Duncan Ongeng

Survival of Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium in manure and manure‐amended soil under tropical climatic conditions in Sub‐Saharan Africa

Aims:  To establish the fate of Escherichia coli O157:H7 and Salmonella Typhimurium in manure and manure‐amended agricultural soils under tropical conditions in Sub‐Saharan Africa.

Fate of Escherichia coli O157:H7 and Salmonella enterica in the manure-amended soil-plant ecosystem of fresh vegetable crops: A review

Abstract Enterohemorrhagic Escherichia coli (EHEC) and Salmonella enterica have been implicated in several disease outbreaks linked to consumption of fresh vegetables. Both ruminant and non-ruminant animals carry EHEC and S. enterica in their gastrointestinal tracts and can shed the pathogens in the faecal matter both in symptomatic and asymptomatic states. Application of animal waste in soil fertility management and irrigation of crops with contaminated waste water has been recognised as an important route through which EHEC and S. enterica can contaminate fresh vegetables during primary production. The behavior of E. coli O157:H7 and S. enterica in the agricultural environment has been extensively studied in the last decades. Several microbiological detection methods have been applied. This review therefore puts together current knowledge on the behavior of E. coli O157:H7 and S. enterica in the manure-amended soil-plant ecosystem of fresh vegetable crops during cultivation under various environmental conditions. The review focuses on methodological issues involved in undertaking survival studies and makes comparative analysis of experimental results obtained from studies conducted under controlled environmental conditions integrating results obtained from field experiments. Finally, a theoretical discussion on the potential likely impact of climate change on pre-harvest safety of field-cultivated vegetables is highlighted.

Transfer and internalisation of Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium in cabbage cultivated on contaminated manure-amended soil under tropical field conditions in Sub-Saharan Africa

Surface contamination and internalisation of Escherichia coli O157:H7 and Salmonella Typhimurium in cabbage leaf tissues at harvest (120 days post-transplantation) following amendment of contaminated bovine manure to soil at different times during crop cultivation were investigated under tropical field conditions in the Central Agro-Ecological Zone of Uganda. Fresh bovine manure inoculated with rifampicin-resistant derivatives of non-virulent strains of E. coli O157:H7 and S. Typhimurium was incorporated into the soil to achieve inoculum concentrations of 4 and 7 log CFU/g at the point of transplantation, 56 or 105 days post-transplantation of cabbage seedlings. Frequent sampling of the soil enabled the accurate identification of the survival kinetics in soil, which could be described by the Double Weibull model in all but one of the cases. The persistence of 4 log CFU/g E. coli O157:H7 and S. Typhimurium in the soil was limited, i.e. only inocula applied 105 days post-transplantation were still present at harvest. Moreover, no internalisation in cabbage leaf tissues was observed. In contrast, at the 7 log CFU/g inoculum level, E. coli O157:H7 and S. Typhimurium survived in the soil throughout the cultivation period. All plants (18/18) examined for leaf contamination were positive for E. coli O157:H7 at harvest irrespective of the time of manure application. A similar incidence of leaf contamination was found for S. Typhimurium. On the other hand, only plants (18/18) cultivated on soil amended with contaminated manure at the point of transplantation showed internalised E. coli O157:H7 and S. Typhimurium at harvest. These results demonstrate that under tropical field conditions, the risk of surface contamination and internalisation of E. coli O157:H7 and S. Typhimurium in cabbage leaf tissues at harvest depend on the inoculum concentration and the time of manure application. Moreover, the internalisation of E. coli O157:H7 and S. Typhimurium in cabbage leaf tissues at harvest seems to be limited to the worst case situation, i.e., when highly contaminated manure is introduced into the soil at the time of transplantation of cabbage seedlings.

