Pathogenic Escherichia coli: An Overview on Pre-Harvest Factors that Impact the Microbial Safety of Leafy Greens

Consumption of fresh leafy greens has been repeatedly reported and linked to pathogenic Escherichia coli-associated foodborne illnesses outbreaks. Leafy greens are mostly eaten raw, based on the increased consumers’ preferences for natural, nutritious diets. Recent studies indicate the incidence of infections caused by pathogenic Escherichia coli remained almost unchanged or even increased. In this context, fresh produces increased the awareness about their primary contamination level, namely the pre-harvest phase. Fully eliminating pathogenic Escherichia coli from pre-harvest environment proved to be impossible. Emphasis must be placed on the pre-harvest factors that affect the food safety and, subsequently, on the identification of possible mitigation strategies that can be used on-farm for reducing the risk of leafy greens contamination with pathogenic Escherichia coli.

Plant Bioactive Compounds as an Intrinsic and Sustainable Tool to Enhance the Microbial Safety of Crops

Outbreaks of produce-associated foodborne illness continue to pose a threat to human health worldwide. New approaches are necessary to improve produce safety. Plant innate immunity has potential as a host-based strategy for the deactivation of enteric pathogens. In response to various biotic and abiotic threats, plants mount defense responses that are governed by signaling pathways. Once activated, these result in the release of reactive oxygen and nitrogen species in addition to secondary metabolites that aim at tempering microbial infection and pest attack. These phytochemicals have been investigated as alternatives to chemical sanitization, as many are effective antimicrobial compounds in vitro. Their antagonistic activity toward enteric pathogens may also provide an intrinsic hurdle to their viability and multiplication in planta. Plants can detect and mount basal defenses against enteric pathogens. Evidence supports the role of plant bioactive compounds in the physiology of Salmonella enterica, Escherichia coli, and Listeria monocytogenes as well as their fitness on plants. Here, we review the current state of knowledge of the effect of phytochemicals on enteric pathogens and their colonization of plants. Further understanding of the interplay between foodborne pathogens and the chemical environment on/in host plants may have lasting impacts on crop management for enhanced microbial safety through translational applications in plant breeding, editing technologies, and defense priming.

Gram stain and addition of amphotericin B to improve the microbial safety of human donor corneas

To determine the effectiveness of two methods to improve the microbial safety of human corneas preserved in organ culture. We compared the number of positive preservation solutions of corneas in organ culture in which the initial short-term hypothermic corneal maintenance solution was supplemented with amphotericin B 2.5 µg/mL and the historical data of microbial test results (2015–2019). In addition, we appraised the efficacy of Gram stain to detect bacterial or fungal contamination in the organ culture solutions of corneas from at-risk donors compared to the culture tests of corneas from not-at-risk donors. Statistical analysis was performed using STATA and statistical significance set at p < 0.05. The number of positive culture tests after preservation was 15 (0.5%) in 2020 compared to a mean of 37 (1.2%) in the period 2015–2019 (p < 0.01), with 10 (1.0%) positive samples in the cohort of 998 corneas from at-risk donors and 5 (0.2%) in the 2046 corneas from not-at-risk donors (p < 0.01). All corneas from at-risk donors tested positive at Gram stain and the results were available 1–3 days before those of the conventional culture tests. Amphotericin B supplementation in the short-term maintenance solution markedly reduced the number of positive microbial tests after organ culture and the early detection of contaminants, including slow-growing microorganisms, by Gram stain before the standard culture results. This meant fewer corneas being discarded and a greater likelihood of preventing post-graft infections.

Effect of Packaging on the Stability of Stored Dry Silver Cyprinid (Rastrineobola argentea)

Dried silver cyprinid (Rastrineobola argentea) has the potential to provide an affordable and accessible food-based strategy to fight malnutrition among Ugandans and enrich diets of the vulnerable persons. However, there is inadequate information on changes in the nutritional content and safety of stored dry silver cyprinid along the local handling chain. This study evaluated the effect of conventionally used packaging on microbial safety and nutrient quality of dry silver cyprinid during storage. Freshly dried silver cyprinid was obtained from stores at four landing sites on Lake Victoria and stored in open and closed gunny bags for 8 weeks. Samples were collected at 0, 1, 2, 4, 6 and 8 weeks of storage and assessed for nutritional and microbial quality. The type of packaging used (open or closed gunny bags) had no significant effect on most nutrient content and microbial safety parameters (p >0.05) except iron content, aflatoxin content, and TVBN content. Open gunny bags had higher aflatoxin content, greater iron degradation and greater variation in TVBN as compared to closed gunny bags throughout the storage duration. The observed difference in some of the quality parameters can be attributed to increased permeability to oxygen and moisture in open gunny bags as compared to closed gunny bags.

Microbial Safety of Milk from Vending Machines in the Informal Settlements of Nairobi, Kenya

The microbial quality of milk is an important parameter in determining its safety. Processes such as pasteurization are meant to ensure milk is safe for consumption; however, postpasteurization activities could lead to milk contamination, hence threatening the health of consumers. This study sought to determine the microbial safety of milk obtained from vending machines that were located in Nairobi’s informal settlements of Kibra and Dagoretti North. 37 milk samples were collected both from the storage tanks and vending machines located in the study area using a cross-sectional design and tested for microbial safety. Data were then recorded in datasheets and analyzed using frequencies and t-test with the aid of Statistical Package for Social Sciences software. Milk samples tested had acceptable levels of pH with a mean of 6.75; however, the pH of samples from the vending machines was lower than that of samples from the storage tanks. Milk samples from the vending machines had high levels of total viable count (Log 4.7028 cfu/mL) with 81% of the samples having counts beyond the acceptable standard. High levels of Staphylococcus aureus (Log 2.5485 cfu/mL) were also detected in 51% of the samples. Escherichia coli was detected in 27% of the milk samples from the vending machines, while Salmonella spp. was not detected. There was a significant increase in the number of total viable counts ( P ≤ 0.001 ), Staphylococcus aureus ( P ≤ 0.007 ), and Escherichia coli ( P ≤ 0.015 ) in milk samples from the vending machines compared to samples from the storage tanks. Study findings show that milk from the vending machines in the selected informal settlements of Nairobi is highly contaminated and can pose a health risk to consumers if taken without any further heat treatment. Milk vending machine handlers should be trained on practices that safeguard the quality and safety of milk. Public awareness should also be created on the general safety of milk from vending machines to protect consumers from potential health risks resulting from drinking contaminated milk.