Microbiological Parameters in the Primary Production of Berries: A Pilot Study

Foodborne Pathogen and Microbial Community Differences in Fresh Processing Tomatoes in Xinjiang, China

The microbes on fresh processing tomatoes correlate closely with diseases, preservation, and quality control. Investigation of the microbial communities on processing tomatoes from different production regions may help define microbial specificity, inform disease prevention methods, and improve quality. In this study, surface microbes on processing tomatoes from 10 samples in two primary production areas of southern and northern Xinjiang were investigated by sequencing fungal internal transcribed spacer and bacterial 16S rRNA hypervariable sequences. A total of 133 different fungal and bacterial taxonomies were obtained from processing tomatoes in the two regions, of which 63 genera were predominant. Bacterial and fungal communities differed significantly between southern and northern Xinjiang, and fungal diversity was higher in southern Xinjiang. Alternaria and Cladosporium on processing tomatoes in southern Xinjiang were associated with plant pathogenic risk. The plant pathogenic fungi of processing tomatoes in northern Xinjiang were more abundant in Alternaria and Fusarium. The abundance of Alternaria on processing tomatoes was higher in four regions of northern Xinjiang, indicating that there is a greater risk of plant pathogenicity in these areas. Processing tomatoes in northern and southern Xinjiang contained bacterial genera identified as gut microbes, such as Pantoea, Erwinia, Enterobacter, Enterococcus, and Serratia, indicating the potential risk of contamination of processing tomatoes with foodborne pathogens. This study highlighted the microbial specificity of processing tomatoes in two tomato production regions, providing a basis for further investigation and screening for foodborne pathogenic microorganisms.

Human Norovirus Surrogate Is Highly Stable in Berry Smoothies and under In Vitro Simulated Digestion

Human noroviruses are major causes of foodborne outbreaks linked to berries. The overall goal of this study was to investigate the persistence of a human norovirus surrogate, Tulane virus (TV), in berry smoothies and under simulated digestion through the gastrointestinal track. Two types of smoothies were prepared from blueberries and strawberries. Tulane virus was spiked into each smoothie and incubated either at 37 or 4 °C for 2, 60, and 120 min. Furthermore, the virus-spiked smoothies were subjected to sequential oral (2 min), gastric (10 and 60 min), and intestinal (15 and 120 min) digestion according to the standardized INFOGEST model. Quantification of infectious TV was carried out using the TCID50 assay. At 4 °C, in both berry smoothies, TV infectivity did not show significant changes throughout the 120 min period. At 37 °C, TV infectivity showed significant reduction (~0.5 log TCID50/mL) only in blueberry smoothies starting at 60 min. During the oral, gastric, and intestinal digestion phases, the mean log reduction in TV infectivity in blueberry did not exceed ~0.5 log, while infectious TV in strawberry smoothies under all phases was stable. Given the notable stability of infectious viruses in berry smoothies and the gastrointestinal tract, prevention of norovirus contamination of berries is paramount to reduce virus outbreaks linked to berries.

