title: Postantibiotic effect of colistin alone and combined with vancomycin or meropenem against Acinetobacter spp. with well defined resistance mechanisms.
abstract: Previous studies found short postantibiotic effect of colistin on Acinetobacter baumannii. Many studies have evaluated the potential for synergy between colistin and other antibiotics against A. baumannii. The aim of this study was to determine in vitro synergy and postantibiotic effect (PAE) of colistin alone and combined with other antibiotics (vancomycin or meropenem) against eight carbapenem-non-susceptible Acinetobacter spp. strains with defined resistance mechanisms. It was hypothesised that vancomycin or meropenem would prologue the PAE of colistin since it was previously found that they exert synergism with colistin in time-kill kinetics and chequerboard analysis. After exposure of 1 hour colistin alone exhibited the negative ( - 0.07 hour) (OXA-143), short (0.2-1.82 hours) (OXA-24, OXA-58, OXA-72, VIM-1+OXA-23, OXA-58+NDM-1, ISAba1/OXA-69) or moderate PAE (3.2 hours) for OXA-23 positive strain. When combined with vancomycin, the PAE was moderate (1.7-4 hours) with OXA-23, OXA-23+VIM-1, OXA-72 and OXA-24 positive strains while with OXA-58, OXA-143, OXA-58/NDM-1 and ISAba1/OXA-69 positive strains, it was not possible to calculate mean duration of PAE because there was no regrowth after exposure to antibiotics or it was longer than 5 hours. The combination with meropenem resulted in short (0.2 hours) (OXA-143), moderate (2.4-3.73 hours) (OXA-24, OXA-58, OXA-23, OXA-23+VIM-1), long PAE of 5 hours (OXA-23) or longer than 5 hours (OXA-58+VIM-1, ISAba1/OXA-69). From the clinical point of view, the prolongation of colistin PAE when combined with other antibiotics could provide a rationale for the modification of the dosing interval and could be important for the optimization of the treatment regimen and the minimization of drug-induced side effects.
authors: a Department of Microbiology , School of Medicine, University of Zagreb , Croatia.|b Department of Clinical and Molecular Microbiology , Clinical Hospital Center Zagreb , Croatia.
authors: Branka
authors: B
authors: Bedenić
authors: a Department of Microbiology , School of Medicine, University of Zagreb , Croatia.|b Department of Clinical and Molecular Microbiology , Clinical Hospital Center Zagreb , Croatia.
authors: Natasa
authors: N
authors: Beader
authors: c Department for Sanitary Engeneering , Faculty of Health Sciences, University of Ljubljana , Slovenia.
authors: Karmen
authors: K
authors: Godič-Torkar
authors: a Department of Microbiology , School of Medicine, University of Zagreb , Croatia.
authors: Esmina
authors: E
authors: Prahin
authors: d Department of Gynecology and Opstetrics , Clinical Hospital Center Zagreb , Croatia.
authors: Ljiljana
authors: L
authors: Mihaljević
authors: e St. Antonius Hospital Kleve , Germany.
authors: Marko
authors: M
authors: Ćačić
authors: a Department of Microbiology , School of Medicine, University of Zagreb , Croatia.|f Department of Microbiology , Zagreb Institute of Public Health, 'Andrija Štampar' , Croatia.
authors: Jasmina
authors: J
authors: Vraneš
mesh_terms: D000151:Acinetobacter Infections / Q000188:drug therapy; D040981:Acinetobacter baumannii / Q000187:drug effects*; D003091:Colistin / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D000077731:Meropenem; D008826:Microbial Sensitivity Tests; D013845:Thienamycins / Q000494:pharmacology*; D014640:Vancomycin / Q000494:pharmacology*
chemical_list: D013845:Thienamycins; D014640:Vancomycin; D000077731:Meropenem; D003091:Colistin
keywords: Acinetobacter baumannii, Colistin; Meropenem; Vancomycin