High genetic diversity of nitrofurantoin- or mecillinam-resistant Escherichia coli indicates low propensity for clonal spread

OBJECTIVES: The empirical treatment with trimethoprim or ciprofloxacin of urinary tract infections (UTIs) is now questioned, partly due to the global expansion of a few resistant clonal groups of Escherichia coli. METHODS: In this study we investigated the clonal structure of 34 strains of E. coli (collected from non-pregnant women aged 18-65 years with uncomplicated UTIs in Europe and Canada) resistant to either of two other common treatment alternatives for uncomplicated UTIs, mecillinam or nitrofurantoin, using multilocus sequence typing (MLST). RESULT: The 34 isolates were, despite high levels of multiresistance, distributed all over the E. coli genetic diversity spectrum with little association of antibiotic resistance to specific clonal groups. CONCLUSIONS: The results of this study indicate a low probability of a future clonal spread of resistance to mecillinam and nitrofurantoin.