Foodborne Pathogenic Bacteria Research Articles

Intelligent Identification of Foodborne Pathogenic Bacteria by Self-Transfer Deep Learning and Ensemble Prediction Based on Single-Cell Raman Spectrum

Foodborne pathogenic infections pose a significant threat to human health. Accurate detection of foodborne diseases is essential in preventing disease transmission. This study proposed an AI model for precisely identifying foodborne pathogenic bacteria based on single-cell Raman spectrum. Self-transfer deep learning and ensemble prediction algorithms had been incorporated into the model framework to improve training efficiency and predictive performance, significantly improving prediction results. Our model can identify simultaneously gram-negative and positive, genus, species of foodborne pathogenic bacteria with an accuracy over 99.99%, as well as recognized strain with over 99.49%. At all four classification levels, unprecedented excellent predictive performance had been achieved. This advancement holds practical significance for medical detection and diagnosis of foodborne diseases by reducing false negatives.

Siamese neem tree as a natural preservative: Chemical profile, antioxidant properties, and antibacterial efficacy against foodborne pathogens and spoilage bacteria

The objective of the present study was to investigate the effect of various ethanol in water solvent systems (0, 25, 50, 75 and 100% v/v) on the extraction crude yield, total phenolic content, total flavonoid content, and chemical profile of Azadirachta indica (Siamese neem tree) leaf extracts. In addition, the antioxidant and antimicrobial properties were investigated using in vitro assays. Crude yield was highest for the water extract (5.78 g/100 g DW) and decreased with increased ethanol. Total phenolic and flavonoid contents were highest in the 75% ethanol extract (26.95 mg GAE/g crude and 23.73 mg QE/g crude, respectively). GC-MS analysis of the 75% ethanol extract revealed 33 bioactive compounds, accounting for 96.33% of the total area. Significant components included benzene, 1,4-bis(phenylmethyl)- (15.05%), and naphthalene, 1,6-dimethyl- (10.98%); also present were sterols, fatty acids, hydrocarbons, aromatic, and heterocyclic compounds, indicating a complex chemical profile. In antioxidant assays, the 75% ethanol extract revealed the highest DPPH radical scavenging activity (IC50: 143.03 mg/L), reducing power (IC50: 378.69 mg/L), and lipid peroxidation (IC50: 526.25 mg/L). However, the absolute ethanol extract exhibited both the highest metal chelating activity (IC50: 382.60 mg/L) and the strongest antimicrobial activity, inhibiting all 11 tested foodborne pathogenic and spoilage bacteria. The lowest minimum inhibitory concentration (MIC) of 25 mg/mL was observed for Staphylococcus aureus, Aeromonas hydrophila, Pseudomonas fluorescens, Latilactobacillus sakei, Streptococcus sp., and Lactococcus cremoris, with inhibition zone diameters of 27.21, 28.79, 28.19, 17.60, 15.09 and 11.20 mm, respectively. Similarly, the lowest minimum bactericidal concentration (MBC) of 25 mg/mL was obtained for S. aureus and L. sakei, indicating potent antibacterial effects against these species. Future studies should include direct comparative analyses of neem extracts and synthetic preservatives to evaluate further their relative efficacy and applicability in real-world food systems.

Silver nanoparticles/carbon dots nanocomposite with potent antibiofilm and long-term antimicrobial activity doped into chitosan/polyvinyl alcohol film for food preservation.

