Journal of enzyme inhibition and medicinal chemistryShuaibu Abdullahi Hudu, Najlaa Saadi, Emad A Morad, Albashir Tahir, Abdulgafar Olayiwola Jimoh
Candida auris is a major public health concern worldwide due to its efficient transmission, environmental persistence, and broad resistance to approved antifungal classes. This review consolidates recent pharmacological developments in this regard, focusing on mechanistic insights and late-stage therapeutics. Novel agents demonstrate activity against multidrug- and pan-resistant isolates via distinct mechanisms of action and enhanced specific binding to CYP51. Repositioned drugs, host-defense peptides, and quorum-sensing modulators also expand the treatable spectrum, particularly for biofilm-associated and device-related infections. Concurrently, artificial intelligence (AI)-guided discovery, nanocarrier-enabled delivery, and multi-omics profiling are greatly accelerating target identification and enhancing the drug metabolism of small-molecule fragments. The emerging combined approaches mark a transition towards mechanism-based antifungal development to combat the increasing clinical burden posed by C. auris. Ongoing integration of precision diagnostics, pharmacodynamic optimization, and novel discovery platforms will be key to translating these advances into durable, real-world therapeutic solutions.
Gut microbesBeatriz Nafria, Olga P Nyssen, Jone Narbaiza, Mila Montes, Pablo Parra, Javier P Gisbert, Luis Bujanda
BACKGROUND & AIMS: Antibiotic resistance is a major determinant of the efficacy of Helicobacter pylori (H. pylori) eradication treatment. Our objective was to evaluate the prevalence and geographical distribution of primary antibiotic resistance in patients infected with H. pylori across Europe over the last four decades. METHODS: Bibliographical searches were conducted from 1990 to 2024 in the PubMed database with no language restrictions. Selected studies evaluated the primary resistance of H. pylori to clarithromycin, metronidazole, levofloxacin, amoxicillin, tetracycline and rifampicin in adults. Data were grouped by country and time intervals (1990-1999, 2000-2009, 2010-2019, 2020-2024) to identify potential trends. High resistance thresholds were defined as ≥15% for clarithromycin and levofloxacin, and ≥30% for metronidazole. RESULTS: A total of 216 studies were included: 188 with information on clarithromycin resistant strains (86,917 patients), 138 on metronidazole (83,995 patients), and 77 on levofloxacin (40,619 patients). The overall prevalence of primary resistance to clarithromycin, levofloxacin, and metronidazole was 16% (95% confidence interval, 7-24%), 18% (10-21%), and 33% (29-36%), respectively. Primary resistance to clarithromycin and levofloxacin increased steadily across all periods, reaching 24% and 21%, respectively, in the most recent period. Primary resistance to amoxicillin, tetracycline, and rifampicin remained low, at 2.3%, 1%, and 4%, respectively. Overall, Southern European countries had higher resistance rates than Northern European countries. CONCLUSIONS: In Europe, the prevalence of primary H. pylori resistance to clarithromycin and levofloxacin has increased over time and is high in recent years. Variability exists between countries, with Southern European regions showing higher rates.
VirulenceYvette Kazungu, Shrilakshmi Hegde, Parul Sharma, Amy Marriott, Andrew Steven, Jesus Reine, Jessica Dagley, Matthias Mack, Anja Kipar, James P Stewart, Joseph D…
SARS-CoV2 can induce an acute respiratory distress syndrome (ARDS), provoked by a dysregulated hyper-inflammatory pulmonary immune response. Here, we used the keratinocyte-18 humanized angiotensin converting enzyme-2 (K18-hACE2) mouse model of SARS-CoV2, where expression of the CoV2 spike protein receptor, hACE-2, is restricted to epithelia, to characterize inflammatory pulmonary immune responses post-intranasal infections with the delta isolate SARS-CoV2(∆) B.1.617.2. Immune-profiling by focused transcript analysis, inflammatory protein array, and multi-color flow cytometry, confirmed that clinically relevant markers of COVID-19 (IL-6, GM-CSF, neutrophils, inflammatory monocytes) were significantly elevated in lungs of mice at day 5 post-infection and that remdesivir antiviral active metabolite (GS441524) treatment significantly modified SARS-CoV2∆ viral loads and pulmonary inflammation. Chemokine ligands of CCR2 (CCL2/7/8) were among the top 5% upregulated pulmonary transcripts in a focused human infection response array to SARS-CoV2∆. CCL2 was confirmed as elevated in protein assays in SARS-CoV2∆ infected lungs. To address the functional relevance of the CCR2 pathway of inflammatory cell recruitment to the lungs mediating disease, mice were administered with anti-CCR2 antibody daily at the point of infection for up to 6 d. Anti-CCR2 treated mice showed significant improved welfare scores, were protected from weight loss, modified myeloid pneumonitis, and displayed significantly blunted cytokine and chemokine response in the lungs, despite not affecting pulmonary viral loads. Our data supports therapeutic benefit of modifying CCR2-dependent cell recruitment in the treatment of viral-induced ARDS.
