Research

18 pages, 2228 KiB

Open AccessArticle

Control of Foodborne Staphylococcus aureus by Shikonin, a Natural Extract

by Yangli Wan, Xiaowen Wang, Pengfei Zhang, Meng Zhang, Mingying Kou, Chao Shi, Xiaoli Peng and Xin Wang

Foods 2021, 10(12), 2954; https://doi.org/10.3390/foods10122954 - 01 Dec 2021

Cited by 15 | Viewed by 2260

Abstract

Foodborne Staphylococcus aureus (S. aureus) has attracted widespread attention due to its foodborne infection and food poisoning in human. Shikonin exhibits antibacterial activity against a variety of microorganisms, but there are few studies on its antibacterial activity against S. aureus. [...] Read more.

Foodborne Staphylococcus aureus (S. aureus) has attracted widespread attention due to its foodborne infection and food poisoning in human. Shikonin exhibits antibacterial activity against a variety of microorganisms, but there are few studies on its antibacterial activity against S. aureus. This study aims to explore the antibacterial activity and mechanism of shikonin against foodborne S. aureus. The results show that the minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) of shikonin were equal for all tested strains ranging from 35 μg/mL to 70 μg/mL. Shikonin inhibited the growth of S. aureus by reducing intracellular ATP concentrations, hyperpolarizing cell membrane, destroying the integrity of cell membrane, and changing cell morphology. At the non-inhibitory concentrations (NICs), shikonin significantly inhibited biofilm formation of S. aureus, which was attributed to inhibiting the expression of cidA and sarA genes. Moreover, shikonin also markedly inhibited the transcription and expression of virulence genes (sea and hla) in S. aureus. In addition, shikonin has exhibited antibacterial ability against both planktonic and biofilm forms of S. aureus. Importantly, in vivo results show that shikonin has excellent biocompatibility. Moreover, both the heat stability of shikonin and the antimicrobial activity of shikonin against S. aureus were excellent in food. Our findings suggest that shikonin are promising for use as a natural food additive, and it also has great potential in effectively controlling the contamination of S. aureus in food and reducing the number of illnesses associated with S. aureus. Full article

(This article belongs to the Special Issue Pathogens on Fresh Produce: Detection and Reduction)

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8 pages, 268 KiB

Open AccessCommunication

Extended-Spectrum Beta-Lactamase-Producing Enterobacteriaceae in Fresh Produce

by Alberto Pintor-Cora, Laura Álvaro-Llorente, Andrés Otero, Jose M. Rodríguez-Calleja and Jesús A. Santos

Foods 2021, 10(11), 2609; https://doi.org/10.3390/foods10112609 - 28 Oct 2021

Cited by 13 | Viewed by 2314

Abstract

Fresh vegetables are an essential part of a healthy diet, but microbial contamination of fruits and vegetables is a serious concern to human health, not only for the presence of foodborne pathogens but because they can be a vehicle for the transmission of [...] Read more.

Fresh vegetables are an essential part of a healthy diet, but microbial contamination of fruits and vegetables is a serious concern to human health, not only for the presence of foodborne pathogens but because they can be a vehicle for the transmission of antibiotic-resistant bacteria. This work aimed to investigate the importance of fresh produce in the transmission of extended-spectrum β-lactamases (ESBL)-producing Enterobacteriaceae. A total of 174 samples of vegetables (117) and farm environment (57) were analysed to determine enterobacterial contamination and presence of ESBL-producing Enterobacteriaceae. Enterobacterial counts above the detection limit were found in 82.9% vegetable samples and 36.8% environmental samples. The average count was 4.2 log cfu/g or mL, with a maximum value of 6.2 log cfu/g in a parsley sample. Leafy vegetables showed statistically significant higher mean counts than other vegetables. A total of 15 ESBL-producing isolates were obtained from vegetables (14) and water (1) samples and were identified as Serratia fonticola (11) and Rahnella aquatilis (4). Five isolates of S. fonticola were considered multi-drug resistant. Even though their implication in human infections is rare, they can become an environmental reservoir of antibiotic-resistance genes that can be further disseminated along the food chain. Full article

(This article belongs to the Special Issue Pathogens on Fresh Produce: Detection and Reduction)

15 pages, 3828 KiB

Open AccessArticle

Development of Strategies to Minimize the Risk of Listeria monocytogenes Contamination in Radish, Oriental Melon, and Carrots

by Nagendran Rajalingam, Hyo-Bin Chae, Hyeon-Jin Chu, Se-Ri Kim, Injun Hwang, Jeong-Eun Hyun and Song-Yi Choi

Foods 2021, 10(9), 2135; https://doi.org/10.3390/foods10092135 - 09 Sep 2021

Viewed by 1849

Abstract

Contamination by Listeria monocytogenes in packaged produce is a major concern. The purpose of this study was to find natural and affordable sanitizers to reduce L. monocytogenes contamination in agricultural products. Organic acids, ultraviolet-C (UV-C), and ethanol were analyzed either alone or in [...] Read more.