Exploration of robust antiseptics with antibiofilm performance and long-term antimicrobial activity is of great significance to effectively destroy foodborne pathogenic bacteria. Herein, a silver nanoparticles (Ag NPs) /carbon dots (CDs) nanocomposite (Ag@CDs) was constructed by the reaction of Ag+ with CDs, which has strong antibacterial ability, and mighty biofilm inhibition and destruction ability toward E. coli and S. aureus. Notably, low concentration of Ag@CDs (40.0 and 80.0μg/mL) could ablate 86.11% E. coli and 75.86%S. aureus biomass of mature biofilm. To our knowledge, this is the first bactericide with powerful biofilm destruction activity. In addition, Ag@CDs exhibited long-term (30 d) antibacterial effect on the substrates of plastic, cotton, gauze, and glass. Ag@CDs was evenly dispersed into the matrix of chitosan (CS)/polyvinyl alcohol (PVA) to fabricate well-blended food packaging films. Among which, the 3% Ag-CP film exhibited improved mechanical performance, excellent UV-Vis light blocking ability, and intensive antimicrobial activity. Despite seven days of storage, 3% Ag-CP still could preserve the freshness and safety of the pork and shrimp, certifying it extends the storage life of packaged foods.

Occurrence and growth characteristics of Cronobacter species in dried plant-based and functional foods intended for direct consumption

Cronobacter is a genus of emerging opportunistically pathogenic foodborne bacteria that can cause life-threatening diseases in neonates and infants, predominantly upon administration of contaminated powdered infant formula. The origin of this bacterial genus is assumed to be associated with plants. Because of the bacterium's xerotolerant nature, dried plant-based food products are considered to be a possible source of contamination. Due to the absence of microbiological criteria in food categories other than dried infant formulae and dried dietary foods for special medical purposes intended for infants and a lack of reporting obligations, the prevalence and the occurrence of infections are only sparsely characterized and very likely underestimated.In this study, 89 dried plant-based and functional food products intended for direct consumption were screened for the presence of Cronobacter spp., resulting in an overall positivity rate of 28.1%.Challenge tests in overnight oats revealed C. sakazakii to be able to reach high concentrations within 24 h when incubated at 20 °C and 30 °C but not when incubated at 6 °C. Cronobacter spp. also grew to quantifiable concentrations within 24 h when incubated at 20 °C and 30 °C upon rehydration of selected samples found to be contaminated during the screening.The obtained results emphasize the importance of storage of rehydrated dried plant-based food preparations at proper temperatures to avoid bacterial growth and prevent potential infections. The collected data suggest the evaluation of additional microbiological criteria for food categories with a high prevalence of Cronobacter spp. likely to be consumed by susceptible adult population groups.

DETECTION, IDENTIFICATION, AND ANTIBIOTIC RESISTANCE PATTERNS OF FOODBORNE BACTERIAL AND FUNGAL PATHOGENS

Background: Foodborne diseases are verry common and easily spread, among strains of Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, and Clostridium spp. Purpose: To isolate and characterize foodborne pathogenic bacteria and fungi in various foodstuffs. Method: A total of 260 samples (130 each from Peshawar and Mardan) were collected and analyzed. Only 61 tested positive for various types of bacterial and fungal pathogens. Then evaluated for their antibiotic/anti-fungal sensitivity patterns towards a panel of selected antibiotics and anti-fungal. Result: The Gram-positive isolates showed the highest resistance to methicillin (79%) and amoxicillin (63%), most sensitive to ceftriaxone (88%), levofloxacin (86%), and cefotaxime (77%). Intermediate activities were exhibited by azithromycin (50%) and vancomycin (55%). In terms of the Gram-negative bacteria, the best activities were shown by ciprofloxacin (100%), cefoxitin (100%), chloramphenicol (100%), and ceclor (100%). Intermediate activity was discovered for cefixime (50%), cefuroxime (50%), and linezolid (50%). Three anti-fungal drugs (fluconazole, voriconazole, and nystatin) were used to assess their potency against the fungal pathogens. Mucor spp. proved relatively more susceptible to all anti-fungal drugs. The only Fusarium spp. isolate was highly resistant to all anti-fungal in this research. Conclusion: The prevalence of Gram-positive bacteria is greater than Gram-negative bacteria in the current study. The frequency of fungal pathogens was relatively high in both raw and ready-to-eat foods, while packaged foods were free from fungal contamination. We recommend that appropriate safety when handling and cooking food. Moreover, food products should be screened for different pathogenic microbes.

