RESUMEN

The corrosion inhibition action of Phalaris canariensis extract on 316 L stainless steel in the H2O-35 (wt%) LiCl mixture at different temperatures has been evaluated with the aid of weight loss, potentiodynamic polarization curves, linear polarization resistance and electrochemical impedance spectroscopy tests. These studies were complemented by Fourier Transformed Infrared spectroscopy, FTIR, gas/mass chromatography analytical techniques and detailed scanning electronic microscopy studies. Results have indicated that Phalaris canariensis extract is an efficient inhibitor, with an efficiency that increases with its concentration, but it decreases as the temperature increases. Phalaris canariensis extract is physically adsorbed onto stainless steel according to a Temkin type of adsorption isotherm. Phalaris canariensis extract affected both anodic and cathodic electrochemical reactions with a stronger effect on the anodic ones, acting, thus, as a mixed type of inhibitor. Main compounds contained in the Phalaris canariensis extract were palmitic and oleic acids, responsible for its inhibitory properties.

RESUMEN

Non-destructive electromagnetic tests based on magnetic noise analysis have been developed to study, among others, residual stress, heat treatment outcomes, and harmful microstructures in terms of toughness. When subjected to thermal cycles above 550 °C, duplex stainless steels form an extremely hard and chromium-rich constituent that, if it is superior to 5%, compromises the steel's corrosion resistance and toughness. In the present work, a study was carried out concerning the interaction of excitation waves with duplex stainless steel. Hence, by analyzing the magnetic noise and variations in the amplitude of the first harmonic of the excitation waves, the detection of the deleterious sigma phase in SAF 2205 steel is studied. To simplify the test, a Hall effect sensor replaced the pick-up coil placed on the opposite surface of the excitation coil. Sinusoidal excitation waves of 5 Hz and 25 Hz with amplitudes ranging from 0.25 V to 9 V were applied to samples with different amounts of the sigma phase, and the microstructures were characterized by scanning electron microscopy. The results show that the best testing condition consists of applying waves with amplitudes from 1 V to 2 V and using the first harmonic amplitude. Thus, the test proved effective for detecting the formation of the deleterious sigma phase and can follow the ability to absorb energy by impact and, thus, the material embrittlement.

RESUMEN

OBJECTIVES: To identify the characteristics of patients and femur fractures treated with a stainless steel intramedullary nail (ESIN) in children under 15 years of age. Know the results of using the ESIN of related steel in the service. METHODS: Retrospective study with review of hospital records and organization of data in spreadsheets. RESULT: 24 cases were identified, 17 male cases and 7 female cases. A minimum age of 4 years and a maximum of 11 years were observed (average of 7 years). The 3 most common trauma mechanisms were being run over (n:8, 33%) and falling from a height (n:8, 3%). The most common location of the fractures was in the mid-diaphyseal region (n: 20, 88%), only one case presented a bilateral femur fracture. The most common associated trauma was traumatic brain injury. The observation period observed several months between 2 and 5. With regard to complications, 3 cases were observed (12.5%) being bursitis, vicious construction and loss of reduction. CONCLUSION: Steel HIF shows similar good results. As the study includes the retrospective profile, the absence of a group and the small sample size. Level of Evidence IV, Case series.

OBJETIVOS: Identificar as características dos pacientes e das fraturas de fêmur tratadas com haste intramedular flexível (HIF) de aço inoxidável em menores de 15 anos. A partir disso, conhecer os resultados relacionados ao uso da HIF de aço inoxidável no serviço. Métodos: Estudo retrospectivo, com revisão de prontuários hospitalares e organização dos dados em planilhas. RESULTADO: Identificados 24 casos, sendo 17 do gênero masculino e sete do gênero feminino. Foram observadas idade mínima de 4 anos e máxima de 11 anos (média de 7 anos). Os mecanismos de trauma mais comuns foram atropelamento (n: 8, 33%) e queda de altura (n: 8, 33%). A localização mais comum das fraturas foi na região médio diafisária (n: 20, 88%), apenas um caso apresentou fratura de fêmur bilateral. O trauma associado mais comum foi traumatismo crânio-encefálico. O período de consolidação observado variou entre 2 e 5 meses. No que se refere a complicações, foram observados três casos (12,5%), sendo estes: bursite, consolidação viciosa e perda de redução. Conclusão: A HIF de aço apresenta bons resultados, semelhantes aos das hastes de titânio. As limitações do estudo incluem o perfil retrospectivo, a ausência de grupo controle e o número pequeno da amostra. Nível de evidência IV, Série de casos.

RESUMEN

The main objective of this work was to propose and evaluate a methodology for shielding-gas selection in additive manufacturing assisted by wire arc additive manufacturing (WAAM) with an austenitic stainless steel as feedstock. To validate the proposed methodology, the impact of multi-component gases was valued using three different Ar-based blends recommended as shielding gas for GMA (gas metal arc) of the target material, using CMT (cold metal transfer) as the process version. This assessment considered features that potentially affect the building of the case study of thin walls, such as metal transfer regularity, deposition time, and geometrical and metallurgical characteristics. Different settings of wire-feed speeds were conceived to maintain a similar mean current (first constraint for comparison's sake) among the three gas blends. This approach implied different mean wire-feed speeds and simultaneously forced a change in the deposition speed to maintain the same amount of material deposited per unit of length (second comparison constraint). The composition of the gases affects the operational performance of the shielding gases. It was concluded that by following this methodology, shielding-gas selection decision-making is possible based on the perceived characteristics of the different commercial blends.

