Soft Samples Research Articles

PyFMLab: Open-source software for atomic force microscopy microrheology data analysis

Background Atomic force microscopy (AFM) is one of the main techniques used to characterize the mechanical properties of soft biological samples and biomaterials at the nanoscale. Despite efforts made by the AFM community to promote open-source data analysis tools, standardization continues to be a significant concern in a field that requires common analysis procedures. AFM-based mechanical measurements involve applying a controlled force to the sample and measure the resulting deformation in the so-called force-distance curves. These may include simple approach and retract or oscillatory cycles at various frequencies (microrheology). To extract quantitative parameters, such as the elastic modulus, from these measurements, AFM measurements are processed using data analysis software. Although open tools exist and allow obtaining the mechanical properties of the sample, most of them only include standard elastic models and do not allow the processing of microrheology data. In this work, we have developed an open-source software package (called PyFMLab, as of python force microscopy laboratory) capable of determining the viscoelastic properties of samples from both conventional force-distance curves and microrheology measurements. Methods PyFMLab has been written in Python, which provides an accessible syntax and sufficient computational efficiency. The software features were divided into separate, self-contained libraries to enhance code organization and modularity and to improve readability, maintainability, testability, and reusability. To validate PyFMLab, two AFM datasets, one composed of simple force curves and another including oscillatory measurements, were collected on HeLa cells. Results The viscoelastic parameters obtained on the two datasets analysed using PyFMLab were validated against data processing proprietary software and against validated MATLAB routines developed before obtaining equivalent results. Conclusions Its open-source nature and versatility makes PyFMLab an open-source solution that paves the way for standardized viscoelastic characterization of biological samples from both force-distance curves and microrheology measurements.

Gingivo-Periosteal Expansion of Edentulous Jaw Crest with An Osmotic Self-Inflatable Expander: A Preclinical in Vivo Study.

This study examined the biocompatibility and expansion volume of tissue expanders utilizing rabbits and beagles as experimental models. The self-inflatable expander was provided using a Tissue balloon® (Neobiotech Co., Seoul, Korea). In 9 adult rabbits, a Tissue balloon® was placed under the lateral mandibular periosteum via an extraoral approach. After 2, 3, and 4 weeks (n=3), the expanders were removed, and soft tissue and bone samples were collected for analysis. Histomorphometric analysis and measurements of expander characteristics were performed. In 5 Beagles, all premolars were extracted. Three months after extraction, tissue expanders were placed in the maxilla and mandible, adjacent to dental extraction sites, and removed after 3 weeks. Gingival parameters were measured before and after expansion. Blood perfusion in the oral mucosa was assessed using a laser Doppler flowmeter at different time points. After three weeks, dogs were euthanized, and tissue samples were collected for histologic analysis, focusing on inflammatory response, bone formation, and gingival thickness changes. In the rabbit study, measurements of size, weight, and volume showed significant increases over 4 weeks. Swelling peaked at 2 weeks postimplantation and then gradually stabilized. Histologic examination revealed no signs of inflammation, and expanders were covered by collagen-rich capsules. Some bone resorption was noted due to pressure from the expanders, but the resorption was not significant. In the beagle study, twenty tissue expanders were implanted; 1 expander was lost, and 9 wounds dehisced during soft tissue healing. However, no signs of infection were noted. Histologic evaluation showed bone atrophy, attributed to swelling pressure, at the recipient site. Gingival thickness was not decreased. Perfusion measurements indicated that expansion did not affect microvascular circulation adversely. Overall, both studies suggest that tissue expanders demonstrate biocompatibility and successful expansion volume in vivo, with minimal adverse effects on surrounding tissues and microvascular circulation.