Bacteriophage P22 to challenge Salmonella in foods

In this study we considered the influence of phage addition on the fate of Salmonella enterica serovar Typhimurium in different foods. Phage P22 was applied to the following: liquid eggs, energy drinks, whole and skimmed milk, apple juice, chicken breast and chicken mince all spiked with its host, whose growth was monitored for 24 and 48 h at 4 °C. Appreciable host inactivation, generally in the order of 2 log cycles, was achieved compared to phage-free controls in all food matrices when 10(4) UFC/g host inoculum was used. Furthermore, wild food strains belonging to the serotypes Typhimurium, Enteritidis, Derby Give, Newport, Muenchen and Muenster were assayed towards phage P22. Only isolates of Salmonella Typhimurium as well as Salmonella Derby and Salmonella Enteritidis was inhibited by the presence of P22 phage. Additional challenge experiments were carried out by spiking liquid-eggs, chicken breast and chicken mince with mixes of wild Salmonella Typhimurium (at concentration of about 10(4) UFC/g) strains along with their relative phage P22. The results showed a reduction of 2-3 log cycles after 48 h at 4 °C depending on both mix of strains and the specific food. Overall, the results indicate that phages may be useful in the control of food-borne pathogens. The food matrices considered, the liquid more than the solid, do not seem to affect the phage ability of infection compared to similar tests performed in vitro.

Rhizosphere effect on survival of Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium in manure-amended soil during cabbage (Brassica oleracea) cultivation under tropical field conditions in Sub-Saharan Africa.

The effect of cabbage (Brassica oleracea) rhizosphere on survival of Escherichia coli O157:H7 and Salmonella Typhimurium in manure-amended soils under tropical field conditions was investigated in the Central Agro-Ecological Zone of Uganda. Three-week old cabbage seedlings were transplanted and cultivated for 120 days on manure-amended soil inoculated with 4 or 7 log CFU/g non-virulent E. coli O157:H7 and S. Typhimurium. Cabbage rhizosphere did not affect survival of the 4log CFU/g inocula in manure-amended soil and the two enteric bacteria were not detected on/in cabbage leaves at harvest. The 7 log CFU/g E. coli O157:H7 and S. Typhimurium survived in bulk soil for a maximum of 80 and 96 days, respectively, but the organisms remained culturable in cabbage rhizosphere up to the time of harvest. At 7 log CFU/g inoculum, E. coli O157:H7 and S. Typhimurium contamination on cabbage leaves occurred throughout the cultivation period. Leaf surface sterilisation with 1% AgNO(3) indicated that the organisms were present superficially and in protected locations on the leaves. These results demonstrate that under tropical field conditions, cabbage rhizosphere enhances the persistence of E. coli O157:H7 and S. Typhimurium in manure-amended soil at high inoculum density and is associated with long-term contamination of the leaves.

Performance perceptions among food supply chain members

– A good supply chain relationship quality (RQ) is a crucial precursor for any stable exchange relationship which ensures relationship continuity. Although empirical research suggests that strengthening RQ improves supply chain performance (SCP), most studies have focused on dyadic business relationships. To fully understand the relational behaviour of a firm embedded in a supply chain, we need to look beyond the dyad into triads. The purpose of this paper is to investigate how SCP is influenced by RQ in a triadic agribusiness supply chain. , – Evidence is drawn from a quantitative survey of 150 agribusiness firms in the maize supply chain in Uganda. Data were collected in triadic context from 50 direct supply chains each composing of a supplier, focal firm and customer. Multi-group structural equations modelling (SEM) was used to assess the differences in perception on the influence of RQ on SCP amongst the supply chain members. , – Results provides empirical support for the positive influence of RQ on SCP. SEM reveals differences in perception between the upstream and downstream and amongst the supply chains members. While focal firms considered conflict, coercive power, commitment and trust to be important; suppliers considered trust, dependency and non-coercive power; and customers considered trust, dependency and coercive power to be important RQ factors affecting SCP. , – For agribusiness managers to enhance business performance there is need to cultivate strong and mutual relationship with supply chain members. It is also important to know how to handle conflicts and use of power so as to realise the benefits of supply chain relationships. , – The paper is novel in that it assesses SCP in a triadic context in an agribusiness sector from a developing country context. The authors used novel approaches including analysis of a triad, and multiple groups SEM to assess perceptions of each supply chain member’s.

