Occurrence of CTX-M producing E. Coli in cattle and the farm environment in Burgundy, France

Abstract

International audienceExtended spectrum beta lactamase (ESBL) producing Escherichia coli have recently emerged worldwide. The aim of this study was to sur vey cattle and the farm environment to determine if they are potential reservoirs for these strains. Samples of cattle feces (n=271) were collected from 182 farms in Burgundy (France). ESBL-producing E. coli were isolated on selective media containing cefotax im or ceftazidim. Thirteen ESBL-producing isolates were obtained from 3 farms, and these were characterized for the presence of bla genes. Of the 13 strains, five and eight strains carried blaTEM genes and blaCTX-M genes, respectively. Soil, water and store d manure obtained from the 3 positive farms were evaluated for the presence of ESBL-producing E. coli . Ten strains of CTX-M producing E. coli were isolated from cultivated and pasture soils an d composted manure from 2 of the farms. A genotypic analysis of the strains by rep-PCR using the Diversilab system revealed that the environmental strains were clonally related to the strains isolated from animals. In some cases soils had not been manured for over a year, thus suggesting that some strains may be environment ally adapted. A larger scale study was performed to detect the prevalence of blaCTX-M in soil. Soil DNA from 120 sites in Burgundy (Reseau de Mesure de la Qualite des Sols, 16x16 km grid) was tested using real time PCR with specific primers and probe. The blaCTX-M targets were detected in 20% of the DNA extracts tested. This study confirms the occurrence of CTX-M producing E. coli in cattle. To our best knowledge, this is the first report of such strains in cultivated soils. The environmental competence of such strains might explain their long term survival since CTX-M isolates were recovered from a soil that was last amended with manure one year before sampling. The blaCTX-M gene was found to be very widespread in a regional soil survey. Further studies are underway to determine the spread of blaCTX-M genes