Prevalence, detection and characterisation of fosfomycin-resistant Escherichia coli strains carrying fosA genes in Community of Madrid, Spain.

Abstract

The aim of this this study was to describe the presence of different variants of the fosA gene in fosfomycin-resistant Escherichia coli strains in Madrid, Spain. fos genes were searched for in 55 E. coli strains collected from seven representative hospitals located in Madrid. A phenotypic screening test was performed following the disk diffusion method with sodium phosphonoformate added as described by Nakamura et al. Additionally, a molecular study based on PCR was used to confirm the screening results. Positive strains for fos genes were further subjected to whole-genome sequencing (WGS). Phenotypic screening was positive in 9/55 strains (16.4%), although genotypic detection was positive in only 3 (fosA3, fosA4 and fosA6). Thus, the prevalence of fos genes in Madrid was 5.5% (3/55). WGS data were not available for the fosA6-positive strain. One isolate with fosA3 (ST69) carried a blaCTX-M-55 gene and seven virulence genes (air, eilA, iha, iss, lpfA, sat and senB). The fosA4-positive isolate (ST4038) carried the virulence genes iss, lpfA, iroN and mchF. Both fos genes were located between two IS26 mobile elements of a plasmid. We detected the presence of different variants of plasmid-mediated fosA genes in fosfomycin-resistant E. coli strains in Madrid, Spain. Despite the few reports in Europe, it would be of interest to monitor the spread of these acquired resistance genes.