From field to plate: How do bacterial enteric pathogens interact with ready-to-eat fruit and vegetables, causing disease outbreaks?

Natural borneol improves cellular uptake of curcumin to enhance its photodynamic bactericidal activity against Escherichia coli ATCC 8739

Photodynamic inactivation (PDI), a non-thermal sterilization method, has attracted considerable attention due to its broad-spectrum antimicrobial activity, environmental friendliness and cost-effectiveness. Curcumin (Cur), a food-grade photosensitizer, exhibits photodynamic antimicrobial activity based primarily on its efficiency in intracellular accumulation. However, Cur's low water solubility and the barriers presented by the outer membrane of Gram-negative bacteria challenge its ability to penetrate the cytoplasm. Natural borneol (NB), a monoterpene food flavoring agent, has also been shown to improve the efficiency of drug absorption. In this study, we demonstrated that NB significantly improved the cellular uptake of Cur, thereby enhancing its photodynamic bactericidal activity against Gram-negative Escherichia coli (E. coli) ATCC 8739, a potential alternative to enterohemorrhagic E. coli O157:H7. This effect was attributed to NB's ability to disrupt the integrity of the E. coli bacterial membrane, thereby increasing cellular permeability. Transcriptomic analysis further confirmed that NB dysregulated the expression of genes associated with bacterial membrane structure and function in E. coli. Consequently, the increased accumulation of Cur in E. coli led to excessive production of intracellular reactive oxygen species (ROS) upon exposure to 6.5 J/cm2 blue light (BL). These ROS, analyzed biochemically and transcriptionally, primarily disrupted bacterial membrane structure and function, the antioxidant system, and ultimately caused bacterial death. Remarkably, this combined strategy not only reduced E. coli contamination in the tested orange juice, but also preserved its nutritional quality. In conclusion, this research provides an innovative and effective approach to maintaining food safety.

Salmonella and Salmonellosis in Wild Birds

Salmonella enterica is an important bacterial pathogen in humans and warm-blooded animals. Wild bird species represent both a potential reservoir for zoonotic infection and as a susceptible host to infection by host-adapted variants. Historically, wild birds were considered to be a major source of Salmonella infection in livestock, but in recent years, it has been more apparent that birds are more likely to act as a reservoir for recycling infection on farms rather than as the primary source of infection. Birds may also transmit infection to humans directly from feces or indirectly through fecal contamination of foods, including peanut butter. While many bird species can be infected with Salmonella, the rates of infection are variable, and most cases lead to intestinal carriage rather than disease. In this case, fecal shedding of Salmonella bacteria from birds can represent a risk for transmission to humans. As such, care is needed when in contact with fecal material such as that found on bird tables or feeders. In recent years, there have been emergences of Salmonella Typhimurium genotypes associated with high mortality in songbirds or passerine birds, resulting in 'die offs' in Europe, Israel, New Zealand and the US. Additionally, S. typhimurium DT2 and other variant Copenhagen genotypes are associated with high mortality disease in pigeons. These genotypes show evidence of evolution towards adaptation to specific hosts, with pseudogenes leading to loss of functional metabolic pathways and specific virulence factors. These 'signatures of adaptation' are common in host-adapted Salmonella serovars and suggest these S. typhimurium isolates are evolving to adapt to specific avian hosts.

Carbapenemase-producing Klebsiella quasipneumoniae ST688 (NDM-1) and Klebsiella michiganensis ST40 (KPC-2) in food destined for hospitalized patients

OBJECTIVES

Klebsiella spp. are leading causes of nosocomial infections. Their ability to harbour antimicrobial resistance genes makes them an important public health threat. This study aimed to report the genomic background of carbapenemase-producing Klebsiella quasipneumoniae (HV55B) and Klebsiella michiganensis (HV55D) strains isolated from fresh vegetables destined for hospitalized inpatients.

METHODS

Microbiological and molecular methods were used to isolate and identify the strains, which were submitted to the antimicrobial susceptibility test and pH tolerance assays. Whole genome sequencing was performed on MiSeq and NextSeq platforms, and online available tools were applied to bioinformatic analysis of clinically relevant information.

RESULTS

Both isolates were considered multidrug-resistant and tolerated pH ≥ 4 for 24 h. HV55B belonged to sequence type (ST) ST668, and presented a broad resistome and plasmids from four incompatibility groups. HV55D belonged to ST40. Both strains HV55B and HV55D were genetically close to isolates responsible for human infections around the world, which stands for the plausibility of such bacteria to cause disease in patients of the studied institution.

