Speciation and Frequency of Virulence Genes of Enterococcus spp. Isolated from Rainwater Tank Samples in Southeast Queensland, Australia

In this study, 212 Enterococcus isolates from 23 rainwater tank samples in Southeast Queensland (SEQ), Australia were identified to the species level. The isolates were also tested for the presence of 6 virulence genes associated with Enterococcus related infections. Among the 23 rainwater tank samples, 20 (90%), 10 (44%), 7 (30%), 5 (22%), 4 (17%), 2 (9%), and 1 (4%) samples yielded E. faecalis, E. mundtii, E. casseliflavus, E. faecium, E. hirae, E. avium, and E. durans, respectively. Among the 6 virulence genes tested, gelE and efaA were most prevalent, detected in 19 (83%) and 18 (78%) of 23 rainwater tank samples, respectively. Virulence gene ace was also detected in 14 (61%) rainwater tank samples followed by AS, esp (E. faecalis variant), and cylA genes which were detected in 3 (13%), 2 (9%), and 1 (4%) samples, respectively. In all, 120 (57%) Enterococcus isolates from 20 rainwater tank samples harbored virulence genes. Among these tank water samples, Enterococcus spp. from 5 (25%) samples harbored a single virulence gene and 15 (75%) samples were harboring two or more virulence genes. The significance of these strains in terms of health implications remains to be assessed. The potential sources of these strains need to be identified for the improved management of captured rainwater quality. Finally, it is recommended that Enterococcus spp. should be used as an additional fecal indicator bacterium in conjunction with E. coli for the microbiological assessment of rainwater tanks.