Meta-analysis of the prevalence of norovirus and hepatitis a virus in berries

Norovirus (NoV) and hepatitis A virus (HAV) stand as the predominant agents associated with viral foodborne infections. Outbreaks have been documented to be caused by various types of food items, including fresh and/or frozen berries. Comprehensive data concerning crucial viral pathogens in berries remain limited and are not currently available in aggregate form. Consequently, the present study aimed to compile the existing information regarding the prevalence of NoV and HAV in this matrix. Records of foodborne viruses were systematically extracted from database repositories up to December 2022, adhering to PRISMA standards and were subjected to a multilevel random effect meta-analysis model to determine the mean occurrence rate of NoV and HAV. A high heterogeneity across studies was observed (I2 = 82 %), reflecting variations in the prevalence of sampling locations, years, berry types, and sample conditions, among other potential contributing factors. The prevalence of NoV and HAV in berries was calculated at 2.12 % (95 % CI 1.74-2.59 %), and no statistically differences were observed among the viral types or genogroup categories. However, it is important to clarify that this estimate should be taken with caution given the high heterogeneity. There was no discernible correlation between viral prevalence and any particular berry type. However, there was a temporal correlation observed with the year of sampling, revealing a significantly decreasing trend throughout the study period. A significant influence of the sample condition (fresh or frozen) was observed in relation to the prevalence of NoV GII and HAV. Overall higher viral prevalences were identified in berries originating from African countries as compared to those sourced from other continents. It was also noted that the prevalence of NoV GI was significantly higher in samples collected directly from farms compared to those obtained from retailers. The outcomes of this comprehensive meta-analysis propose that while viral contamination of berries is diminishing in more recent times, the prevalence remains substantial in certain African countries, having a significant risk for foodborne infections. It is imperative to implement intervention strategies in these regions to enhance product safety.

Detection of Hepatitis A RNA, Hepatitis E RNA, Human Adenovirus F DNA, and Norovirus RNA in Fresh and Frozen Berry Products at Point of Retail in Ireland

Soft fruits are at particular risk of contamination with enteric viruses such as Hepatitis A virus (HAV), Hepatitis E Virus (HEV), Norovirus (NoV), Human Adenovirus (HAdV) and Sapovirus (SaV). The aim of this study was to investigate, for the first time, the presence of these biological agents in ready to eat (RTE) berries at point of retail in Ireland. A sampling strategy was designed in which RTE fresh and frozen strawberries and raspberries were purchased from five retailers between May and October 2018. Reverse Transcriptase Polymerase Chain Reaction (RT-qPCR) assays for HEV RNA, Nov RNA, SaV RNA, and human Adenovirus species F DNA (HAdV-F) were performed on 239 samples (25g portions). Viral nucleic acid was present in 6.7% (n = 16) of samples tested as follows: HAV RNA (n = 5), HAdV-F DNA (n = 5), HEV RNA (n = 3) and NoV GII RNA (n = 3). Sapovirus RNA was not detected in any product. No significant differences were found between berry type, fresh/frozen status, or supermarket source. This study suggests a risk that exists across all retail outlets however only low levels of nucleic acid ranging from 0 to 16 genome copies/g were present. Although these findings may reflect non-viable/non-infectious virus the continued provision of risk mitigation advice to consumers is warranted and further work is required to ensure control measures to reduce contamination are implemented and enforced.

Survey on technical management of strawberries in Morocco and evaluation of their post-harvest microbial load

The climatic conditions of the growing regions influence the fruit's microbiological quality and their tolerance to post-harvest pathogens. The present work aims to identify the prevalence of bacterial and fungal strains of strawberries (Fragaria × ananassa) in the Gharb and Loukkos regions of Morocco. Thus, to establish a correlation between the microbial load and the climatic conditions of the two targeted regions. The bacteriological analyses were studied according to the International Organization for Standardization (ISO) methodologies. Regarding the mycological study, fungal species determination was performed using identification keys. Yeast species determination was done using genus analysis, assimilation, and fermentation tests. Emberger bioclimatic quotients (Q₂) were calculated for the Gharb and Loukkos regions and bioclimatic stages were determined. Salmonella spp. was not detected in the studied samples. However, Listeria monocytogenes and Escherichia coli were isolated from the Gharb samples. Sulfite-reducing clostridia spores were found in two Gharb samples versus one Loukkos sample. Coagulase-positive staphylococci were negative in all samples analyzed. Loukkos and Gharb regions were contaminated by Bacillus cereus with percentages of occurrence of 5.2 and 7.8%, respectively. The fungi found in strawberries from both regions were Aspergillus niger, Botrytis cinerea, Fusarium spp., Penicillium spp., Rhizopus spp., and Alternaria alternata with a significant predominance in the Loukkos samples. Indeed, a marked presence is noted for Candida sake and Rhodotorula glutinis in strawberries from Loukkos. Gharb is located on the semi-arid stage, while Loukkos is located on the sub-humid stage. Climatic conditions have a strong influence on plant microbial load, which explains the prevalence of bacteria in strawberries from Gharb and the prevalence of fungi in strawberries from Loukkos.