Study on the failure modes of water-bearing soft rock under different low-frequency disturbance

To investigate the evolution of failure modes in soft rock under various low-frequency disturbances and varying moisture content, a creep impact dynamic disturbance loading system was employed. Experiments were conducted on soft rock samples with different moisture contents, while the loading process was monitored using an acoustic emission system. The fracture development and propagation characteristics were reconstructed using a CT scanning system. The experimental results reveal that: (1) The failure mode of dry soft rock transitions from “shear-tension-shear” with increasing initial disturbance, whereas water-bearing soft rock primarily undergoes tensile failure. (2) During disturbance, saturated soft rock exhibits significant fluctuations in acoustic emission characteristic parameters, with the initiation of larger fractures. As the initial disturbance increases, failure transitions from plastic to brittle, resembling the behavior of dry samples. (3) Microcracks in both dry and saturated soft rock predominantly range from 500 to 1000 µm, while those in naturally moist soft rock are less than 500 µm. Although the volume of primary fractures varies slightly among different states, the overall degree of damage increases with higher moisture content. These findings elucidate the evolution of failure modes and fracture development in soft rock under low-frequency disturbances, providing valuable insights for monitoring, early warning, and mitigation of dynamic disasters in deep mines.

Studi Empiris Faktor Penentu Kinerja UMKM Kuliner Kota Padang Provinsi Sumatera Barat

The research objective is to determine the influence of digital technology, competitiveness, business strategy and innovation on the performance of Padang city culinary MSMEs. The research method uses an associative method with a quantitative approach. The research population was 4,454 culinary MSMEs and a sample of 135 MSMEs was taken by purposive sampling using the Rao soft sample size calculator technique. The data collection technique uses a questionnaire. All instrument tests and classical assumption tests are met before the data is processed. Multiple linear regression results Y = 1.375 + 0.879X1 + .784X2 + 0.693X3 + 0.791X4 + e. Hypothesis testing at a significance level of 5% shows that digital technology, competitiveness, business strategy and innovation have a significant positive effect on the performance of culinary MSMEs in the city of Padang, West Sumatra province, partially and simultaneously.

High-angular-sensitivity X-ray phase-contrast microtomography of soft tissue through a two-directional beam-tracking synchrotron set-up.

Two-directional beam-tracking (2DBT) is a method for phase-contrast imaging and tomography that uses an intensity modulator to structure the X-ray beam into an array of independent circular beamlets that are resolved by a high-resolution detector. It features isotropic spatial resolution, provides two-dimensional phase sensitivity, and enables the three-dimensional reconstructions of the refractive index decrement, δ, and the attenuation coefficient, μ. In this work, the angular sensitivity and the spatial resolution of 2DBT images in a synchrotron-based implementation is reported. In its best configuration, angular sensitivities of ∼20 nrad and spatial resolution of at least 6.25 µm in phase-contrast images were obtained. Exemplar application to the three-dimensional imaging of soft tissue samples, including a mouse liver and a decellularized porcine dermis, is also demonstrated.

Determination of Nicotine in Juices, Soft and Energy Drinks collected from Libyan Local Markets Using UV–Visible Spectrophotometer

This study aims to determine the nicotine in juices, soft and energy drinks using a UV-Visible spectrophotometer. In the presented study, sixteen samples (four juices, seven soft drinks, and five energy drinks) are collected from local markets in El-Beida - Libya. A rapid, simple, and reliable extraction method is developed and validated for the determination of nicotine in the samples under study using spectrophotometric methods. The method is validated over a wide linear range of 1.62–81.06 µg/mL with correlation coefficients being consistently greater than 0.9999 by UV-Visible Spectrophotometer. The minimum nicotine level was observed in the juices samples, while the energy drinks samples showed the highest nicotine content. The spectrophotometric measurement indicates that the results of nicotine concentrations in juices samples are in the range of 0.3233 - 0.5238 µg/mL, whereas its concentrations in soft drinks samples are in the range of 0.7251 - 0.9949 µg/mL, and the concentrations in energy drinks samples are in the range of 0.8521 - 1.3471 µg/mL. The criteria considered for validation are linearity, the limit of detection, and the limit of quantitation. The nicotine contents in all the samples analyzed in our study were below the allowable limits set by the US Food and Drugs Administration.

