The Impact of Water Intrusion on Pathogenic Species to Inland Brackish Waters of China.

The estuary is the ecological niche of pathogenic spp. as it provides abundant organic and inorganic nutrients from seawater and rivers. However, little is known about the ecology of these species in the inland brackish water area. In this study, their co-occurrence and relationships to key environmental constraints (salinity and temperature) in the Hun-Tai River of China were examined using the most probable number polymerase chain reaction (MPN-PCR) approach. We hereby report 2-year continuous surveillance based on six water indices of the Hun-Tai River. The results showed that seawater intrusion maximally reached inland as far as 26.5 km for the Hun-Tai River. Pathogenic spp. were detected in 21.9% of the water samples. In particular, , , and were isolated in 10 (10.4%), 20 (20.8.5%), and 2 (2.08%) samples, respectively. All strains were gene negative, 10% were positive for the gene. Multi-locus sequence typing (MLST) divided strains into 12 sequence types (STs) for the Hun-Tai River. Five STs were respectively present in various locations along the Hun-Tai River. The PCR assay for detecting six virulence genes and seventh pandemic island I and II revealed three genotypes in 12 isolates. The results of our study showed that seawater intrusion and salinity have profound effects on the distribution of pathogenic spp. in the inland river, suggesting a potential health risk associated with the waters of the Hun-Tai River used for irrigation and drinking.