Comparison Study and Evaluation of Selective Enrichment Broth for Coliforms with Commercial Broth Media

Abstract

Background: Several bacteriological broths and solid media are available for growth of coliforms. Many are generalized and some of them works as selective. Now a days, in this category with development of chromogenic and flourogenic media, enumeration and detection have work become very easy. Despite the fact most of the countries are using approved methods like IS-5887 (Part-I) 1976 and IS-5401 Part-1 (2012) protocol for monitoring E. coli and coliforms in dairy products respectively. This is due to reliability of these media in giving results. Even though results obtained using these methods need confirmation as there are chances to have other organisms/contaminants in the broth or media which does not actually belong to coliforms groups. This leads to further testing to get presence of coliforms and E. coli. Methods: The present investigation comprised comparison and evaluation of formulated selective coliforms broth (Gawai, 2020) with commercially available broths namely Lactose broth, Coliform broth, Tergitol-7 broth, MacConkey’s broth, Violet red bile broth, Lauryl sulphate tryptose broth and nutrient broth at specified time intervals. Result: The growth pattern of Escherichia coli ATCC 25922, Coliforms cocktail and Salmonella typhimurium ATCC 14028 were studied in developed selective coliform broth along with seven commercial broths. It was observed that E.coli ATCC 25922 showed good growth in all the broth tested and highest growth was reported with Formulated broth i.e. 9.60 log cfu/ml and least growth was in MacConkey broth i.e. 8.60 log cfu/ml after 24 h of incubation. Coliform cocktail culture showed the best result in Formulated selective broth and Tergitol broth after 24 h of incubation i.e. 9.40 log cfu/ml while formulated coliforms broth showed the best reduction of Salmonella typhi ATCC 14028 in comparison with other tested broths.