Post-blast histological changes to three animal bones exposed to close-range chemical detonation.

A range of investigative practices to aid explosive-related death investigations currently exist, although the use of histopathological bone samples to diagnose blast exposure and the distance of individuals from the blast source has not been previously reported. Forensic histopathology has been used effectively on soft tissue samples to define blast-related injuries effectively, analysing human organs such as the lungs, brain, liver, and skeletal muscles, providing important and useful forensic pathology interpretations. However, no studies currently exist examining the post-blast histological changes in human or animal bones subjected to blasts for forensic pathology practice, despite the opportunity that hard tissue bone samples present, given their significantly lower rate of decomposition over soft tissue. This study presents the first evidence-based findings on the post-blast histological changes in three animal bones when exposed to close-range chemical detonation (C4). The study's qualitative findings highlight critical changes in the tissue architecture of three different animal bone sources due to blast effects with range from the blast source. This emphasises the potential use of histopathological bone sample analysis in future blast-related death investigations, while providing ideas to further explore this work using larger-scale experiments and post-blast case studies in aid of applying this work to human samples and forensic pathology practice.

Soft soil foundation treatment of hydraulic fill site based on vibration boosting drainage consolidation method

Reclamation from the sea is a method of expanding urban area, but it also faces the problem of difficult treatment of soft soil foundation by hydraulic reclamation. Therefore, a soft soil consolidation method that combines vibration pressure boosting drainage and piled-load static pressure stacking is now proposed. To verify the effectiveness of this method, a consolidation test based on soft soil samples was designed and conducted in the study. The test results showed that when the sampling height was 240mm, the overall moisture content of the consolidated soil sample was the highest, 44.3%, and the consolidation effect was the worst. When the sampling height was 140mm, the overall moisture content obtained from the test was the lowest, 43.1%, and the consolidation effect was the best. The displacement of corner 2 and center point at the intersection of the preceding and following periods was greater, with values of 37.1 mm and 39.2 mm, respectively. At this point, the displacement of corner 1 was significantly smaller, at 30.9 mm. In the later loading stage, the slope of the vertical displacement curve significantly increased. When the experimental time reached 7000 min, the mixed method designed in this study had a drainage rate of 0.53 ml/min, which was significantly higher than other traditional methods. The experiment outcomes indicated that the method designed in this study had certain application potential for improving the consolidation effect of soft soil foundation in hydraulic fill sites.

Effect of watery extract of Curcuma longa powder (Turmeric) on multidrug- resistant Bacillus cereus recovered from fresh soft cheeses in Kirkuk

Bacterial contamination is an important cause of foodborne diseases. Herbal medicine is known as botanical medicine or phytomedicine, which means a plant or any part of the plant, is used to prepare medicine to assist in the healing process during illness and disease. Medicinal plants contain natural chemicals, which are acceptable to human and animal systems. Curcumin Is extensively used as an aromatic medicinal cosmetic .It has been in traditional use and it is mentioned as a remedy for various diseases. These findings indicated that action of curcumin had significant inactivation effect on foodborne bacteria, the present study investigate action of curcumin on foodborne bacteria Bacillus cereus (B. cereus). The frequency and distribution pattern of Bacillus cereus in cow soft cheese were investigated indifferent regions in Kirkuk. 50 Pooled soft cheeses samples from different regions in Kirkuk were collected during February until June (2020), ten samples collected monthly from different supermarkets as same as proportion above. Modified procedures for isolation and identification were dependent, Gram stain, oxidase &catalase reaction aid in segregation. Modified Congo red assay used to detect biofilm and Kirby-Bauer disc diffusion method was used for determination sensitivity of isolates to ampicillin (AM 10µg),cephalexin (CLX, 30µg), azithromycin (AZM, 15µ) and vancomycin (VA 30µg). The results confirmed recovery of In conclusions. cheese production in Kirkuk are encountered by the problems of bacterial contamination and presence of multidrug resist strain of Bacillus cereus that considered a risk to public health, may be due both insufficient and misuse treatment with antibiotics or in somewhat due to bad quality and/or poor hygiene of processing involved in milk production. Thus recommended monitoring these products for better hygienic status.

