A selective medium facilitating the isolation and recognition of Bordetella bronchiseptica in pigs

Abstract

A medium was developed that in most instances allowed the isolation from pigs of Bordetella (Alcaligenes) bronchiseptica in pure, or virtually pure, culture from such sites as the nasal cavity, which contains many other bacteria. If not suppressed, some of the latter can inhibit, sometimes completely, the growth of the bordetellae on artificial media. Besides being markedly selective, the new medium is simple to prepare, reasonably cheap and practically noninhibitory to B bronchiseptica. This organism produces a distinctive colony that is easily differentiated on morphological grounds from the few other bacteria (such as Alcaligenes faecalis and Pseudomonas spp) which also grow on this medium. Parallel examination of specimens from the nasal cavities of 219 pigs in the field in southern England confirmed that this medium was better than hitherto recommended for the detection of B bronchiseptica. This was particularly true when the organism occurred in small numbers only and/or when bacteria little affected by the inhibitors in the previously recommended media were present in the nasal flora.