<prompt> Preferred bacteriological indicator of faecal contamination of water: March 2012Faecal streptococciCl. prefringensFaecal staphylococciE.coli  <response>: Ans: D i.e. E. coli The primary bacterial indicator recommended for acceptability purpose is the coliform group of organisms as a whole. The coliform group includes both faecal E.coli and non faecal organisms Klebsiella aerogens Supplementary indicator organisms, such as faecal streptococci and sulphite-reducing clostridia, may sometimes be useful in determining the origin of faecal pollution as well as in assessing the efficiency of water treatment processes. 