Occurrence of Norovirus, Rotavirus, Hepatitis a Virus, and Enterovirus in Berries in Argentina

Berries have been implicated as the probable vehicle of infection in multiple outbreaks of norovirus and hepatitis A virus (HAV). These foods often receive minimal or no processing and may be exposed to virus contamination at each stage of production. In an increasingly globalized world, berries have a wide distribution and can give rise to the spread of diseases in distant parts of the world. With the aim of describing the virological quality of the berries cultivated in Argentina, a total of 184 soft fruits of different varieties (strawberries, blueberries, raspberries, blackberries, currants, pomegranate arils, cassis, and elder) were collected during the periods 2016-2018 and 2020. Viral particles were eluted and concentrated by polyethylene glycol precipitation according to ISO 15216-2:2019 guidelines. Genome detection of norovirus (NoV) genogroups I (GI) and II (GII), HAV, rotavirus, and enterovirus was performed by real-time RT-PCR with TaqMan probes. Positive samples were amplified by conventional RT-PCR and the amplicons were purified and sequenced in both directions. Phylogenetic analysis was performed using the Neighbor-Joining method based on the evolutionary model Kimura-2-parameters. NoV GII.6 was detected in 1/184 (0.5%) of the soft fruits, corresponding to a raspberry sample obtained during the fall of 2017. No presence of other human enteric viruses was found in the other berries analyzed. The collected data are the first in Argentina in relation to the prevalence of enteric viruses in berries and is useful as reference data for a risk assessment of soft fruits as vehicles of foodborne pathogenic viruses.

Pathogenic potential of the surviving Salmonella Enteritidis on strawberries after disinfection treatments based on ultraviolet-C light and peracetic acid

Fresh fruits, especially strawberries, are usually consumed raw without any step to ensure their food safety. Salmonella enterica is one of the most important etiologic agents for foodborne diseases throughout the world and its ability to respond to some stress responses makes it even more dangerous. In the present investigation, we study the survival of S. Enteritidis (CECT-4300) on strawberries after 2-min of various disinfection steps (NaClO (200 ppm), peracetic acid (PAA; 40 ppm), water-assisted UV-C (WUV-C), and the combination WUV-C and 40 ppm of PAA (WUV-C + PAA)) and after 5 days of cold storage (4 °C). Moreover, the pathogenic potential of the surviving bacteria, such as the ability to survive throughout the gastrointestinal tract (GI) and subsequently the capability to adhere to and invade Caco-2 cells, was tested at each sampling point. After 2-min of washing procedures, reductions of S. Enteritidis on strawberries were ≥1.2 log, with no significant differences among treatments. However, the use of WUV-C + PAA treatment achieved the highest reductions in washing water, in which S. Enteritidis was not detected (<DL). At the end of 5-day storage period, reductions of the WUV-C + PAA treated-samples were lower in comparison with PAA-treated samples (P < 0.05). The effect of the treatments used did not interfere with the survival of S. Enteritidis along the GI tract. After disinfection and subsequent GI simulation, all remaining populations demonstrated an elevated ability to adhere in Caco-2 cells (67.5-81.1%) compared with those obtained on untreated strawberries (61.4%). Concerning the ability of invasion, no significant differences could be observed. Remarkably, after 5 days at 4 °C, the adherence of S. Entertidis significantly decreased in the samples with the combined treatment meanwhile the invasion ability was not detected for any treatment. The results of the present study are essential for the quantitative microbial risk estimations.

