Escherichia coli resistant to fosfomycin from urinary tract infections: Detection of the fosA3 gene in Spain.

OBJECTIVES

The aim of this study was to report the epidemiological and genetic background of fosfomycin-resistant Escherichia coli isolates causing urinary tract infections (UTIs) in Spain.

METHODS

A retrospective observational study of 39 randomly selected fosfomycin-resistant E. coli from urine samples collected during 2017 in Getafe (Spain) was performed. Medical records of 39 patients were reviewed. Phylogenetic groups were identified and the pandemic E. coli ST131 and clades thereof were sought by PCR and multilocus sequence typing (MLST). Screening and identification of fos genes and determination of their genetic environment (linkage to IS26) was performed by PCR.

RESULTS

Of the 39 E. coli strains, 49% were ESBL-producers. Most of the strains belonged to phylogenetic group B2 (23/39; 59%), and all of these belonged to ST131 but to different clades (20 to clade C and 3 to clade B). Two isolates from phylogenetic group A (both ST10) carried a plasmid-borne fosA3 gene flanked by IS26. Of the 39 patients, 31 were female (mean age 78 years) and 8 were male (mean age 71 years). Moreover, 27 patients (69%) were diagnosed with complicated UTIs and the remaining 12 (31%) had uncomplicated UTIs, and 33 patients (85%) had been previously treated with fosfomycin.

CONCLUSION

This study shows that fosfomycin-resistant E. coli strains are mainly isolated from elderly people with complicated UTIs and belong to the pandemic ST131 clone. To our knowledge, here we describe the fosA3 gene for the first time in Spain, which alerts for potential future dissemination that should be monitored.