Microbial Contamination and Public Health: An Overview

A Study of Bioactivities and Composition of a Cocktail of Supernatants Derived from Lactic Acid Bacteria for Potential Food Applications

Growing interests in replacing conventional preservatives and antibiotics in food and pharmaceutical industries have driven the exploration of bacterial metabolites, especially those from strains with generally recognized as safe (GRAS) status, such as lactic acid bacteria (LAB). In this study, a supernatant cocktail derived from multiple LAB strains was prepared and its bioactivities-antimicrobial, antibiofilm, antioxidant, cytotoxicity, and stability-were thoroughly investigated. The cocktail's main components were identified using thermal and protease treatments, gas chromatography coupled to mass spectrometry (GC-MS), and flame ionization detection (GC-FID). The results demonstrated that the supernatant cocktail had a broad inhibition spectrum and was effective against food-related bacterial indicators with the highest activity observed on Bacillus cereus ATCC9634 (inhibition zone sizes 12.33 mm) and the lowest on Enterococcus faecium DSM 13590 (3.31 mm). It showed dose- and time-dependent delaying effects on the growth of tested fungi. Regarding the antibiofilm activity, it was more effective in preventing biofilm formation (40% biofilm mass reduction) than in degrading preformed biofilm (20% reduction). Additionally, the cocktail showed antioxidant capacity of 10.1 ± 0.3 g Trolox equivalent (TE)/kg and dose-dependent cytotoxicity on HEK-293 and HT-29 cell lines. The main bioactive compounds in this cocktail are organic acids (particularly acetic acid), volatiles, and bacteriocin-like compounds. The antimicrobial capacity of this supernatant cocktail was highly reproducible across different fermentation batches, and it remained highly stable at 4 °C. Overall, these findings provided novel insights into the functional potentials of LAB metabolites, broadening their application as customizable biopreservatives for food and pharmaceutical industry.

Laser Speckle Image analysis for identifying the minimum lethal concentration of ampicillin in Escherichia coli liquid cultures

Understanding a pathogen's sensitivity to antimicrobial drugs through Minimum Lethal Concentration (MLC) is crucial for effective treatment planning for bactericidal drugs. In this paper, we propose a novel approach using Laser Speckle Imaging (LSI) to determine the MLC of Escherichia coli (E. coli), a common pathogenic bacterial species. LSI enables the capture and analysis of the dynamic changes in speckle patterns caused by alterations in optical scattering and shape alterations of bacterial cells as a response to antibiotic treatments through a label-free approach. The observed speckle pattern changes are correlated with the gold standard method to determine the MLC, representing the lowest concentration at which E. coli is lethally affected. The results demonstrate the potential of LSI as a reliable and rapid method for determining the MLC of E. coli. This method has much potential for antimicrobial research since it provides a quick, non-destructive evaluation of bacterial responses to various bactericidal antibiotic doses without requiring labor-intensive processes like pour plate tests to calculate the MLC.

Antibacterial and Photocatalytic Activities of Leonotis ocymifolia (L. ocymifolia)-Mediated ZnO Nanoparticles Annealed at Different Temperatures

This research achieved the successful synthesis of zinc oxide (ZnO) NPs through an eco-friendly method, utilizing the leaf extract of Leonotis ocymifolia (L.O.). This innovative approach not only highlights the potential of green synthesis but also underscores the effectiveness of natural resources in nanoparticle production. The influence of annealing temperature on the properties and performance of the synthesized ZnO NPs was evaluated by varying the annealing temperatures as follows: unannealed (000), 350 °C (350), 550 °C (550), and 750 °C (750). The XRD analysis of L.O-mediated ZnO NPs confirmed the synthesis of highly crystalline wurtzite-structured ZnO NPs, with calculated average crystallite sizes that ranged between 13.8 and 20.4 nm. The UV-Vis spectra revealed a single strong absorption peak ranging from 354 to 375 nm, and the absorption peaks red-shifted with an increase in annealing temperature. The SEM micrographs showed that annealing temperature had an effect on the morphology, particle size, and distribution, with the average particle of 53.7-66.3 nm. The BET analysis revealed that the surface area of the prepared ZnO NPs was between 31.6 and 13.2 m2/g. In addition to its significant impact on the characteristics of the L.O-mediated, annealing temperature notably boosts the L.O-mediated capacity to photodegrade Methylene blue (MB) dye. Moreover, it exhibited significant antibacterial efficacy against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The photodegradation studies under UV irradiation and in 180 min revealed 750 (71.1%) had the highest degradation efficiency compared to 000, 350, and 550. The antibacterial tests showed that 000 had greater antibacterial efficacy than 350, 550, and 750. The results from this work suggest that annealing temperature had a significant effect on the structural, morphological, and optical properties and performance of L.O-mediated ZnO NPs.

