Genetic characterization of <i>Salmonella</i> and <i>Shigella</i> spp. isolates recovered from water and riverbed sediment of the Apies River, South Africa

Abstract

Riverbed sediment is a vital component of river ecosystems and plays an important role in many geomorphological and ecological processes. However, when re-suspension occurs, pathogenic bacteria associated with sediment particles may be released into the water column, thus creating a health risk to those who use such water for drinking, household and recreational purposes. The aim of this study was to investigate the presence of bacterial pathogens Salmonella spp. and Shigella spp. in the Apies River and to ascertain whether there was any level of genetic relatedness between river water and riverbed sediment isolates of these pathogenic bacteria. A total of 124 water and sediment samples were collected from a site located on the Apies Rivers upstream of the Daspoort Wastewater Treatment Works, Pretoria, Gauteng, South Africa, between August and November 2014. In order to detect and identify the target bacteria, samples were analysed by culture-dependent and culture-independent techniques (quantitative real-time PCR). Genetic relatedness was established using Sanger sequencing of the invA gene of Salmonella spp. and ipaH of Shigella spp. Results of this study displayed the presence of the target bacteria both in the water and sediment of the river. The phylogenetic tree of Salmonella spp. revealed a ≥ 99% and 99% genetic relatedness between river water and riverbed sediment isolates for Salmonella spp. and Shigella spp., respectively. The degree of genetic relatedness between sediment and water pathogen isolates suggests that these organisms could possibly have a common origin and that there could be possible movement of microorganisms between the water column and the sediments.

Molecular detection of virulence genes in Salmonella spp. isolated from chicken faeces in Mafikeng, South Africa

“…The disease causing potential of Salmonella isolates is derived from the virulent genes that they may carry. So, this study undertook to determine the presence of these virulent genes to understand how potentially pathogenic the strains were (Ekwanzala et al 2017 ; Sunar et al 2014 ). Forty-six ( n = 46) Salmonella isolates were analysed for the presence of seven known virulence genes, namely inv A, Sdf I, hil A, misL, Spy, orfL and spiC .…”

“…It was interesting to note that all the tested virulence genes were detected by this study in differing proportions. All 46 ( n = 46) isolates were positive for inv A, indicating that all of them have the ability to invade and to cause gastroenteritis (Ekwanzala et al 2017 ; Hu et al 2008 ; Lan et al 2018 ; Odjadjare & Olaniran 2015 ; Sunar et al 2014 ) and can survive in macrophages (Goodman et al 2017 ). The inner membrane of Salmonella contains protein coded for by invA, which is vital for invasion into epithelial cells (Salehi, Mahzounieh & Saeedzadeh 2005 ).…”

Occurrence of Potentially Pathogenic Bacteria in Epilithic Biofilm Forming Bacteria isolated from Porter Brook River-stones, Sheffield, UK

“…However, investigation of the occurrence of the Shigella spp. in water and riverbed sediments samples retrieved from the Apies River, South Africa suggest the need to investigate the genetic relatedness of Shigella spp in water and riverbed sediments at the genetic level ( Ekwanzala et al, 2017 ). In the Apies River samples, Shigella sonnei , Shigella dysenteriae, Shigella boydii and Shigella flexneri were found more abundant in both water and sediments, suggesting that these species could have a common origin (99% genetic relatedness) and the bacteria could possibly be moved between the water column and the sediments.…”

“…Shigella spp. are commonly found in water polluted with human excreta, indicating the human faecal contamination ( Ekwanzala et al, 2017 ). The isolation of Shigella sonnei MBB13 here might suggest the possible movement of these species and other isolated bacteria through the water column and the potential interaction with and resuspend from epilithic biofilms.…”

Biological HRPs in wastewater

“…Shigella dysenteriae has also been detected in 35 sewage samples collected from hospital and residential areas (Peng et al, 2002). Furthermore, Shigella dysenteriae was isolated from water and riverbed sediment of the Apies River, South Africa (Ekwanzala et al, 2017)…”