VirulenceYuying Zhang, Jiabao Xing, Hang Zhang, Jingchun Kong, Sue C Nang, Meng Zhang, Yushan Pan, Yajun Zhai, Li Yuan, Jinxin Zhao, Hua Wu
Acinetobacter baumannii AB5075 is a clinically relevant multidrug-resistant (MDR) isolate that poses a major therapeutic challenge. Although colistin has been reinstated as a last-resort antibiotic against MDR Gram-negative infections, the rapid emergence of colistin resistance threatens its clinical utility. Here, we employed a CRISPR-Cas9-based genome editing system to generate an A. baumannii AB5075 ΔrcnB mutant and uncovered a previously underappreciated role of rcnB in modulating colistin susceptibility. Loss of rcnB markedly potentiated colistin-mediated killing through multiple associated changes, including compromised membrane integrity, impaired oxidative stress defenses, and reduced efflux pump activity. Transcriptomic profiling further revealed that rcnB deletion reshaped global stress-response networks, including suppression of fatty acid biosynthesis and reactive oxygen species (ROS)-detoxifying pathways, alongside altered metal ion and sulfur metabolism during colistin exposure. Collectively, our findings suggest that rcnB may contribute to colistin susceptibility of colistin resistance and provide mechanistic insights that may inform the development of targeted strategies to enhance colistin efficacy against MDR A. baumannii.
Food microbiologyHisaya K Ono, Tamako Kimura, Oku Okamoto, Yasunori Suzuki, Yusuke Sato'o, Taishi Tanabe, Dong-Liang Hu
Staphylococcus aureus in poultry is a potential source of food contamination and staphylococcal food poisoning. However, its carriage patterns and toxigenic potential at the slaughterhouse stage remain insufficiently characterized in Japan. This study investigated the prevalence and molecular characteristics of S. aureus in spent laying hens entering the processing line over a one-year period. Three anatomical sites (head, wing, and leg) were sampled per carcass (n = 800). S. aureus was detected in 649 of 800 birds (81.1%), and 995 isolates were obtained. Virulence gene profiling showed that 503 of 995 isolates (50.6%) carried one or more staphylococcal enterotoxin (SE) genes, with seh being the most prevalent, followed by sed and ser. se gene carriage was strongly site-dependent: isolates from the head and wing were predominantly se gene-positive, whereas most leg-derived isolates lacked these genes. Multilocus sequence typing of representative isolates revealed clonal heterogeneity, including newly registered sequence types with site-associated distributions. To assess toxigenic potential beyond gene carriage, we quantified production of selected enterotoxins in culture supernatants from broth cultures by enzyme-linked immunosorbent assay (ELISA) under different temperature conditions and further examined enterotoxin accumulation in chicken minced meat as a food-relevant matrix. In addition, SE accumulation above the detection limit was confirmed in chicken minced meat inoculated with a representative isolate under permissive temperature conditions (25 °C and 37 °C). These findings indicate that spent laying hens entering the processing line harbor S. aureus isolates from different anatomical sites with distinct virulence and toxigenic characteristics. The results provide baseline information on the microbiological status of birds at slaughterhouse entry and support the importance of temperature management during subsequent handling and processing to limit enterotoxin accumulation.
