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Time-temperature data for queso fresco (QF) cheese varieties stored in a residential refrigerator operating at 5°C and a predictive microbiology secondary model for Listeria monocytogenes in QF were used to estimate a refrigerator performance indicator (RPI) of microbial preservation. RPI values were used to assess how compressor technology (single [SS] and variable speed [VS]), ambient temperature (21.1°C [LT] and 32.2°C [HT]), and refrigerator load (22.5 kg regular load and 39 kg higher load) affected preservation performance. All deterministic and probabilistic RPI estimations slightly exceeded the desirable 1.0 value, i.e., the variable temperatures for the QF kept in the refrigerator were worse than keeping it constantly at the temperature recommended by food safety agencies for QF. Furthermore, the mean comparison of estimates of the time-temperature equivalent indicator previously developed by French researchers showed similar behavior to those observed for RPI. Finally, statistical analysis showed that Tambient was the factor with the highest impact on refrigerator performance because of its impact on the sample temperature increase during door openings and when exposed to ambient temperature during product use. This highlights the need to reduce the time for product temperature recovery by improving the compressor operation logic. Also important are consumer behavior changes such as a reduction in product exposure to ambient temperature and in the door opening duration and frequency. PRACTICAL APPLICATION: This study demonstrated how a quantitative tool (RPI) can assess refrigerator preservation performance. Although the findings presented can be applied to any cold chain segment, the data used was collected for its weakest link, the domestic refrigerator. Surveys show that 77% of them operate above the recommended 4°C. The RPI methodology is ready for use by refrigerator designers to assess performance improvements possible by modifications of the compressor operation logic. Moreover, it can be integrated into smart-hubs monitoring the frequency and duration of refrigerator door openings to inform consumers when their habits are compromising the preservation performance of the refrigerator.

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A complete and comprehensive chemical and biological study of Drimys granadensis, a native Ecuadorian aromatic plant, was conducted. By conventional steam distillation from dried leaves, a yellowish, translucent essential oil (EO) with a density of 0.95 and a refractive index of 1.5090 was obtained. The EO was analyzed by gas chromatography coupled to a mass spectrometer (GC/MS) and an FID detector (GC/FID), respectively. Enantiomeric distribution was also carried out by GC/MS using a chiral selective column (diethyl tert-butylsilyl-BETA-cyclodextrin). The microdilution broth method was employed to assess the antibacterial and antifungal activity of the EO against a panel of opportunistic microorganisms. Antioxidant capacity was measured using diphenyl picryl hydrazyl (DPPH) and azino-bis 3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radicals. Finally, the inhibitory potential of the EO against acetylcholinesterase was also valued. Sixty-four chemical compounds, constituting 93.27% of the total composition, were identified, with major components including γ-muurolene (10.63%), spathulenol (10.13%), sabinene (5.52%), and δ-cadinene (4.22%). The characteristic taxonomic marker of the Drimys genus, Drimenol, was detected at very low percentages (<2%). Two pairs of enantiomers ((1S,5R)-(+)-α-pinene/(1S,5S)-(-)-α-pinene; (1S,5R)-(+)-ß-pinene/(1S,5S)-(-)-ß-pinene) and one pure enantiomer (1R,4S)-(-)-camphene were identified. Regarding antimicrobial potency, the EO exhibited a significant moderate effect on Listeria monocytogenes with a minimal inhibitory concentration (MIC) value of 250 µg/mL, while with the remaining microorganisms, it exerted less potency, ranging from 500 to 2000 µg/mL. The EO displayed moderate effects against the ABTS radical with a half scavenging capacity of 210.48 µg/mL and no effect against the DPPH radical. The most notable effect was noticed for acetylcholinesterase, with a half inhibition concentration (IC50) of 63.88 ± 1.03 µg/mL. These antiradical and anticholinesterase effects hint at potential pharmacological applications in Alzheimer's disease treatment, although the presence of safrole, albeit in low content (ca. 2%), could limit this opportunity. Further in vivo studies are necessary to fully understand their potential applications.

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Listeria monocytogenes is a human opportunistic foodborne pathogen that produces life-threatening infections with a high mortality rate. The control of Listeria in the food production environment and effective clinical management of human listeriosis are challenging due to the emergence of antibiotic resistance. Hence we evaluate the in vitro anti-Listeria activity of two synthetic cruzioseptins reproducing their natural sequences CZS-9, and CZS-12, and one engineered sequence based on CZS-1, named [K4K15]CZS-1. The assessment of the in vitro potential of cruzioseptins, highlighted the promising antibacterial effect of [K4K15]CZS-1 in very low concentrations (0.91 µM) and its thermal stability at high-temperature conditions, is compatible with the food industry. Microscopic and metabolomic analyses suggest cruzioseptin induces anti-Listeria bioactivity through membrane disruption and changes in the intracellular metabolome. We also report that [K4K15]CZS-1 is not resistant to peptidases/proteases emphasizing a key advantage for their use as a food preservative. However, there is a need for further structural and functional optimisations for the potential clinical application as an antibiotic. In conclusion, [K4K15]CZS-1 stand out as membrane-active peptides with the ability to induce shifts in the bacteria metabolome and inspire the development of strategies for the prevention of L. monocytogenes emergence and dissemination.