Determinants of knowledge, practice, belief and adherence to taboos on egg consumption in Kwazulu-Natal province of South Africa

Eggs are considered to be one of the cheapest sources of protein, hence, support for their consumption ought to be particularly sought after in a nation like South Africa where many may be food insecure. With much of the population being unemployed and the unsteady economy that has contributed to the higher cost of living, malnutrition remains a challenge. The recognition and dissection of the socio-economic variables that lead to the avoidance of egg consumption will allow the implantation of programs that will encourage the incremental utilization of eggs, to improve on the moderately lower per capita consumption when compared to some African countries. This study examines the determinants of knowledge, practice, belief, and adherence to taboos on egg consumption in the KwaZulu-Natal Province of South Africa where there is the lowest level of egg consumption compared to other provinces in the country. A descriptive and quantitative research design using a multi-stage sampling technique and the Rao Soft sample size calculator were used to select 125 households. Data were obtained with the use of a structured questionnaire and analysed with t-test statistics, Principal Component analysis and Probit regression analysis. The results show a significant relationship between egg consumption and taboos. The results revealed a decreasing order on the levels of knowledge, practice, belief and adherence to taboos among respondents. The study concluded that cultural reasons exercise a greater influence on egg consumption than socioeconomic, economic and availability factors. It is, therefore, recommended that interventions such as educational programs that encourage healthier eating behaviours should be designed and implemented. These programs should be designed in a way that will incorporate culturally relevant approaches that people in Kwazulu-Natal can resonate with to enhance their potential effectiveness in improving the frequency of egg consumption. Furthermore, it is recommended that future research should delve deeper into the history of the specific cultural norms, beliefs and practices surrounding egg consumption within the region. Key words: egg consumption, South Africa, food security, KwaZulu-Natal, food taboos

Antimicrobial Susceptibility Patterns of Escherichia coli Isolates from Hospitalized Patients with Different Infections in Isfahan, Iran: Impact on Empiric Antibiotic Therapy in Associated Infections

Background: Escherichia coli is an important cause of urinary tract, bloodstream, and surgical site infections. Objectives: We investigated the organism's antibiotic susceptibility in hospitalized patients under different clinical conditions. Methods: This prospective study was conducted in three referral hospitals located in Isfahan, Iran. Different clinical samples were tested using standard routine microbiological methods to identify E. coli strains and determine their antibiotic susceptibility patterns by the disk diffusion method according to CLSI recommendations. After conducting a clinical investigation, contaminated samples were excluded, and the hospital or community source and infection site were identified. Data on antibiotic susceptibility testing were extracted using WHONET software. Data analysis was then conducted using SPSS Statistics version 18.0. Results: Of 1248 E. coli isolates, 71.9% were from urine, 15.1% from blood, and 7.8% from skin and soft tissue samples. High susceptibility was observed to Imipenem (98%), Meropenem (98.0%), and Amikacin (94.6%); intermediate sensitivity to Gentamicin (68.6%) and Cefepime (51.9%); and low susceptibility to Ceftazidime (46.8%), Ceftriaxone (41.3%), Ciprofloxacin (39.5%), Cefotaxime (39.3%), and Trimethoprim-sulfamethoxazole (32.4%). Conclusions: Antibiotics, including Imipenem, Meropenem, or Amikacin, would be beneficial in the empiric therapy of severe infections where E. coli is the main cause.

