Diversity of Bacteroides fragilis strains in their capacity to recover phages from human and animal wastes and from fecally polluted wastewater

Great differences in capability to detect bacteriophages from urban sewage of the area of Barcelona existed among 115 strains of Bacteroides fragilis. The capability of six of the strains to detect phages in a variety of fece s and wastewater was studied, Strains HSP40 and RYC4023 detected similar nu mbers of phages in urban sewage and did not detect phages in animal feces. The other four strains detected phages in the frees of different animal spe cies and in wastewater of both human and animal origin. Strain RYC2056 reco vered consistently higher counts than the other strains and also detected c ounts ranging from 10(1) to approximately 10(3) phages per mi in urban sewa ge from different geographical areas. This strain detected bacteriophages i n animal feces even though their relative concentration with respect to the other fecal indicators was significantly lower in wastewater polluted with animal feces than in urban sewage.