Prevalence and distribution of Listeria pathogens in the final effluents of a rural wastewater treatment facility in the Eastern Cape Province of South Africa

Abstract

We assessed the prevalence of free-living and plankton-associated Listeria species in the final effluents of a South African wastewater treatment facility and its receiving watershed between August 2007 and July 2008 as well as the antibiotic susceptibilities of effluent isolates. The physicochemical quality of the raw sewage and treated effluents was also determined. Free-living Listeria were more prevalent (96%), compared to plankton-associated Listeria species (58-67%). Listeria pathogens were sensitive to 11 (55%) of the 20 tested antibiotics, and showed varying (7-71%) levels of resistance to eight antibiotics. Turbidity, COD, NO 3 , PO 4 and Listeria density fell short of recommended standards after treatment; while pH, temperature, TDS, DO and NO 2 were compliant with target quality after treatment. We conclude that final effluents of wastewater treatment plants are potential sources of Listeria pathogens in the aquatic milieu of South Africa.

Municipal Wastewater Effluents as a Source of Listerial Pathogens in the Aquatic Milieu of the Eastern Cape Province of South Africa: A Concern of Public Health Importance

“…The observation could be as a result of higher nutrient levels in the wastewater effluents compared to the receiving watershed, in agreement with previous reports [10,11,38]. Consistent with the observation of this study, high prevalence of Listeria species has been reported in water systems impacted by wastewater effluents in Iraq [8,9], Poland [10] France [11], the United Kingdom [12] and rural South Africa [13]. Watkins and Sleath [12] reported 100% prevalence of Listeria species in sewage, river water, and trade effluent at densities (7.0 × 10 2 to >1.8 × 10 4 Most Probable Number (MPN)/mL), slightly higher than those observed in this study.…”

“…Based on this standard, the water quality across the studied water system and throughout the year (Table 2) fell short of acceptable target limits for domestic applications, thus disqualifying the waters for use in drinking and other domestic purposes. Listeria abundance did not vary significantly with season, either as free-living or plankton-associated species, consistent with the observation of Murrel et al [36], but contrary to our previous report [13]. The significant positive correlation observed between Listeria species attached to large (180 μm) planktons and those attached to small (20 μm) planktons suggests that the two groups of Listeria species may occupy the same niche in the ecosystem; this is contrary to our previous report [13], where Listeria species attached to large (180 μm) planktons negatively correlated with those attached to small (20 μm) planktons.…”

“…Listeria abundance did not vary significantly with season, either as free-living or plankton-associated species, consistent with the observation of Murrel et al [36], but contrary to our previous report [13]. The significant positive correlation observed between Listeria species attached to large (180 μm) planktons and those attached to small (20 μm) planktons suggests that the two groups of Listeria species may occupy the same niche in the ecosystem; this is contrary to our previous report [13], where Listeria species attached to large (180 μm) planktons negatively correlated with those attached to small (20 μm) planktons. The lack of significant correlations between and among other treatments in this study suggests that free-living Listeria species and Listeria species attached to medium-sized (60 μm) planktons occupy separate niches in the water system, different from those occupied by Listeria species attached to large (180 μm) and small (20 μm) planktons.…”

Water quality assessment: surface water sources used for drinking and irrigation in Zaria, Nigeria are a public health hazard

“…Such water sources are vulnerable to contamination with faecal pathogens, which pose serious public health risks linked to excessive nutrient levels and the presence of enteric pathogens in drinking and irrigation waters (Shuval 1990;Hitzfeld et al 2000;Pruss et al 2002). Nonpoint sources of such contamination include domestic and wild animal defecation, malfunctioning sewage and septic systems, stormwater drainage and urban runoff, while point sources include as industrial effluents and municipal wastewater treatment plants (Kistemann et al 2002;Albek 2003;Okoh et al 2007;Igbinosa and Okoh 2009;Odjadjare and Okoh 2010). Furthermore, rapid population growth, land development along river banks and in the catchment areas, urbanization and industrialization place increased demand on surface waters both as sources of water for different uses and as carriers of treated and untreated wastewaters (Suthar et al 2010;Solaraj et al 2010).…”

Inadequately Treated Wastewater as a Source of Human Enteric Viruses in the Environment

“…In particular the indicator bacteria survival in water does not correlate with that of enteric viruses [56]. Our recent studies [57][58][59] have shown that the wastewater treatment facilities in the Eastern Cape Province of South Africa are a veritable source of pathogens in aquatic environments of this study area and negatively impact physico-chemical quality of receiving watershed [60], therefore it is highly probable that they might also be a source of enteric viruses in the aquatic environment.…”