The prevalence of hydatid cyst in raw meat products: a global systematic review, meta-analysis, and meta-regression

Hydatid cyst contamination in food presents a persistent and pervasive threat to public health. Hence, several studies have been published on hydatid cysts in raw meat products. The current study aimed to meta-analyze the prevalence of hydatid cysts in meat. The search was performed in international databases, including PubMed, Web of Science, Scopus, and Google Scholar, from January 1, 2000, to February 10, 2024. A meta-analysis of prevalence was conducted using the metaprop command in the subgroups of countries, animals, and WHO regions. Meta-regression of the prevalence of hydatid cysts in meat over time and sanitation services ranking was conducted using a random effects model (restricted maximum--likelihood). Fifty-seven published references with 130 data reports were included in the study. The lowest and highest prevalence of hydatid cysts in raw meat was observed in Sudan at 0.01%, 95%CI (0.01-0.02) and Italy at 69.86%, 95%CI (68.14-71.55), respectively. The highest prevalence of hydatid cysts was observed in Sheep (12.32%), Cattle (11.85%), and Buffalo (10.65%). The lowest and highest prevalence of hydatid cysts was South-East Asian Reg (2.77%) and European Region (33.21%), respectively. Meta-regression showed that the prevalence of hydatid cysts has significantly decreased over time (p-value = 0.021) and insignificantly decreased with sanitation services ranking (p-value = 0.679). Therefore, in order to maintain the existing conditions and even reduce the burden of hydatidosis, public health education, promotion of hygienic practices, and investment need to be carried out continuously.

Prussian-Blue-Nanozyme-Enhanced Simultaneous Immunochromatographic Control of Two Relevant Bacterial Pathogens in Milk

Salmonella typhimurium and Listeria monocytogenes are relevant foodborne bacterial pathogens which may cause serious intoxications and infectious diseases in humans. In this study, a sensitive immunochromatographic analysis (ICA) for the simultaneous detection of these two pathogens was developed. For this, test strips containing two test zones with specific monoclonal antibodies (MAb) against lipopolysaccharides of S. typhimurium and L. monocytogenes and one control zone with secondary antibodies were designed, and the double-assay conditions were optimized to ensure high analytical parameters. Prussian blue nanoparticles (PBNPs) were used as nanozyme labels and were conjugated with specific MAbs to perform a sandwich format of the ICA. Peroxidase-mimic properties of PBNPs allowed for the catalytic amplification of the colorimetric signal on test strips, enhancing the assay sensitivity. The limits of detection (LODs) of Salmonella and Listeria cells were 2 × 102 and 7 × 103 cells/mL, respectively. LODs were 100-fold less than those achieved due to the ICA based on the traditional gold label. The developed double ICA was approbated for the detection of bacteria in cow milk samples, which were processed by simple dilution by buffer before the assay. For S. typhimurium and L. monocytogenes, the recoveries from milk were 86.3 ± 9.8 and 118.2 ± 10.5% and correlated well with those estimated by the enzyme-linked immunosorbent assay as a reference method. The proposed approach was characterized by high specificity: no cross-reactivity with other bacteria strains was observed. The assay satisfies the requirements for rapid tests: a full cycle from sample acquisition to result assessment in less than half an hour. The developed ICA has a high application potential for the multiplex detection of other foodborne pathogens.

Proposing an Affordable Plasma Device for Polymer Surface Modification and Microbial Inactivation

This study proposes an affordable plasma device that utilizes a parallel-plate dielectric barrier discharge geometry with a metallic mesh electrode, featuring a straightforward 3D-printed design. Powered by a high-voltage supply adapted from a cosmetic plasma device, it operates on atmospheric air, eliminating the need for gas flux. Surface modification of polyethylene treated with this device was characterized and showed that the elemental composition after 15 min of plasma treatment decreased the amount of C to ~80 at% due to the insertion of O (~15 at%). Tested against Candida albicans and Staphylococcus aureus, the device achieved a reduction of over 99% in microbial load with exposure times ranging from 1 to 10 min. Simultaneously, the Vero cell viability remained consistently high, namely between 91% and 96% across exposure times. These results highlight this device's potential for the surface modification of materials and various infection-related applications, boasting affordability and facilitating effective antimicrobial interventions.