CONCLUSIONS

Our results confirm the presence of carbapenemase-producing Klebsiella spp. in fresh foodstuffs intended for hospitalized inpatients' consumption. The genomes characterized here also provide clinically and genomically relevant information to forthcoming epidemiological surveillance studies.

Temperature-driven divergence in molecular distribution and microbial invasion and the associated texture softening during dual-phase fermentation of Paocai

Temperature is an important driving force that shapes the texture of fermented vegetables through driving the molecular distribution and microbial invasion between the liquid phase (brine) and the solid phase (vegetables) during fermentation. The objective of this study was to investigate the texture softening by investigating firmness, microstructure, physicochemical properties, molecular distribution and microbial community between brine and vegetables of Paocai as affected by fermentation temperatures of 10 °C, 20 °C and 30 °C. Results demonstrated that, compared with 10 °C and 30 °C, 20 °C attenuated softening of Paocai by restraining microbial invasion and suppressing pectinolysis. Moreover, at 20 °C, a balanced molecular distribution and microbial community were achieved between vegetables and brine, thus accomplishing acid-production fermentation. By contrast, 10 °C and 30 °C promoted nonfermentative microbial genera, retarding fermentation. This study provided an understanding of the divergent influence of temperature on quality formation of fermented vegetables during fermentation.

Impact of Various Washing Protocols on the Mitigation of Escherichia coli Contamination in Raw Salad Vegetables

Vegetables are an essential component of a balanced diet. The consumption of ready-to-eat foods may lead to the risk of infections and illnesses due to microbial contamination. To mitigate the potential of microbial contamination risks, it is critical to promote safe handling practices among consumers. In this study, our research evaluated the efficacy of different vegetable washing methods, specifically with lettuce, tomato, and cucumber, to establish optimal practices for reducing microbial contamination. This study consisted of two phases. Initially, a survey was distributed to 150 volunteers using snowball sampling to assess everyday vegetable handling and washing methods. The survey's results identified four predominant methods: washing with a 5% vinegar solution for 3 min followed by tap water rinse (37.3% of participants), rinsing with tap water for 1 min (29.3%), washing with a 5% salt solution (vegetable soap) for 3 min followed by a tap water rinse (16.6%), and a 3 min tap water rinse (14%). A minor segment (3.33%) reported not washing their vegetables at all. The survey's findings guided the second phase, which tested the aforementioned washing protocols' effectiveness in reducing Escherichia coli (E. coli) levels on spiked contaminated salad vegetables. The tested vegetables were sterilized using UV light, inoculated with 0.5 McFarland E. coli, and then washed using the four identified methods. After that, E. coli enumeration after washing was performed using 3M™ Petrifilm and the comparison was analyzed via one-way ANOVA. During this study, it was revealed that the cucumbers had the highest E. coli contamination levels in comparison to the lettuce and tomato after washing. Interestingly, by comparing the three washing methods, it was found that washing the vegetables with vinegar proved to be the most effective solution for reducing microbial presence on both lettuce and cucumbers. Notably, the natural smoothness of tomato skin led to no significant differences in contamination levels across washing methods. In summary, vinegar washing effectively reduces microbial contamination from salad vegetables, highlighting the need for informed consumer practices to prevent foodborne outbreaks. This study emphasizes the importance of monitoring contamination sources and using safe washing techniques.

Growth of Listeria monocytogenes in fresh vegetables and vegetable salad products: An update on influencing intrinsic and extrinsic factors

The ability of foodborne pathogens to grow in food products increases the associated food safety risks. Listeria monocytogenes (Lm) is a highly adaptable pathogen that can survive and grow under a wide range of environmental circumstances, including otherwise inhibitory conditions, such as restrictive cold temperatures. It can also survive long periods under adverse environmental conditions. This review examines the experimental evidence available for the survival and growth of Lm on fresh vegetables and ready-to-eat vegetable salads. Published data indicate that, depending on certain intrinsic (e.g., nutrient composition) and extrinsic factors (e.g., storage temperature, packaging atmosphere), Lm can survive on and in a wide variety of vegetables and fresh-cut minimally processed vegetable salads. Studies have shown that temperature, modified atmosphere packaging, relative humidity, pH, water activity, background microbiota of vegetables, microbial strain peculiarities, and nutrient type and availability can significantly impact the fate of Lm in vegetables and vegetable salads. The influence of these factors can either promote its growth or decline. For example, some studies have shown that background microbiota inhibit the growth of Lm in vegetables and minimally processed vegetable salads, but others have reported a promoting, neutral, or insignificant effect on the growth of Lm. A review of relevant literature also indicated that the impact of most influencing factors is related to or interacts with other intrinsic or extrinsic factors. This literature synthesis contributes to the body of knowledge on possible strategies for improving food safety measures to minimize the risk of Lm-associated foodborne outbreaks involving vegetables and vegetable salads.

