Abstract
An improved selective medium, neomycin-paromomycin-nalidixic acid-lithium chloride (NPNL) agar, was developed for the enumeration of bifidobacteria in dairy products containing bifidobacteria, lactobacilli and streptococci. NPNL agar was BL agar without blood containing neomycin sulfate (100μg/ml), paromomycin sulfate (200μg/ml), nalidixic acid (15μg/ml), and lithium chloride (3mg/ml). It was employed as a plating medium. Incubation was carried out at 37C for 2 days in an anaerobic steel-wool jar filled with an atmosphere of 100% CO2.
In the case of dispensation with anaerobic jars, modified NPNL agar in combination with the shake culture tube method with an additional agar medium overlaid was also proved to be useful for the same purpose. Modified NPNL agar was BL agar without blood containing neomycin sulfate (30μg/ml), paromomycin sulfate (50μg/ml), nalidixic acid (15μg/ml), and lithium chloride (3mg/ml).