An Evaluation of the Sensitivity and Applicability of a Droplet Digital Polymerase Chain Reaction Assay to Simultaneously Detect Pseudomonas aeruginosa and Pseudomonas fragi in Foods

Achieving effective control over microbial contamination necessitates the precise and concurrent identification of numerous pathogens. As a common bacterium in the environment, Pseudomonas is rich in variety. It not only has pathogenic strains, but also spoilage bacteria that cause food spoilage. In this research, we devised a remarkably sensitive duplex droplet digital PCR (dddPCR) reaction system to simultaneously detect pathogenic Pseudomonas aeruginosa (P. aeruginosa) and spoilage Pseudomonas fragi (P. fragi). By employing comparative genomics, we identified four genes of P. fragi. Through a specific analysis, the RS22680 gene was selected as the detection target for P. fragi, and the lasR gene was chosen for P. aeruginosa, which were applied to construct a dddPCR reaction. In terms of specificity, sensitivity and anti-interference ability, the constructed dddPCR detection system was verified and analyzed. The assay showed excellent sensitivity and applicability, as evidenced by a limit of detection of 100 cfu/mL. When the concentration of natural background bacteria in milk or fresh meat was 100 times that of the target detection bacteria, the method was still capable of completing the absolute quantification. In the simulation of actual sample contamination, P. aeruginosa could be detected after 3 h of enrichment culture, and P. fragi could be detected after 6 h. The established dddPCR detection system exhibits exceptional performance, serving as a foundation for the simultaneous detection of various pathogenic bacteria in food products.

Application of the Peroxidase‒like Activity of Nanomaterials for the Detection of Pathogenic Bacteria and Viruses

Infectious diseases caused by pathogenic bacteria and viruses pose a significant threat to human life and well-being. The prompt identification of these pathogens, characterized by speed, accuracy, and efficiency, not only aids in the timely screening of infected individuals and the prevention of further transmission, but also facilitates the precise diagnosis and treatment of patients. Direct smear microscopy, microbial culture, nucleic acid-based polymerase chain reaction (PCR), and enzyme-linked immunosorbent assay (ELISA) based on microbial surface antigens or human serum antibodies, have made substantial contributions to the prevention and management of infectious diseases. Due to its shorter processing time, simple equipment requirements, and no need for professional and technical personnel, ELISA has inherent advantages over other methods for detecting pathogenic bacteria and viruses. Horseradish peroxidase mediated catalysis of substrate coloration is the key for the detection of target substances in ELISA. However, the variability, high cost, and environmental susceptibility of natural peroxidase greatly limit the application of ELISA in pathogen detection. Compared with natural enzymes, nanomaterials with enzyme-mimicking activity are inexpensive, highly environmentally stable, easy to store and mass producing, etc. Based on their peroxidase-like activities and unique physicochemical properties, nanomaterials can greatly improve the efficiency and ease of use of ELISA-like detection methods for pathogenic bacteria and viruses. This review introduces recent advances in the application of nanomaterials with peroxidase-like activity for the detection of pathogenic bacteria (both gram-negative bacteria and gram-positive bacteria) and viruses (both RNA viruses and DNA viruses). The emphasis is on the detection principle and the evaluation of effectiveness. The limitations and prospects for future translations are also discussed.

Thymol incorporation within chitosan/polyethylene oxide nanofibers by concurrent coaxial electrospinning and in-situ crosslinking from core-out for active antibacterial packaging

Active packaging systems that are sustainable and capable of delivering antimicrobial agents are in demand in food industry. In this work, Thymol (Thy) was encapsulated into Polyethylene oxide (PEO)/Chitosan (CS) to form core-shell nanofibers via coaxial electrospinning. Various dose of the crosslinker-genipin (GP) were encapsulated into the core layer to achieve in-situ etching crosslink with the CS of shell layer during the electrospinning process. The core-shell structure of the nanofiber was confirmed by transmission electron microscopy. The microstructures, mechanical properties, water vapor permeability, swelling ratios, wettability, thermal stability, biocompatibility and antibacterial properties of the crosslinked films were characterized. The results showed that the crosslinked films had compact structures, strong water resistance, better mechanical property and thermal stability, the sustained release profiles and antioxidant activity were also improved. More importantly, the antibacterial assays indicated that the Thy loaded nanofiber films could effectively inhibit the growth of two common food spoilage bacteria-E. coli and S. aureus.

