Quantum dot biosensor combined with antibody and aptamer for tracing food-borne pathogens

Due to the increasing number of food-borne diseases,more attention is being paid to food safety.Food-borne pathogens are the main cause of food-borne diseases,which seriously endanger human health,so it is necessary to detect and control them.Traditional detection methods cannot meet the requirements of rapid detection of food due to many shortcomings,such as being time-consuming,laborious or requiring expensive instrumentation.Quantum dots have become a promising nanotechnology in pathogens tracking and detection because of their excellent optical properties.New biosensor detection methods based on quantum dots are have been gradually developed due to their high sensitivity and high specificity.In this review,we summarize the different characteristics of quantum dots synthesized by carbon,heavy metals and composite materials firstly.Then,attention is paid to the principles,advantages and limitations of the quantum dots biosensor with antibodies and aptamers as recognition elements for recognition and capture of food-borne pathogens.Finally,the great potential of quantum dots in pathogen detection is summarized.

Antimicrobial effects of carnosic acid,kaempferol and luteolin on biogenic amine production by spoilage and food-borne pathogenic bacteria

Antimicrobial effects of carnosic acid,kaempferol and luteolin on biogenic amine(BA)production by five spoilage(Photobacterium damselae,Proteus mirabilis,Enterobacter cloacea,Pseudomonas luteola and Serratia liquefaciens)and five food-borne pathogenic bacteria(Staphylococcus aureus ATCC29213,Enterococcus faecalis ATCC29212,Escherichia coli ATCC25922,Salmonella Paratyphi A NCTC13 and Yersinia enterocolitica NCTC 11175)were investigated.The formation of ammonia(AMN),trimethylamine(TMA)and BAs by all bacterial strains were observed using ornithine decarboxylase broth.BAs,AMN,and TMA were determined by using high performance liquid chromatography(HPLC)method.The results showed that significant differences were observed(P≤0.05)in formation among spoilage and also food-borne bacteria.The impact of phenolic compounds on AMN,TMA and BAs production was dependent on bacterial strains.When total amount of cadaverine(CAD),putrescine(PUT),histamine(HIS)and tyramine(TYR)was considered,the phenolic compounds presented antimicrobial activity against fish spoliage bacteria and food-borne pathogens following the order;kaempferol>carnosic acid>luteolin.These phenolics have potential to be used as food preservatives.

Survival of some food-borne bacteria in kefir produced by microbial levan and pullulan

Kefir is a fermented milk product produced by kefir grains traditionally or lyophilized starter culture.Some quality characteristics of kefir produced at 22℃ and 30℃ using kefir grains after addition of microbial levan and pullulan were investigated for 14 days.Additionally,the survival of different Gram-positive and Gram-negative bacteria strains which were inoculated before and after fermentation were investigated during storage.The pH and titratable acidity were in the ranges of 4.67–4.39 and 1.10–0.87%,respectively.The highest exopolysaccharide values(458.3–465.3 mg/kg)were found in the samples produced with the addition of 1%(w/v)of microbial levan at 30℃.Yeast counts were in the ranges of 6.73–5.11 log CFU/mL while the lactobacilli and lactic streptococci counts were in the ranges of 9.64–7.91 and 9.64–8.69 log CFU/mL,respectively.The microbial polysaccharide addition did not show any significant differences in the enumeration of lactic acid bacteria in kefir(p>0.05).All Gram-positive and Gram-negative bacteria grew/survived during fermentation however Listeria monocytogenes was the most susceptible test bacterium to metabolites during storage.The highest reduction in the counts of L.monocytogenes was determined as 2.39 log units after 24 h of fermentation at 30℃ in the samples which were inoculated before fermentation and produced with the addition of pullulan.Kefir samples produced at 30℃ without polysaccharide addition were considered as the best with respect to appearance,taste,consistency and overall acceptability.

Natural bioactive substances for the control of food-borne viruses and contaminants in food

Food-borne viruses and contaminants,as an important global food safety problem,are caused by chemical,microbiological,zoonotic,and other risk factors that represent a health hazard.Natural bioactive substances,originating from plants,animals,or microorganisms,might offer the possibility of preventing and controlling foodborne diseases.In this contribution,the common bioactive substances such as polyphenols,essential oils,proteins,and polysaccharides which are effective in the prevention and treatment of food-borne viruses and contaminants are discussed.Meanwhile,the preventive effects of natural bioactive substances and the possible mechanisms involved in food protection are discussed and detailed.The application and potential effects of natural bioactive substances in the adjuvant treatment for food-borne diseases is also described.

