Increase over time in the prevalence of multiple antibiotic resistance among isolates of Listeria monocytogenes from poultry in Spain

► The prevalence and antibiotic resistance of L. monocytogenes on chicken were assessed. ► Data obtained in 1993 and 2006 from the same retail outlets in Spain were compared. ► Similar contamination rates were observed in 1993 (32.0%) and 2006 (24.5%). ► Multi-resistance was less common in 1993 than in 2006 (18.6% and 84.0%, respectively). ► The mean number of resistances per strain increased from 1.60 in 1993 to 4.24 in 2006.