Plate Count Method Research Articles

Mycoplasma bovis Invades Non-Phagocytic Cells by Clathrin-Dependent Endocytic Pathways and Escapes from Phagocytic Vesicles

Mycoplasma bovis (M. bovis) is capable of causing pneumonia, arthritis, mastitis, and various other ailments in cattle of all age groups, posing a significant threat to the healthy progression of the worldwide cattle industry. The invasion of non-phagocytic host cells serves as a pivotal mechanism enabling M. bovis to evade the immune system and penetrate mucosal barriers, thereby promoting its spread. To investigate the differences in M. bovis invasion into four types of non-phagocytic cells (Madin–Darby bovine kidney (MDBK) cells, embryonic bovine lung (EBL) cells, bovine embryo tracheal (EBTr) cells and bovine turbinate (BT) cells) and further elucidate its invasion mechanism, this study first optimized the experimental methods for M. bovis invasion into cells. Utilizing laser scanning confocal microscopy, transmission electron microscopy, and high-content live-cell imaging systems, the invasion process of M. bovis into four types of non-phagocytic cells was observed. The invasion rates of three different strains of M. bovis (PG45, 07801, 08M) were quantified through the plate counting method. In order to clarify the specific pathway of M. bovis invasion into cells, chlorpromazine (CPZ), amiloride (AMI), and methyl-β-cyclodextrin (M-β-CD) were used to inhibit CLR-mediated clathrin-dependent endocytosis (CDE) pathway, macropinocytosis, and lipid raft pathway, respectively. Subsequently, the invasion rates of PG45 into these four types of cells were measured. Using siRNA technology, the expression of clathrin (CLR) in EBL cells was knocked down to further verify the role of CLR in the invasion process of M. bovis. The results showed that the optimal conditions for M. bovis to invade non-phagocytic cells were a multiplicity of infection (MOI) of 1000 and an optimal invasion time of 4 h. All three strains of M. bovis have the ability to invade the four types of non-phagocytic cells, yet their invasion abilities vary significantly. Observations from transmission electron microscopy further confirmed that at 120 min post-infection, PG45 had successfully invaded EBL cells and was present within endocytic vesicles. It is noteworthy that almost all PG45 successfully escaped from the endocytic vesicles after 240 min of infection had passed. Through chemical inhibition experiments and CLR protein knockdown experiments, it was found that when the CDE and lipid raft pathways were blocked or CLR protein expression was reduced, the invasion rates of PG45, 07801, and 08M in MDBK, EBL, EBTr, and BT cells were significantly decreased (p < 0.05). The above results indicate that M. bovis can invade all types of non-phagocytic cells through endocytic pathways involving CDE (clathrin-dependent endocytosis) or lipid raft-mediated endocytosis, and possesses the ability to escape from phagosomes.

Application of the Electrical Microbial Growth Analyzer Method for Efficiently Quantifying Viable Bacteria in Ready-to-Eat Sea Cucumber Products

Accurate and efficient quantification of viable bacteria in ready-to-eat food products is crucial for food safety and public health. The rapid and accurate assessment of foodborne bacteria in complex food matrices remains a significant challenge. Herein a culture-based approach was established for easily quantifying viable bacteria in ready-to-eat sea cucumber (RSC) products. Samples of the liquid companion within the package were directly transferred into test tubes to determine bacterial growth curves and growth rate curves, utilizing the electrical microbial growth analyzer. Viable bacteria in the samples were then quantified based on the time required to attain the maximum growth rate indicated on the growth rate curve. At a concentration of 5.0 × 103 CFU/mL of viable bacteria in the liquid companion, the recovery rates were 108.85–112.77% for Escherichia coli (E. coli) and 107.01–130.54% for Staphylococcus aureus (S. aureus), with standard deviations of 1.60 and 3.92, respectively. For the solid content in the package, the quantification was performed using the same methodology following an additional homogenization step. At a concentration of 5.0 × 103 CFU/mL of viable bacteria in the sample, the recovery rates were 91.94–102.24% for E. coli and 81.43–104.46% for S. aureus, with standard deviations of 2.34 and 2.38, respectively. In instances where the viable bacterial concentration was 5.0 × 103 CFU/mL in RSC products, the total time required for the quantification did not exceed 10.5 h. This method demonstrated advantages over traditional plate counting and PCR methods regarding simplicity and efficiency, representing a promising alternative for the quantification of viable bacteria in food like RSC products.