Contamination by Listeria monocytogenes in packaged produce is a major concern. The purpose of this study was to find natural and affordable sanitizers to reduce L. monocytogenes contamination in agricultural products. Organic acids, ultraviolet-C (UV-C), and ethanol were analyzed either alone or in combination to assess their ability to reduce L. monocytogenes population in radish, oriental melon, and carrot samples. In radish samples, 3% malic acid combined with UV-C at a dosage of 144 mj/cm² significantly reduced (>4 log CFU/g) the population of L. monocytogenes (1.44 ± 0.5) compared to the control sample (5.14 ± 0.09). In the case of the melon samples, exposure to UV-C at a dosage of 144 mj/cm² combined with 3% lactic acid (2.73 ± 0.75) or 50% ethanol (2.30 ± 0.01) was effective against L. monocytogenes compared to the control sample (5.10 ± 0.19). In carrot samples, 3% lactic acid combined with 144 mj/cm² dosage UV-C reduced L. monocytogenes population (4.48 ± 0.25) more than in the control sample (5.85 ± 0.08). These results reveal that sanitizers that are effective for one crop are less effective for another crop indicating that effective prevention methods should be customized for each crop to prevent pathogen cross contamination during postharvest washing. Full article

(This article belongs to the Special Issue Pathogens on Fresh Produce: Detection and Reduction)

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18 pages, 1783 KiB

Open AccessArticle

Survival of Escherichia coli and Listeria innocua on Lettuce after Irrigation with Contaminated Water in a Temperate Climate

by Bernardino Machado-Moreira, Karl Richards, Florence Abram, Fiona Brennan, Michael Gaffney and Catherine M. Burgess

Foods 2021, 10(9), 2072; https://doi.org/10.3390/foods10092072 - 02 Sep 2021

Cited by 5 | Viewed by 3395

Abstract

Microbial disease outbreaks related to fresh produce consumption, including leafy green vegetables, have increased in recent years. Where contamination occurs, pathogen persistence may represent a risk for consumers’ health. This study analysed the survival of E. coli and L. innocua on lettuce plants [...] Read more.

Microbial disease outbreaks related to fresh produce consumption, including leafy green vegetables, have increased in recent years. Where contamination occurs, pathogen persistence may represent a risk for consumers’ health. This study analysed the survival of E. coli and L. innocua on lettuce plants watered with contaminated irrigation water via a single irrigation event and within stored irrigation water. Separate lettuce plants (Lactuca sativa var. capitata) were irrigated with water spiked with Log₁₀ 7 cfu/mL of each of the two strains and survival assessed via direct enumeration, enrichment and qPCR. In parallel, individual 20 L water microcosms were spiked with Log₁₀ 7 cfu/mL of the individual strains and sampled at similar time points. Both strains were observed to survive on lettuce plants up to 28 days after inoculation. Direct quantification by culture methods showed a Log₁₀ 4 decrease in the concentration of E. coli 14 days after inoculation, and a Log₁₀ 3 decrease in the concentration of L. innocua 10 days after inoculation. E. coli was detected in water samples up to 7 days after inoculation and L. innocua was detected up to 28 days by direct enumeration. Both strains were recovered from enriched samples up to 28 days after inoculation. These results demonstrate that E. coli and L. innocua strains are able to persist on lettuce after a single contamination event up until the plants reach a harvestable state. Furthermore, the persistence of E. coli and L. innocua in water for up to 28 days after inoculation illustrates the potential for multiple plant contamination events from stored irrigation water, emphasising the importance of ensuring that irrigation water is of a high quality. Full article

(This article belongs to the Special Issue Pathogens on Fresh Produce: Detection and Reduction)

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12 pages, 1634 KiB

Open AccessArticle

Is Fresh Produce in Tigray, Ethiopia a Potential Transmission Vehicle for Cryptosporidium and Giardia?

by Tsegabirhan Kifleyohannes, John James Debenham and Lucy J. Robertson

Foods 2021, 10(9), 1979; https://doi.org/10.3390/foods10091979 - 25 Aug 2021

Cited by 7 | Viewed by 1925

Abstract

In rural Ethiopia, where people often share their homes with their livestock, infections of humans and animals with Cryptosporidium and Giardia are relatively common. One possible transmission route is consumption of contaminated fresh produce; this study investigated the occurrence of Cryptosporidium and Giardia [...] Read more.

