In vitro efficacy of fosfomycin against clinical strains

Objective: Fosfomycin is an alternative drug for treatment of uncomplicated urinary tract infections. This study aimed to investigate in vitro activity of fosfomycin against methicillin-resistant Staphylococcus aureus (MRSA), methicillinresistant coagulase negative staphylococci (MRCoNS), vancomycin-resistant Enterococcus faecium (VR E. faecium), Escherichia coli, Klebsiella pneumoniae, and Enterobacter isolates. Methods: Clinical isolates of MRSA, MRCoNS, E. coli, K. pneumoniae and Enterobacter spp. and VRE isolates which were isolated from rectal swaps were identified with Vitek 2 Compact (Biomeriux, France) and BD Phoenix (BD USA) automated systems. The Kirby-Bauer disc diffusion method was used to determine the susceptibility to fosfomycin. Results: All the MRSA (n=40), MRCoNS (n=40), and VR E. faecium (n=62) isolates were susceptible to fosfomycin. The fosfomycin susceptibility rates for E. coli, K. pneumoniae, and Enterobacter spp. were 97.5% (39 of 40), 97.3% (36 of 37), and 86.9% (20 of 23), respectively. One (2.7%) isolate of K. pneumoniae and three (13.1%) isolates of Enterobacter spp. showed intermediate susceptibility to fosfomycin. Resistance to fosfomycin was detected in only one (2.5%) isolate of E. coli. Conclusion: Based on the results of our study, fosfomycin is highly active against a collection of several gram-positive and gram-negative bacteria, including multidrug resistant isolates, and is an alternative drug in the treatment option. J Microbiol Infect Dis 2014;4(2): 55-58