Identification and characterization of a novel bacteriocin PCM7-4 and its antimicrobial activity against Listeria monocytogenes

Listeria monocytogenes, a pathogenic bacterium causing zoonotic diseases, necessitates the urgent search for novel anti-Listeria monocytogenes drugs due to the continuous emergence of drug-resistant bacteria. In this study, we isolated and identified a bacteriocin-producing strain CM7–4 from seawater as Bacillus velezensis through 16S rRNA sequence analysis. Moreover, we successfully purified a novel bacteriocin named PCM7–4 from Bacillus velezensis CM7–4. The molecular weight of PCM7–4 was determined to be 40,228.99 Da. Notably, PCM7–4 exhibited broad-spectrum antibacterial activity against both Gram-positive and Gram-negative bacteria with a minimum inhibitory concentration (MIC) of 5.625 μg/mL against Listeria monocytogenes specifically. It demonstrated heat resistance and high stability within the pH range of 2–12 while being sensitive to proteinase K degradation without any observed hemolytic activity. Furthermore, SEM analysis revealed that PCM7–4 effectively inhibited biofilm formation and disrupted cell membranes in Listeria monocytogenes cells. Transcriptome analysis revealed that PCM7–4 exerts an impact on genes associated with crucial metabolic pathways, encompassing the biosynthesis of secondary metabolites, phosphotransferase systems (PTS), and starch/sucrose metabolism. These findings highlight the significant potential of bacteriocin PCM7–4 for the development of effective antimicrobial interventions targeting food-borne pathogenic bacteria.

Classification and Identification of Foodborne Bacteria in Beef by Utilising Surface-Enhanced Raman Spectroscopy Coupled with Chemometric Methods.

The detection and classification of foodborne pathogenic bacteria is crucial for food safety monitoring, consequently requiring rapid, accurate and sensitive methods. In this study, the surface-enhanced Raman spectroscopy (SERS) technique coupled with chemometrics methods was used to detect and classify six kinds of foodborne pathogenic bacteria, including Salmonella typhimurium (S. typhimurium), Escherichia coli (E. coli) O157:H7, Staphylococcus aureus (S. aureus), Listeria monocytogenes (L. monocytogenes), Listeria innocua (L. innocua), and Listeria welshimeri (L. welshimeri). First, silver nanoparticles (AgNPs) with different particle sizes were prepared as SERS-enhanced substrates by changing the concentration of sodium citrate, and the volume ratio of silver nanosol to bacterial solution was optimised to obtain the optimal SERS signal. Then, principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used to classify the SERS spectra of six bacteria at three classification levels (Gram type level, genus level and species level), and appropriate classification models were established. Finally, these models were validated on 540 spectra using linear discriminant analysis (LDA), achieving an average accuracy of 95.65%. Overall, it was concluded that the SERS technique combined with chemometrics methods could achieve the rapid detection and classification identification of foodborne pathogenic bacteria, providing an effective means for food safety monitoring.

Supernatant of plant-associated bacteria potency against biofilms formed by foodborne pathogen and food spoilage bacteria

