Investigation of Fosfomycin and Chloramphenicol Susceptibility of Carbapenemase-Producing Klebsiella pneumoniae Strains

Objective: Antimicrobial resistance is one of the most mportant health problems of recent years. Multidrug-resistant Klebsiella pneumoniae strains have been causing serious problems in many countries including Turkey in recent years. Aim of this study was to detect molecular mechanisms behind the carbapenem resistance in carbapenem-resistant K. pneurnoniae strains isolated from rectal swab samples and investigate the susceptibility of two potentially alternative drugs, fosfornycin, and chloramphenicol. Methods: 46 K. pneumoniae strains isolated from rectal screening cultures of intensive care unit patients by using MacConkey agar containing 2 mg/L meropenem were included in this study. Carbapenem resistance of strains were confirmed by minimum inhibitor concentrations of meropenem obtained with gradient strip test. Presence of the bla(KPC,) bla(NDM) and bla(OXA), bla(IMP) and bla(VIM) genes were investigated by the real-time polymerase chain reaction. Broth microdilution method was used to investigate chloramphenicol susceptibility, and gradient strip test was used to investigate fosfomycin susceptibility of the strains. Results: At least one carbapenemase gene was detected in all K. pneumoniae strains. While all strains were found positive for the presence of OXA-48 type carbapenemase gene, 12 (26%) out of 46 were positive for both OXA-48 and NDM-1 carbapenemase genes, and only one (2%) strain was positive for OXA-48, NDM-1, and IMP-1 carbapenemase genes. Only 3 (6%) out of 46 strains were found susceptible to fosfomycin while 23 (50%) of them were susceptible to chloramphenicol. Additionally, we observed that the resistance rates to fosfomycin and chloamphenicol tended to be higher among carbapenemase producers. Conclusions: It is estimated that fosfomycin is not going to be a good option for the treatment of infections caused by carbapenemresistant K. pneumoniae strains in Turkey since only 6% of them were susceptible. Although the chloramphenicol susceptibility rate (50%) was higher than fosfomycin, further clinical studies are required to provide a better knowledge about the usage of this antibiotic in systemic infections. Moreover, multiple carbapenemase producers tended to be more resistant to fosfomycin and also chloramphenicol.