Escherichia coli exposure pathways in some unplanned settlements in Lusaka District, Zambia: A case of food safety

Abstract

Poor sanitation has been characteristic of most peri-urban areas in Zambia resulting in environmental contamination with pathogens such as Escherichia coli consequently leading to high morbidity of enteric diseases. Foodborne E. coli transmission is recognized as being responsible for a major proportion of these infections. Low sanitation service coverage has downstream effects on food safety and hygiene giving rise to endemic diarrheal disease outbreaks. One of the major organisms used as an indicator of poor sanitation is E. coli and it is ubiquitous in nature resulting in a high chance of contracting it. The major pathways responsible for contamination have been identified to be food and water. Studies have been conducted in Accra Ghana indicating that waste water irrigation was a major exposure pathway for fresh crop produce to humans. A cross sectional study was conducted in 3 residential areas to determine Escherichia coli exposure pathways. The nine exposure pathways of Escherichia coli were identified in Chawama, Chazanga and George settlements in Lusaka District in a cross-sectional study that involved the collection of two hundred fifty (n=250) environmental samples and various foods. Environmental samples were analysed using the IDEXX kit. Further, behavioural survey data was collected from seven hundred eighty (n=780) participants to assess the relative exposure to E. coli contamination. Through laboratory analysis seventy-two (72) E. coli isolates were isolated and of these, twenty-four (24) were presumed invasive on MacConkey-Congo red media and ten (10) were Extended Spectrum Beta-Lactamases producing. Antibiotic susceptibility of isolated E. coli was carried out by disk diffusion method against the commonly used drugs in human and animal medicine. Sulfamethoxazole/Trimethoprim with E. coli isolates from seven (7) pathways being 100% resistant and Cefotaxime with E. coli isolates from five (5) pathways being 100% resistant showed the highest rate of resistance while Streptomycin showed the least resistance. The study highlighted the roles that the environment and behaviour play in human exposure to E. coli contamination and in turn poor food safety outcomes. Dominant pathways of exposure varied across residential areas and age groups, with dominant pathways for adults including fresh crop produce and drinking water, and dominant pathways for children including stormwater, drainage water, fresh crop produce and surface water. It was recommended that intensive sensitisation be conducted in these areas to highlight the identified exposure pathways.