Isolation and identification of Salmonella from curry samples and its sensitivity to commercial antibiotics and aqueous extracts of Camelia sinensis(L.) and Trachyspermum ammi(L.)

Objective:To isolate Salmonella from curry samples and to evaluate the drug sensitivity of the food-borne Salmonella and its susceptibility to specific plant extracts.Methods:Salmonella was isolated from the curry samples by standard microbiological methods and was confirmed by biochemical tests.The antibiotic susceptibility test was conducted by disc diffusion method using commercially available antibiotics such as ampicillin,tetracycline,chloramphenicol,kanamycin,and penicillin.In addition,the susceptibility of the food-borne Salmonella was also evaluated against the aqueous extracts of Camelia sinensis(L.) Theaceae(tea leaves) and the Trachyspermum ammi(L.) Apiaceae(ajwain or omum seeds).Results:Out of fifty curry samples,only seven samples were identified to have Salmonella contamination.The Salmonella isolates showed a significant drug resistance pattern except for kanamycin.The plant extracts showed a considerable antibacterial activity against the isolates,indicating the presence of antimicrobial principle which can be exploited after complete pharmacological investigations.Conclusions:The present study demonstrates the occurrence of Salmonella in the curry samples,and shows significant drug resistance against most of the commercially available antibiotics,except kanamycin.Antimicrobial effect of the plant extracts against the food-bone Salmonella suggests that dietary including medicinal herbs would be one strategy to manage food borne pathogens.

Isolation, serotype diversity and antibiogram of Salmonella enterica isolated from different species of poultry in India

Objective: To study the occurrence and serotype diversity of Salmonella isolates in different species of poultry(chicken, emu and duck) and determine their resistance pattern against various antibiotics of different classes.Methods: About 507 samples comprising 202 caecal contents and 305 fecal samples from chicken, emu and duck were processed for isolation of Salmonella enterica. Salmonellae were isolated and detected by standard protocol of ISO 6579 Amendment 1: Annex D. Genetic confirmation was also made by using 16 S r RNA genus specific PCR. Serotype specific PCR was also done to detect the most common serovars viz. Salmonella Enteritidis, Salmonella Typhimurium and Salmonella Gallinarum. All obtained isolates were subjected to a set of 25 antibiotics to study their antibiogram by using Baeur-Kirby disk diffusion method.Results: Out of 507 samples processed, 32 isolates of Salmonella enterica(18 from caecal contents and 14 from faecal samples) were obtained, of which 24 belonged to 6 different serovars, 6 were untypeable and 2 were rough strains. Salmonella Enteritidis was the most predominant serotype(9), followed by Salmonella Typhimurium(5), Salmonella Virchow(4), Salmonella Gallinarum(3), Salmonella Reading(2) and Salmonella Altona(1). Antibiotic resistance pattern was maximum(100%) to oxacillin, penicillin and clindamycin, followed by ampicillin(68.75%), tetracycline(65.62%), nalidixic acid(56.25%) and colistin(46.87%). High sensitivity of isolates was recorded for chloramphenicol(96.87%) followed by meropenem(84.37%). Conclusions: Occurrence of high proportion of serovars in our study which can cause serious gastroenteritis in humans is a matter of concern. Salmonella Altona has been detected for the first time in India from poultry. This serotype is known to cause serious outbreaks of gastroenteritis in humans. Multidrug resistant isolates were recovered at high percentage which can be attributed to non-judicious use of antibiotics both in prophylaxis and treatment regimen. This observation draws serious attention as poultry serves as an important source of transmission of these multidrug resistant Salmonella serovars to humans.

Antimicrobial Activity of Wild Plant Seed Extracts against Human Bacterial and Plant Fungal Pathogens