Evaluation of the genotypes of the Kazakh-Siberian nursery (KASIB) in the conditions of the Novosibirsk region

The paper presents the results of evaluation of the KASIB-22 nursery soft wheat samples resistance to the main wheat pathogens. The research material was 44 wheat samples obtained from different regions of Russia and Kazakhstan within the framework of the KASIB shuttle breeding program (A.I. Barayev Research and Production Centre for Grain Farming, Omsk State Agrarian University, ICiG SB RAS, Karabalyk AES, Karaganda AES, North-Kazakhstan AES, FSBSI "Omsk ASC", HE SAU of the Northern Trans-Urals, Aktyubinsk AES, Kurgan Research Institute of Agriculture, Pavlodar AES, agrokomplex "Kurgansemena", Samara Research Institute of Agriculture, Chelyabinsk Research Institute of Agriculture). The following breeding lines were identified as highly productive and possessing high and medium resistance to brown rust, powdery mildew and loose smut: Line Pt-311 (Kurgan Research Institute of Agriculture), Lutescens 1462, Lutescens 1486, Line1616ae14 (Samara Research Institute of Agriculture), Lutescens 1356 (ICiG SB RAS). The yield of the selected samples averaged 42.1–51.2 c/ha. Genotypes Novosibirskaya 41, Line 435/12 and Lutescens 1364 are of interest for selection for quality. The gluten content of the nursery genotypes ranged from 24.1 (Line 23/07 in 2022) to 38.0% (variety Astana 2 in 2021), protein ranged from 13.4 (variety Tertia in 2022) to 19.5% (Lutescens 1364 in 2022). Each of the selected lines is of practical value for breeding, and the samples from the KASIB-22 nursery allow to expand the genetic diversity of spring soft wheat by selecting the most resistant forms to local populations of powdery mildew, leaf rust and loose smut pathogens.

Magnetic-Dielectric Cantilevers for Atomic Force Microscopy.

Atomic force microscopy (AFM) is a technique that relies on detecting forces at the nanonewton scale. It involves using a cantilever with a tiny tip at one end. This tip interacts with the short- and long-range forces of material surfaces. These cantilevers are typically manufactured with Si or Si3N4 and synthesized using a lithography technique, which implies a high cost. On the other hand, through simple chemical methods, it is possible to synthesize a magneto-dielectric composite made up of artificial SiO2 opals infiltrated with superparamagnetic nanoparticles of Fe3O4. From these materials, it is possible to obtain tipless cantilevers that can be used in AFM analysis. Tipless cantilevers are an alternative tool in nanoscale exploration, offering a versatile approach to surface analysis. Unlike traditional AFM probes, tipless versions eliminate the challenges associated with tip wear, ensuring prolonged stability during measurements. This makes tipless AFM particularly valuable for imaging delicate or soft samples, as it prevents sample damage and provides precise measurements of topography and mechanical and electromechanical properties. This study presents the results of the characterization of known surfaces using magneto-dielectric cantilevers and commercial cantilevers based on Si. The characterization will be carried out through contact and non-contact topography measurements.

Shear Strength of Soft Soil Reinforced with Singular Bottom Ash Column

Structures construct on soft clays are often affected by stability and settlement problems due to high compressibility, low shear strength and low permeability of soft clay which will lead to bearing capacity failure and excessive settlement. The soft clay samples had the dimensions of 50 mm diameter and 100 mm in height. The bottom ash column had two (2) different area replacement ratios which were 4% and 9% (10 mm and 15 mm diameters respectively) with the bottom ash column penetration ratio of 0.3, 0.7 and 1.0. The results of the unconfined compression test show that there is an improvement in shear strength of soft kaolin clay when reinforced with bottom ash column. For samples with area replacement ratio 4%, the results show the increment of 25%, 37.5% and 50% at height penetrating ratio of 0.3, 0.7 and 1.0, respectively in shear strength. Meanwhile, for samples of 9% area replacement ratio, the shear strength of the soft kaolin clay increased about 14.29, 28.57 and 57.14%, respectively. It can be concluded that by reinforcing the soft clay using singular bottom ash column, the shear strength of the soils increases and become more significant as the area replacement ratios and the column penetration ratios increase.

