Prevalence of helminth eggs on raw vegetables used for salads

The presence of helminth eggs on raw vegetables, including lettuce, parsley, green onions, cucumbers, carrots, red cabbage, tomatoes, rockets (Eruca sativa), and green-peppers from wholesalers in Ankara, Turkey was determined. A total of 203 unwashed and 406 washed samples were assayed by light microscopy. Helminth eggs were detected in 12 (5.9%) of 203 unwashed samples and not in any washed samples (p<0.05).Helminth eggs detected in unwashed samples included Taenia spp. (3.5%), Toxocara spp. (1.5%), and Ascaris lumbricoides (1.0%) eggs. Taenia spp. eggs were recovered to be highest number (n=130), followed by Toxocara spp. eggs (n=21). Approximately 11% of unwashed lettuce and parsley was contaminated compared with only 2.5% of carrot samples. No helminth eggs were detected in red cabbage, rockets, tomatoes or green-peppers.These results highlight the potential for transmission of helminth eggs by unwashed salad vegetables in Turkey and the importance of properly washing/disinfecting raw vegetables before consumption.     

Seasonal study of parasitic contamination in fresh salad vegetables marketed in Shahrekord,Iran

This survey was conducted to determine the parasitic contamination in fresh salad vegetables marketed in Shahrekord, Iran. The samples composed of unwashed and pre-washed cucumber, tomato, lettuce, cabbage, pepper, carrot, mushroom, and onion were purchased from vegetable markets. It was found that the rate of parasitic contamination was significantly higher (P < 0.05) in unwashed salad vegetables [25.2% (114/453)] than in pre-washed ones [6.03% (27/448)]. The parasites detected in unwashed salad vegetables included Ascaris lumbricoides (8.17%), Cryptosporidium spp. (2.87%), Enterobius vermicularis (2.65%), Taeniid spp. (4.86%), Strongyloides spp. (1.1%), Toxocara spp. (3.97%), and Entamoeba coli (2.43%). While the parasites namely A. lumbricoides (3.57%), Cryptosporidium spp. (1.79%), and E. vermicularis (1.12%) were detected in pre-washed ones. The rate of contamination in unwashed salad vegetables obtained during summer was significantly higher (P < 0.05) than those obtained during the other seasons. Occurrence of the parasites was the highest in lettuce, followed by cabbage and carrot both in unwashed and pre-washed vegetables. The unwashed field-origin vegetables like cucumber, tomato, and pepper showed significantly higher contamination (P < 0.05) than their greenhouse-origin counterparts. The results indicate the potential hazard of unwashed and pre-washed salad vegetables in transmission of parasites to humans, and also show the importance of proper washing before preparation of salads.     

Parasitological contamination in salad vegetables in Tripoli-Libya

BackgroundFresh vegetables are an important part of a healthy diet. Raw vegetables can be agent of transmission of intestinal parasites. The aim of the present study was to determine the parasitological contamination of salad vegetables sold at wholesale and retail markets in Tripoli-Libya.MethodsA total of 126 samples of salad vegetables obtained from wholesale and retail markets were examined for helminth eggs and Giardia spp. cysts of using standard methods.ResultsOf the 36 tomato, 36 cucumber, 27 lettuce, and 27 cress samples examined eggs of Ascaris spp. were detected in 19%, 75%, 96% and 96%, respectively; eggs of Toxocara cati in 11%, 14%, 48% and 41%; eggs of Toxocara canis in 3%, 8%, 37% and 33%; and eggs of Taenia/Echinococcus spp. in 6%, 25%, 33% and 30%, respectively. Cysts of Giardia spp. were detected in 3%, 19%, 4% and 11%, respectively.ConclusionParasitological contamination of raw salad vegetables sold in wholesale and retail markets in Tripoli may pose a health risk to consumers of such products.     