Genome characterization of a multi-drug resistant Escherichia coli strain, L1PEag1, isolated from commercial cape gooseberry fruits (Physalis peruviana L.)

Introduction

Foodborne infections, which are frequently linked to bacterial contamination, are a serious concern to public health on a global scale. Whether agricultural farming practices help spread genes linked to antibiotic resistance in bacteria associated with humans or animals is a controversial question.

Methods

This study applied a long-read Oxford Nanopore MinION-based sequencing to obtain the complete genome sequence of a multi-drug resistant Escherichia coli strain (L1PEag1), isolated from commercial cape gooseberry fruits (Physalis peruviana L.) in Ecuador. Using different genome analysis tools, the serotype, Multi Locus Sequence Typing (MLST), virulence genes, and antimicrobial resistance (AMR) genes of the L1PEag1 isolate were determined. Additionally, in vitro assays were performed to demonstrate functional genes.

Results

The complete genome sequence of the L1PEag1 isolate was assembled into a circular chromosome of 4825.722 Kbp and one plasmid of 3.561 Kbp. The L1PEag1 isolate belongs to the B2 phylogroup, sequence type ST1170, and O1:H4 serotype based on in silico genome analysis. The genome contains 4,473 genes, 88 tRNA, 8 5S rRNA, 7 16S rRNA, and 7 23S rRNA. The average GC content is 50.58%. The specific annotation consisted of 4,439 and 3,723 genes annotated with KEEG and COG respectively, 3 intact prophage regions, 23 genomic islands (GIs), and 4 insertion sequences (ISs) of the ISAs1 and IS630 families. The L1PEag1 isolate carries 25 virulence genes, and 4 perfect and 51 strict antibiotic resistant gene (ARG) regions based on VirulenceFinder and RGI annotation. Besides, the in vitro antibiotic profile indicated resistance to kanamycin (K30), azithromycin (AZM15), clindamycin (DA2), novobiocin (NV30), amikacin (AMK30), and other antibiotics. The L1PEag1 isolate was predicted as a human pathogen, matching 464 protein families (0.934 likelihood).

Conclusion

Our work emphasizes the necessity of monitoring environmental antibiotic resistance, particularly in commercial settings to contribute to develop early mitigation techniques for dealing with resistance diffusion.

Bacterial community structure of Physalis peruviana L. fruit exocarp and the presence of pathogens with possible implications on food safety

Introduction

Cape gooseberry (Physalis peruviana L.) is a wellconsumed crop in Ecuador, whose fruits are abundant in bioactive molecules. Its rapid post-harvest deterioration and safety limit its market potential.

Methodology

To gather baseline data on the prevalence of bacterial taxa among groups, we employed 16S ribosomal RNA (16S rRNA) amplicon gene sequencing to detect changes in the bacterial community structure in cape gooseberry fruits harvested from an organic farm production system (# 270 samples x two ripeness stages), and fruits obtained from an open-air market (#270).

Results

This is the first report of bacterial taxa inhabiting cape gooseberry fruits. Shannon's diversity index revealed that the fruits purchased from the market and the unripe stage had the highest level of bacterial diversity (average Shannon indices of 3.3 and 3.1) followed by those collected from the field at the mature ripe stage (2.07). Alpha diversity analysis indicated that there were no significant differences in the number of taxa or evenness within the sample, whereas there was a significant difference in beta diversity between the groups. Rhizobiaceae was the most abundant family in fruits originating from the field regardless of the ripe stage, while Acetobacteraceae, Pseudomonadaceae, Fusobacteriaceae, Bacteroidaceae, and Erwiniaceae were the most abundant families in the market group. At the genus level, Liberibacter was the most abundant phytopathogen in fruits originating from the field, while Gluconobacter was the most abundant in samples collected from the market. The phytopathogen Candidatus_Liberibacter was the most abundant in samples collected from the field, while the fruits purchased from the market stands contained opportunistic enteric pathogens such as Escherichia vulneris, Klebsiella pneumoniae, and K. variicola, their relative abundance varied with the sample. In addition, potential pathogens of animal origin such as Fusobacterium necrophorum, Porphyromonas levii, Helcococcus ovis, and Trueperella pyogenes were found in almost all samples at varying relative abundance.

Conclusion

Our study provides basic information on the microbiome of cape gooseberries from agriculture fields to the table along with the detection of several pathogenic microorganisms with possible impact on food safety and public health therefore, strategies for reducing bacterial contamination in both farm and retail markets are compulsory.