Dietary carbohydrates modulate Streptococcus mutans adherence and bacterial proteome.

Streptococcus mutans adherence to the tooth surface and subsequent biofilm development is modulated by the carbohydrate source, but the corresponding effect on bacterial proteome has not been previously studied. This study aimed to assess the effect of different carbohydrates on S. mutans viability and bacterial proteome at two-time points, early attachment (8 h) and biofilm maturation (24 h). Hydroxyapatite (HAp) discs coated with parotid saliva proteins were inoculated with S. mutans UA159 in Tryptone Soy Broth without dextrose supplemented with one of the following carbohydrates (n=12/treatment/time point): 1% Sucrose (S); 0.525% Glucose + 0.525% Fructose (G+F); 10% Xylitol (X); 10% Xylitol + 1% Sucrose (X+S); or culture medium without supplementation as negative control (C). Once inoculated, HAp discs were incubated for 8 h or 24 h at 37 °C and 10% CO2. After each incubation period, adhered bacteria were quantified using the plate-counting method for 6 HAp discs/group, and the remaining 6 HAp discs/group were used to extract bacterial cell wall proteins. Extracted proteins were analyzed using liquid chromatography coupled with mass spectrometry and then classified by their biological process. The study was conducted in three independent assays and the number of bacteria adhered to the HAp discs was determined at each time point and analyzed by two-way ANOVA followed by Bonferroni test (=5%). The results suggest that xylitol significantly repressed bacterial adherence and metabolism at 8 h and 24 h; however, bacterial adherence and metabolism were significantly enhanced when xylitol was combined with sucrose, showing no negative effect on S. mutans at both time points. Bacterial proteome was modulated by the carbohydrate source. The cariogenicity of S. mutans biofilms may be reduced by the alternative sweetener xylitol; however, the combination with fermentable sugars may inhibit such a beneficial effect.

Monitoring of Bacillus spore-forming dynamics through flow cytometry.

The plate counting method is a traditional and widely accepted technique for live cell counting, often employed for Bacillus enumeration and spore forming rate calculations. However, this method requires at least 12 h to generate results, making it unsuitable for real-time monitoring of bacterial growth status and spore transformation rate. Bacillus thuringiensis crystals, produced during sporulation, are widely used as microbial pesticides, with high demand for industrial scale production. Variations in cultivation conditions and harvest timing during large-scale pore production of Bacillus thuringiensis significantly affect spore forming rate, impacting crystallization yield. Nevertheless, there is a lack of real-time monitoring methods for spore conversion rate. Flow cytometry (FCM), a well-established technique for single-cell analysis in eukaryotic cells, has been successfully applied in bacterial detection in environmental and food samples. In this study, we introduced a rapid flow cytometry-based method for determining spore forming rate of Bacillus thuringiensis, with two nucleic acid dyes, SYTO24 and LDS751. The method enables dynamic monitoring of spore, vegetative cell, and viable but non-culturable/dead cell proportions during the whole cultivation process, and spore forming rate could be gained within 30 min. Data of spore forming rate by FCM method is consistent with that by plate counting method, offering a faster and more efficient approach for assessing sporulation status in industrial Bacillus thuringiensis microbial pesticide production.

Evaluation of the Antibacterial Activity of Antibiotics with different Antibacterial Mechanisms using Electrochemical Signals of Heat‐Treated Escherichia Coli