Food microbiologyJirapat Dawan, Yong Hyeok Yoo, Jin-Chul Kim, Sang Soo Lee
Staphylococcus aureus biofilms on stainless-steel surfaces show high tolerance to disinfectants, particularly in multidrug-resistant (MDR) strains, posing risks in food and pharmaceutical processing. Repurposing Generally Recognized as Safe (GRAS) compounds for low-dose biofilm control is therefore attractive. This study evaluated the antibacterial and antibiofilm efficacy and key mechanisms of mixed bile salt-weak base disinfectants against wild-type and MDR S. aureus biofilms. In brief, sodium cholate (CHO) and sodium chenodeoxycholate (CHE) were combined with ammonium hydroxide (AMH) or sodium bicarbonate (BIC) and tested against SA. ATCC and a multidrug-resistant SA. CCARM strains. Antibacterial activity and interactions were determined by minimum inhibitory concentration and checkerboard assays. Biofilms on sandblasted stainless-steel discs were assessed by viable cell counts, biofilm formation index, and extracellular DNA and polysaccharide levels. Transmission electron microscopy and quantitative real-time PCR of selected genes were used to examine structural damage and stress-response modulation. All preparations showed antibacterial activity, with higher MICs in the MDR strain. CHO + AMH displayed clear synergy against both strains, whereas CHE + BIC ranged from synergistic to additive. On stainless steel, CHO + AMH produced the greatest and most sustained reduction in biofilm-associated cells and the lowest biofilm formation indices, together with marked depletion of matrix components. TEM revealed extensive envelope disruption and cell damage under CHO + AMH compared with single agents. Combination treatments altered stress-response and efflux gene expression in patterns consistent with severe cellular injury and limited adaptive capacity. Accordingly, mixed bile salt-weak base disinfectants, particularly CHO + AMH, enhance antibacterial and antibiofilm activity against wild-type and MDR S. aureus by targeting cell envelopes, biofilm matrix, and stress-adaptation pathways. These GRAS-based combinations represent promising low-dose disinfectant candidates for controlling S. aureus biofilms on stainless-steel surfaces in processing environments.
The global spread of colistin (COL) resistance, particularly mediated by mcr-1, threatens the efficacy of this last-line antibiotic against multidrug-resistant (MDR) Gram-negative pathogens. This development underscores the urgency of developing innovative therapeutic strategies to counteract antimicrobial resistance mechanisms. This study demonstrates that piperine (PIP), a natural alkaloid, functions as a potent adjuvant that restores COL efficacy through a multi-target mechanism. The combination of PIP and COL exhibits significant synergism against clinically relevant pathogens, including mcr-1-positive strains (FICI: 0.07-0.281), and was not susceptible to the development of drug resistance. Additionally, this combination effectively inhibits and eradicates biofilms. Mechanism studies and omics analysis confirmed that PIP combined with COL could cause bacterial membrane disruption, proton motive force (PMF) disruption, efflux pumps inhibition, resulting in accumulation of bacterial reactive oxygen species (ROS) and finally cell death. Furthermore, PIP suppresses MCR-1 through dual suppression of gene expression and protein function. The therapeutic potential was confirmed in murine infection models, where the combination significantly improved survival rates, reduced bacterial loads, and attenuated inflammatory responses. This study provides the first comprehensive elucidation of the multi-target synergy between COL and PIP, offering a promising therapeutic strategy that simultaneously overcomes existing resistance and impedes resistance development.