ObjectivesFood products are often contaminated by pathogens and spoilage bacteria. Most of them can form biofilms, a community of cells embedded in protective extracellular matrix layers resistant to harsh conditions, including antibiotics. Therefore, alternative antibiofilm agents are required to overcome biofilm formation. This study aims to determine and quantify the antibiofilm activity of supernatants from plant-associated bacteria against biofilms of foodborne pathogen and food spoilage bacterium, namely Bacillus cereus and Bacillus subtilis.ResultsPlant-associated bacteria (PAB) have shown promising antibiofilm activities against biofilm-forming pathogens in previous studies. Thirteen PAB isolated from Ternate, Indonesia were used in this study. Supernatants of PAB were subjected to antimicrobial activity and quorum quenching detection, both using the well diffusion method. Four supernatants inhibited the growth of B. subtilis, but none affected the growth of B. cereus. Eight supernatants were able to disrupt the quorum sensing system of an indicator bacterium, wild-type Chromobacterium violaceum. Biofilm inhibition and destruction were quantified using 96-well microplates. The highest biofilm inhibition and destruction activities of PAB supernatants against each of B. cereus and B. subtilis biofilms were > 76%, and were later confirmed by light microscope and scanning electron microscope. Brine shrimp lethality assay (BSLA) was conducted and revealed that the selected PAB supernatants were non-toxic. The 16S rRNA gene of PAB were sequenced and they showed similarities to Bacillus, Priestia, and Chryseobacterium. Compounds in the supernatants were determined by GC–MS which revealed contents of fatty acids, ethyl esters, and diketopiperazines. Therefore, PAB supernatants have potential as antibiofilm agents against biofilm formed by Bacillus cereus and Bacillus subtilis.

Wastewater-associated plastispheres: A hidden habitat for microbial pathogens?

Wastewater treatment plants (WWTPs) receive wastewater from various sources. Despite wastewater treatment aiming to remove contaminants, microplastics persist. Plastic surfaces are quickly colonized by microbial biofilm ("plastispheres"). Plastisphere communities are suggested to promote the spread and survival of potential human pathogens, suggesting that the transfer of plastispheres from wastewater to the environment could pose a risk to human and environmental health. The study aimed to identify pathogens in wastewater plastispheres, specifically food-borne pathogens, in addition to characterizing the taxonomic diversity and composition of the wastewater plastispheres. Plastispheres that accumulated on polypropylene (PP), polyvinyl chloride (PVC), and high-density polyethylene propylene (HDPE) surfaces exposed to raw and treated wastewater were analyzed via cultivation methods, quantitative reverse transcription PCR (RT‒qPCR) and 16S rRNA amplicon sequencing. RT‒qPCR revealed the presence of potential foodborne pathogenic bacteria and viruses, such as Listeria monocytogenes, Escherichia coli, norovirus, and adenovirus. Viable isolates of the emerging pathogenic species Klebsiella pneumoniae and Acinetobacter spp. were identified in the plastispheres from raw and treated wastewater, indicating that potential pathogenic bacteria might survive in the plastispheres during the wastewater treatment. These findings underscore the potential of plastispheres to harbor and disseminate pathogenic species, posing challenges to water reuse initiatives. The taxonomic diversity and composition of the plastispheres, as explored through 16S rRNA amplicon sequencing, were significantly influenced by the wastewater environment and the duration of time the plastic spent in the wastewater. In contrast, the specific plastic material did not influence the bacterial composition, while the bacterial diversity was affected. Without efficient wastewater treatment and proper plastic waste management, wastewater could act as a source of transferring plastic-associated pathogens into the food chain and possibly pose a threat to human health. Continued research and innovation are essential to improve the removal of microplastics and associated pathogenic microorganisms in wastewater.

Identification of Bacterial Pathogens in Organic Food of Animal Origin in Poland.

The consumption of organic food has increased in recent years. In organic rearing animals are exposed to outdoor conditions, which may increase their risk of infection from various pathogens. In the present study the occurrence of the most significant foodborne pathogenic bacteria in organic meat and ready-to-eat organic meat products was assessed. Out of 100 raw organic meat samples tested, 72 were contaminated with bacterial pathogens. The highest percentage of contaminated samples was observed in poultry meat (92.5%) followed by pork meat (66.7%). Furthermore, 50.0% of beef origin samples were positive for the bacteria tested. L. monocytogenes was found in 39.0% of samples, S. aureus was identified in 37.0%, Campylobacter in 20.0%, Salmonella in 8.0% and Shigatoxin-producing E. coli in 4.0% of raw meat samples. In 31.0% of samples a co-occurrence of two (83.9%) or three (16.1%) pathogens was observed. Among 100 samples of organic meat products tested, only L. monocytogenes was found in 5.0% of samples. The result of the present study indicated that organic food may be a source of harmful microorganisms that may pose foodborne infections to consumers.