The Australian Food and Trust Survey: Demographic indicators associated with food safety and quality concerns

Objective

Safety and quality associated with the production, marketing and consumption of food, together with overall levels of trust in the food supply chain, are increasing in importance in our society. The aim of this study was to identify the demographic differences in a range of safety and quality variables in regard to levels of consumer trust in the food supply chain.

Design

An Australia-wide population telephone survey on a random sample of the Australian population aged 18+ years of age was undertaken. Univariate and multivariate analyses were undertaken on each of the eight safety and quality variables and one composite variable.

Setting

Australia.

Subjects

In total, 1108 interviews with 49.3% of the sample males and with a mean age of 45.12 years (SD 17.63).

Results

Multivariate analysis indicated that gender (females), age (older persons) and annual household income (lower income) were the demographic groups more likely to be included in the final models that considered various quality and safety issues to be important. Higher education was related to more importance being placed on the variable assessing the importance of the producer maintain control of hygiene but lower education level was related to the variable assessing the importance of the premises being tested regularly by inspectors.

Conclusion

The perceptions that adults place upon the safety and quality of food are important in ultimately defining, amongst other things, their food buying choices. As such, this research has highlighted demographic characteristics associated with the importance placed on a wide range of safety and quality issues so as to assist in providing evidence for targeting of appropriate campaigns to increase consumer confidence.     

Contamination of vegetables sold in markets with helminth eggs in Zaria metropolis,Kaduna State,Nigeria

The increasing use of waste waters from human and animal wastes for irrigation of Agricultural produce as well as the indiscriminate defecation by both humans and animals in the environment has led to contamination of vegetables and salad crops with helminth eggs. The extent of contamination of vegetables sold in markets in Zaria metropolis, Kaduna state of Nigeria was determined in 199 vegetables using sucrose flotation medium of 1.21 specific gravity. Helminth eggs were found in 57.8% of the vegetables and the distribution was as follows: Toxocara spp. 48.3%, Strongyloides spp. 19.2%, Taenia spp./Echinococcus spp. 18.3%, Ancylostoma spp. 10.0%, Trichuris spp. 3.3 and Enterobius spp. 0.8%. Spinach (Spinacia oleracea) had the highest contamination rate (84.6%), followed by Waterleaf (Talinum triangulare) 84.0%, Carrot (Daucus carota var sativa) 76.9, Lettuce (Lactuca sativa) 56.5%, Jute mallow (Conchorus olitorius) 54.5%, Tomato (Lycopersicon esculentum) 48.0%, Fluted pumpkin (Telferia occidentalis) 38.5% and Cabbage (Brassica oleracea var capitata) 19.2%. Of the three markets examined, Sabo market had the highest contamination rate (65.5%) followed by Ahmadu Bello University community market (58.8%) and Samaru market (50.0%). Sixty eight (59.1%) of the vegetables examined were contaminated with helminth eggs in the pre-rainy period while 47 (56.0%) were contaminated in the rainy period. There was significant association (χ² = 39.53; p = 0.0000) between helminth eggs and types of vegetables examined. On the other hand there were no statistical associations (p > 0.05) between prevalence of helminth eggs, markets sampled and the periods of study. This study has shown that vegetables sold in markets in Zaria metropolis are contaminated with helminth eggs. This is of public health significance. Hence there is need to compost human and animal wastes before they are used as manure. Thorough washing of vegetables is also recommended prior to consumption.     

Prevalence of parasitic contamination in vegetables used for raw consumption in Shahrekord, Iran: Influence of season and washing procedure

