A collection comprising 14 isolates of Pediococcus pentosaceus and one Pediococcus acidilactici from the fermentation of caper fruits was studied. All isolates showed very similar fermentation profiles and produced a limited number of exoenzymes. All isolates carried large plasmids of diverse sizes between 20 and 55 kb, while some also contained smaller plasmids between 10 and 16 kb. Cluster analysis of plasmid profiles revealed four main groups with various degrees of similarities. All amino acid decarboxylation tests were negative, suggesting that pediococci are not involved in generation of biogenic amines. None of the isolates showed hemolytic activity. Antimicrobial resistance tests revealed that all isolates were sensitive to 11 different antimicrobials while being resistant to ciprofloxacin (MIC > or =2 mg/liter) and intrinsically resistant to vancomycin (MIC > or =16 mg/liter) and teicoplanin (MIC > or =16 mg/liter).