Evaluation of three Arcobacter selective agars for selective enumeration of Arcobacter butzleri in beef

• Specificity of Arcobacter selective agars
• Inhibition of indigenous beef microflora by Arcobacter selective agar
• Enumeration of A. butzleri by Arcobacter selective agar

Arcobacter spp. is an emerging foodborne pathogen due to increasing association with foods of animal origin. A number of Arcobacter selective broths and agars are available for the enrichment, isolation and detection of Arcobacter spp. from food, fecal and environmental sources. However, studies have not examined the specificity of different Arcobacter selective agars for selective enumeration of Arcobacter spp. in beef. The purpose of this study is to determine which of the three published Arcobacter selective agars (Houf, JM and AC agar) can provide acceptable counts while inhibiting the growth of selected indigenous meat microflora during direct plating. Houf and AC agar were able to supress the growth of all selected indigenous meat microflora tested while JM agar supported the growth of Leuconostoc carnosum. In the Arcobacter butzleri recovery efficiency trial, Houf, JM and AC agar achieved recovery rates between 81–98%, 12–52% and 77–97%, respectively, in comparison to TSA. JM and AC agar were unable to supress the growth of indigenous beef microflora from temperature abused retail ground beef even at dilutions as high as 10− 6. Houf agar was able to effectively suppress indigenous beef microflora at dilutions as low as 10− 1. This study showed that Houf agar is more suitable compared to JM or AC agar for use in meat challenge studies as a direct plating agar for enumeration of A. butzleri.