Novel, eco-friendly α-tocopherol/layered double hydroxides/poly(3-hydroxyoctanoate)-based active packaging materials with enhanced antimicrobial, barrier and antioxidant activities

Among various climate actions taken as a response to environmental concerns, important and highly influential are ones related to the packaging industry being still one of the largest plastic sectors responsible for the majority of post-consumer wastes. Therefore, in this manuscript, for the first time assessment of the potential application of biodegradable bacterially derived poly(3-hydroxyoctanoate) (P(3HO)) doped with functional 2D nanoparticles as a more sustainable active packaging material has been investigated. In particular, P(3HO) combined with two types of layered double hydroxide (LDHs) modified with α-tocopherol (type of vitamin E) was applied for the fabrication of polymeric nanocomposite films and a comprehensive investigation of their structure and relevant properties (mechanical, barrier, bactericidal, and antioxidative) was performed. Permeation study revealed that P(3HO)-based films with 4 wt% tocopherol-modified nanoparticles meet the barrier requirements for storing fruits and vegetables, whereas antibacterial assay indicated inhibited growth of Gram-positive bacteria (particularly S. Aureus). Monitoring of polyphenols (PPH) content in strawberries after 6 days of storage at room conditions showed a slightly higher level of PPH with reference to fresh fruits, which indicates the preserved freshness of strawberries kept in P(3HO) containing 4 wt% Zn-based LDHs modified with tocopherol contrary to fruits kept in commercial polypropylene packaging which led to significant drop in PPH content. Thus, the application-focused experiments indicated that investigated P(3HO)-based nanocomposites are promising candidates for more sustainable active packaging that may extend the shelf-life of fruits and protect consumers from food-borne pathogenic bacteria.

Zoonotic Pathogens Isolated from an Introduced Population of Red Swamp Crayfish (Procambarus clarkii) in Tenerife (Canary Islands, Spain)

The red swamp crayfish (Procambarus clarkii) is a widely distributed invasive species that is listed in the Delivering Alien Invasive Species Inventory for Europe. Native to North America, it has been introduced to numerous regions, such as the Canary Islands, Spain. Previous studies have confirmed the role of this crayfish in the maintenance of several foodborne pathogenic bacteria. Therefore, the aim of this study was to analyze the main zoonotic bacterial and parasitic pathogens present in a P. clarkii population introduced to the island of Tenerife, Canary Islands, and to assess the potential risk to public health and native fauna. A total of 22 crayfish from Tenerife were analyzed using Biofire FilmArray Gastrointestinal Panels and culture–PCR methods. The results show the presence of Plesiomonas shigelloides, Shigella/enteroinvasive Escherichia coli, enteropathogenic Escherichia coli, Salmonella ser. Enteritidis, Salmonella ser. Typhimurium, and Salmonella ser. Typhi. These results demonstrate the presence of a variety of pathogenic bacteria in the red swamp crayfish in Tenerife that represent a significant concern in terms of public health and conservation. Implementing educational campaigns to inform the community about the risks associated with handling and consuming contaminated crayfish, as well as initiatives for the restoration of the contaminated ecosystem, are necessary to prevent the transmission of the foodborne pathogens.