Non-typhoidal Salmonella (NTS) is a leading bacterial pathogen responsible for foodborne outbreaks worldwide, with poultry products being a major source of human salmonellosis. While previous studies have predominantly focused on Salmonella transmission in the chicken production chain, ducks have received comparatively little attention as a potential reservoir host. In this study, we investigated Salmonella contamination across a commercial duck breeder-hatchery-grow-out (BHG) production system in Inner Mongolia, Hebei, and Shandong, China, comprising five breeder duck farms, one hatchery, and one commercial grow-out duck farm. From January 2022 to July 2025, a total of 7765 samples were collected across the duck BHG production system, from which 796 Salmonella isolates were recovered, yielding an overall prevalence of 10.25%. Serotyping analysis identified 16 serovars, dominated by S. Typhimurium (52.51%, 418/796), followed by S. Anatum (18.72%, 149/796) and S. Enteritidis (16.21%, 129/796). To further explore genomic relationships and potential transmission routes, 212 of the 418 S. Typhimurium isolates, representing diverse sampling time points, production stages, sample sources, locations, and antimicrobial-resistance profiles, were selected for whole-genome sequencing (WGS). Core-genome single nucleotide polymorphism (cgSNP) analysis revealed the presence of both vertical and horizontal transmission of S. Typhimurium from breeder ducks to commercial ducks. Antimicrobial susceptibility testing showed that 83 S. Typhimurium isolates (26.35%) exhibited antimicrobial resistance (AMR) to more than three classes of antibiotics. These isolates exhibited high resistance rates to ampicillin, amoxicillin, tetracycline, nalidixic acid, and streptomycin. A comparative genomic analysis of multidrug resistance genes identified an IS26-mediated chromosomal replacement event, leading to the replacement of a chromosomal region with a multidrug resistance region (MRR). This genomic rearrangement may contribute to the persistence and dissemination of multidrug-resistant clones within the production system. Overall, these findings demonstrate that Salmonella circulating in breeder ducks and farm environments can disseminate through eggs and the hatchery to commercial meat ducks, suggesting that the hatchery may serve as key points for amplification and cross-contamination. These results underscore the need for strengthened hatchery biosecurity, including routine surveillance, strict workflow separation, and enhanced cleaning and disinfection, to reduce the dissemination of antimicrobial-resistant Salmonella along the duck production chain.
Escalating resistance in Pseudomonas aeruginosa (PA) underscores the need for resistance-agnostic immunotherapies. In this study, we generated a panel of 20 monoclonal antibodies against the flagellin protein FliC and identified 16G10 as a high-affinity lead. Epitope mapping revealed a conserved linear site within the D1 domain (Gly71-Ile88), a region essential for filament assembly. In vitro, 16G10 induced bacterial aggregation, suppressed swimming motility, and significantly reduced adhesion to and invasion of A549 cells, while limiting biofilm biomass by SEM and confocal 3D imaging. In vivo, in murine pneumonia, where 16G10 administered either after pre-incubation with imipenem-resistant PA strain or as post-infection therapy, it improved survival, lowered lung bacterial loads, reduced IL-6 and TNF-α concentrations, and attenuated histologic inflammation. Protection extended across serotype A and B flagellated strains, indicating broad coverage. These data nominate 16G10 as a promising candidate for immunotherapy of drug-resistant PA lung infections and establish a druggable flagellin epitope for future vaccine and antibody designs.
Food microbiologyNatoavina T Faliarizao, Teresa M Bergholz, Kirk D Dolan
Dried chilies, although widely used as food ingredients such as paprika, present food safety risks across the production chain due to bacterial contamination, including Salmonella. This study assesses the fate of Salmonella Montevideo on red peppers during microwave drying and compares predictive models incorporating the effects of dynamic temperature and water activity (aw). Fresh red chilies (aw = 0.98) were sliced lengthwise, inoculated with Salmonella Montevideo, then dried at two power levels in a microwave oven for 45 min (120W) and 18 min (240W) to achieve aw<0.60. Temperature dynamics (24.5-87.6°C) were captured using an infrared camera, then the aw and Salmonella counts were measured at each sampling point. Salmonella survival parameters were estimated with four primary models (Weibull, log-linear, Geeraerd, and Cerf models), and then the Bigelow-type model was incorporated into the selected primary model to characterize the effects of temperature and aw on Salmonella inactivation. All models were assessed using the corrected Akaike information criterion (AICc). Higher microwave power resulted in lower Salmonella survival over time (p < 0.05) with a reduction range of 2.3-3.2 log. The log-linear/Bigelow (zT) yielded the lowest AICc value (11.94), which was the best-fitted model with D77°C-value of 4.24 min and a zT-value of 9.15°C. Temperature changes are determinant to describe Salmonella survival during chili drying, as the log-linear/Bigelow (zT) model better described the nonlinear reduction of Salmonella during the process. These findings serve as a basis to develop and refine spice drying conditions to improve Salmonella control while maintaining quality.