A soft robot tactile fingertip for grasping surface posture detection

Abstract The application field of robots is gradually extending from traditional industrial manufacturing to commercial services, medical care and other fields. Stable grasping is a necessary prerequisite for various complex robot application scenarios. The existing research on robot tactile sensor mainly focus on sensing tactile information, such as pressure or sliding. However, grasping surface posture as a tactile information that has a significant impact on the stability of grasping is often ignored. This study proposed a novel soft robot tactile fingertip that can not only detect the grasping force but also simultaneously detect the grasping surface posture. It is capable of recognizing 19 grasping surface postures in real-time using Mamdani fuzzy control method. The soft robot tactile fingertip has a simple structure and easy to fabricate at low cost. The application example of the two-finger mechanical hand using the soft tactile fingertip samples for stable grasping is demonstrated. This study shows that the soft robot tactile fingertip has great application prospects in the filed of robot intelligent grasping.

Peran Lingkungan Keluarga, Motivasi, dan Pengetahuan Kewirausahaan terhadap Minat Berwirausaha Mahasiswa

This study aims to investigate the effect of family environment, entrepreneurial motivation, and entrepreneurial knowledge on the entrepreneurial interest of students of the Faculty of Economics and Business (FEB) of XXX University in Padang City. The population used in this study were active students of FEB of XXX University in Padang City in the 2020 and 2021 academic years, totaling 384 people. The non-probability sampling technique was used for sample selection, and sampling was carried out using the Rao soft Sample Size Calculator Software Technique so that a sample of 102 respondents was obtained. The results of research and data analysis show that entrepreneurial motivation is the most influential variable on entrepreneurial interest, with a beta value of 0.496. This indicates that students who have high entrepreneurial motivation tend to have greater entrepreneurial interest. However, family environment and entrepreneurial knowledge also have a significant influence on student entrepreneurial interest, although not as strong as entrepreneurial motivation.

Large‐wavelength Gaussian deconvolution phase‐contrast computed tomography for THz continuous wave (0.11 THz)

AbstractThis letter was to present an attempt of large‐wavelength Gaussian deconvolution phase‐contrast computed tomography (LW‐GD‐PCCT) for promotion of image quality reconstructed in low‐frequency band of terahertz (THz) spectrum at 0.11 THz. The interaction between the imaging samples and the THz Gaussian beam were formulated firstly in this paper, where the unwrapped phase was extracted specifically to portray the spatial structure distribution of the samples. Additionally, a Gaussian deconvolution was employed for the further reduction of spatial distortions. Moreover, an image reconstruction was carried out with the obtained phase sinograms based on phase‐used inverse Radon transform from the different positions on the sample. For an experimental assessment of the concept of LW‐GD‐PCCT, a single ellipsoid reflector‐based THz Gaussian beam generating system was established and samples such as polystyrene (PS) foam cuboid (Sample 1), and cylinder (Sample 2) with hollow defects (air holes and triangles) were prepared carefully in this work. To experimentally evaluate the performance of the contributing to the structural imaging over soft samples. Two‐dimensional topographies of each sample were reconstructed successfully, and the obtained cross root‐mean‐square error (cross‐RMSE), cross peak signal‐to‐noise ratio (cross‐PSNR), and cross structural similarity (cross‐SSIM) were 151.6451, 26.3225, and 0.9616 for Sample 1 with a high dose of 180 projections respectively, as well as 30.3242, 33.3129, and 0.9711 for Sample 2 with a low dose of 36 projections, respectively. The obtained imaging indicators of this work showed a superiority of imaging quality over those of recent works. Furthermore, the investigation of the bearing capacity has shown promise in enhancing image quality even in low‐dose conditions. The presented results suggest that the unwrapped phase combining with Gaussian deconvolution in low‐frequency band of THz imaging would be useful to improve the reconstructed image quality, potential to highly feasible non‐destructive testing of polymer foam via large wavelength.

