SOUTH AFRICA – Bacterial pathogens and multidrug-resistant organisms are threatening food safety in South Africa’s fresh produce sector, according to recent research led by scientists at the University of Pretoria and the Water Research Commission.
The team has found high levels of Escherichia coli and multidrug-resistant bacteria in surface water sources used to irrigate crops, posing potential health risks for consumers.
The researchers have spent two decades analyzing water quality in South Africa, developing new methods to determine whether water used before and after harvest is safe for produce irrigation.
Their findings indicate that pathogens such as E. coli and Salmonella can transfer from irrigation water to vegetables, especially when consumed raw or inadequately washed.
Multidrug-resistant bacteria in irrigation water
The team, currently led by Dr. Lise Korsten and Dr. Loandi Richter-Mouton from the University of Pretoria, and Dr. Eunice Ubomba-Jaswa and Dr. Samkelisiwe Hlophe-Ginindza from the Water Research Commission, has tracked multidrug-resistant bacteria in South African water systems.
Their studies have shown that irrigation water on smallholder farms transfers Salmonella and E. coli to both soil and produce. Investigations into spinach production revealed multidrug-resistant bacteria were present throughout supply chains, including at commercial farms.
At retail level, research has shown unsafe practices, such as vendors placing spinach in dirty water to keep it fresh, which exposes consumers to bacterial pathogens with expanded antimicrobial resistance profiles.
Gaps in water quality guidelines
Current South African water quality guidelines focus mainly on indicator organisms such as E. coli linked to fecal contamination, but do not account for multidrug-resistant bacteria or emerging pathogens.
The researchers say this gap leaves the food system vulnerable to hidden health hazards.
The team has also found that rooftop-harvested rainwater, though widely used in water-scarce rural areas, can harbor E. coli and Enterococcus.
Without regular cleaning, storage tanks accumulate biofilms that provide an environment for microbial survival and growth, raising concerns for households using this water on homegrown vegetables.
Call for new standards and surveillance
The researchers are calling for collaboration among farmers, academics, and government to develop new water quality standards tailored to local contamination risks, reports The Conversation.
Continuous surveillance and real-time data are needed, particularly in areas with poor water quality, to detect contamination early and protect consumers.
They emphasize that South Africa requires a comprehensive food safety policy, alongside greater participation in continental frameworks to align regulation and control measures across Africa.
The team is currently tracking antibiotic resistance in rivers to inform practical interventions for safer irrigation and reduced antimicrobial resistance in food production.
They highlight that while water is essential for all stages of food production, its safety remains a critical, yet under-monitored, pillar of public health.