Synergistic Strategies of Heat and Peroxyacetic Acid Disinfection Treatments for Salmonella Control

The food industry has recognized a pressing need for highly effective disinfection protocols to decrease the risk of pathogen emergence and proliferation in food products. The integration of antimicrobial treatments in food production has occurred as a potential strategy to attain food items of superior quality with respect to microbiological safety and sensory attributes. This study aims to investigate the individual and synergistic effects of heat and peroxyacetic acid on the inactivation of bacterial cells, considering various contact times and environmental conditions. Four Salmonella serotypes, isolated from industrial meat production surfaces, were employed as model organisms. By systematically assessing the impacts of individual factors and synergistic outcomes, the effectiveness of bacterial cell inactivation and the efficiency of heat and peroxyacetic acid could be predicted. To better approximate real-world food processing conditions, this study also incorporated a bovine albumin-rich condition as a simulation of the presence of organic loads in processing steps. The findings revealed the essential need for a synergistic interplay of investigated parameters with the following optimized values: 1.5% concentration of peroxyacetic acid, temperature range of 60-65 °C, and contact time of 3 min for the complete effect regardless of the degree of contamination.

Resistance and Virulence Surveillance in Escherichia coli Isolated from Commercial Meat Samples: A One Health Approach

Escherichia coli is a key indicator of food hygiene, and its monitoring in meat samples points to the potential presence of antimicrobial-resistant strains capable of causing infections in humans, encompassing resistance profiles categorized as serious threats by the Centers for Disease Control and Prevention (CDC), such as Extended-Spectrum Beta-Lactamase (ESBL)-a problem with consequences for animal, human, and environmental health. The objective of the present work was to isolate and characterize ESBL-producing E. coli strains from poultry, pork, and beef meat samples, with a characterization of their virulence and antimicrobial resistance profiles. A total of 450 meat samples (150 chicken, 150 beef, and 150 pork) were obtained from supermarkets and subsequently cultured in medium supplemented with cefotaxime. The isolated colonies were characterized biochemically, followed by antibiogram testing using the disk diffusion technique. Further classification involved biofilm formation and the presence of antimicrobial resistance genes (blaCTX-M, AmpC-type, mcr-1, and fosA3), and virulence genes (eaeA, st, bfpA, lt, stx1, stx2, aggR, iss, ompT, hlyF, iutA, iroN, fyuA, cvaC, and hylA). Statistical analysis was performed via the likelihood-ratio test. In total, 168 strains were obtained, with 73% originating from chicken, 22% from pork, and 17% from beef samples. Notably, strains exhibited greater resistance to tetracycline (51%), ciprofloxacin (46%), and fosfomycin (38%), apart from β-lactams. The detection of antimicrobial resistance in food-isolated strains is noteworthy, underscoring the significance of antimicrobial resistance as a global concern. More than 90% of the strains were biofilm producers, and strains carrying many ExPEC genes were more likely to be biofilm formers (OR 2.42), which increases the problem since the microorganisms have a greater chance of environment persistence and genetic exchange. Regarding molecular characterization, bovine samples showed a higher prevalence of blaCTX-M-1 (OR 6.52), while chicken strains were more likely to carry the fosA3 gene (OR 2.43, CI 1.17-5.05) and presented between 6 to 8 ExPEC genes (OR 2.5, CI 1.33-5.01) compared to other meat samples. Concerning diarrheagenic E. coli genes, two strains harbored eae. It is important to highlight these strains, as they exhibited both biofilm-forming capacities and multidrug resistance (MDR), potentially enabling colonization in diverse environments and causing infections. In conclusion, this study underscores the presence of β-lactamase-producing E. coli strains, mainly in poultry samples, compared to beef and pork samples. Furthermore, all meat sample strains exhibited many virulence-associated extraintestinal genes, with some strains harboring diarrheagenic E. coli (DEC) genes.

Dynamic headspace GC-MS/MS analysis of ethylene oxide and 2-chloroethanol in dry food commodities: a novel approach

With frequent RASFF notifications from the EU countries, the residue testing of ethylene oxide (EtO) and its metabolite 2-chloroethanol (2-CE) in food commodities has become essential to check their compliance with MRLs. This study, for the first time, aimed at establishing a dynamic headspace-GC-MS/MS method for the simultaneous determination of these two analytes in acetonitrile extracts of cumin, ashwagandha, chilli powder, turmeric powder, guar gum, locust bean gum, and ginger powder. The samples (4 g) were extracted using acetonitrile (10 mL). A dispersive-solid phase extraction cleanup step with primary secondary amine sorbent (50 mg/mL) reduced the interfering signal of (matrix-derived) acetaldehyde by >40% in chilli powder, ginger, turmeric, and guar gum. This cleanup was not required for sesame seeds. With high selectivity and sensitivity, the GC-MS/MS approach identified and quantified both compounds simultaneously. At the spiking levels of 0.01, 0.02, and 0.05 mg/kg, the recoveries and precision were satisfactory (70-120%, RSDs, ≤15%). The headspace method-performance was similar to liquid injections. The method provided reproducible results when evaluated by two different laboratories. The method provided high-precision results for incurred residue analysis. Given its efficiency, the validated method is anticipated to improve the effectiveness of monitoring of EtO residues in food commodities.