Three in one: A multifunctional oxidase-mimicking Ag/Mn3O4 nanozyme for colorimetric determination, precise identification, and broad-spectrum inactivation of foodborne pathogenic bacteria

A multifunctional oxidase-mimicking Ag/Mn3O4 was prepared, catalyzing the 3, 3′, 5, 5′-tetramethylbenzidine (TMB) chromogenic reaction. Six foodborne pathogenic bacteria species, including Escherichia coli, Staphylococcus aureus, Salmonella enterica, Listeria monocytogenes, Bacillus cereus, and Cronobacter sakazakii, were observed to differentially inhibit its oxidase-like activity, resulting in decelerating the TMB chromogenic reaction. Owing to these properties, the following achievements were achieved: colorimetric determination of these bacteria with high sensitivity can be achieved using Ag/Mn3O4 + TMB reaction system; precise identification of these bacteria at different concentrations, including individual bacterium, binary mixtures, and even multivariate mixtures, can be effectively realized by combining the Ag/Mn3O4-based colorimetric sensor array with principal component analysis (PCA); broad-spectrum inactivation of these bacteria can be remarkably realized through catalyzation of Ag/Mn3O4 to generate superoxide anion free radicals. Therefore, our proposed Ag/Mn3O4 holds significant application potential in the colorimetric determination, precise identification, and broad-spectrum inactivation of foodborne pathogenic bacteria.

Antimicrobial Action of Lactobacillus spp. Isolated from Yoghurt against Escherichia coli, Salmonella Enteritidis and Listeria monocytogenes: A Pilot Study

Milk has been a dietary staple around the world for centuries. In recent years, consumer interest in healthy foods and organic products has increased due to their health-promoting properties. Fermented dairy products, including yoghurt, are receiving special attention for their properties and the presence of probiotic bacteria. The quantitative and qualitative (MALDI TOF MS) evaluation of lactic acid bacteria (LAB) in different types of yoghurt (with different shelf lives) was carried out. The effect of the Lactobacillus spp. strains isolated from yoghurts (with potential antimicrobial activity) against foodborne pathogenic bacteria (Escherichia coli, Salmonella Enteritidis and Listeria monocytogenes) was evaluated. The presence of Lactobacillus spp. (Lactobacillus rhamnosus and Lactobacillus paracasei) in the tested yoghurts was demonstrated. In the samples tested, not all the lactic acid bacteria (LAB) declared by the manufacturer were identified. The number of live bacteria present in the product was influenced by the type of yoghurt. The number of bacteria did not fall below the World Health Organization (WHO) recommended level by the last day of validity. It was shown that a mixed culture (L. rhamnosus and L. paracasei, isolated from tested yoghurts) had the most significant effect on changing the number of pathogenic microorganisms. The consumption of dairy products, which are a source of LAB, can reduce the risk of foodborne pathogen infections.

Polyethylene glycol enhanced antibacterial activity of EDTA and ethyl maltol blended PLA against Staphylococcus aureus for biodegradable active packaging

Poly (lactic acid) (PLA) has limited promise as a bio-based antimicrobial packaging material due to its lack of plasticization, which limits antimicrobial agent release and antimicrobial efficiency. PLA were plasticized with polyethylene glycol (PEG) and blended with ethyl maltol or ethylenediaminetetraacetic acid (EDTA) as antibacterial agents by melt extrusion. The effects of combining PEG, EDTA, and ethyl maltol on sheet properties and antibacterial activity were investigated. Incorporation of ethyl maltol created a dense and smooth homogeneous surface, while EDTA addition caused large pores in the PLA sheet microstructure impacting swelling degree, water solubility and surface hydrophilicity. Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) showed that both ethyl maltol and EDTA addition modified the amorphous and crystalline phases of plasticized PLA. FTIR results suggested interaction between the functional groups of PLA chains, PEG, ethyl maltol or EDTA which affected the glass transition temperature (Tg), degree of crystallinity, and thermal stability of PLA. Adding PEG into PLA-EDTA enhanced antibacterial activity against Gram-positive Staphylococcus aureus (reduction of 1.35 log CFU/mL from the initial inoculum). The higher water solubility of sheets corresponded to a suitable release rate and sufficient amounts of antimicrobial compounds against Staphylococcus aureus. In vitro antifungal testing, PLA-PEG-EDTA sheets did not exhibit a clear zone of inhibition but delayed Penicillium sp. spore formation until day 5 of incubation. PEG plasticized PLA sheets functionalized with ethyl maltol and EDTA showed potential as active biomaterials against food-borne pathogen bacteria Staphylococcus aureus.

