Rambach agar and SM-ID medium sensitivity for presumptive identification of Salmonella subspecies I-VI

Abstract

The cultural characteristics of 112 Salmonella serovars belonging to subspecies I-VI were examined on Rambach agar and SM-ID medium. Colonies showing the typical red coloration were seen with 100 of 112 serovars assayed on SM-ID, and with 87 of 112 on Rambach agar. Atypical colourless colonies were observed on Rambach agar with ONPG-negative serovars S. Choleraesuis, S. Isangi, S. Typhi S. Worthington and S. Yoff of the subspecies I, S. II 52:d:e,n,x,z, 15 of the subspecies II, S. IV 6,7:Z 4 ,Z 24 :- and S. IV 11:g,Z 51 :- of the subspecies IV, and S. 40:Z 35 :- belonging to S. bongori (V) species. Atypical blue, bluegreen, blue-violet or violet colonies were observed on both media with all the ONPG-positive serovars of the subspecies IIIa (four of four strains) and IIIb (six of six strains) and with one of the two ONPG-positive (out of five) strains of the subspecies VI. Four serovars of S. bongori showed blue-green colonies on Rambach agar and typical red colonies on SM-ID, although they were all ONPG-positive. These results suggest that SM-ID medium is more sensitive than Rambach agar. However, the relatively low sensitivity of both media makes them suitable for use only in association with a traditional selective medium in both medical and environmental bacteriology, as well as for epidemiological purposes.