Open Access<p>In vitro and in vivo activity of ciprofloxacin/fosfomycin combination therapy against ciprofloxacin-resistant <em>Shigella flexneri</em> isolates</p>
Author(s) -
Yanyan Liu,
Hongru Li,
Yalong Zhang,
Ying Yan,
Yufeng Gao,
Jiabin Li
Publication year - 2019
Publication title -
infection and drug resistance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.033
H-Index - 39
ISSN - 1178-6973
DOI - 10.2147/idr.s208071
Subject(s) - ciprofloxacin , fosfomycin , shigella flexneri , microbiology and biotechnology , bacillary dysentery , in vivo , antibiotics , medicine , biology , dysentery , escherichia coli , gene , biochemistry
Objective: Ciprofloxacin resistance (CIP R ) for Shigella isolates is becoming more prevalent. This study systematically investigated the antibacterial activity of ciprofloxacin (CIP)/fosfomycin (FOS) combination in vitro and in vivo against CIP R S. flexneri isolates. Method: Eighty CIP R S. flexneri isolates were selected for synergy studies by the microtiter plate checkerboard assay. Two S. flexneri isolates (GN120471, CIP R FOS R ; GN120454, CIP R FOS S ) were used to investigate the efficacy of the CIP/FOS combination by the time-kill methodology. Clinically relevant concentrations (CIP, 0.5, 1, or 2.5 μg/mL; FOS, 30, 150, or 300 μg/mL) were combined, and the colony counts were conducted at 3, 5, 8, and 24 hours. The in vivo activity of the CIP/FOS combination was assessed using a Galleria mellonella larvae model. Results: In checkerboard assays, 31 strains (38.75%) showed synergy for the CIP/FOS combination. For the isolate GN120471, monotherapy with CIP or FOS at all concentrations produced little or no bacterial killing, while the CIP/FOS combination produced enhanced bacterial killing with FOS concentrations of 150 and 300 μg/mL, especially when combined with CIP at 2.5 μg/mL. For the isolate GN120454, the CIP/FOS combination at all concentrations produced more rapid and extensive killing (up to 5log 10 colony forming units (CFU)/mL with many combinations) than with either antibiotic alone. Mortality at 96 hours was around 80% at approximately 10 4 CFU/larva for GN120471 and GN120454. When CIP at 2.5 μg/mL was combined with FOS at 150 μg/mL for the bactericidal activity in vivo, the survival rates for CIP/FOS combination against GN120471-infected and GN120454-infected larvae were significantly higher than that of CIP (68.75% vs 25%, P =0.013; 81.25% vs 37.5%, P =0.012, respectively). Conclusion: Against CIP R S. flexneri isolates, the CIP/FOS combination induced synergy, and increased bacterial killing in vitro and in a simple invertebrate model of infection.