Investigation of the effects of eravacycline alone or in combination with various antibiotics against clinical strains of the genus achromobacter

The genus Achromobacter, particularly Achromobacter xylosoxidans, are bacteria responsible for a variety of infections that have been increasingly identified in clinics over the past decade. Especially they are increasingly being described in Cystic Fibrosis (CF) patients by their ability to permanently colonize the airway of these patients. Today, relatively little is known about its clinical impact and optimal therapy management. In the present study, the in-vitro bactericidal or sinergistic activities of eravacycline which is a new tetracycline, either alone or in combination with colistin, meropenem and seftazidime, were assessed using Achromobacter strains isolated from CF patients. Minimal inhibitory concentrations (MICs) were determined by broth microdilution technique. Bactericidal and synergistic effects of the tested antibiotic combinations were determined by using the time-kill curve technique. Based on the time-kill curves, we found that 4×MIC colistin has bactericidal effect at 6h and 24h. According to combination study results, only eravacycline-colistin combination at 4×MIC has synergistic and bactericidal activities against Achromobacter strains, at 24 h. Eravacycline-meropenem combinations and eravacycline-seftazidime combinations were found to be neither bactericidal nor synergistic. No antagonism was observed with any combination tested. The findings of this study reveal some important in-vitro data for empirical or combination therapy with the antibiotics tested.