This study aimed to determine the prevalence of intestinal parasites in raw vegetables consumed in Shahrekord, Iran; and efficacy of season and washing procedures to remove parasites from the vegetables. A total of 304 field vegetable samples composed of parsley, spearmint, scallion, basil, coriander, dill, cress, leek, tarragon, radish and purslane were purchased from the vegetable markets. Each sample was divided into three groups. One group was used as the unwashed sample and the second and third groups were washed with traditional and standard washing procedures, respectively. Intestinal parasites were detected in 32.6% of unwashed, 1.3% of traditionally washed and not in any standard washed samples (P < 0.001). The parasites were detected in unwashed vegetable samples included Ascaris lumbricoides eggs (14.1%), Taeniid spp. eggs (9.2%), Toxocara spp. eggs (3.3%), Trichostrongylus spp. eggs (4.3%), Giardia spp. cysts (8.2%) and non-pathogenic protozoan Entamoeba coli cysts (9.2%). The rate of parasitic contamination in different seasons was found to be 55% in spring, 45.5% in summer, 14.9% in autumn and 12.3% in winter (P < 0.005). The results highlight the potential of unwashed raw vegetables in transmission of intestinal parasites to human, and also emphasize the use of standard washing procedure (proper washing and disinfecting) before consumption of vegetables instead of traditional procedure (quick washing without disinfecting).     

Survey of microbial quality of plant-based foods served in restaurants

This study was carried out to evaluate the microbiological quality of plant-based foods obtained from foodservice establishments. The samples included cereals, legumes, fruits and vegetables. According to the European Commission Regulation (No. 2073/2005 and No. 1441/2007) and Spanish microbiological criteria (No. 3484/2000), vegetables were the plant-based dishes where more samples exceed the adopted limits of mesophilic aerobic counts and Enterobacteriaceae. Furthermore, Staphylococcus aureus and Escherichia coli were also found in several vegetable dishes. E. coli and Salmonella spp. were detected in 6.6% and 0.7% of lettuce samples, respectively. However, all the samples were negative for Listeria monocytogenes. Salads ingredients are eaten as fresh vegetables without cooking processes and lettuce was one of the most contaminated samples. As ready-to-eat salads which have been previously cleaned, this means that contamination might be caused by incorrect cleaning practices or inadequate hygienic handling. These results emphasize the necessity to apply and to maintain good hygienic practices in the restaurants.     

Prevalence of intestinal helminth eggs on vegetables grown in wastewater-irrigated areas of Titagarh,West Bengal,India

A total of 46 wastewater samples (untreated: 24 and treated: 22), 35 soil samples and 172 vegetable samples were collected from the wastewater-irrigated area of Titagarh to assess its contamination level with intestinal helminth. 83.3% of raw wastewater, 68.2% of treated wastewater, 68.6% of soil and 44.2% of vegetables in the study area were found to be positive for helminth ova. Vegetables grown in this area were found positive for Ascaris lumbricoides (36%), Trichuris trichiura (1.7%) and hookworms (6.4%). A. lumbricoides was the most predominant species observed in all the samples. Of all the vegetables examined, Pudina was most commonly contaminated followed by Lettuce, Spinach, Coriander, Celery and Parsley. High percentage of viable-stage intestinal helminth egg positive vegetable samples grown in the wastewater-irrigated study area may pose serious public health hazards.     

Estimated daily intake of pesticide residues exposure by vegetables grown in greenhouses in Al-Qassim region,Saudi Arabia

Residues of 23 pesticides (13 insecticides, 3 fungicides, 3 herbicides, 2 acaricides, 1 rodenticide and 1 nematicide) in 160 different vegetable samples cultivated under greenhouse conditions and collected from 4 major supermarkets located in Al-Qassim region, Saudi Arabia were monitored. A multiresidue method was carried out by gas chromatography with mass spectrometry (GC–MS). Residues were found in 89 samples. Fifty four samples were found above the maximum residue levels (MRLs). The most frequently found pesticides were carbaryl followed by biphenyl and then carbofuran. MRL values exceeded most often in cabbage (11 samples) followed by squash, green pepper and carrot (7 samples each) followed by cucumber and lettuce (6 samples each), egg-plant (5 samples) and then tomato (4 samples). Also, cabbage showed the highest contamination rates (16 samples), followed by carrot, cucumber and green pepper (12 samples each), squash (11 samples), lettuce and tomato (9 samples each) and egg-plant (8 samples). The highest concentrations were determined in lettuce followed by squash, cabbage and carrot. Al-Qassim region population’s average daily intake (EDI) has been estimated between 2 × 10^?5 and 0.597 μg/kg body weight/day and the hazard index (EDI/acceptable daily intake (ADI)) less than the unity for the tested compounds. The data illustrated that the intakes are much lower than the ADIs and the exposure level to whole pesticides was below the level to produce health risk. The data indicated also the need for regular monitoring programs for pesticide residues in vegetables cultivated under greenhouse conditions, at the national level, to protect consumers’ health.     