White brined cheeses can provide a suitable environment for the persistence of spore-forming bacteria such as Clostridioides difficile. This study examined the behaviour of C. difficile during the controlled manufacture and 90-day ripening of laboratory-scale white brined cheeses and assessed the inhibitory effects of two probiotic combinations. After pasteurization, C. difficile spores were inoculated into designated batches, while two formulations previously shown to suppress the pathogen in vitro (commercial probiotic + isolate 43; YF-L901 + isolate 33) were added to separate groups. Physicochemical and microbiological parameters were monitored throughout ripening. Six experimental white-brined cheese groups were produced, consisting of rennet-only control cheeses with and without Clostridioides difficile inoculation, as well as probiotic-containing cheeses prepared with two different culture combinations under both inoculated and non-inoculated conditions. In the rennet-only batch containing C. difficile, counts decreased from 6.54 to 5.00 log CFU/g by day 90. C. difficile counts declined from 5.61 to 4.20 log CFU/g in cheeses containing the commercial probiotic + isolate 43, and from 5.54 to 4.38 log CFU/g in those with YF-L901 + isolate 33. Probiotic-supplemented cheeses also showed stronger lactic acid bacteria development, confirming successful colonisation of the cheese matrix. Although typical ripening changes in pH, moisture and salt were observed, these factors alone did not account for the reductions in C. difficile. Overall, probiotic-containing cheeses exhibited a more pronounced decline in C. difficile than the non-probiotic control. These results indicate that inhibition may be influenced not only by acidification but also by broader microbial interactions associated with the added cultures.
Food microbiologyNada Ahmed, Mohamed El-Fateh, Xianhua Yin, Kelly Ross, Moussa S Diarra, Xin Zhao
Salmonella Enteritidis (S. Enteritidis) is a persistent challenge within the poultry industry. The silent colonization allows S. Enteritidis establish themselves in the gut and reproductive tract, leading to persist, spread, and contaminate eggs and meat. This study investigated the anti-virulence potential of a sweet cherry pomace extract (CPE) as a potential natural decontaminant to disrupt S. Enteritidis colonization. The total phenolic content (TPC) and composition of ethanolic extracts from CPE were investigated via HPLC. Antimicrobial activities of CPE were evaluated by minimal inhibitory (MIC) and minimal bactericidal (MBC) concentrations determinations, as well as by growth kinetics and time-kill assays. Anti-virulence at sub-inhibitory concentrations (sub-MICs) was evaluated through swimming/swarming motility, biofilm formation (crystal violet), and auto-aggregation. The efficacy of CPE in reducing S. Enteritidis colonization was validated on chicken skin and visualized through scanning electron microscopy (SEM). The studied CPE was rich in phenolic compounds, predominantly anthocyanins; and exhibited an inhibitory effect against S. Enteritidis at a MIC of 64 mg/mL and MBC of 128 mg/mL. Concentrations ≤8 mg/mL did not significantly affect growth kinetics or viability. Importantly, sub-MIC levels significantly reduced swarming and swimming motility as well as biofilm formation, and auto-aggregation in a dose-dependent manner. SEM topographic analysis confirmed that CPE reduced S. Enteritidis colonization on treated chicken skin. These findings demonstrate that at sub-MICs, CPE functions as a non-bactericidal anti-virulence agent that interferes with S. Enteritidis colonization mechanisms, supporting its potential as a natural decontaminant for poultry processing.
