Modified crystal violet pectate medium (CVP) based on a new polypectate source (Slendid) for the detection and isolation of soft rot erwinias

The selective-diagnostic crystal violet pectate (CVP) medium for the detection and isolation of soft rot erwinias was modified and improved to allow the use of a new source of sodium polypectate (Slendid type 440), as the previous polypectate (Bulmer) is no longer available. Two formulations were developed: CVP-S1 medium was less transparent but otherwise similar to the Bulmer polypectate-based CVP medium (CVP-B) except that NaOH was added and CaCl2 concentration reduced. CVP-S2 medium was prepared by mixing equal volumes of two double strength preparations containing 1) polypectate and NaO-H, and 2) all other ingredients, both sterilised separately. Although erwinia cavity formation was slower, it showed a number of advantages over CVP-B and CVP-S1 media, thereby facilitating colony/cavity detection and enumeration. These included the absence of precipitate, greater firmness and a reduced risk of liquefaction in the presence of large erwinia numbers, and a reduction in the number of saprophytic bacteria.