Five wild plant species belonging to different families (Chenopodium album, Plantago major, Elytrigia elongata, Filipendula ulmaria and Nigella sativa) widely spread in Russian Federation and the former USSR were evaluated for their ability to inhibit growth of two important human food-borne pathogens (Escherichia coli O157:H7 and Listeria monocytogenes strain EGD-e) and eight plant pathogens (Alternaria alternata, Alternaria tenuissima, Bipolaris sorokiniana, Stagonospora nodorum, Fusarium solani, Fusarium oxysporum, Fusarium culmorum and Phytophtora infestans). To isolate biologically active compounds from seeds, a step-wise procedure including extraction with hexane, ethyl acetate, ethanol, and 10% acetic acid followed by reversed-phase HPLC was developed. Using disc-diffusion assay, the highest activity against E. coli O157:H7 was observed with extracts from F. ulmaria (hexane and ethyl acetate extracts and the unbound RP-HPLC fraction) and P. major (ethyl acetate extract and the unbound RP-HPLC fraction);E. elongate (the unbound RP-HPLC fraction) was less active. The extracts from P. major and E. elongate (the unbound RP-HPLC fractions) were equally highly active against L. monocytogenes, while those of F. ulmaria (the unbound RP-HPLC fraction) and N. sativa (hexane and ethyl acetate extracts) were less active against this pathogen. The dynamics of L. monocytogenes EGD-е and E. coli O157:H7 growth in the presence of two most potent extracts (RP-HPLC-unbound fractions of P. major and E. elongate and the hexane extract of F. ulmaria) was studied.

Isolation of <i>Bacillus cereus</i>in a Facility Preparing School Meals

Food safety is a fundamental requirement in mass catering, as large numbers of meals are served each day to potentially vulnerable consumers, such as children. Food Business Operators implement plans for the microbiological monitoring of the meals prepared and served in the catering sector, and for the swab-sampling of surfaces. From January 2018 to June 2019, our laboratory analyzed both food and swab samples from four catering facilities. Considering the EFSA 2018 data, we specifically focused on samples analyzed for Bacillus cereus. Our data substantially showed episodic contamination due to a piece of equipment that is not usually subjected to microbiological control, thus suggesting that every aspect should be scrutinized in order to identify critical points. While Bacillus cereus is widespread in nature and common in soil, it is adapted for growth in the intestinal tracts of insects and mammals. It is often present in a variety of foods, and may cause an emetic or a diarrheal type of food-associated illness. B. cereus produces several toxins. Multiplex PCR enables seven toxin genes to be detected (hblC, hblD, hblA, nheA, nheB, nheC and cytK).

Comparative prevalence of pathogenic and spoilage microbes in chicken sausages from Egypt and Greece

This study investigated the spread of foodborne pathogens: Listeria monocytogenes, Es-cherichia coli O157:H7, Staphylococcus aureus and Salmonella in chicken sausage samples collected from retail markets in Greece and Egypt during 2006 and from Egypt through 2010. Other microbiological parameters;total viable count (TVC), lactic acid bacteria (LAB), pseudomonads (PS), staphylococci (STAPH), Brochothrix thermosphacta (BT), Enterobacteriaceae (EN), Escherichia coli (EC), yeasts and moulds (Y&M) were also counted. Egyptian chicken sausage samples were found to harbor L. mono- cytogenes, Staph. aureus and E. coli O157:H7;with frequencies equivalent to 24%, 60% and 26% of the total samples during 2006 and 37.87%, 64.44% and 41.11% of the total samples during 2010, respectively, while Greek samples were entirely free of theses pathogens. Enrichment techniques indicated the absence of Salmonella from both Greek and Egyptian samples. The obtained results may mobilize food producers and handlers in developing countries to take the due measures reducing food-borne pathogen risks and spoilage flora alongside the poultry chain.

Deconvolution of the Error Associated with Random Sampling

In this work empirical models describing sampling error (&#916;) are reported based upon analytical findings elicited from 3 common probability density functions (PDF): the Gaussian, representing any real-valued, randomly changing variable x of mean &#956;?and standard deviation &#963;the Poisson, representing counting data: i.e., any integral-valued entity’s count of x (cells, clumps of cells or colony forming units, molecules, mutations, etc.) per tested volume, area, length of time, etc. with population mean of &#956;?and;binomial data representing the number of successful occurrences of something (x+) out of n observations or sub-samplings. These data were generated in such a way as to simulate what should be observed in practice but avoid other forms of experimental error. Based upon analyses of 104 &#916;?measurements, we show that the average &#916;?() is proportional to ?(&#963;x&#8226;&#956;-1;Gaussian) or ?(Poisson & binomial). The average proportionality constants associated with these disparate populations were also nearly identical (;±s). However, since ?for any Poisson process, . In a similar vein, we have empirically demonstrated that binomial-associated ?were also proportional to &#963;x&#8226;&#956;-1. Furthermore, we established that, when all ?were plotted against either ?or &#963;x&#8226;&#956;-1, there was only one relationship with a slope = A (0.767 ± 0.0990) and a near-zero intercept. This latter finding also argues that all , regardless of parent PDF, are proportional to &#963;x&#8226;&#956;-1?which is the coefficient of variation for a population of sample means (). Lastly, we establish that the proportionality constant A is equivalent to the coefficient of variation associated with &#916;?() measurement and, therefore, . These results are noteworthy inasmuch as they provide a straightforward empirical link between stochastic sampling error and the aforementioned Cvs. Finally, we demonstrate that all attendant empirical measures of &#916;?are reasonably small (e.g., ) when an environmental microbiome was well-sampled: n = 16 - 18 observations with &#956;&#8764;3?isolates per observation. These colony counting results were supported by the fact that the two major isolates’ relative abundance was reproducible in the four most probable composition observations from one common population.