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Human listeriosis is an infectious disease caused by Listeria monocytogenes. The invasive form of this disease leads to a high rate of hospitalizations and fatality. The main mode of transmission is through contaminated ready-to-eat foods such as dairy, vegetables and meat products. The knowledge of the diversity and population dynamics of isolates collected from human and food sources is essential for the detection of clusters and the identification of common sites of infection. The aim of this study was the molecular characterization of L. monocytogenes isolates in Argentina. We sequenced a total of 63 isolates, 35 from human and 28 from food sources, collected between 2018 and 2023. Our genomic study divided the isolates into two lineages, four serogroups, 17 sequence types and 15 clonal complexes (CCs). The hypervirulent clone CC1 (lineage I; serogroup IVb) predominated in human and food samples. The phylogenomic analysis showed a high and possible epidemiological relationship between isolates from human and/or food sources, suggesting the presence of transmission chains in our country. These findings highlight the need to strengthen genomic surveillance of L. monocytogenes in Argentina. The identification of geographic distribution and characteristics of predominant and emerging clones from human and food sources might help to focus action plans and public health policies better directed at the control and prevention of listeriosis.

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Listeria (L.) monocytogenes is an opportunistic foodborne pathogen that causes listeriosis in humans and animals, reaching up to 30% case mortality. There are only a few reports in Mexico about the L. monocytogenes strains found in various foods. The aim of this study was to determine the prevalence of L. monocytogenes, serogroups, virulence genes, and antimicrobial resistance in different foods from Reynosa, Tamaulipas, Mexico. L. monocytogenes strains were characterized by microbiological and molecular methods. Susceptibility to 12 antibiotics was determined according to CLSI and EUCAST. A total of 300 samples of seafood, pasteurized and raw milk, cheese, beef, and chicken were collected from supermarkets and retail markets. The presence of L. monocytogenes was detected in 5.6% of the samples. Most strains belonged to serogroups 4b, 4d, and 4e (68.4%). All strains presented a minimum of four virulence genes; the most common were actA, hly, and plcB (92.1%). A high percentage of antimicrobial susceptibility was observed, with resistance only to STX-TMP (78.9%), STR (26.3%), MEM (21.0%), and E (2.6%). These results show that the foods in Reynosa, Tamaulipas, are a reservoir of L. monocytogenes and represent a potential health risk.

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Pediococcus pentosaceus ST65ACC is a bacteriocinogenic lactic acid bacteria (LAB) isolated from Brazilian artisanal cheese that is capable of inhibiting different food pathogens, mainly Listeria monocytogenes. The production of bacteriocins can be influenced by several growth conditions, such as temperature, pH, and medium composition. This study aimed to evaluate the effect of different culture media on the production of bacteriocins and antimicrobial activity of P. pentosaceus ST65ACC on L. monocytogenes Scott A. The strains were inoculated alone and in coculture in four different media: BHI broth, MRS broth, meat broth, and reconstituted skim milk (RSM) 10% (w/v). The culture media were then incubated at 37 °C for 96 h, and count analysis, pH measurement, and bacteriocin production were performed at 0, 24, 48, 72 and 96 h. L. monocytogenes was inhibited to nondetectable levels in coculture with P. pentosaceus ST65ACC in MRS broth within 96 h, consistent with the high production of bacteriocin throughout the analysis period (3,200-12,800 AU/mL). However, lower inhibitory activities of P. pentosaceus ST65ACC on L. monocytogenes Scott A were recorded in BHI, RSM, and meat broth, with low or no production of bacteriocins at the analyzed times. The composition of these culture media may have repressed the production and activity of bacteriocins and, consequently, the antagonist activity of P. pentosaceus ST65ACC on L. monocytogenes Scott A. The results showed that the antimicrobial activity was more effective in MRS broth, presenting greater production of bacteriocins and less variability when compared to the other media analyzed.

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Background: Listeria monocytogenes, a Gram-positive bacillus, primarily affects immunocompromised individuals. Endocarditis is a rare but severe complication of L. monocytogenes bacteremia, irrespective of native or prosthetic valves. While there is no standardized treatment, the use of ampicillin proves effective in most cases. Surgical intervention is reserved for cases involving valve dehiscence, heart failure, or myocardial abscess. Case presentation: A 54-year-old female, with mitral valve replacement, presented with fever, chest pain and dyspnea at rest. Patient was initially diagnosed with bacterial pneumonia; however, subsequent evaluation revealed L. monocytogenes bacteremia, resulting in endocarditis. Surgical management was contraindicated due to multiple prior valve replacement surgeries. Symptoms resolution, along with improvements in echocardiographic and clinical parameters, was achieved through extended antibiotic treatment only with no surgical intervention. Conclusion - key takeaways: This case underscores the critical importance of individualized treatment approaches in endocarditis, particularly in patients with surgery approach contraindication, and emphasized the success achieved through ampicillin-based management.

