Growth of Aeromonas spp. on cefsulodin-Irgasan-novobiocin agar selective for Yersinia enterocolitica

Abstract

Twenty-eight strains of Aeromonas spp. were analyzed for their ability to grow on two different kinds of cefsulodin-Iragasan (triclosan; Ciba-Geigy AG, Basel, Switzerland)-novobiocin (CIN) agar containing 15 or 4 mg of cefsulodin per ml and on inositol-bile salts-brilliant green (IBB) agar. Relative to blood agar, 68% of the strains were inhibited by more than 2 logs (i.e., less than 1% growth) at 37.degree. C (39% at 25.degree. C) on CIN I (high cefsulodin concentration), 7% were inhibited at either temperature on CIN II (low cefsulodin concentration), 4% were inhibited on IBB agar at 37.degree. C, and none were inhibited on IBB agar at 25.degree. C. These results reflect the MICs of cefsulodin on CIN Base: the MIC for 50% of the strains was 8 mg/liter at 37 and 25.degree. C, and the MICs for 90% of the strains were 16 mg/liter at 37.degree. C and 64 mg/liter at 25.degree. C. The MICs of Irgasan and novobiocin were far beyond the concentrations used in CIN media. We argue that CIN agar containing 4 mg of cefsulodin per ml (CIN II) can be used for the simultaneous detection of Aeromonas spp. and Yersinia spp.