In rural Ethiopia, where people often share their homes with their livestock, infections of humans and animals with Cryptosporidium and Giardia are relatively common. One possible transmission route is consumption of contaminated fresh produce; this study investigated the occurrence of Cryptosporidium and Giardia in fresh produce in four districts of rural Tigray in Ethiopia. Fresh produce samples (n = 55) were analysed using standard laboratory procedures. Overall, 15% (8/55) of samples were found to be contaminated. Although contamination levels were mostly low, a few samples had high numbers of Giardia cysts (up to around 70 cysts per 30 g sample). Molecular analyses were largely unsuccessful, but Giardia Assemblage A was identified in one sample. Contamination with these parasites was identified in two of the four districts, but, although a similar pattern has already been described for water contamination, this may be at least partially explained by sampling bias. Nevertheless, we speculate that access to clean water sources may be an important factor for reducing the occurrence of these pathogens. Given the public health and veterinary burden associated with both parasites, the factors which are of importance for their circulation in the communities and environments deserve further investigation. Full article

(This article belongs to the Special Issue Pathogens on Fresh Produce: Detection and Reduction)

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9 pages, 266 KiB

Open AccessArticle

Occurrence and Accumulation of Human Enteric Viruses and Phages in Process Water from the Fresh Produce Industry

by Enric Cuevas-Ferrando, Ana Allende, Alba Pérez-Cataluña, Pilar Truchado, Natalia Hernández, Maria Isabel Gil and Gloria Sánchez

Foods 2021, 10(8), 1853; https://doi.org/10.3390/foods10081853 - 11 Aug 2021

Cited by 7 | Viewed by 2503

Abstract

The virological quality of process water (PW) used by the produce industry has received limited attention. As a first step to overcoming technical limitations in monitoring viruses in PW, the analytical performance of ultrafiltration was assessed to concentrate viral particles from 20 L [...] Read more.

The virological quality of process water (PW) used by the produce industry has received limited attention. As a first step to overcoming technical limitations in monitoring viruses in PW, the analytical performance of ultrafiltration was assessed to concentrate viral particles from 20 L of spiked PW. The selected method used for sample concentration of PW was carefully validated, thus enabling the accurate quantification and estimation of viral titers of human enteric viruses and phages. PW from the produce industry was collected periodically from the washing tanks of commercial facilities. The analysis of coliphages was performed by plaque assay, while the occurrence of enteric viruses and crAssphage was determined by molecular techniques. Significant differences in the physicochemical composition of PW, mostly due to the different nature of fresh produce types and differences in the sanitizer used in commercial operation, were observed. Accumulation of crAssphage and coliphages was observed in PW, but correlation with human enteric viruses was not possible due to the low prevalence of these pathogens in the PW analyzed. The obtained results showed that depending on the type of product washed, the product/water ratio and the residual concentrations of the sanitizers, the prevalence and concentration of bacteriophages changed significantly. Full article

(This article belongs to the Special Issue Pathogens on Fresh Produce: Detection and Reduction)

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Graphical abstract

8 pages, 259 KiB

Open AccessArticle

Evaluation of PhageDX Salmonella Assay for Salmonella Detection in Hydroponic Curly Lettuce

by Nathanyelle Soraya Martins de Aquino, Susana de Oliveira Elias and Eduardo Cesar Tondo

Foods 2021, 10(8), 1795; https://doi.org/10.3390/foods10081795 - 03 Aug 2021

Cited by 3 | Viewed by 1833

Abstract

Lettuce is one of the most consumed leafy vegetables worldwide and has been involved in multiple foodborne outbreaks. Salmonella is one of the most prevalent etiological agents of foodborne disease (FBD) in lettuces, and its detection may take several days depending on the [...] Read more.