Microbiological quality of ready-to-eat minimally processed vegetables consumed in Brazil

Minimally processed leafy vegetables are ready-to-eat (RTE) products very attractive to consumers looking for healthy and convenient meals. However, the microbiological safety of these foods is of special concern due to the absence of lethal treatments during processing. In the present study, indicator microorganisms, Listeria spp. and Salmonella spp. were determined for 162 samples of minimally processed leafy vegetables commercialized in Brazil. Psychrotrophic aerobic bacterial populations >5 log CFU/g were found in 96.7% of the samples, while total and thermotolerant coliforms were detected respectively in 132 (81.5%) and 107 (66%) of vegetables analyzed. Escherichia coli was present in 86 (53.1%) samples analyzed and Listeria spp. and Salmonella spp. were detected respectively in 6 (3.7%) and 2 (1.2%) samples. These results indicate the need of implementing quality programs in the production chain of RTE vegetables to improve shelf life and microbiological safety.     

Stable isotope ratio and elemental composition parameters in combination with discriminant analysis classification model to assign country of origin to commercial vegetables – A preliminary study

Recently, increased public attention has been paid to the geographical authentication of food, including vegetables, which are considered to be one of the major health-promoting components in a balanced diet. The purpose of the present study was to investigate the suitability of the use of isotopic compositions of light elements (δ¹³C, δ¹⁵N, δ¹⁸O, δ³⁴S) in combination with multi-elemental fingerprinting (P, S, Cl, K, Ca, Mn, Fe, Zn, Br, Rb, Sr) to provide rapid, robust and inexpensive screening methods for distinguishing lettuce, sweet pepper, and tomato samples according to their given country of origin (i.e., Slovenia, Austria, Spain, Morocco, Italy, Greece), and thus ensuring their traceability in terms of their authenticity. The classification efficiency of the proposed multivariate statistical models using supervised pattern-recognition analysis, namely multivariate discriminant analysis, was sufficient for rapid and robust screening purpose. The predictions of the suggested discriminant analysis models per kind using cross-validation leave-one-out were 86.2%, 71.1% and 74.4% for lettuce, sweet pepper and tomato, respectively. The first use of the proposed methodology on vegetable samples on European and Mediterranean scales provides a valuable and necessary contribution to the development and implementation of a new national surveillance system that can be used to trace the geographical origins of vegetables.     

The contamination of various fruit and vegetable with Enterobius vermicularis,Ascaris eggs,Entamoeba histolyca cysts and Giardia cysts

A total of 55 fruit and vegetable samples were collected in Kahramanmaraş in order to assess their contamination level. The following fruit and vegetables were selected for this experiment: lettuce, parsley, cress, spinach and strawberry. The samples were collected in four different seasonal periods. The strawberry samples were obtained from commercial sources in Kahramanmaraş. In addition, four samples of water from canal that was used directly for the irrigation of crops and four soil samples were collected from four locations on two periods between 2002 fall and 2003 spring. Of the 10 Enterobius vermicularis positive samples were in lettuce, 12 in parsley, three in cress, four in spinach, 40 in strawberry, two in soil, one in irrigation water. Of the seven Ascaris eggs positive samples were in lettuce, four in parsley, two in spinach, and 20 in strawberry. Of the eight Entamoeba histolyca cysts positive samples were in lettuce, nine in parsley, and 12 in strawberry. Of the three Giardia cysts were found to be positive in lettuce, 18 in strawberry. In parsley, cress and spinach samples Giardia cysts were not found. In cress and spinach samples Entamoeba histolyca cysts and in cress samples Ascaris eggs were not observed. In 2002 spring and 2003 fall all of the parasite forms were detected in soil samples. As regards the irrigation water, in 2002 spring none of the form was detected but in 2003 fall all of the parasite forms were observed.     