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Listeriosis is a disease caused by L. monocytogenes, a relevant microorganism as a causative agent of foodborne diseases - FBD. This study aimed to evaluate the distribution of Listeria spp., and L. monocytogenes in different production areas in two small plants (A and B) and two micro-food processing plants (C and D) producing meat derivatives, located in different cities of Colombia. The methodology implemented was i. The analysis of sampling points is based on a harmonised tool. ii. Four samplings in each production plant between 2019 and 2020. iii. Isolation and identification of microorganisms through conventional microbiology, a semi-automated system, molecular serotyping and clonal characterisation by ERIC-PCR. L. monocytogenes frequency in the production plants belonging to the study ranged between 5.9 and 28.6 %; for Listeria spp., plants A and D had isolated, plant A had the highest proportion, while for L. monocytogenes geno-serotypes found were: 1/2a, 1/2c, 4a-4c, 4b, 4d - 4e, with geno-serotype 4b as the most frequent. Furthermore, possible persistent isolates were detected in plant C as the feasible sources of contamination, based on failures in flow management, raw material contaminated with L. monocytogenes, lack of standardised cooking processes and transfer of the microorganism through equipment and surfaces. Finally, in three of the four production plants assayed, L. monocytogenes or Listeria spp. were present in the packaging area in some of the samples taken during the study, which calls for increased and frequent monitoring, as well as constant technical support for the control of L. monocytogenes in micro and small-scale production plants.

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This study assessed the microbiological quality and safety of mozzarella during various production stages in northern Tocantins, Brazil, by identifying critical biological points in the industrial environment within a tropical climatic region. Batches of mozzarella were evaluated, from raw milk to primary packaging, with a shelf life of 120 d at 4°C. Indicator microorganisms were quantified, and through microbiological and biomolecular approaches, Salmonella spp. and Listeria monocytogenes were identified. In addition, the toxigenic potential of coagulase-positive staphylococci (CPS) was characterized. Results indicated that the raw milk used for mozzarella production had low microbiological quality; pasteurization of raw milk effectively eliminated all identified pathogens and reduced microbiological counts (p > 0.05). An increase in bacterial counts (>2 log colony-forming unit [CFU]/g) and recontamination with Salmonella spp. and CPS, which potentially produce staphylococcal enterotoxin B, were observed during milk coagulation and curd draining. Stretching of the fermented curd reduced the enterobacteria, total coliforms, and Escherichia coli median values by 2.56, 2.64, and 2.3 log CFU/mL, respectively. Similarly, brining the pieces by immersion reduced the quantity of enterobacteria and total coliforms by 2.3 and 1.6 log CFU/mL, respectively. Of interest, in the freshly finished product, Salmonella spp. was present but L. monocytogenes was absent; however, after the shelf-life period, L. monocytogenes was present but Salmonella spp. was absent. Considering the environmental conditions that can promote the multiplication and preservation of pathogens and spoilage of dairy products in tropical climates, it is necessary to review operational hygiene procedures, particularly in milk coagulation vats and fermentation tables. This will ensure the production of high-quality mozzarella cheese with a reduced consumption risk.

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Las infecciones del sistema nervioso central son potencialmente mortales, causadas por patógenos, como bacterias, virus y hongos. Para llegar hasta el cerebro, los microorganismos utilizan diversas vías y formas. Este patogeno es una bacteria grampositiva corta, flagelar e intracelular, con la capacidad de inducir su internalización en células fagocíticas (monocitos/macrófagos) y no fagocíticas (células endoteliales). Al infectar los macrófagos, estos microorganismos se valen de su capacidad de fijación, adhesión y migración transendotelial, para cruzar la barrera hematoencefálica, finalmente, generando meningitis bacteriana. En esta revisión describimos el mecanismo de caballo de Troya usado por Listeria monocytogenespara invadir el cerebro en el desarrollo de enfermedades infecciosas e incorporamos nuevos conocimientos sobre moléculas que intervienen en dicho mecanismo(AU)

Central nervous system infections are life-threatening, caused by pathogens such as bacteria, viruses and fungi. To access the brain, microorganisms use various mechanisms. Listeria monocytogenes is a short, flagellar and intracellular gram-positive bacterium, with the ability to induce its internalization in phagocytic (monocytes/macrophages) and non-phagocytic (endothelial cells) cells. By infecting macrophages, these microorganisms take advantage of their binding, adhesion, and transendothelial migrationcapacity to cross the blood-brain barrier, finally generating bacterial meningitis. In this review we describe the Trojan horse mechanism used by Listeria monocytogenesto invade the brain in the development of infectious diseases and we incorporate new knowledge about molecules that intervene in this mechanism(AU)

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