Prevalence, serotype, antimicrobial susceptibility, contamination factors, and control methods of Salmonella spp. in retail fresh fruits and vegetables: A systematic review and meta-analysis

This research presents a comprehensive review of Salmonella presence in retail fresh fruits and vegetables from 2010 to 2023, utilizing data from recognized sources such as PubMed, Scopus, and Web of Science. The study incorporates a meta-analysis of prevalence, serovar distribution, antimicrobial susceptibility, and antimicrobial resistance genes (ARGs). Additionally, it scrutinizes the heterogeneous sources across various food categories and geographical regions The findings show a pooled prevalence of 2.90% (95% CI: 0.0180-0.0430), with an increase from 4.63% in 2010 to 5.32% in 2022. Dominant serovars include S. Typhimurium (29.14%, 95% CI: 0.0202-0.6571) and S. Enteritidis (21.06%, 95% CI: 0.0181-0.4872). High resistance rates were noted for antimicrobials like erythromycin (60.70%, 95% CI: 0.0000-1.0000) and amoxicillin (39.92%, 95% CI: 0.0589-0.8020). The most prevalent ARGs were blaTEM (80.23%, 95% CI: 0.5736-0.9692) and parC mutation (66.67%, 95% CI: 0.3213-0.9429). Factors such as pH, water activity, and nutrient content, along with external factors like the quality of irrigation water and prevailing climatic conditions, have significant implications on Salmonella contamination. Nonthermal sterilization technologies, encompassing chlorine dioxide, ozone, and ultraviolet light, are emphasized as efficacious measures to control Salmonella. This review stresses the imperative need to bolster prevention strategies and control measures against Salmonella in retail fresh fruits and vegetables to alleviate related food safety risks.

Hyaluronic acid-based multifunctional bio-active coating integrated with cinnamaldehyde/hydroxypropyl-β-cyclodextrin inclusion complex for fruit preservation

Natural preservatives such as cinnamaldehyde (CIN) are garnering increasing interest to replace their synthetic counterparts in maintaining fruit freshness and safety. However, their long-term effectiveness and widespread application have been greatly limited due to high volatility and potent aroma. To address these challenges, we developed a viable and simple strategy to prepare a multifunctional active coating for fruit preservation by incorporating host-guest inclusion complex of CIN and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) CIN@HP-β-CD into hyaluronic acid (HA), a natural polysaccharide with exceptional film-forming properties. The as-prepared HA/CIN@HP-β-CD coatings exhibited universal surface affinity, excellent antimicrobial performance, and satisfactory antioxidant properties with no potential toxicity. Release kinetic studies have demonstrated that CIN in the coating is continuously and slowly released. Furthermore, freshness preservation experiments on bananas and fresh-cut apples demonstrated that the developed coating is effective in preserving the color of fruit, decreasing the weight loss rate, preventing the microorganism's growth, and significantly extending the period of freshness, exhibiting the potential for application in fruit preservation.

Chemical Composition of Turmeric (Curcuma longa L.) Ethanol Extract and Its Antimicrobial Activities and Free Radical Scavenging Capacities

Turmeric (Curcuma longa L.) is a perennial tuberous plant from the genus Curcuma (Zingiberaceae) and has been widely used in foods for thousands of years. The present study examined the ethanol extract of turmeric for its chemical composition, antimicrobial activity, and free radical scavenging properties. UHPLC-MS/MS analysis tentatively identified eight compounds in the turmeric extract. Potential antimicrobial effects of 0.1, 1.0, and 10 mg turmeric equivalents (TE)/mL were evaluated in vitro against a variety of Gram-negative bacteria (i.e., Escherichia coli, Klebsiella pneumoniae, and Pseudomonas sp.) and Gram-positive bacteria (i.e., Enterococcus faecalis, Listeria innocua, and Staphylococcus aureus). Concentrations of 0.1 and 1.0 mg TE/mL inhibited the growth of S. aureus and significantly suppressed that of Pseudomonas sp., E. faecalis, and L. innocua. The growth of all strains, including E. coli, was inhibited by 10 mg TE/mL. Moreover, free radical scavenging capacities were determined using HO●, ABTS●+, and DPPH● (HOSC, ABTS, and RDSC, respectively) radicals. The turmeric ethanol extract had a TPC value of 27.12 mg GAE/g, together with HOSC, RDSC, and ABTS values of 1524.59, 56.38, and 1.70 μmol TE/g, respectively. Our results suggest that turmeric extract has potential applications for use in functional foods to reduce microbial burdens and oxidative stress-related health problems.