Grape Phenolic Extract Potentially Useful in the Control of Antibiotic Resistant Strains of <i>Campylobacter</i>

In this work, a grape phenolic extract obtained by methanol extraction has been demonstrated to be effective in inhibiting the growth of different strains and species of Campylobacter, one of the most important bacterial foodborne pathogens causing gastroenteritis worldwide. Noteworthily, it was particularly effective against several strains presenting multiple antibiotic resistances. In all cases, the minimum inhibitory concentration (MIC) was lower than 300 mg GAE/L, being of 60 mg GAE/L for one of the most resistant strains (C. coli LP2), while the others were between 120 mg GAE/L and 180 mg GAE/L. The analytical study of the main phenolic compounds in the grape extract revealed that it was mainly constituted by catechins (85.7%) and phenolic acids (13.7%). However, experiments developed using pure standards demonstrate that phenolic acids (such as gallic, p-hidroxibenzoic, vanillic, and homovanillic acids) were the most active, provoking a Campylobacter growth decrease between 6.7 and 7.6 log, while epicatechin was the only catechin with activity as pure compound (1 log of growth decrease).

Marine Fish Toxins in Thailand: Report of 6 Suspected Ciguatera Cases

Food poisoning or gastroenteritis is a common diagnosis for individuals who have nausea, vomiting and diarrhea after ingestion of fish. When also manifesting neurological symptoms, these are blamed on puffer fish poisoning, but ciguatera fish poisoning (CFP) can also manifest only with gastroenteritis, without neurological complications and remain undiagnosed. We report patients who fulfilled criteria of CFP suffering from severe GI disturbances, neurological manifestations, compromised cardiovascular status and autonomic dysfunction. All recovered within 1 - 3 days with supportive treatment. There were two small outbreaks: one in Bangkok in 2007 (2 patients) and another (2009) in Phuket (4 patients). All patients consumed the same unidentified fish portion and had severe GI symptoms. One had acute ventilatory failure requiring intubation whereas the remaining had neurological disturbances consisting of paresthesia, severe vertigo and ataxia. Absence of reflex tachycardia was noted in all patients who had severe volume depletion and shock. The most severe patient could be extubated within 24 hours and was discharged in 48 hours. All of the remaining recovered completely within 48 hours. Severe abdominal pain, nausea and vomiting and autonomic dysfunction in the form of bradycardia in the presence of hypotension were seen. Dramatic recovery within 48 hours occurred in all cases. None of the fish considered to have been responsible was available for testing. Physicians should be aware of CFP intoxication in the differential diagnosis of gastroenteritis-like syndromes after eating seafood.

Bacteriocins as antimicrobial and preservative agents in food:Biosynthesis,separation and application

Emerging evidence shows the trend of using safe and natural preservatives like bacteriocins in food processing.The increasing demand by the food industry to extend keeping quality and prevent spoilage of various food products has appealed for new preservatives and new methods of conservation.Further,to discover the novel spectrum of antimicrobial compounds that could effectively battle food-borne pathogens,bacteriocins have been intensively studied in the last few years.Recently,great attention has been paid to the application of lactic acid-bacterial bacteriocins targeting food spoilage-causing or pathogenic microorganisms with no significant side effects.Different mechanisms of action like pore-formation,retarding cell-wall/nucleic acid/protein synthesis have been proposed and described for diverse bacteriocins.Therefore,the syntheses,purification of bacteriocins in addition to their applications as antimicrobial and preservative agents in food processing are reviewed in detail.The review will also discuss the preservative effect of bacteriocins and their combinations having multiple modes of action(hurdle approach)to reduce the microbial load as well as antimicrobial resistance.