AbstractElectrochemistry with purines as indicators may be a promising new method for antibiotic activity testing. However, the traditional electrochemical detection method (S‐LSV) requires a long accumulation time for purines and has low signal intensity. High‐temperature treatment of bacterial samples may significantly enhance the signal intensity and speed of detection. However, this process may also impact the structure and metabolism of bacteria. Further research is necessary to determine how electrochemical signals respond to antibiotic antibacterial activity. In this paper, the electrochemical detection method based on heat‐treated Escherichia coli (E. coli, H‐LSV) was used to investigate the effects of 11 antibiotics with four different antibacterial mechanisms on the electrochemical behavior of E. coli. The results showed that compared to the S‐LSV, the electrochemical signal of E. coli detected by the H‐LSV increased by 362%, and showed a strong linear relationship with bacterial counts up to 1.88×108 CFU/mL, with a detection limit of 1.15×106 CFU/mL. The electrochemical signal consistently correlated with changes in viable E. coli counts following treatment with the four different antibacterial mechanisms. HPLC analysis further confirmed that the changes in purine contents in bacteria after antibiotic treatment were consistent with the trends in electrochemical signals. The evaluation of antibiotic antibacterial ability by H‐LSV showed good consistency with results from plate counting and turbidity methods, but was closer to the results of plate counting. The inhibition rates of antibiotics on E. coli detected by H‐LSV and S‐LSV also showed high consistency, indicating that short‐term high‐temperature treatment of E. coli did not affect the response of the bacterium to the inhibitory activity of antibiotics.

An Alternative Approach to Validate the Cleaning Efficiency of a Skin Cleansing Wipe

A key functionality for cleansing wipes is their efficiency in removing dirt and microbial contamination from the skin to safe or non-detectable levels, traditionally determined using the gravimetric method, which has been reported to be prone to experimental errors. This study evaluates the efficiency of a water-based cleansing wipe, WaterWipes® (WaterWipes, UC, Drogheda, Ireland), for removing synthetic faecal matter (FecloneTM, SiliClone Creations LLC, Havertown, PA, United States) and Escherichia coli (NCTC 10538) from volunteers’ skin, the former using a dermal analytical device called the Antera 3DTM camera (Miravex Ltd., Dublin, Ireland), and the latter using standard microbiological methods. FecloneTM was applied to participants’ forearms and the Antera 3DTM camera captured detailed images of the skin surface before and after wiping. The Antera 3DTM camera approach was found to be effective in measuring cleaning efficiency, with the wipe removing all detectable traces of the FecloneTM applied. The total pore area (mm2), pore count, and total pore volume (mm3) in test participants post-wiping were observed to be reduced on average by 39.05%, 34.39%, and 39.98%, respectively. The wipe removed 99.99% of E. coli (NCTC 10538) applied, as measured using the microbial plate count method. In conclusion, the Antera 3DTM camera method was observed to be effective in evaluating removal of topically applied FecloneTM.

Synthesis of Sulfonated Chitosan as An Active Agent of Antibacterial Packaging for Fish Fillets

Modifying chitosan by increasing its hydrophilic properties through sulfonation reactions will increase its solubility in water and antibacterial activity and expand the application of chitosan. This study aims to determine the antibacterial activity of sulfonated chitosan film applied as fish fillet packaging using the total plate count method. Sulfonated chitosan in this study was successfully synthesized by reacting chitosan with 1,3-propane sultone. Sulfonated chitosan products were characterized using FTIR and UV-Vis spectrophotometers, while antibacterial activity was measured using the disc diffusion method. The optimum temperature for sulfonated chitosan synthesis was 60°C (SCS60). The resulting SCS 60 was a yellowish-white solid soluble in water with a yield of 61.46% and a degree of substitution of 33%. The diameters of the SCS 60 inhibition zone against E. coli and S. aureus isolates were 7 and 10 mm, respectively. SCS60-gelatin film is elastic (elongation 272%) and more hydrophobic with a contact angle of 90.12° compared to chitosan-gelatin film (62.8°). SCC60-gelatin film was able to suppress bacterial growth in fish fillets by up to 0.3 × 104 cfu/g compared to unpackaged fish (30 × 104 cfu/g). Sulfonated chitosan has the potential to be an antibacterial food packaging material.

