinafloxacin at which 90% of the gonococci with decreased susceptibility to ciprofloxacin and ofloxacin were inhibited were all 0.016 microgram/ml, which was eightfold higher than those for ciprofloxacin-susceptible gonococci. Our report substantiates prior observations that diminished susceptibility to one quinolone is often associated with diminished susceptibility to other quinolones.

Tentative criteria for determining the in vitro susceptibilities of Haemophilus influenzae, including quality control parameters, to two fluoroquinolones (grepafloxacin and PD 131628)

Grepafloxacin (OPC 17116) and PD 131628 were evaluated against 150 Haemophilus influenzae isolates to propose susceptibility testing criteria for both broth dilution and disk diffusion procedures using haemophilus test medium. Grepafloxacin-susceptible isolates are defined as those for which minimum inhibitory concentrations (MICs) are < or = 0.06 micrograms/ml and zones of inhibition are > or = 27 mm. PD 131628-susceptible strains of H. influenzae included those that exhibited MICs < or = 0.03 micrograms/ml, and the zones were > or = 32 mm. All MICs were well below concentrations that can be achieved in the blood and tissues of patients treated with either study drug. Criteria for defining a resistant category cannot be determined until strains with elevated MICs are available for study. The proposed quality control guidelines for H. influenzae ATCC 49247 and the disk test are 32-39 mm in diameter for grepafloxacin and 34-42 mm for PD 131628. The preliminary broth microdilution MIC control limits for this strain are 0.002-0.016 micrograms/ml for grepafloxacin and 0.002-0.008 micrograms/ml for PD 131628.

Cross-resistance analysis for DU-6859a, a new fluoroquinolone, compared to six structurally similar compounds (ciprofloxacin, clinafloxacin, fleroxacin, levofloxacin, ofloxacin, and sparfloxacin)

Emerging resistance to the current fluoroquinolones has encouraged synthesis of new compounds in this class. We have evaluated the activity of DU-6859a, a novel halogenated quinolone, against a panel of 300 bacteria, relative to the activity of ciprofloxacin, clinafloxacin, fleroxacin, levofloxacin, ofloxacin, and sparfloxacin. DU-6859a was the most active of the fluoroquinolones studied and retains potentially useful activity against 80% of isolates resistant (minimum inhibitory concentration, > or = 4 micrograms/ml) to ciprofloxacin. Continued clinical investigation of DU-6859a and similar new quinolones is urged.