Comparison of novel and standard diagnostic tools for the detection of Schistosoma mekongi infection in Lao People’s Democratic Republic and Cambodia

Background:Given the restricted distribution of Schistosoma mekongi in one province in Lao People’s Democratic Republic(Lao PDR)and two provinces in Cambodia,together with progress of the national control programmes aimed at reducing morbidity and infection prevalence,the elimination of schistosomiasis mekongi seems feasible.However,sensitive diagnostic tools will be required to determine whether elimination has been achieved.We compared several standard and novel diagnostic tools in S.mekongi-endemic areas.Methods:The prevalence and infection intensity of S.mekongi were evaluated in 377 study participants from four villages in the endemic areas in Lao PDR and Cambodia using Kato-Katz stool examination,antibody detection based on an enzyme-linked immunosorbent assay(ELISA)and schistosome circulating antigen detection by lateral-flow tests.Two highly sensitive test systems for the detection of cathodic and anodic circulating antigens(CCA,CAA)in urine and serum were utilized.Results:Stool microscopy revealed an overall prevalence of S.mekongi of 6.4%(one case in Cambodia and 23 cases in Lao PDR),while that of Opisthorchis viverrini,hookworm,Trichuris trichiura,Ascaris lumbricoides and Taenia spp.were 50.4%,28.1%,3.5%,0.3%and 1.9%,respectively.In the urine samples,the tests for CCA and CAA detected S.mekongi infections in 21.0%and 38.7%of the study participants,respectively.In the serum samples,the CAA assay revealed a prevalence of 32.4%,while a combination of the CAA assay in serum and in urine revealed a prevalence of 43.2%.There was a difference between the two study locations with a higher prevalence reached in the samples from Lao PDR.Conclusions:The CCA,CAA and ELISA results showed substantially higher prevalence estimates for S.mekongi compared to Kato-Katz thick smears.Active schistosomiasis mekongi in Lao PDR and Cambodia might thus have been considerably underestimated previously.Hence,sustained control efforts are still needed to break transmission of S.mekongi.The pivotal role of highly sensitive diagnostic assays in areas targeting elimination cannot be overemphasised.

Recent developments of lactic acid bacteria and their metabolites on foodborne pathogens and spoilage bacteria:Facts and gaps

Lactic acid bacteria(LAB)are common microorganisms found in various ecosystems including in plants,fermented foods,and the human body.Exploring the biodiversity of lactic acid microflora and characterization of LAB is a new approach to form a variety of starter communities to create innovative nutritional food matrices.There has been growing interest in LAB isolated from non-dairy environments as these bacteria exhibit significant metabolic diversity and have unique taste-forming activities.Disease may be prevented,or treated by LAB but the treatment of disease conditions with LAB is highly dependent on the host's microbiome and diet and varies in both effectiveness and side effects from individual to individual.Future perspectives on the study of LAB may be related to the expansion of our knowledge in the fields of genetics and genetic engineering.The application of genetic science may help to improve existing strains and develop new strains with characteristics designed for specific purposes.Therefore,the preservative effects of LAB and their metabolites,as well as their interaction on the growth of food borne pathogens and food spoilage microorganisms were elucidated.In addition,the competitive models for microbial growth between LAB and other microorganisms as well as the role of LAB in the elimination of toxic compounds in food products were discussed.Moreover,the review provided an overview of the risks and benefits of using LAB in the food industry.

Evidence on antimicrobial activity of essential oils and herbal extracts against Yersinia enterocolitica - A review

Yersinia enterocolitica is a very common food-borne pathogen which causes gastrointestinal infections (yersiniosis) in humans and a wide array of animals (e.g.cattle,deer,pigs,and birds).Due to the increasing interest in innovative plant-based substances as common food preservatives,several essential oils and herbal extracts have been investigated deeply that resulted in the emergence of novel anti-Yersinia additives.We reviewed relevant work done by 53 researchers covering literature from the year 2002 to till date.Some species such as Origanum vulgare ,Rosmarinus officinalis ,Thymus vulgaris ,Ocimum basilicum have been extensively investigated and identified that 1,8-cineole,linalool and γ-terpinene as compounds found in the essential oils of these plants have anti-Yersinia activity active food packaging agents.In the same direction,some promising results have been mentioned about the herbal extracts of Murrya koenigii ,Tanacetum vulgare and Tanacetum balsamita,but further investigations are needed for their sustainable implications.According to hierarchical cluster analysis,we found that Lamiaceae and Lauracea as the most significant families with anti-Yersinia activity.Towards the end,we proposed new research trends in order to enhance a global knowledge about the use of natural products against Y.enterocolitica .