Propidium monoazide (PMA) qPCR assay compared to the plate count method for quantifying the growth of Salmonella enterica serotypes in vacuum-packaged turkey breast combined with a mathematical modeling approach

This study compares the plate count (PC) and the Propidium Monoazide-quantitative Polymerase Chain Reaction (PMA-qPCR) methods to assess the growth of a cocktail of three serotypes of Salmonella enterica (Heidelberg, Typhimurium, and Enteritidis) in cooked, sliced, and vacuum-packaged turkey breast (STB) under isothermal storage temperatures (8 °C–20 °C), using predictive models. Standard curves were developed for PMA-qPCR, demonstrating high efficiency (101%) and sensitivity, with quantification limits ranging from 1 to 2 log10 CFU/g for all temperatures studied. Comparative analysis revealed a significant correlation (R2 = 0.99; 95% CI) between the PC and PMA-qPCR methods; however, the agreement analysis indicated a mean difference (Bias) of −0.11 log10 CFU/g (p < 0.05), suggesting underestimation by the PC method. This indicates the presence of stressed or viable but nonculturable (VBNC) cells, detectable by PMA-qPCR but not by PC. The Baranyi and Roberts model showed a good ability to describe the behavior of S. enterica cocktail in STB for PC and PMA-qPCR data under all isothermal conditions. The exponential secondary model more accurately represented the temperature dependence of the maximum specific growth rate compared to the Ratkowsky square root model, with R2 values ≥ 0.984 and RMSE values ≤ 0.011 for both methods. These results suggest that combining PMA-qPCR with predictive modeling allows for a more accurate prediction of S. enterica growth, compared to PC method. In the event of cold chain disruptions of meat products, the use of PMA-qPCR method allow the quantification of VBNC cells, that can still pose a health risk to consumers, especially in ready-to-eat products.

Potential Fermentation of Sweet Potato Pickle (Ipomoea batatas L.) with Lactobacillus plantarum B1765 in the Production of Short Chain Fatty Acids

Short-chain fatty acid (SCFA) is the final metabolic product of inulin that can provide various health benefits. In this study, the effect of fermentation duration of sweet potato pickle using Lactobacillus plantarum B1765 starter culture in the production of SCFA was studied, as well as its relationship with total Lactic Acid Bacteria (LAB), pH, and Total Titratable Acid (TTA). Fermentation was carried out with the addition of starter culture as much as 10% (v/v) at 37ºC for 4, 8, 12, 24, and 0 hours which was used as a control. The number of LAB was measured using the Total Plate Count (TPC) method, pH value was measured with a pH meter, TTA was measured using the acid-alkalimetric titration method, and SCFA was measured using an HPLC instrument with 0.1% H3PO4 eluent and 25% acetonitrile. Fermentation duration affects LAB growth, TTA, SCFA, and pH. The results showed that total LAB growth was optimal at 8 hours fermentation time at 2.81×108 CFU/mL, which increased by 2 log cycles from the initial fermentation time of 0 hours. Still, the pH decreased until it reached 3.23 ± 0.20, and TTA increased to 0,56 ± 0.02% until the end of fermentation at 24 hours. SCFA also increased until the end of fermentation at 24 hours, where acetic acid levels showed the highest levels (6.85 ± 0.30 mg/mL), followed by propionic acid (5.04 ± 0.20 mg/mL) and butyric acid (2.14 ± 0.10 mg/mL). Sweet potato pickles fermented with L. plantarum B1765 starter culture have met the SNI 01-3784-1995 standard and have the potential to be developed as a functional food source of SCFA, which has many health benefits.

Effect of Red Guava (Psidium guajava L.) Juice Concentration on Product Quality and Antioxidant Activity of Red Guava Synbiotic Yoghurt

Red guava juice has very strong antioxidant activity and has the potential to be processed into synbiotic functional beverage products that have health benefits. This study examined the effect of red guava juice concentration on product quality and antioxidant activity of red guava synbiotic yoghurt. Product quality tested included microbiological quality (total LAB) and chemical quality (pH value and Total Tritable Acid (TTA )value). The concentrations of red guava juice used were 0%, 10%, 20%, 30%, and 40%. Fermentation was carried out for 6 hours at 37⁰C by Lactic Acid Bacteria (LAB) from powdered mixed culture. Then organoleptic testing using the hedonic test, total LAB testing using the Total Plate Count (TPC) method, pH value testing using a pH meter, TTA value testing using the acid-base titration method, and antioxidant activity testing using the DPPH (2,2-diphenyl-1-picrylhydrazil) method. Test data were analyzed using SPSS software to determine the effect of red guava juice concentration on test results. The concentration of red guava juice in red guava synbiotic yoghurt affects the pH value, TTA value, and IC50 value as the result of antioxidant activity testing. Red guava juice concentration did not affect total LAB testing. Organoleptic assessment of red guava symbiotic yoghurt is in the range of like to like very much. The best formulation was red guava synbiotic yoghurt with 30% red guava juice concentration, which had strong antioxidant activity with an IC50 value of 59.637 ppm, pH value of 3.94, TTA value of 1.98%, and total LAB as much as 1.81x10⁸ colonies/g, so it has met the quality requirements of yoghurt according to Indonesian National Standard SNI 2981: 2009.