Lettuce is one of the most consumed leafy vegetables worldwide and has been involved in multiple foodborne outbreaks. Salmonella is one of the most prevalent etiological agents of foodborne disease (FBD) in lettuces, and its detection may take several days depending on the chosen method. This study evaluates a new rapid method that uses recombinant bacteriophages to detect Salmonella in hydroponic curly lettuce. First, the ability of the assay to detect six Salmonella serovars at three different concentrations (1, 10, and 100 CFU/well) was tested. Second, the detection of Salmonella was tested in lettuces using a cocktail of the same Salmonella serovars and concentrations after a 7 h enrichment. The results of these experiments showed that the detection limit was dependent on the serovar tested. Most serovars were detected in only 2 h when the concentration was 100 CFU/well. Salmonella was detected in 9 h (7 h enrichment + 2 h bioluminescence assay) in all lettuce samples with 10 CFU/25 g or more. Salmonella detection was not influenced by natural microbiota of lettuces. This study demonstrated that the phage assay was sensitive and faster than other detection methods, indicating that it is a better alternative for Salmonella detection on lettuces. Full article

(This article belongs to the Special Issue Pathogens on Fresh Produce: Detection and Reduction)

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20 pages, 4477 KiB

Open AccessArticle

Analysis of Biofilm Formation on the Surface of Organic Mung Bean Seeds, Sprouts and in the Germination Environment

by Marcin Kruk and Monika Trząskowska

Foods 2021, 10(3), 542; https://doi.org/10.3390/foods10030542 - 05 Mar 2021

Cited by 5 | Viewed by 2685

Abstract

This study aimed to analyse the impact of sanitation methods on the formation of bacterial biofilms after disinfection and during the germination process of mung bean on seeds and in the germination environment. Moreover, the influence of Lactobacillus plantarum 299v on the growth [...] Read more.

This study aimed to analyse the impact of sanitation methods on the formation of bacterial biofilms after disinfection and during the germination process of mung bean on seeds and in the germination environment. Moreover, the influence of Lactobacillus plantarum 299v on the growth of the tested pathogenic bacteria was evaluated. Three strains of Salmonella and E. coli were used for the study. The colony forming units (CFU), the crystal violet (CV), the LIVE/DEAD and the gram fluorescent staining, the light and the scanning electron microscopy (SEM) methods were used. The tested microorganisms survive in a small number. During germination after disinfection D2 (20 min H₂O at 60 °C, then 15 min in a disinfecting mixture consisting of H₂O, H₂O₂ and CH₃COOH), the biofilms grew most after day 2, but with the DP2 method (D2 + L. plantarum 299v during germination) after the fourth day. Depending on the method used, the second or fourth day could be a time for the introduction of an additional growth-limiting factor. Moreover, despite the use of seed disinfection, their germination environment could be favourable for the development of bacteria and, consequently, the formation of biofilms. The appropriate combination of seed disinfection methods and growth inhibition methods at the germination stage will lead to the complete elimination of the development of unwanted microflora and their biofilms. Full article

(This article belongs to the Special Issue Pathogens on Fresh Produce: Detection and Reduction)

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10 pages, 589 KiB

Open AccessArticle

Removal of Parasite Transmission Stages from Berries Using Washing Procedures Suitable for Consumers

by Tamirat T. Temesgen, Lucy J. Robertson, Vetle M. Stigum and Kristoffer R. Tysnes

Foods 2021, 10(2), 481; https://doi.org/10.3390/foods10020481 - 23 Feb 2021

Cited by 7 | Viewed by 3444

Abstract

Due to the delicate nature of berries and the reduced shelf-life once washed, producers usually do not wash berries. Therefore, consumers are expected to wash the berries prior to consumption, and this might be a more effective way of infection prevention. However, the [...] Read more.

Due to the delicate nature of berries and the reduced shelf-life once washed, producers usually do not wash berries. Therefore, consumers are expected to wash the berries prior to consumption, and this might be a more effective way of infection prevention. However, the efficacy of consumer berry-washing procedures in removing the parasite contaminants from the berries surface has not been investigated. The aim of the present study was, therefore, to compare the efficacy of three different washing techniques in removing parasite contaminants. Three alternatives to washing berries before consumption were compared on berries artificially contaminated with oo/cysts of Cyclospora cayetanensis, Cryptosporidium parvum, and Giardia duodenalis. The results show that simple washing of berries under the cold tap for 1 min could remove on average at least 80% of the parasites, except for C. cayetanensis, which seems to be stickier than both G. duodenalis and C. parvum. The percent removal was slightly lower for raspberries as compared to blueberries. Although the differences are expected, a relevant result of the study is that washing contaminated berries prior to consumption by the consumer removes a considerable proportion of parasites and thereby lowers the risk of ingesting parasites’ transmission stages. Full article

(This article belongs to the Special Issue Pathogens on Fresh Produce: Detection and Reduction)

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