Contamination of fresh produce sold on the Italian market with Cyclospora cayetanensis and Echinococcus multilocularis

To investigate the presence of Cyclospora cayetanensis, Toxoplasma gondii and Echinococcus spp. in fresh produce sold in Italy, 324 locally produced 'ready-to-eat' (RTE) mixed-salad packages belonging to three brands and 324 berries packages (blueberries and blackberries imported from Peru and Mexico, respectively, and raspberries grown in Italy) were purchased at retail. Nine individual packages from each of the six types of fresh produce were collected monthly for one year, and with the same produce pooled, this resulted in a total of 72 pools for the whole year. Using microscopy (FLOTAC), a Cyclospora-like oocyst was detected in a blueberry sample and a taeniid egg was detected in a RTE-salad sample. Molecular tools confirmed these to be C. cayetanensis and Echinococcus multilocularis, respectively. Toxoplasma gondii was not detected in any of the samples. This study shows for the first time in Europe that imported berries on the Italian market may be contaminated with C. cayetanensis and RTE salads grown in Italy with E. multilocularis. The results indicate a new epidemiological scenario and highlight that current management of fresh produce, locally produced or imported, does not ensure products are free from parasite contamination.

Agricultural Detection of Norovirus and Hepatitis A Using Fecal Indicators: A Systematic Review

Fresh-produce consumers may be at risk of pathogen infection due to fecal contamination of the agricultural environment. Indicators of fecal contamination may be used as a proxy to evaluate the potential presence of human pathogens, such as norovirus and hepatitis A, on agricultural samples. The objective of this systematic review was to determine whether the presence of human norovirus or hepatitis A was associated with microbial indicators in agricultural samples including fresh produce, equipment surfaces, and hands. Four databases (Embase, PubMed, Web of Science, and Agricola) were systematically searched and fifteen articles met inclusion and exclusion criteria. After data extraction, individual indicator-pathogen relationships were assessed using Cohen's Kappa coefficient. The level of agreement between norovirus with adenovirus was 0.09 (n = 16, 95% CI -0.05, 0.23), indicating poor agreement using Landis and Koch's criterion. Similarly, the Kappa coefficient between norovirus with E. coli (κ = 0.04, n = 14, 95% CI -0.05, 0.49) or total coliforms (κ = 0.03, n = 4, 95% CI -0.01, 0.02) was also poor. The level of agreement between hepatitis A with adenovirus (κ = -0.03, n = 3, 95% CI -0.06, 0.01) or fecal coliforms (κ = 0, n = 1, 95% CI 0, 0) was also poor. There were moderate relationships between hepatitis A with E. coli (κ = 0.49, n = 3, 95% CI 0.28, 0.70) and total coliforms (κ = 0.47, n = 2, 95% CI 0.47, 0.47). Based on these limited results, common indicator organisms are not strong predictors of the presence of norovirus and hepatitis A virus in the agricultural environment.

Multiplex Quantitative PCR Analysis of Strawberries from Bogotá, Colombia, for Contamination with Three Parasites

ABSTRACT

Berries are potential vehicles for the transmission of parasites and have been implicated in illness outbreaks in various countries around the world, particularly in the United States. Although data on contamination of fresh produce with foodborne parasites have been obtained from various global regions, data from Colombia are lacking even though South American countries are major producers of fresh produce, which is both consumed nationally and exported. In this study, we used a previously published multiplex quantitative PCR approach to investigate contamination of strawberries purchased in either supermarkets or local markets in 20 localities. Strawberries were washed in a detergent solution after purchase, and the eluate was concentrated and sent to Norway for molecular analysis. Of the 120 strawberry samples analyzed, wash eluate from 6 samples (5%) tested positive for Toxoplasma gondii DNA, and 1 sample (0.83%) was positive for Cyclospora cayetanensis DNA. These results indicate that strawberries for sale in Bogotá, Colombia, may be contaminated with T. gondii and C. cayetanensis and, therefore, could act as transmission vehicles for these parasites. These data also indicate that cat and human fecal contamination of the strawberries has occurred at some point in their production, transportation, or storage. These findings highlight the need for a hazard analysis critical control point investigation of the strawberry production chain and implementation of measures to reduce the risk of strawberry contamination, thereby minimizing the risk of transmission of parasitic infection via these fruits, which are usually consumed raw.