Study on Antioxidant Activity of Purple Sweet Potato (Ipomoea Batatas) Juice Fermented with Lactobacillus plantarum B1765

Purple sweet potatoes are a source of anthocyanins, which are antioxidants. However, the anthocyanin compounds in purple sweet potatoes are naturally bound in glycosidic form, so their potential as antioxidants is still limited. Fermentation is one method that can be used to degrade glycosidic bonds to liberate free phenolics so that it can increase the antioxidant potential of purple sweet potato. This research aims to study the growth of lactic acid bacteria (LAB), pH, total titratable acid (TAT), phenolic content, anthocyanin content, and antioxidant activity of sweet potato juice (Ipomoea batatas) fermented with Lactobacillus plantarum B1765 starter culture for 0.2, 4,6,8,10,12 and 14 hours. Total LAB was measured using the Total Plate Count (TPC) method, pH was measured using a pH meter, TAT was measured using acid-base titration, total phenolic content (TPC) was measured using the Folline-Ciocalteu method, anthocyanin content used the differential pH method and antioxidant activity was measured using the radical scavenging method 2, 2-diphenyl-1-picrylhydrazyl (DPPH) which is expressed in IC50 values. The results showed that fermentation time affected (p&lt;0.05) total LAB, pH, TAT, phenols, anthocyanin levels, and antioxidant activity in purple sweet potato juice. Total BAL increased to reach an optimum of 2.6 x 108 CFU/mL within 6 hours. However, until the end of fermentation for 14 hours, there was still a decrease in pH to 3.73, an increase in TAT reaching 0.426%, an increase in total phenolics up to 324.21 mg GAE/g, a reduction in anthocyanin levels (13.68 mg/L) and an increase in antioxidant activity with an IC50 of 47 .05 ppm which is classified as very strong. This product meets the Indonesian National Standards for fermented drinks and can potentially be a source of antioxidants.

Phage-Modified Clear Hydrogel for Simultaneous Detection of Multiple Bacteria.

The proliferation speed of live foodborne pathogens is fast. A small number of pathogens will have a great impact on food and the environment if positive samples are not detected timely. In this study, transparent porous hydrogel stir bars, modified by two different phages (corresponding to two different bacteria (Escherichia coli and Hafnia sp)), have been developed for rapid detection of foodborne bacteria. A large number of samples can be analyzed simultaneously with a small animal live imager device to screen out the positive samples, while an adenosine triphosphate (ATP) bioluminescence sensor can be used to quantify the number of bacteria in the positive samples. The phage has good specificity and capture ability to bacteria, which makes the method highly sensitive. In addition, the use of multiple phages also enables the method to detect multiple bacteria simultaneously. The three-dimensional structure of the hydrogel allows it to modify more phages, and its transparent nature also allows the inside bioluminescence to be detected. Both can enhance the sensitivity of the detection. Finally, the reagents needed for bioluminescence, such as d-luciferin, can also be preencapsulated in the hydrogel, thus simplifying the detection step. Under the best conditions, the detection range of the method is 102-108 CFU·mL-1, and the limit of detection is 30 CFU·mL-1 within 11 min. The test results of actual samples show that there is no difference between using the method developed through this study and the traditional plate counting method, but the detection time is greatly shortened.