Effect of hydrogen peroxide vapor treatment for inactivating Salmonella Typhimurium,Escherichia coli O157:H7 and Listeria monocytogenes on organic fresh lettuce

In this study, the efficacy of hydrogen peroxide vapor (HPV) for reducing Salmonella Typhimurium, Escherichia coli O157:H7 and Listeria monocytogenes on lettuce was investigated as well as its effect on lettuce quality. Lettuce was inoculated with a cocktail containing three strains of each pathogen then treated with vaporized hydrogen peroxide for 0, 2, 4, 6, 8 and 10 min. The concentrations of hydrogen peroxide used were 0, 1, 3, 5 and 10%. With increasing treatment time and hydrogen peroxide concentration, HPV treatment showed significant (P < 0.05) reduction compared to the control (0%, treated with vaporized distilled water). In particular, vaporized 10% hydrogen peroxide treatment for 10 min was the most effective combination for reducing the three pathogens on lettuce. The reduction levels of S. Typhimurium, E. coli O157:H7 and L. monocytogenes on lettuce were 3.12, 3.15 and 2.95 log₁₀ CFU/g, respectively. Furthermore, there were no significant (P > 0.05) quality changes (color and texture) of lettuce among all tested samples, and hydrogen peroxide residues were not detected after 36 h storage time in any of the treated samples. These results suggest that HPV treatment could be an alternative method for reducing S. Typhimurium, E. coli O157:H7 and L. monocytogenes on fresh produce.     

Incidence of Salmonella spp. in raw vegetables in Selangor,Malaysia

A total of 43 samples of ‘selom’ (Oenanthe stolonifera), 26 samples of ‘pegaga’ (Centella asiatica), 25 samples of ‘kangkong’ (Ipomoea aquatica) and 18 samples of ‘kesum’ (Polygonum minus) were examined for the presence of Salmonella spp. Salmonellae were detected from 40 (35%) of the vegetables samples examined. The most common serotypes isolated were S. weltevreden (23.5%), S. agona (16.2%), S. senftenberg (10.1%) and S. albany (6.7%). The other 27 Salmonella serovars were isolated at frequencies from 0.6% to 3.4%. Several of the Salmonella serotypes isolated in this study have been implicated in human infections in other countries. Although Salmonella species are frequently detected in foods of animal origin, the detection of 31 Salmonella serovars in four local salad vegetables in this study is not very encouraging, and supported the notion that these vegetables can be potential health hazards.     

Microbiological quality of organic and conventional vegetables sold in Brazil

While searching for healthier diets, people became more attentive to organic produce. Yet, organic foods may be more susceptible to microbiological contamination because of the use of organic fertilizers, a possible source of pathogenic bacteria. In this study, 130 samples of different organic and conventional vegetable varieties sold in Brazil were analyzed for mesophilic aerobic bacteria, yeasts and molds, total coliforms, Escherichia coli and Salmonella spp. Most of the mesophilic aerobic bacteria counts in organic and conventional vegetables ranged from 6 to 7 log10 CFU/g; most of the yeasts and molds counts ranged from 5 to 6 log10 CFU/g and most of the total coliforms counts ranged from 4 to 5 log10 CFU/g. E. coli was found in 41.5% of the organic and 40.0% of the conventional vegetables, and most samples had counts ranging from 1 to 2 log10 CFU/g. Salmonella spp. was not found in any sample. Comparative analyses of the microbial counts of organic and conventional vegetables showed that some organic varieties have greater counts. However, the global results show that this is not a trend. These results indicate the need of good farming practices, and proper sanitization before consumption, to ensure food quality and safety.     