Dynamic characteristics and microstructure of clay reinforced by the splitting grouting method under subway dynamic loading

The splitting grouting reinforcement method is typically used to improve the stability of surrounding rock when constructing subways in water-rich and weak strata. However, in contrast to normal soil, the dynamic characteristics and microstructure of reinforced soil under cyclic loading of a subway necessitates further clarification to obtain a technical basis for controlling the deformation and settlement of the reinforced soil during later stages. Based on field-reinforced soft clay samples, this study analyzed the dynamic characteristics and microstructure of reinforced soft clay under cyclic loading through stress-controlled undrained cyclic triaxial and scanning electron microscope tests. The results showed that the lower the frequency or the larger the cyclic dynamic stress amplitude, the faster the residual strain development of the reinforced soft clay. There were three cyclic creep characteristic curves of reinforced soft clay: peak, base, and valley creep curves, and the development of base creep represented the overall trend of cyclic creep in reinforced soft clay. In addition, calcium silicate hydrate and ettringite were produced in the reinforced soft clay, which improved the connectivity between the soil particles.

Repeatability and reproducibility of physically consistent single sheet testing with H-coil

Measurements of magnetic losses of electric steel are usually performed by International Electrotechnical Commission standardized Epstein testers or Single Sheet Testers (SSTs). According to round robin tests, the corresponding levels of repeatability are of the order of 0.1%, and those of reproducibility are of the order of 1%. However, orders of absolute accuracy are unknown due to the applied “current method.” Here, we report corresponding tests for the so-called “physically consistent SST.” Consistency is achieved by a “giant” tangential field coil on a 50 cm long and 17 cm wide soft magnetic sample, using a thin amorphous yoke for magnetization. Tests were made in two labs with very different working conditions (sea levels of 200 and 1100 m, respectively), with very similarly built-up testers. Measurements were made for peak inductions between 1 and 1.9 T. For two distributed samples, the repeatability errors were lower than 0.3%, and the reproducibility errors were lower than 1%. This indicates that SSTs with an H-coil are not less reliable than current based ones. However, the absolute accuracy can be estimated to be much better, being close to 2%.

Comparison of real-time PCR and nested PCR based on the HlyA gene for the detection of Listeria monocytogenes. Application on cheese samples.

The aim of the present study was to compare the performance of a nested polymerase chain reaction (nPCR) and a real-time PCR based on the amplification of the HlyA gene from Listeria monocytogenes using a plasmid DNA standard. Nested PCR was developed with an internal amplification control (IAC). Both techniques were validated in soft cheese samples by comparing their results with the results of the microbiological reference method ISO 11290-1:2017. Cheese samples artificially contaminated with 3.5 to 3,500 UFC/25g were processed by ISO 11290-1:2017 and, at several times of culture, DNA samples were extracted. All cheeses contaminated with L. monocytogenes were positive for the microbiological method 96h post contamination and for nPCR and real-time PCR 48h post contamination. At this time, the HlyA gene was amplified in all contaminated samples. Both molecular techniques showed the same sensitivity, 30 copies/reaction or 3.5 UFC/25g, when plasmid DNA standard or artificially contaminated cheese samples were used. Finally, eighty soft cheese samples obtained from local retail stores and tested by three methods were negative, indicating a 100% concordance in results. The development of an nPCR with IAC reinforces the reliability of the negative results without increasing the costs of the reaction. Besides, nPCR showed less sensitivity to the presence of inhibitory substances in the reaction. The use of one of these molecular techniques could be easily coupled to the microbiological method, serving as a screening method in the food industry for hygiene monitoring and early identification of contaminated foods.