Advancing environmental remediation through tailored TiO2 nanomaterials in water and air purification

This study investigates the green synthesis of TiO2 nanoparticles at varying concentrations (0 %, 0.1 %, 2.5 %, 5 %, and 10 %) using Viola betonicifolia plant extract, focusing on their application in environmental purification, specifically in water and air decontamination. X-ray diffraction (XRD) analysis confirmed the anatase crystal structure of TiO2 nanoparticles, with an average crystallite size of approximately 22 nm. Transmission electron microscopy (TEM) revealed a median diameter of around 22 nm, corroborating the findings from XRD. The effectiveness of these TiO2 nanomaterials was evaluated through bench-scale models simulating real-world conditions, targeting a broad range of pollutants, including heavy metals, organic dyes, volatile organic compounds (VOCs), and microbial pathogens. Advanced analytical techniques such as High-performance liquid chromatography (HPLC), Inductively coupled plasma mass spectrometry (ICP-MS), and microbial plate count methods quantified the pollutant removal efficiency, demonstrating the significant potential of the synthesized TiO2 nanoparticles. Dynamic light scattering (DLS) analysis showed a mean hydrodynamic diameter of 22 nm and a polydispersity index (PDI) below 0.1, indicating a uniform size distribution. The FTIR spectrum revealed a broad absorption band at 3400 cm−1, corresponding to O–H stretching vibrations, indicative of hydroxyl groups crucial for the photocatalytic activity of TiO2. The UV–visible spectroscopy indicated a maximum absorption at 642 nm, associated with the п-п* transition. Photocatalytic degradation of methylene blue under UV irradiation achieved a degradation efficiency of 94 % after 120 min, underscoring the superior efficiency of the green synthesis method.

Water quality index of selected borehole locations in Jos North LGA of Plateau State, Nigeria

Prevalence of water borne diseases is a public health concern. The study assessed the quality of selected borehole waters in Jos North for their potability. The physicochemical parameters were assessed in addition to chlorides, phosphates, nitrates, and sulphates, total solids, total dissolved solids, total suspended solids, total hardness, using standard methods. Atomic absorption spectrophotometry used for elemental analysis of samples for manganese, lead, cadmium, copper and zinc. microbial analysis was carried out to test for presence of anaerobic bacteria, coliforms, Escherichia coli, Salmonella typhi, yeast and mould, Staphylococcus aureus using the plate count method. Water Quality Index by Weighted Arithmetic Index Method. Results ranged from 22.19-56.22 mg/L (chlorides), 0.00-0.07 mg/L (phosphates), 0.11-0.19 mS/cm (conductivity), 141.40-169.40 mg/L (alkalinity) and 86.70-160 mg/L (TSS). Kyan Primary school had Mn 0.632 mg/L against 0.500mg/L recommended by WHO. Microbial analysis revealed that Kyan primary school had 1 cfu per 100 mL water for E. coli, Salmonella typhi, yeast and mould. This indicated faecal contamination. The WQI revealed Village hostel, Kyan Village, Gadabiu had values of 6.54, 19.41, 10.97 are potable, Government College, Angwan Jarawa, Kyan Primary school had 28.90, 61.50, 93.60 are potable, poor, very poor, not potable.

Portable real-time determination of Escherichia coli O157:H7 and Staphylococcus aureus based on smartphones and hydrogels

The aptamers functionalized orange-emission carbon dots (OCDs) and green-emission carbon dots (GCDs) had dual-emission peaks with single excitation. Tungsten disulfide nanosheets (WS2 NSs)-triggered fluorescence quenching achieved the ratiometric fluorescence determination of Escherichia coli O157:H7 (E. coli O157:H7) and Staphylococcus aureus (S. aureus) with wide ranges of 18–1.8 × 106 and 37–3.7 × 107 CFU/mL and low detection limits of 8 and 20 CFU/mL, respectively. The results in real sample with recoveries of 90–101 % and RSD < 4.12 % were no significant difference from standard plate counting method. Meanwhile, the dual-color CDs were further adopted in the smartphone-assisted hydrogel platform and achieved speedy, sensitive, portable and real-time determination of E. coli O157:H7 and S. aureus in real samples. This work has not only developed ratiometric fluorescence detection and constructed a portable hydrogel platform, but also provided a unique strategy in developing a time-efficient and easy-to-use portable device in food safety monitoring.

