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

Abstract

We evaluated the effluent quality of an urban wastewater treatment facility in South Africa and its impact on the receiving watershed for a period of 12 months. The prevalence and antimicrobial susceptibility of potential Listeria pathogens (L. ivanovii and L. innocua) and the physicochemical quality of the treated wastewater effluent was assessed, with a view to ascertain the potential health and environmental hazards of the discharged effluent. Total listerial density varied between 2.9 × 100 and 1.2 × 105 cfu/mL; free living Listeria species were more prevalent (84%), compared to Listeria species attached to planktons (59–75%). The treated effluent quality fell short of recommended standards for turbidity, dissolved oxygen, chemical oxygen demand, nitrite, phosphate and Listeria density; while pH, temperature, total dissolved solids and nitrate contents were compliant with target quality limits after treatment. The Listeria isolates (23) were sensitive to three (15%) of the 20 test antibiotics, and showed varying (4.5–91%) levels of resistance to 17 antibiotics. Of seven resistance gene markers assayed, only sulII genes were detected in five (22%) Listeria strains. The study demonstrates a potential negative impact of the wastewater effluent on the receiving environment and suggests a serious public health implication for those who depend on the receiving watershed for drinking and other purposes.

In VitroAntilisterial Properties of Crude Methanol Extracts ofGarcinia kola(Heckel) Seeds

“…The bacteria were previously isolated from wastewater effluents in the Eastern Cape Province of South Africa and belonged to three species groups which are L. ivanovii , L. grayi , and L. monocytogenes [20]. …”

Diversity of Listeria Species in Urban and Natural Environments

“…can be isolated from various different environments, including soil, vegetation, surface water, sewage, animal feeds, farm environments, and food-processing environments (58). Most studies on Listeria prevalence in the natural environment have focused on farm environments and associated croplands (8,16,30,35,43,45), and only limited data on Listeria prevalence in nonagricultural environments (usually urban and suburban environments) are available (28,29,40,47,48,71). A number of reports indicate a fairly high prevalence of Listeria spp.…”

In Vitro Anti-Listerial Activities of Crude n-Hexane and Aqueous Extracts of Garcinia kola (heckel) Seeds

“…The bacteria were previously isolated from wastewater effluents and belonged to three specie groups which are L. ivanovii , L. grayi and L. monocytogenes [20]. …”