Bacillus cereus is a major foodborne pathogen characterized by robust biofilm formation and increasing antimicrobial resistance. This study identified 2-Methoxycinnamaldehyde (MCA) from Toona sinensis as the principal antibacterial compound and evaluated its inhibitory mechanisms and preservation potential. MCA exhibited potent activity against B. cereus ATCC 11778 (MIC = 150 μg/mL; MBC = 200 μg/mL) and resistant strains. In vitro assays demonstrated that MCA induced concentration-dependent membrane disruption, DNA damage, and intracellular protein leakage. Furthermore, treatment at 1 MIC and 2 MIC significantly impeded biofilm maturation; the secretion of extracellular proteins was reduced by 45.3% and 54.5%, polysaccharides by approximately 93%, and extracellular DNA (eDNA) by over 99%. Correspondingly, biofilm metabolic activity declined by 85.9% and 90.3%, and initial cellular adhesion was reduced by up to 88.1%. Untargeted metabolomic analysis revealed that these phenotypic defects stem from profound disturbances in amino acid biosynthesis, the TCA cycle, and nucleotide metabolism. Molecular docking revealed that MCA targets multiple essential bacterial enzymes, including ribonucleotide reductase, lysyl-tRNA synthetase, pyruvate kinase, betaine aldehyde dehydrogenase, and 5'-nucleotidase, through stable hydrogen bonding and π-interactions. In a refrigerated pork model, MCA completely eliminated B. cereus by day 7 while significantly delaying pH increases and color deterioration. These findings provide the first evidence for MCA as an antibacterial and antibiofilm agent against B. cereus, highlighting its potential in food preservation.
Food microbiologyJincheng Ma, Yingwen Tang, Shaojin Wang, Byron D Chaves, Long Chen
A major cause of Salmonella spp. foodborne outbreaks in milk powder is cross-contamination in production environments. Transfer experiments under different conditions were performed between different donors and acceptors (stainless steel coupon, paper towel, and milk powder). A Monte Carlo simulation was developed to model the cross-contamination of Salmonella Enteritidis PT 30 (S. PT 30) and dry cleaning interventions in milk powder production environments under 8 scenarios. Inputs to the model included the initial level of S. PT 30, the proportion of milk powder in contact with the surface, the normal force for dry wiping, the log transfer coefficient (log TC) under various conditions, and the reduction proportion on the surface with inoculated milk powder residues after dry cleaning. The model's outputs mainly included the quantity and the concentration (log CFU/g) of contaminated milk powder. Initial level, normal force, inoculation method, and transfer direction significantly affected the log TC (p < 0.05). After a contamination breach on the contact surface in scenario 1, milk powder was contaminated. Milk powder could still be contaminated with a low concentration even after multiple S. PT 30 transfer steps from different contamination sources to the contact surface in scenarios 2-5. Dry wiping effectively reduced the quantity and the concentration of contaminated milk powder in scenarios 6-7. But multiple dry wipes were needed to remove all S. PT 30 from the surface in scenario 8. The developed model can be used to evaluate the risk of cross-contamination in various scenarios in milk powder production environments and provide guidance for hygiene intervention strategies.
Hepatitis E virus (HEV) belongs to the Paslahepevirus balayani species (Hepeviridae family) and harbours a positive-sense, single-stranded RNA genome. HEV genotypes 3 and 4 (HEV-3 and-4) are mainly transmitted from animal reservoirs (primarily domestic pig), either through direct contact or by consuming meat from infected animals. Heat treatment is the main food technological process used to inactivate HEV in pork products. It is crucial to implement robust methods for assessing HEV infectivity to ensure the effectiveness of such inactivation processing. Even if several cell lines are permissive to HEV, cell culture-based methods still present several drawbacks (high technical expertise, time-consuming, low throughput). The aims of this study were to optimize a capsid-integrity-RT-qPCR assay to study the thermal resistance of HEV in simple matrix (PBS, cell culture medium), to validate its application to deli meat products (cooked ham and emulsified sausage), and to compare its performance to a cell culture assay using HepaRG cells. Among several candidates, PtCl4 was identified as the most effective capsid-integrity marker to bind viral RNA, and a concentration of 2.5 mM PtCl4 provided the highest reduction in genomic titre for both heat-inactivated strains of HEV-3 tested (HEV-3c and HEV-3f) without affecting the viral genomes from intact viral particles. The capsid-integrity-RT-qPCR was successfully validated in food matrices (cooked ham and emulsified sausage), with reductions >4 log10 achieved for heat-inactivated HEV whatever the strain tested. Sensitivity analysis showed reliable detection of infectious HEV in both suspensions and food matrices down to 2 log10 genome equivalents/mL. When applied to assess the effectiveness of thermal inactivation of ≥63°C for ≥5 min or ≥75°C for 5 min, our results showed effective inactivation of HEV, with both molecular and cell culture detection methods showing parallel trends. Capsid-integrity-RT-qPCR showed a time- and temperature-dependent reduction in HEV genomic titres that correlated with the loss of infectivity observed in cell culture assays. These findings support the use of capsid-integrity-RT-qPCR as a useful first-line screening tool for evaluating HEV thermal inactivation, to be complemented by cell culture assays when feasible, particularly in complex food matrices. This complementary use of both methods is intended to be further assessed for validating viral inactivation processes in the food industry.