Comparative assessment of plate count and PMA-qPCR methods for modeling the growth of lactic acid bacteria in smoked Turkey ham

This study compared the quantitative polymerase chain reaction (qPCR) method combined with propidium monoazide (PMA) and the plate count (PC) method, both combined with predictive modeling, to describe the behavior of lactic acid bacteria (LAB) in vacuum-packaged sliced smoked turkey ham (STH). The PMA-qPCR method does not allow the DNA amplification of died cells but allow the amplification of viable cells, including the non-culturable. The standard curves relating quantification cycle (Cq) and log10 CFU/g demonstrated good linearity (R2 > 0.95), evidencing its accuracy and reproducibility. These curves were used to quantify Leuconostoc mesenteroides and Weissella viridescens in artificially inoculated STH samples stored at different isothermal temperatures (8, 10, 12, 16 and 20 °C). Firstly, the PMA-qPCR and PC methods were compared, and the analysis demonstrated a good correlation (R2 = 0.99) and agreement between the results. However, the PC method underestimated the quantification of W. viridescens cells by 0.76 log10 CFU/g at 8 °C, suggesting bacterial stress at this temperature, which was not observed for L. mesenteroides. In terms of growth, the maximum specific growth rate increased with rising temperature for both LAB. Predictive modeling indicated that the growth of L. mesenteroides and W. viridescens at 8 °C suggests a shelf life of approximately 4.25 days for STH based on PC data, and 4.13 days based on PMA-qPCR data. In conclusion, the PMA-qPCR method presented an advantage in terms of accuracy, especially under bacterial stress conditions, and proved to be a promising alternative for the quantification of LAB in refrigerated ready-to-eat meat products. The predictive models used were suitable for describing microbial growth, reinforcing the importance of the PMA-qPCR method in shelf life and food safety studies.

Green synthesis of multifunctional bamboo-based nonwoven fabrics for medical treatment

Medical nonwovens fabrics are pivotal materials in modern healthcare systems, and find extensively application in surgical gowns, masks, nursing pads, and surgical instrument packaging. As healthcare requirements evolve and medical technology advances, the demand for functional nonwoven medical devices is continuously increasing. In addition, numerous environmental challenges and the need to transition to a sustainable society have increased the popularity of studies on environmentally friendly multifunctional nonwoven materials prepared from biomass fibers. Therefore, in this study, ecofriendly bamboo fibers were used to fabricate multifunctional medical nonwoven materials with superhydrophobic, antibacterial, flame-retardant, and biocompatible properties. Specifically, ZIF-67 was grown in situ on natural bamboo cellulose fibers (BCFs) extracted from natural bamboo and coated with polydimethylsiloxane to construct an environmentally friendly and versatile nonwoven fabric. The treated nonwoven fabric exhibited superhydrophobicity with contact angle of 163° and possess excellent self-cleaning properties. The antibacterial activity of the samples was investigated by the plate-counting method; the results showed that the untreated BCFs did not exhibit antibacterial activity, whereas the treated bamboo nonwoven fabrics demonstrated significant antibacterial activity (p < 0.001), with an antibacterial rate of >99 % against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus subtilis, and Candida albicans. In addition, when the samples were exposed to different temperatures (−4 and 50 °C) and humidities (0 % and 95 %), they demonstrated an antibacterial activity of >99 % against E. coli (F5,10 = 0.602; p = 0.670) and S. aureus (F4,10 = 0.289; p = 0.879). The heat release rate and smoke production rate of the nonwoven fabric decreased by 54.64 % and 93.18 %, respectively, compared to those of the BCFs, indicating excellent flame retardancy. The nonwoven fabric also exhibited satisfactory biocompatibility and breathability, ensuring user comfortability. This research not only has significant implications for producing low-cost, environmentally friendly, sustainable, and multifunctional medical products and openi up new pathways for the diversified utilization of bamboo, thereby expanding its applicability.

Sonodynamic effect based on vancomycin-loaded microbubbles or meropenem-loaded microbubbles enhances elimination of different biofilms and bactericidal efficacy.