Bioinspired Superhydrophobic Nanocoating Based on Polydopamine and Nanodiamonds to Mitigate Bacterial Attachment to Polyvinyl Chloride Surfaces in Food Industry Environments

Polyvinyl chloride (PVC) is commonly utilized as a food-contact surface by the food industry for processing and storage purposes due to its durability, ease of fabrication, and cost-effectiveness. Herein, we report a composite coating for the superhydrophobization of PVC without the use of polyfluoroalkyl chemistry. This coating rendered the PVC superhydrophobic, exhibiting a static water contact angle of 151.9 ± 0.7° and a contact angle hysteresis of only 3.1 ± 1.0°. The structure of this composite coating, consisting of polydopamine, nanodiamonds, and an alkyl silane, was investigated by utilizing both scanning electron microscopy and atomic force microscopy. Surface chemistry was probed using attenuated total reflectance-Fourier transform infrared, and the surface wetting behavior was thoroughly characterized using both static and dynamic water contact angle measurements. It was demonstrated that the superhydrophobic PVC was cleanable using a food-grade surfactant, becoming wet in contact with high concentration surfactant solutions, but regaining its nonwetting property upon rinsing with water. It was demonstrated that the coating produced a 2.1 ± 0.1 log10 reduction (99.2%) in the number of Escherichia coli O157:H7 cells and a 2.2 ± 0.1 log10 reduction (99.3%) in the number of Salmonella enterica Typhimurium cells that were able to adsorb onto PVC surfaces over a 24 h period. The use of this fluorine-free superhydrophobic coating on PVC equipment, such as conveyor belts within food production facilities, may help to mitigate bacterial cross-contamination and curb the spread of foodborne illnesses.

Microbial and heavy metal contamination in herbal medicine: a prospective study in the central region of Saudi Arabia

INTRODUCTION

Herbal medicine is a medical system based on the utilization of plants or plant extracts for therapy. The continual increase in global consumption and the trade of herbal medicine has raised safety concerns in many regions. These concerns are mainly linked to microbial contamination, which could spread infections with multi-resistant bacteria in the community, and heavy metal contamination that may lead to cancers or internal organs' toxicity.

METHODS

This study was performed using an experimental design. A total of 47 samples, herbal medicine products sold in local stores in Qassim region, were used in the experiments. They were tested for bacterial contamination, alongside 32 samples for heavy metal analysis. Bacterial contamination was determined by the streak plate method and further processed to determine their antimicrobial susceptibility patterns using MicroScan WalkAway96 pulse; heavy metals were determined using a spectrometer instrument.

RESULTS

A total of 58 microorganisms were isolated. All samples were found to be contaminated with at least one organism except three samples. The majority of the isolated bacterial species were gram negative bacteria, such as Klebsiella spp., Pseudomonas spp. and E. coli., which could be of fecal origin and may lead to pneumonia, skin, or internal infections. Furthermore, most of the gram-positive bacteria were found to be multi-drug resistant. Moreover, for heavy metals, all samples had levels exceeding the regulatory limits.

CONCLUSION

This study demonstrated the presence of bacteria and heavy metals in samples of herbal medicines. Using these contaminated products may spread resistant infections, metal toxicities, or even cancers in the community.

Evaluation of the Novel mTA10 Selective Broth, MSB, for the Co-Enrichment and Detection of Salmonella spp., Escherichia coli O157 and Listeria monocytogenes in Ready-to-Eat Salad Samples

Multiplex assays implementing DNA-based methods have been demonstrated as suitable alternatives to culture-based microbiological methods; however, in most cases, they still require a suitable enrichment step. Finding suitable enrichment conditions for different bacteria may result in challenges. In the present study, a novel selective broth named MSB (mTA10 selective broth) was formulated for the simultaneous recovery of Salmonella spp., E. coli O157:H7 and L. monocytogenes. Attention was paid to ensure the optimal enrichment of L. monocytogenes as its enrichment is more challenging. To this end, cellobiose was added to increase the growth of L. monocytogenes, and sodium pyruvate was also added to improve the recovery of stressed bacteria. Four selective agents were added, namely nalidixic acid, sodium cholate, lithium chloride and potassium tellurite, to control the growth of interfering microorganisms. It was concluded that the novel broth was suitable for the simultaneous enrichment of the target pathogens, allowing them to reach concentrations higher than 7 log CFU/mL for each bacterium in pure culture. Furthermore, all heavily contaminated ready-to-eat salad samples reached concentrations higher than 5 log CFU/g. Finally, after 24 h of enrichment of spiked salad, it was possible to detect concentrations below 10 CFU/25 g.