Enterophages, a group of phages infecting Enterococcus faecalis, and their potential as alternate indicators of human faecal contamination

Abstract

We have developed a method for the detection of viruses in environmental samples that we have called enterophages, that specifically infect Enterococcus faecalis. This method has allowed us to determine the prevalence and to study the ecology of this group of phages. The enterophages replicate at 37°C, and at 41°C. The presence of NaN3 in the media inhibits the growth of background microbiota and allows an accurate, specific and rapid detection of these viruses. Enterophages were present in raw domestic sewage at lower concentrations (average 1.8 × 102 PFU/100 mL) than those of coliphages (average 1.7 × 105 PFU/100 mL). Phages were characterised by transmission electron microscopy showing icosahedral capsids, some with non-contractile tails as well as icosahedral non-tailed capsids. Different isolates had capsid sizes ranging from 20 nm to about 75 nm in diameter. These data describe a new group of phages that may serve as alternate indicators of human faecal pollution, especially in recreational waters. The ecology of these enterophages indicates that these may be strictly of human origin.