Modeling the Fate of Escherichia coli O157:H7 and Salmonella enterica in the Agricultural Environment: Current Perspective

The significance of fresh vegetable consumption on human nutrition and health is well recognized. Human infections with Escherichia coli O157:H7 and Salmonella enterica linked to fresh vegetable consumption have become a serious public health problem inflicting a heavy economic burden. The use of contaminated livestock wastes such as manure and manure slurry in crop production is believed to be one of the principal routes of fresh vegetable contamination with E. coli O157:H7 and S. enterica at preharvest stage because both ruminant and nonruminant livestock are known carriers of E. coli O157:H7 and S. enterica in the environment. A number of challenge-testing studies have examined the fate of E. coli O157:H7 and S. enterica in the agricultural environment with the view of designing strategies for controlling vegetable contamination preharvest. In this review, we examined the mathematical modeling approaches that have been used to study the behavior of E. coli O157:H7 and S. enterica in the manure, manure-amended soil, and in manure-amended soil-plant ecosystem during cultivation of fresh vegetable crops. We focused on how the models have been applied to fit survivor curves, predict survival, and assess the risk of vegetable contamination preharvest. The inadequacies of the current modeling approaches are discussed and suggestions for improvements to enhance the applicability of the models as decision tools to control E. coli O157:H7 and S. enterica contamination of fresh vegetables during primary production are presented.

Kinetic model-based prediction of the persistence of Salmonella enterica serovar Typhimurium under tropical agricultural field conditions.

Aim:  Present a kinetic model‐based approach for using isothermal data to predict the survival of manure‐borne enteric bacteria under dynamic conditions in an agricultural environment.

Stakeholders’ Perceptions of Agronomic Iodine Biofortification: A SWOT-AHP Analysis in Northern Uganda

Agronomic biofortification (i.e., the application of fertilizer to elevate micronutrient concentrations in staple crops) is a recent strategy recommended for controlling Iodine Deficiency Disorders (IDDs). However, its success inevitably depends on stakeholders’ appreciation and acceptance of it. By taking Northern Uganda as a case, this study aimed to capture and compare the perceptions of seven key stakeholder groups with respect to agronomic iodine biofortification. Therefore, we employed a SWOT (Strength, Weaknesses, Opportunities & Threats) analysis in combination with an Analytical Hierarchy Process (AHP). Findings show that stakeholders (n = 56) are generally positive about agronomic iodine biofortification in Uganda, as its strengths and opportunities outweighed weaknesses and threats. Cultural acceptance and effectiveness are considered the most important strengths while the high IDD prevalence rate and the availability of iodine deficient soils are key opportunities for further developing agronomic iodine biofortification. Environmental concerns about synthetic fertilizers as well as the time needed to supply iodine were considered crucial weaknesses. The limited use of fertilizer in Uganda was the main threat. While this study provides insight into important issues and priorities for iodine biofortification technology in Uganda, including differences in stakeholder views, the application of the SWOT-AHP method will guide future researchers and health planners conducting stakeholder analysis in similar domains.

The effect of traditional malting technology practiced by an ethnic community in northern Uganda on in-vitro nutrient bioavailability and consumer sensory preference for locally formulated complementary food formulae

Abstract The occurrence of anti‐nutritional constituents in plants is an important factor that negatively affects bioavailability of nutrients and effectiveness of plant‐based foods in complementary feeding in rural areas in developing countries. However, proven methods that improve bioavailability of nutrients and tailored for application in processing complementary foods among rural communities are largely lacking. This study examined the efficacy of a traditional malting technology practiced by the Acholi ethnic community of northern Uganda to improve protein digestibility and bioavailability of iron and zinc from millet–sesame–soy composite containing 200, 300, and 550 kcal meant for complementary feeding of children aged 6–8, 9–12, and 13–23 years old, respectively. The technology involves washing and soaking of ingredients for 12 hr; malting ingredients individually for 48 hr with water changed after every 6 hr; and sun‐drying malted ingredients for 72 hr. Results showed that the level of anti‐nutritional factors significantly reduced (p ≤ 0.05) in all the composite formulae except the content of total phenolics in 200, tannins in 300 and 550 kcal, composite formula, respectively. In vitro protein digestibility significantly improved (p ≤ 0.05) in all the composite formulae except in the 200 kcal formula. Iron bioavailability significantly increased (p ≤ 0.05) in all the composite formulae except in the 550 kcal energy category. Improvement in zinc bioavailability was only observed in the 300 kcal formula. However, there were significant reductions (p ≤ 0.05) in the level of caregiver preferences for sensory properties and overall acceptability of the composites. These results demonstrate that the traditional malting technology has potential to improve nutrient bioavailability in plant‐based foods but requires improvement in order to increase its efficacy and mitigate negative effects on sensory appeal.