Kombucha tea, a fermented beverage, is widely consumed and gaining global popularity for its perceived functional properties. The kombucha microbial community comprises bacteria and yeast that can produce antimicrobial metabolites during fermentation, thereby suppressing foodborne pathogens. However, this aspect of kombucha's functionality remains only partially characterized under controlled conditions. This study, therefore investigated the survival of Salmonella Enteritidis (S. Enteritidis) and the associated physicochemical parameters during 14 days of black-tea kombucha fermentation. The study also assessed changes in the indigenous microbiota responsible for fermentation over the 14-day fermentation period. Kombucha was prepared using 1.6% (w/v) black tea, 10% (w/v) sucrose, and a commercially available starter culture. The kombucha was inoculated with 7.2 log CFU/mL of S. Enteritidis and fermented at room temperature for 14 days. Pathogen populations, lactic acid bacteria (LAB), total yeast and mold (TYM) counts, pH, titratable acidity, and total phenolic content were monitored over 14 days. The initial S. Enteritidis population (7.24 ± 0.44 log CFU/mL) decreased significantly (p < 0.05) by 5 log on day 10 (2.01 ± 0.1 log CFU/mL) and continued to reduce to 1.4 ± 0.3 log CFU/mL by day 14, whereas the S. Enteritidis population in the black tea increased and remained stable throughout the incubation. The inactivation of S. Enteritidis coincided with increased titratable acidity, reduced pH, and increased total phenolic content. Growth in the populations of LAB and TYM increased, corresponding to acidification and associated with the inhibition of pathogens. Results from this study demonstrate that kombucha fermentation can suppress S. Enteritidis, thereby substantially reducing pathogen growth and the risk of foodborne illness.
Antimicrobials are used in aquaculture to treat bacterial infections, and their use could promote the emergence of antimicrobial-resistant bacteria. Monitoring the antimicrobial resistance profiles of fish-derived bacteria, especially those pathogenic to fish and humans, such as Lactococcus petauri, L. formosensis, and L. garvieae, can be essential for assessing the risk of antimicrobial-resistant bacteria. Therefore, we conducted a pilot study to continuously monitor the contamination and antimicrobial resistance of these bacterial species in retail fish in Japan. We purchased domestic seafood fish samples (n = 490), including wild-caught and farm-raised fish, from supermarkets in Japan between 2023 and 2024. We isolated bacteria from 16.1% of the samples, with L. petauri (8.8%) being the most prevalent species, followed by L. formosensis (5.5%) and L. garvieae (2.2%). Oxytetracycline, erythromycin, and lincomycin resistance rates were 11.6%, 5.8%, and 88.4%, respectively, and we detected resistant isolates both in retail wild-caught and farm-raised fish products. The erythromycin- and oxytetracycline-resistant L. petauri isolate harbored the plasmid harboring the multidrug-resistance genes (erm(B), tet(L), and tet(S)). Phylogenetic analysis revealed that genetically similar isolates were present across the same and different supermarkets over several months. These results suggest that L. petauri, L. formosensis, and L. garvieae could be useful indicators for monitoring antimicrobial-resistant bacteria in seafood, and highlight the potential for bacterial cross-contamination throughout the food supply chain.