HIGHLIGHTS

Microbial interaction between Salmonella enterica and main postharvest fungal pathogens on strawberry fruit

The microbial interaction between Salmonella enterica and the main postharvest fungal pathogens of strawberries was evaluated. Inoculation of fungal suspension was done 2 (D2) and 1 (D1) day(s) before and at the same time (D0) as S. enterica. Fruits were stored at 20 °C and 4 °C. At both temperatures, Botrytis cinerea and Rhizopus stolonifer caused a decrease in S. enterica population. Treatments where the mould was inoculated (D2, D1 and D0) achieved a significant logarithmic reduction (P < 0.05) of S. enterica populations after 48 h (20 °C) and 14 days (4 °C) compared to fungal-uninoculated fruits (CK). Regarding temperature, average reductions were significantly higher at 4 °C (3.38 log₁₀ CFU/wound) than at 20 °C (1.16 log₁₀ CFU/wound) (P < 0.05). Average reductions comprising all treatments were 1.91 and 0.41 log₁₀ CFU/wound for B. cinerea and R. stolonifer at 20 °C, and 3.39 and 3.37 log₁₀ CFU/wound for B. cinerea and R. stolonifer at 4 °C. A linear log₁₀ model was fitted in order to predict the inactivation rate (k_max, log₁₀ CFU/h) of S. enterica. Inactivation rates were higher at 20 °C for D2 treatments than at 4 °C throughout the running time. The main inactivation rate was obtained for B. cinerea at 20 °C (0.160 ± 0.027/h), which was found to have stronger inhibitory activity against S. enterica than R. stolonifer. Univariate analysis ANOVA was carried out to evaluate the effect of different external variables on the inhibition of S. enterica. Results found that single effects were significant (P < 0.05) except for the pH. The inhibitory effect caused by the action of moulds in conjunction with some environmental factors could indicate the potential interactions between strawberry fungal pathogens and S. enterica.

Occurrence of selected viral and bacterial pathogens and microbiological quality of fresh and frozen strawberries sold in Spain

Strawberry production and exports have been increasing in Spain in recent decades. However, little information is available about their microbiological quality. Due to the growing concern about the microbial safety of these fruits, the objective of this investigation was to study the microbiological quality and the prevalence of the main foodborne pathogens on strawberries sold in Spain. Fresh (n = 152) and frozen (n = 31) samples were obtained from marketplaces and fields in 2017 and 2018. The samples were assayed for total aerobic mesophilic microorganisms (TAM), moulds and yeasts (M&Y), total coliforms (TC), Escherichia coli, Salmonella spp., Listeria monocytogenes as well as Norovirus (NoV) GI and GII. The microbiological counts ranged from <1.70 (detection limit, dl) - 5.89 log₁₀ CFU/g (mean 3.78 log₁₀ CFU/g) for TAM; 2.10-5.86 log₁₀ CFU/g (mean 3.80 log₁₀ CFU/g) for M&Y; and <0.70 (dl) - 4.91 log₁₀ CFU/g (mean 2.15 log₁₀ CFU/g) for TC in fresh strawberries. In frozen strawberries, the counts were <1.70 (dl) - 3.66 log₁₀ CFU/g (mean 2.30 log₁₀ CFU/g) for TAM; <1.70 (dl) - 2.76 log₁₀ CFU/g (mean 1.82 log₁₀ CFU/g) for M&Y; and <0.70(dl) - 1.74 log₁₀ CFU/g (mean 0.77 log₁₀ CFU/g) for TC. All the samples in this study tested negative for Salmonella spp., L. monocytogenes. E. coli and NoV GI and GII genome. A global overview of all the data was executed using Principal Component Analysis (PCA), and the results showed that the scores and loadings according to principal components 1 (PC1) and 2 (PC2) accounted for 75.9% of the total variance, allowing a distinction between fresh and frozen samples. The presence of moulds was significantly higher in the supermarket samples whereas the presence of total coliforms was significantly higher in the field samples (p < 0.05). Although pathogenic microorganisms were not found, preventative measures and prerequisites in the strawberry production chain must be considered in order to avoid possible foodborne diseases related to the microbiological quality of the fruit.