Inhibitory Effects of Powdered Liquid Smoke from Mangrove (Avicennia marina) Twigs on Spoilage Bacteria

This study investigated the inhibitory effects of powdered liquid smoke derived from Avicennia marina (mangrove) twigs on spoilage bacteria. The research method used was experimental. Branches of mangrove (A. marina) were burned and distilled to produce liquid smoke. The powdered liquid smoke was subsequently tested for its antibacterial capabilities against foodborne pathogen bacteria. The damage to the bacterial formation was further illustrated using a Scanning electron micrograph. The components of liquid smoke were analysed using GC-MS. GC-MS test results on liquid smoke from mangrove twigs revealed several components including groups of acids such as butanoic acid, 1H-pyrrole-3-propanoic acid, 2-(4-methoxy-3-methylphenyl)-thiazolidine-4-carboxylic acid, hexanedioic acid, 2-bromo propionic acid, carbamic acid, oxalic acid, ritalinic acid and 7-dimethyl-6-octenyl acetate (acetic acid), as well as oxalic acid decyl propyl ester and 1,2-benzene dicarboxylic acid. The phenol group includes cyclohexanol, 2-cyclohexen-1-ol, 2-methyl-5-(1-methylethenyl)-, cis, 1,4-dihydroxy-p-menth-2-ene, phenol, 3-methyl, phenol, 2-methoxy-4-(1-propenyl)-, acetate, 1,2-diphenyl-2-ethanediol and 1,2-ethanediol. The ketone group includes beta-piperidino propiophenone, pyrrolidine-2-one, 5-[2-benzoylethyl]-,benzoyl amino-1-(4-methylphenyl)-3-piperidinyl propane, 3-nonen-5-one, 1-(1-butoxypropan-2-yloxy) propan-2-yl 2-methylbut-2-enoate, 6-octen-1-ol, 3,7-dimethyl, 4-(2,2,6-trimethyl cyclohexyl)-2-butanone and the carbonyl group includes N2-[(phenylmethoxy) carbonyl].

CRISPR/Cas12a-Triggered Visible-Light-Driven Photoelectrochemical Assay with Single-Nucleotide Resolution for Drug-Resistant Foodborne Salmonella Detection.

The prevalence of foodborne pathogenic bacteria, especially drug-resistant strains, such as Salmonella enterica, poses serious threats to public health, highlighting the requirement for the development of rapid and precise detection methods. Herein, a CRISPR/Cas12a-triggered visible-light-driven photoelectrochemical (PEC) assay (CasPEC) was developed using a SiO2-quenched BiVO4/MoS2 p/n-type heterojunction as the photoactive material. The CRISPR/Cas12a recognition endowed the CasPEC assay with high specificity capable of resolving single-nucleotide polymorphisms (SNPs) and identifying SNP-involved drug-resistant bacteria. SiO2 was linked to the surface of the BiVO4/MoS2 heterojunction by single-stranded DNA (ssDNA), which would be cleaved by target-activated CRISPR/Cas12a. This cleavage of ssDNA resulted in the detachment of SiO2, thereby achieving a "signal-on" PEC output. Leveraging the multiple-turnover CRISPR cleavage and the outstanding photoactive performance of PEC signaling, the CasPEC assay for S. enterica showed a detection limit of 103 colony-forming units (CFU)/mL and the ability to detect as few as 0.01% drug-resistant strains. The CasPEC assay can accurately sense the S. enterica contamination in complex food matrices, including beef and milk. These findings demonstrated the great potential of the CasPEC assay for detecting pathogenic bacterial contamination in food, particularly concerning food safety related to SNP-involved drug-resistant bacteria.

