Overlay technique for direct detection and identification of haemolytic Listeria on selective plating medium. Comparison of five media
Investigation published in Zeitschrift für Lebensmittel-Untersuchung und -Forschung
July 1st, 1990
An overlay technique is proposed for the identification and counting of haemolytic Listeria colonies directly on selective plating media. The technique was applied to different Listeria-selective plating media. In pure culture studies with collection strains, the overlay technique was more efficient and reliable for detection haemolytic Listeria species compared with the incorporation of blood into the agar. The efficacy of the overlay technique for the direct detection of haemolytic colonies of Listeria from raw milk samples was related to agar selectivity. The best results were obtained with Listeria-selective agar medium modified (LSAMM). Catalase assay, together with reactions for aesculin and tellurite, were useful and reliable criteria for the identification of Listeria. All colonies on LSAMM which were positive for catalase, tellurite and aesculin while those displaying typical haemolysis corresponded in most cases to L. monocytogenes
Dominguez L., Fernandez-Garayzabal JF., Blanco MM., Briones V., Vazquez-Boland JA., Blanco JL. and Suarez G.
 | Departamento de Sanidad Animal. Facultad de Veterinaria. Universidad Complutense (UCM). |
| Servicio de Identificación y Caracterización Microbiana (ICM). Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM). |
