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

Abstract

<b>ABSTRACT</b>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 of <i>Salmonella</i> spp. by <i>Typha latifolia</i> and <i>Cyperus papyrus</i> in hydroponic microcosms. Presence of <i>Salmonella</i> spp. within roots, rhizomes and shoots was assayed using agar-based methods over a period of 12 days. Concentration of <i>Salmonella</i> spp. in growth media showed 2.7 and 4.8 log unit reduction with <i>T</i>. <i>latifolia</i> and <i>C. papyrus</i>, respectively, and 1.8 and 6.0 log unit in unplanted units. <i>Salmonella</i> spp. was recovered from root and rhizome tissues of <i>T</i>. <i>latifolia</i> (up to 4.4 logCFU/g) and <i>C. papyrus</i> (up to 3.4 logCFU/g), and the bacteria were highly concentrated in the epidermis and cortex. However, <i>Salmonella</i> spp. 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 of <i>Salmonella</i> spp., which could be one pathogen removal mechanism employed by wetland plants.