Microbiological quality of raw berries and their products: A focus on foodborne pathogens

Berry samples (n = 316; strawberries, raspberries, blackberries and blueberries) obtained from a fruit processing plant were examined regarding bacteriological quality and their potential public health risk. Three types of berry products were analysed including raw material, product from the mixing step and final product. Escherichia coli, Salmonella spp., Listeria monocytogenes, Bacillus cereus, sulphite-reducing clostridia spores and coagulase-positive staphylococci were the parameters investigated. Salmonella enterica serovar Braenderup and L. monocytogenes were isolated from one fruit sample of raw material each. Two samples harboured E. coli between 0.7 and 0.9 log cfu g-1, not exceeding the hygienic criteria. Coagulase-positive staphylococci were not detected in the studied samples; however, coagulase-negative staphylococci (CNS) were isolated from a small proportion of samples mainly raspberries. Presumptive B. cereus were isolated from a relatively large proportion of the samples, raspberries and blackberries being the most contaminated fruits. The absence of pathogenic microorganisms in the final product as well as the low prevalence of presumptive B. cereus and CNS indicates proper implementation of good manufacturing and hygiene practices (GMPs/GHPs) by the food industry. Nevertheless, the results indicate that the raw material examined may contain pathogenic bacteria and thereby represent a risk to consumers regarding the manifestation of foodborne diseases.

Microbial Safety of Dairy Manure Fertilizer Application in Raspberry Production

Dairy manure, a by-product in the dairy industry, is also a potential source of nutrients for crops. However, improper application of biological soil amendments of animal origin can be a source of contamination with enteric foodborne pathogens. A 2-year field study was conducted to evaluate impacts of dairy manure fertilizer application on the microbial safety of red raspberry (Rubus idaeus L) production. Fertilizers, including a standard synthetic fertilizer (CON), straight lagoon raw manure (SL), anaerobically digested liquid effluent (DLE), compost (COM) and dairy manure-derived refined fertilizers including ammonium sulfate (AS) and phosphorous solid (PS), were randomly applied in quadruplicate to raspberry plots. Soil, fertilizer, foliar, and raspberry fruit samples were collected during the cropping season for the quantification of indicator microorganisms (total coliform and generic Escherichia coli) and detection of important foodborne pathogens (Shiga toxin-producing E. coli (STEC), Salmonella, and Listeria monocytogenes). Counts of total coliforms in soil were stable over the 2017 cropping season and were not impacted by fertilizer application. In 2018, total coliforms increased with season and soils treated with COM had a significantly higher coliform number than those treated with CON. Both total coliform and generic E. coli in raspberry fruit samples were below the detectable level (3 most probable number/g) regardless of fertilizer types. In both years, no STEC or L. monocytogenes was detected from any of the collected samples regardless of fertilizer treatments. However, Salmonella were detected in some of the fertilizers, including PS (2017), DLE (2018), and SL (2018), which were transferred to soil samples taken directly after application of these fertilizers. Salmonella were not detected in soil samples 2 or 4 months post fertilizer application, foliar, or raspberry fruit samples regardless of fertilizer applications. In summary, one-time application of raw dairy manure or dairy manure-derived fertilizers more than 4 months prior to harvest has no major impact on food safety of red raspberry (6 ft. tall) production in Lynden sandy loam under good agricultural practices.