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Within the scope of a cross-sectional investigation on fattening pig farms conducted in 2011 and 2012, 48 fattening farms in different agricultural regions of Germany were studied. Primary cultures of boot swabs and collective faecal samples were stored at -80°C and screened for the presence of the mcr-1 colistin resistance gene. The laboratory results were linked to farm related data collected via questionnaire. We used logistic regression models to investigate the association between occurrence of mcr-1 and farm related data. Escherichia coli carrying the mcr-1 gene were isolated from 26 out of 216 mixed bacterial cultures (12.0%) originating from 12 out of 48 farms (25.0%). Results of the logistic regression analyses indicate that the transmission between pigs or their direct environment is crucial for the occurrence of these resistant bacteria. However, we found no statistically significant association between antimicrobial use and the occurrence of the mcr-1 gene.