Listeria Isolation and Identification Protocol

Initially, the specimens were inoculated in Buffered Listeria Enrichment Broth (BLEB, Merck, Germany) and were incubated at 4°C for 2 weeks to 1 month. The inoculum was then plated on PALCAM agar (Merck, Germany), Oxford agar (Difco, USA) and CHROM agar Listeria (Paris, France) plates. After 48 h of incubation at 37°C, colonies morphologically resembling Listeria were submitted for confirmatory examinations using Gram staining, catalase and oxidase tests, motility and sugar fermentation tests (xylose, rhamnose, mannitol, α-methyl D-mannopyranoside), hemolysis on 5% sheep blood agar and CAMP test (8 (link), 9 (link)). In CAMP test, the L. monocytogenes isolates were streaked perpendicular to Staphylococcus aureus on 5% sheep blood agar plates and zones of hemolysis were investigated, after 24–48 h of incubation at 35°C (10 (link)).