Determination of fosfomycin susceptibility in carbapenemaseproducing K. pneumoniae strains isolated prior to clinical use of the intravenous formulation in Turkey

Objectives: The incidence of infections caused by carbapenem-resistant Enterobacteriaceae has increased worldwide. Limitations in the development of new antimicrobial agents have led clinicians to reconsider the clinical efficiency of old antibiotics, such as intravenous formulation of fosfomycin, in the treatment of multidrug-resistant Gram-negative bacterial infections. We investigated the fosfomycin susceptibility of carbapenemase-producing Klebsiella pneumoniae strains isolated prior to the clinical use of the intravenous formulation of fosfomycin in Turkey. Materials and Methods: A total of the 155 K. pneumoniae isolates which previously characterized at the molecular level for their carbapenemase were included in this study. The minimum inhibitory concentration of fosfomycin was determined by the agar dilution method. Results: Overall, 65.1% of the isolates were susceptible to fosfomycin. The MIC50 and MIC90 values were 32 and 256 mg/L, respectively. According to our results, at least two-third of carbapenemase-positive K. pneumoniae are susceptible to fosfomycin. Conclusions: Although, the susceptibility of fosfomycin, which has just been put into the clinical use of intravenous formulation in Turkey, is not very high, it can be considered as an alternative