This study investigated vancomycin-microbubbles (Vm-MBs) and meropenem (Mp)-MBs with ultrasound-targeted microbubble destruction (UTMD) to disrupt biofilms and improve bactericidal efficiency, providing a new and promising strategy for the treatment of device-related infections (DRIs). A film hydration method was used to prepare Vm-MBs and Mp-MBs and examine their characterization. Biofilms of methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli were treated with different groups. Biofilm biomass differences were determined by staining. Thickness and bacterial viability were observed with confocal laser scanning microscope (CLSM). Colony counts were determined by plate-counting. Scanning electron microscopy (SEM) observed bacterial morphology. The Vm-MBs and Mp-MBs met the experimental requirements. The biofilm biomass in the Vm, Vm-MBs, UTMD, and Vm-MBs + UTMD groups was significantly lower than in the control group. MRSA and E. coli biofilms were most notably damaged in the Vm-MBs + UTMD group and Mp-MBs + UTMD group, respectively, with mean 21.55% (SD 0.08) and 19.73% (SD 1.25) remaining in the biofilm biomass. Vm-MBs + UTMD significantly reduced biofilm thickness and bacterial viability (p = 0.005 and p < 0.0001, respectively). Mp-MBs + UTMD could significantly decrease biofilm thickness and bacterial viability (allp < 0.001). Plate-counting method showed that the numbers of MRSA and E. coli bacterial colonies were significantly lower in the Vm-MBs + UTMD group and the Mp, Mp-MBs, UTMD, Mp-MBs + UTMD groups compared to the control group (p = 0.031). SEM showed that the morphology and structure of MRSA and E. coli were significantly damaged in the Vm-MBs + UTMD and Mp-MBs + UTMD groups. Vm-MBs or Mp-MBs combined with UTMD can effectively disrupt biofilms and protectively release antibiotics under ultrasound mediation, significantly reducing bacterial viability and improving the bactericidal effect of antibiotics.

Detection of Escherichia coli based on CdS QDs nanomarkers and its application in food hygiene and safety

With the continuous exposure of major food safety issues in recent years, food safety has become the focus of people’s attention. As a widely distributed bacterium, excessive levels of Escherichia coli in food may cause gastrointestinal discomfort symptoms, as well as adverse consequences such as food poisoning, acute gastroenteritis, food allergies, and gastric ulcers. Therefore, to ensure food safety and achieve rapid detection of E. coli, this study uses CdS quantum dots (QDs) nanomarkers to detect E. coli in water. Moreover, electrochemical square wave voltammetry is used to determine the relationship between Cadmium (Cd) ion concentration and E. coli concentration in the complex after enzyme-linked immunosorbent reaction. The experiment showed that the average particle size of CdS QDs nanoparticles was 5 nm and they had good biocompatibility. The current magnitude of electrochemical square wave voltammetry was positively correlated with the concentration of Cd ions and E. coli. When the concentration of E. coli was 50-1.0 × 105cfu/mL, its concentration was linearly positively correlated with the magnitude of the current, with a linear correlation coefficient of 0.9873. Compared to the flat plate counting method, its relative error did not exceed 10%, and in addition, the detection time was only 2 h. The above results indicate that CdS QDs nanomarkers can achieve rapid detection of E. coli, effectively improve the detection sensitivity of E. coli, and weaken non-specific adsorption.

Effect of the Synergistic Interaction of Micro- and Nanostructures with Silver Ions on the Biocompatibility and Antimicrobial Properties of Ti-15Mo-2.5Ag.

Titanium and titanium alloys have the advantages of a low density and a close elastic modulus to natural bone, which can reduce the stress-shielding effect and become one of the first choices for human hard tissue replacement and repair. However, implant site infection is still one of the main reasons for implantation failure. In this paper, 2.5 wt % Ag element was added to Ti-15Mo to obtain a low modulus, and a surface anodization was applied to improve the surface biocompatibility. The elastic modulus, micromorphology, surface elemental valence, corrosion resistance, antimicrobial properties, and cytocompatibility were investigated by mechanical tests, scanning electron microscopy, X-ray photoelectron spectroscopy, electrochemical tests, inductively coupled plasma spectroscopy, plate counting method, and cellular tests. The experimental results showed that the anodized Ti-15Mo-2.5Ag sample exhibited an elastic modulus of 79 GPa, a strong corrosion resistance, a strong antimicrobial ability of ≥99.99%, and good biocompatibility. It was demonstrated that the formation of Ag2O on the surface and Ag ion release improved the antimicrobial properties and that the structural synergism of silver ions with micro- and nanostructures played an important role in promoting the early spreading of cells and improving the cytocompatibility.