In vivo activity of vancomycin combined with colistin against multidrug-resistant strains of Acinetobacter baumannii in a Galleria mellonella model.
BACKGROUND
With increasing antibiotic resistance, the selection of effective treatment of A. baumannii infections is particularly challenging.


METHODS
This study assessed the activities of the combination of vancomycin and colistin combination in vitro and in vivo using a Galleria mellonella model against four colistin-susceptible or colistin-resistant A. baumannii strains.


RESULTS
In checkerboard assays, synergy was observed between vancomycin and colistin for all four strains tested (0.156 ≤ Fractional inhibitory concentration indices [FICI] ≤ 0.281). In time-kill assays, the combination showed continued bactericidal activity and synergy after 24 h for colistin-susceptible strains. For colistin-resistant strains, the combination resulted in bactericidal activity within 8 h, but sustained bacterial re-growth was then observed. Treatment of G. mellonella larvae infected with lethal doses of A. baumannii (except 19606R) resulted in significantly increased survival rates when vancomycin was given with colistin compared to colistin treatment alone (p < 0.05).


CONCLUSIONS
These findings suggest that regimens containing vancomycin may be useful for infections due to multidrug-resistant Acinetobacter baumannii.
a Department of Infectious Diseases.
Haifei
H
Yang
b Department of Dentistry , the First Affiliated Hospital of Anhui Medical University , Hefei , PR China.
Na
N
Lv
a Department of Infectious Diseases.
Lifen
L
Hu
c Institute of Bacterium Resistance, Anhui Medical University , Hefei , PR China.|d Anhui Center for Surveillance of Bacterial Resistance , Hefei , PR China.
Yanyan
Y
Liu
a Department of Infectious Diseases.
Jun
J
Cheng
a Department of Infectious Diseases.|c Institute of Bacterium Resistance, Anhui Medical University , Hefei , PR China.|d Anhui Center for Surveillance of Bacterial Resistance , Hefei , PR China.
Ying
Y
Ye
a Department of Infectious Diseases.|c Institute of Bacterium Resistance, Anhui Medical University , Hefei , PR China.|d Anhui Center for Surveillance of Bacterial Resistance , Hefei , PR China.|e Department of Infectious Diseases , Chaohu Hospital of Anhui Medical University , Hefei , PR China.
Jiabin
J
Li
D000151:Acinetobacter Infections / Q000188:drug therapy*; D040981:Acinetobacter baumannii / Q000187:drug effects*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D003091:Colistin / Q000494:pharmacology* / Q000627:therapeutic use; D004195:Disease Models, Animal; D024901:Drug Resistance, Multiple, Bacterial; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D006801:Humans; D007814:Larva; D009036:Moths; D014640:Vancomycin / Q000494:pharmacology* / Q000627:therapeutic use
D000900:Anti-Bacterial Agents; D014640:Vancomycin; D003091:Colistin
Acinetobacter baumannii; Galleria mellonella; colistin; insect model; vancomycin