Analysis of the Microbiome (Bathing Biome) in Geothermal Waters from an Australian Balneotherapy Centre

Balneotherapy is an ancient practice which remains commonplace throughout the world due to perceived health benefits that include relief of arthritis, fibromyalgia and relaxation. However, bathing environments are not sterile and natural spring waters may harbour natural microbial populations that include potential pathogens. We elucidated the microbial community from water taken from the borehole, pre-filter water (chlorinated, cold and post-bathing water) and post-filter water at a commercial Australian natural hot spring bathing facility.Thiobacillus,SphingobiumandAgrobacteriumwere the predominant genera in samples collected from the borehole. The predominant genera changed toSphingobium,ParvibaculumandAchromobacterfollowing chloride treatment andAzospirareplaced theAchromobacteronce the water reached ambient temperature and was stored ready to be used by bathers. The microbial community changed again following use by bathers, dominated byPseudomonas, althoughSphingobiumpersisted. No total or faecal coliforms were observed in any of the samples except for the post-bathing water; even there, their presence was at very low concentration (2.3 cfu/mL). These results confirm the lack of pathogens present in these hot spring waters but also suggests that good management of post-bathing water is required especially if the water is used for borehole water recharge.