In the context of sustainable waste valorization, we investigated microbiological safety hazards associated with spore-forming bacteria, focusing in particular on Bacillus cereus contamination and diversity during Hermetia illucens (Black Soldier Fly, BSF) bioconversion at different developmental stages. Larvae were reared on authorized (carrots, apricots, wheat bran) and unauthorized substrates (expired unpackaged retail food products and cafeteria waste). After 7 days of spontaneous fermentation of these substrates, total aerobic mesophilic bacterial counts were comparable across substrates; however, aerobic spore counts were significantly higher in unauthorized than authorized substrates. Notably, B. cereus was undetectable in authorized substrates but reached 5.2-6.0 log CFU/g in unauthorized waste. Despite substrate differences, BSF larvae and frass showed similar levels of total mesophilic and spore counts, with B. cereus consistently detected, indicating that vertical transmission may take place. Phylogenetic analysis revealed the persistence of potentially enterotoxigenic B. cereus group III strains harboring nheI and cytK genes throughout the bioconversion process. Additionally, group IV strains initially present in the substrate became dominant in larvae and frass by day 14. These findings demonstrate that BSF larvae are unable to significantly reduce B. cereus during entomoconversion. Frass and larvae from both authorized and unauthorized substrates showed similar contamination levels. Both types of substrates were suitable for larval rearing and did not lead to significant differences in B. cereus levels, however, the persistence of high loads in larvae and frass, regardless of the substrate, may represent a potential health hazard in the absence of further treatment.
Food microbiologyNirosha Ruwani Amarasekara, Deepak Subedi, Joshua B Gurtler, Xuetong Fan
Work-in-process (WIP) ingredients, within the fresh-cut produce industry, are often washed, then held for varying lengths of time, prior to incorporating into finished products. The effects of sanitizer washing and storage temperature on the survival and growth of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella enterica were evaluated on WIP broccoli stalk, Brussels sprout, and kale. WIP produce was inoculated with pathogen cocktails (ca. 8 log CFU/ml), which were untreated or washed with water, free chlorine (ca. 100 ppm), or peracetic acid (PAA, ca. 80 ppm). Following storage at 4, 8, or 12 °C for 7 days, pathogen populations and indigenous microbiota were enumerated. Results showed that at 4 °C, populations declined or remained stable during the 7-day storage period but increased by up to ca. 3 log CFU/g at 12 °C, particularly for E. coli O157:H7 and S. enterica. Sanitizer washing reduced initial pathogen populations, with PAA generally producing greater immediate reductions than chlorine. However, sanitizer washing occasionally resulted in higher growth, particularly for L. monocytogenes, at elevated temperatures. In addition, indigenous microbiota often grew significantly faster on PAA-washed samples than on unwashed controls (e.g., mesophile population growth at 4 °C after 7-days' storage was 1.59 vs. 0.51, 0.96 vs. -0.27, and 1.61 vs. 0.71 log CFU on PAA vs. unwashed broccoli stalk, Brussels sprout, and kale, respectively). These results indicate that sanitizer washing provides only short-term reductions of microbial growth, highlighting temperature control at ≤4 °C as the most critical intervention for ensuring the microbial safety of WIP brassica vegetables.
Food safety is increasingly threatened by contamination with foodborne pathogenic microorganisms, particularly in the context of escalating antimicrobial resistance. Natural antimicrobial peptides, such as temporin-SHf, are considered promising candidates for food preservation; however, their practical application is often limited by poor stability and insufficient antimicrobial efficacy. Herein, a sulfonium-stabilized cyclization strategy was employed to improve the stability and antimicrobial activity of temporin-SHf. By conformationally constraining the peptide, its resistance to serum proteases, pH fluctuations, and saline environments was significantly enhanced. Moreover, the incorporation of sulfonium moieties increased peptide cationicity, thereby reinforcing electrostatic interactions with bacterial cell membranes and resulting in an approximately ten-fold increase in antimicrobial potency relative to the native peptide. Furthermore, TP [4,7]-Ph showed improved antimicrobial activity against selected foodborne bacterial strains and exhibited synergistic effects with several conventional food preservatives. In an S. aureus-inoculated pork model, TP [4,7]-Ph treatment reduced bacterial growth and helped maintain pork quality, as reflected by lower drip loss and delayed physicochemical deterioration. Overall, these findings support the potential of sulfonium-stabilized cyclic temporin-SHf peptides as candidates for food preservatives, while further validation against additional foodborne pathogens in relevant food matrices remains necessary.