Defense mechanisms of Salmonella against antibiotics: a review

Salmonella is a foodborne pathogenic bacterium that causes salmonellosis worldwide. Also, Salmonella is considered a serious problem for food safety and public health. Several antimicrobial classes including aminoglycosides, tetracyclines, phenols, and β-Lactams are used to treat Salmonella infections. Antibiotics have been prescribed for decades to treat infections caused by bacteria in human and animal healthcare. However, intensive use of antibiotics resulted in antibiotic resistance (AR) among several foodborne bacteria including Salmonella. Furthermore, multi-drug resistance (MDR) of Salmonella has increased dramatically. In addition to MDR Salmonella, extensively drug resistant (XDR) as well as pan drug resistant (PDR) Salmonella were reported globally. Therefore, increasing AR is becoming a serious universal public health crisis. Salmonella developed many mechanisms to ensure its survival against antimicrobials. The most prominent defense mechanisms against these antibiotics include enzymatic inactivation, expelling drugs from the cell through efflux pumps, altering the structure of drugs, and changing or protecting the targets of drugs. Additionally, the formation of biofilms and plasmid-mediated AR by Salmonella, enhancing its resistance to various antibiotics, making it a challenging pathogen in both healthcare and food industry settings. This review focuses exclusively on providing a detailed overview of the mechanisms of AR in Salmonella.

Silver nanoparticle-functionalized covalent organic frameworks for the inhibition of foodborne pathogenic bacteria and their application in green grape preservation

Foodborne pathogens continue to pose a significant threat to human health. This study aims to enhance the antimicrobial activity of low-dose silver nanoparticles (AgNPs) against foodborne pathogens and use the enhanced AgNPs to preserve green grapes. A chemical delivery carrier for covalent organic frameworks (COFs) impregnated with AgNPs was developed. We investigated the bacteriostatic properties (minimum bacteriostatic concentration, bacteriostatic growth curve), the mechanism of action of the bacteriostatic agent, and the performance of the bacteriostatic film. The bacteriostatic preservation rate of the AgNPs@COFs composite on green grapes was evaluated. The minimum bacteriostatic concentration of the AgNPs@COFs composite was 10 μg/mL, and the bacteriostatic rate varied between 94.01 % and 98.77 %. The developed antibacterial AgNPs@COFs composite has potential applications in food packaging and preservation.

Microbiological Evaluation of Two Mexican Artisanal Cheeses: Analysis of Foodborne Pathogenic Bacteria in Cotija Cheese and Bola de Ocosingo Cheese by qPCR.

Cotija and Bola de Ocosingo are artisanal ripened cheeses produced in Mexico. Both are made with raw bovine milk from free-grazing cows and with no starter cultures. Unlike culture-based techniques, molecular methods for pathogen detection in food allow a shorter turnaround time, higher detection specificity, and represent a lower microbiological risk for the analyst. In the present investigation, we analyzed 111 cheese samples (95 Cotija and 16 Bola de Ocosingo) by qPCR (TaqMan®) after an enrichment-culture step specific to each foodborne bacterium. The results showed that 100% of the samples were free of DNA from Listeria monocytogenes, Brucella spp., Escherichia coli enterotoxigenic (ETEC), and O157:H7; 9% amplified Salmonella spp. DNA; and 11.7%, Staphylococcus aureus DNA. However, the threshold cycle (Ct) values of the amplified targets ranged between 23 and 30, indicating DNA from non-viable microorganisms. Plate counts supported this assumption. In conclusion, 100% of the cheeses analyzed were safe to consume, and the enrichment step before DNA extraction proved essential to discern between viable and non-viable microorganisms. Hygienic milking, milk handling, cheese manufacturing, and ripening are crucial to achieve an adequate microbiological quality of cheeses made with raw milk.