Microbiological contamination linked to implementation of good agricultural practices in the production of organic lettuce in Southern Brazil

Interviews were conducted with the owners of three organic lettuce farms in the state of Rio Grande do Sul in southern Brazil using a standardized self-assessment questionnaire to ascertain the status of implementation of good agricultural practices and management systems in place. In addition, on each farm 132 samples (manure, field soil, water, workers' hands and equipment, lettuce seedlings, and crops) were collected during four visits throughout the lettuce crop production cycle and subjected to analysis for hygiene indicators (Escherichia coli, coliforms) and presence of Salmonella and E. coli O157. E. coli O157 was detected twice (in irrigation water and in rinse water) out of 27 analyzed water samples. Salmonella spp. was detected in one out of nine manure samples applied as organic fertilizer. In addition, generic E. coli was frequently present in numbers exceeding 10 cfu/g in manure, manured soil, and lettuce samples or more than 1 cfu/100 ml in water. No E. coli O157 was detected in any of the lettuce samples (n = 36), but Salmonella spp. was detected once in lettuce taken during the crop cycle 2 weeks before harvest. It was demonstrated that the combination of the self-assessment questionnaire and microbiological sampling and analysis could identify weak points in current organic farming practices in this region of southern Brazil. It was noted that manure composting was not adequately controlled and appropriate waiting times before application as an organic fertilizer to crop were not respected. Also the selection of the water source and the sanitary quality of the water used for irrigation were not under control. The washing step (with sanitizer) of lettuce crops at harvest, generally considered a potential reduction step for microbial contamination, was often not verified for its efficiency. This may detract from the sanitary quality of the produce and are risk factors for the introduction of pathogens in the lettuce sent to market. The study, combining interviews, sampling, and analysis, contributed to increasing the farmers' awareness of enteric pathogens as a food safety issue in leafy greens. Further communication and training on good agricultural practices are recommended to remediate the weak points identified in the current management system.     

Evaluation of minimally processed salads commercialized in Portugal

During the last decades food borne outbreaks associated with consumption of raw vegetables have been increasing and green leafy vegetables seem to be the most frequently implicated products.In order to determine the microbial quality and the incidence of the major food borne pathogens in Minimally Processed (MP) salads commercialized in Portugal, a survey was conducted in Lisbon Retail Markets, from July 2007 to August 2008, to determine microbial contamination loads and identify potential pathogenic bacteria.A total of 151 samples were purchased from 2 supermarkets: 38 romaine lettuce, 12 various spinach and 101 mixed salads with three or four different ingredients. The samples were tested for aerobic psychotropic micro-organisms (APM), Enterobacteriaceae, Escherichia coli, Listeria spp., presumptive Bacillus cereus, Aeromonas hydrophila and Clostridium perfringens counts as well as for presence of Salmonella spp., Listeria monocytogenes and E. coli O157. Samples were also evaluated for taste quality.The results showed that APM counts of romaine lettuce and mixed salads had a similar median, respectively, 6.2 and 6.5 log cfu/g and mixed spinach had the highest one (7.6 log cfu/g). The median value found for Enterobacteriaceae was 5.44 log cfu/g. Only four samples showed positive result for E. coli (2.65%) but just one (0.8%) had a slightly higher load of contamination. Although the percentage and levels of contamination loads were low, these mustn’t be ignored, for the reason that the strains in three of the samples belong to VTEC group (1.99%). E. coli O157, Salmonella spp. and C. perfringens weren’t detected in any sample. For the enumeration of Listeria spp., two samples (1.32%) had presence of Listeria innocua and L. monocytogenes had an incidence of 0.66%. A. hydrophila was identified in 11 samples (7.28%), and in 8 of them with considerable counts (>10⁵). Contamination with B. cereus was found in 22.7% of samples analyzed, though in small numbers, which doesn’t represent a major concern to food safety. All isolated strains were assessed for its potential toxin production and it was found that 40% of these strains had this ability. Results from sensory panel showed organoleptic differences in salads during its shelf-life period.     

