Internalisation of Salmonella spp. by Typha latifolia and Cyperus papyrus in vitro and implications for pathogen removal in Constructed Wetlands

Freshwater contamination by enteric pathogens is implicated in the high frequency of diarrhoeal diseases in low to middle income countries, typically due to poor wastewater management. Constructed Wetlands are a cost-effective and sustainable alternative to conventional/mechanical treatment technologies, but the pathogen removal mechanisms in Constructed Wetlands are not fully understood. This study investigated for the first time the internalisation ofSalmonellaspp. byTypha latifoliaandCyperus papyrusin hydroponic microcosms. Presence ofSalmonellaspp. within roots, rhizomes and shoots was assayed using agar-based methods over a period of 12 days. Concentration ofSalmonellaspp. in growth media showed 2.7 and 4.8 log unit reduction withT.latifoliaandC. papyrus, respectively, and 1.8 and 6.0 log unit in unplanted units.Salmonellaspp. was recovered from root and rhizome tissues ofT.latifolia(up to 4.4 logCFU/g) andC. papyrus(up to 3.4 logCFU/g), and the bacteria were highly concentrated in the epidermis and cortex. However,Salmonellaspp. was not detected in the stems and leaves of the two plant species. The present study demonstrates for the first time that these macrophytes internalise cells ofSalmonellaspp., which could be one pathogen removal mechanism employed by wetland plants. [GRAPHICS] .