Green biomanufacturing in recombinant collagen biosynthesis: trends and selection in various expression systems

Collagen, classically derived from animal tissue, is an all-important protein material widely used in biomedical materials, cosmetics, fodder, food, etc. The production of recombinant collagen through different biological expression systems using bioengineering techniques has attracted significant interest in consideration of increasing market demand and the process complexity of extraction. Green biomanufacturing of recombinant collagen has become one of the focus topics. While the bioproduction of recombinant collagens (type I, II, III, etc.) has been commercialized in recent years, the biosynthesis of recombinant collagen is extremely challenging due to protein immunogenicity, yield, degradation, and other issues. The rapid development of synthetic biology allows us to perform a heterologous expression of proteins in diverse expression systems, thus optimizing the production and bioactivities of recombinant collagen. This review describes the research progress in the bioproduction of recombinant collagen over the past two decades, focusing on different expression systems (prokaryotic organisms, yeasts, plants, insects, mammalian and human cells, etc.). We also discuss the challenges and future trends in developing market-competitive recombinant collagens.

Current Perspectives on Viable but Non-Culturable Foodborne Pathogenic Bacteria: A Review

Foodborne diseases caused by foodborne pathogens pose risks to food safety. Effective detection and efficient inactivation of pathogenic bacteria has always been a research hotspot in the field of food safety. Complicating these goals, bacteria can be induced to adopt a viable but non-culturable (VBNC) state under adverse external environmental stresses. When in the VBNC state, pathogens cannot form visible colonies during traditional culture but remain metabolically active and toxic. The resulting false negative results in growth-related assays can jeopardize food safety. This review summarizes the latest research on VBNC foodborne pathogens, including induction conditions, detection methods, mechanism of VBNC formation, and possible control strategies. It is hoped that this review can provide ideas and methods for future research on VBNC foodborne pathogenic bacteria.

Training for Food Handlers at Production Level in Italian Regions

Food safety has always been a public health challenge. Globally, food safety control is supported by laws and preventive measures, such as inspections conducted from primary production to market, "from farm to fork" as emphasized by the European Union and training of Food Handlers (FHs). This latter preventive measure plays a very important role, and for this reason a review of training courses regulations provided in the different Italian regions was conducted. Analysis of the results shows that the Italian regions approach this issue in different ways: some regions provide only general guidelines, while others offer detailed instructions. The most significant differences concern the topics dealt with, the stakeholders, the staff training and the verification of results; topics such as allergens and gluten are often absent. More detailed guidelines tailored to fit the local scenario could provide better support to FHs, thus leading to real changes in their behaviors and mindsets and promoting the development of an actual "prevention culture".

Antibacterial Activity of Crocus sativus L. Petals Extracts against Foodborne Pathogenic and Spoilage Microorganisms, with a Special Focus on Clostridia

In recent years, there has been a growing interest in the use of novel antimicrobial agents able to inhibit or kill food-borne bacteria or to interrupt the onset of food spoilage. Crocus sativus L. petals, typically considered as waste obtained from saffron spice production, could be a source of natural bioactive compounds to be used as food preservatives. The purpose of this work was to investigate the antibacterial properties of two hydroalcoholicsaffron petal extracts obtained by maceration (SPEA) and by ultrasonic bath (SPEB) methods. The main polyphenols identified in both extracts were gallic and chlorogenic acids, representing almost 70% of the phenolic fraction monitored. The antibacterial activity was studied by the agar well-diffusion method, against food-borne pathogenic and spoilage bacteria. Both extracts showed activity mainly against Gram-positive bacteria, in particular those belonging to the Clostridiaceae family (C. perfringens, C. botulinum and C. difficile), with inhibition zone diameters ranging from 13 to 18 mm. The antibacterial properties against Clostridia were further analyzed, determining MIC and MBC and performing a time-kill test. SPEA showed lower MIC/MBC values (250 mg/mL) compared to SPEB (500 mg/mL), suggesting that it could be more active against the assayed strains, probably because of its higher content of gallic acid. SPEA and SPEB, tested at a concentration of 1 × MIC, showed bactericidal activity against C. perfringens, C. botulinum and C. difficile and these results suggest that saffron petals could represent a valuable natural alternative source to conventional preservatives. Further investigations are needed to evaluate possible applications in the food industry.