Isolation,identification and antimicrobial resistance of Cronobacter spp. isolated from various foods in China

Cronobacter spp. are important foodborne pathogens that can cause severe diseases such as meningitis, sepsis, and necrotizing enterocolitis in neonates. In this study, 195 food samples, including cereals, cereal products, powdered infant formula (PIF), infant food formula, herbs, spices, vegetables, and fruits, were analyzed for the presence of Cronobacter spp. by culture-based method. The presumptive isolates were further confirmed by targeting the 16S rDNA gene using PCR. Out of 195 samples, 13 samples (6.7%) were positive for Cronobacter species. 12 of 85 cereal and cereal products (14.1%), and 1 of 22 herbs and spices (4.5%) were contaminated. In contrast, no Cronobacter was detected in commercial powdered infant formula, infant food formula, vegetables, or fruits. Alignment of 16S rRNA gene sequences showed that 13 isolates was most closely related to the genus Cronobacter. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis revealed that Cronobacter sakazakii was the only Cronobacter species isolated from various food samples. The antimicrobial susceptibility of 13 Cronobacter isolates was determined by the standard disk diffusion method. All isolated strains, except one resistant to ampicillin, were sensitive or displayed intermediate susceptibility to the 10 antimicrobial agents investigated. No multiple drug resistance was observed.     

Large-volume immunomagnetic separation combined with multiplex PCR assay for simultaneous detection of Listeria monocytogenes and Listeria ivanovii in lettuce

Multiplex polymerase chain reaction (mPCR) has been widely used for the simultaneous detection of various target bacteria in vegetables. However, an enrichment period is necessary to improve the sensitivity of the mPCR method. In this paper, large-volume (10 mL) immunomagnetic separation (IMS) combined with mPCR for the rapid detection of Listeria monocytogenes and Listeria ivanovii in lettuce without further enrichment process is reported for the first time. Various parameters that affected the capture efficiency (CE) of IMS, including the amounts of streptavidin and biotinylated anti-Listeria monoclonal antibodies on the surface of magnetic nanobeads, the amount of immunomagnetic beads, immunoreaction time, and magnetic separation time, were systematically investigated. Moreover, the concentrations of primers, PCR conditions, and genomic DNA isolation for mPCR assay were optimized. Under optimum conditions, the CE of large-volume IMS for L. monocytogenes and L. ivanovii was greater than 90% when the concentration of target bacteria was less than 10⁶ CFU/mL in pure culture, and was more than 80% when the concentration was below 10⁵ CFU/mL in lettuce samples. The limit of detection of IMS combined with mPCR assay reached as low as 1.0 CFU/mL in pure culture and 10 CFU/g in lettuce. The overall assay time, including sample preparation, large-volume IMS, and mPCR assay, took less than 7 h. In summary, the developed large-volume IMS-based mPCR system exhibits great potential for routine screening detection of foodborne pathogenic bacteria for safety monitoring.     

Comparison of two pre-enrichments broths for recovering Listeria spp. from salmon (Salmo salar) and salmon-trout (Oncorhynchus mykiss)

Low levels of occurrence of Listeria spp. in fresh salmon (Salmo_salar ) and salmon-trout (Oncorhynchus mykiss), may be related to the selectivity of the pre-enrichment broth recommended by ISO 11290-1. The purpose of this study was to compare the abilities of Fraser base (without supplements) and 0.1% (w/v) peptone water for recovering Listeria spp. from the fresh fish samples.Fifty-six fish were swabbed and the swabs placed in Fraser base and in 0.1% (w/v) peptone water. Samples were analysed 4–6 h later following the ISO 11290-1 protocol. A total of fifteen Listeria spp. positive samples were found. Three and twelve samples were found to contain respectively, L. monocytogenes and L. innocua. The Fraser base did not detect any of the three L. monocytogenes positive samples. Only two Listeria spp. positive samples were simultaneously recovered by the two broths.