RESUMEN

In the present work, the influence of a corrosive environment and temperature on the corrosion resistance properties of duplex stainless steel S31803 was evaluated. The corrosive process was carried out using solutions of 1.5% HCl (m/m) and 6% FeCl3 (m/m), at temperatures of 25 and 50 °C. The microstructure of UNS S31803 duplex stainless steel is composed of two phases, ferrite and austenite, oriented in the rolling direction, containing a ferrite percentage of 46.2% in the rolling direction and 56.1% in the normal direction. Samples, when subjected to corrosive media and temperature, tend to decrease their mechanical property values. It was observed, in both corrosive media, that with increasing test temperature, there is an increase in the corrosion rate, both uniform and pitting. The sample in HCl solution obtained a uniform corrosion rate of 0.85% at 25 °C and 0.92% at 50 °C and pitting rates of 0.77% and 1.47% at the same temperatures, respectively. When tested in FeCl3 solution, it obtained uniform corrosion of 0.0006% and 0.93% and pitting of 0.53% and 18.5%, at the same temperatures. A reduction in dissolution potentials is also noted, thus characterizing greater corrosion in the samples with increasing temperature.

RESUMEN

This study aimed to evaluate the ability of biofilm formation by L. monocytogenes from the meat processing industry environment, as well as the use of different combinations of detergents, sanitizers, and UV-A radiation in the control of this microorganism in the planktonic and sessile forms. Four L. monocytogenes isolates were evaluated and showed moderate ability to form biofilm, as well as carried genes related to biofilm production (agrB, agrD, prfA, actA, cheA, cheY, flaA, sigB), and genes related to tolerance to sanitizers (lde and qacH). The biofilm-forming isolates of L. monocytogenes were susceptible to quaternary ammonium compound (QAC) and peracetic acid (PA) in planktonic form, with minimum inhibitory concentrations of 125 and 75 ppm, respectively, for contact times of 10 and 5 min. These concentrations are lower than those recommended by the manufacturers, which are at least 200 and 300 ppm for QAC and PA, respectively. Biofilms of L. monocytogenes formed from a pool of isolates on stainless steel and polyurethane coupons were subjected to 14 treatments involving acid and enzymatic detergents, QAC and PA sanitizers, and UV-A radiation at varying concentrations and contact times. All treatments reduced L. monocytogenes counts in the biofilm, indicating that the tested detergents, sanitizers, and UV-A radiation exhibited antimicrobial activity against biofilms on both surface types. Notably, the biofilm formed on polyurethane showed greater tolerance to the evaluated compounds than the biofilm on stainless steel, likely due to the material's surface facilitating faster microbial colonization and the development of a more complex structure, as observed by scanning electron microscopy. Listeria monocytogenes isolates from the meat processing industry carry genes associated with biofilm production and can form biofilms on both stainless steel and polyurethane surfaces, which may contribute to their persistence within meat processing lines. Despite carrying sanitizer tolerance genes, QAC and PA effectively controlled these microorganisms in their planktonic form. However, combinations of detergent (AC and ENZ) with sanitizers (QAC and PA) at minimum concentrations of 125 ppm and 300 ppm, respectively, were the most effective.

Asunto(s)

RESUMEN

The change in the corrosion activities of SS304 and the carbon steel A36 were studied during their exposure for 30 days to hybrid pumice-Portland cement extract (CE), to simulate the concrete-pore environment. The ionic composition and the initial pH (12.99) of the CE were influenced by the reduction of Portland cement (PC) content, volcanic pumice oxides and alkaline activators. Because of the air CO2 dissolution, the pH decreased and maintained a constant value ≈ 9.10 (established dynamic ionic equilibrium). The CE promoted the passivation of both steels and their free corrosion potential (OCP) reached positive values. On the surfaces, Fe and Cr oxides were formed, according to the nature of the steel. Over the time of exposure, the presence of chloride ions in the pumice caused a localized pitting attack, and for carbon steel, this fact may indicate an intermediate risk of corrosion. The chloride effect was retarded by the accumulation of SO42- ions at the steel surfaces. Based on electrochemical impedance (EIS), the polarization resistance (Rp) and the thickness of the passive layers were calculated. Their values were compared with those previously reported for the steels exposed to CEs of Portland and supersulfated cements, and the hybrid cement was considered as a PC "green" alternative.

RESUMEN

Surgical ASTM F139 stainless steel is used for temporary fixtures in the biomedical field. Tribocorrosion is a major concern in this application. The aim of the present work was to study the interplay between tribocorrosion behavior and the surface chemistry of the ASTM F139 stainless steel in phosphate-buffered saline solution (PBS). Sliding wear tests were conducted against alumina balls at different electrochemical potentials: open circuit potential (OCP), cathodic potential (-100 mV versus the OCP), and anodic potentials (+200 mVAg/AgCl and +700 mVAg/AgCl). The normal load was 20 N. The wear volume was estimated based on micrographs obtained from the wear tracks using confocal laser scanning microscopy. Moreover, the wear tracks were also examined by scanning electron microscopy (SEM). The surface chemistry of the ASTM F139 specimens was analyzed by X-ray photoelectron spectroscopy (XPS). The wear volume was dependent on the electrochemical potential, being maximized at +700 mVAg/AgCl. Delamination areas and grooves were observed in the wear tracks. Detailed assessment of the surface chemistry inside the wear tracks allowed identification of the main chemical species and their relative quantities, thus enabling correlation of the passive film composition with the observed tribocorrosion behavior.

RESUMEN

OBJECTIVES: The aim of the study was to investigate the clinical effect of stainless-steel wire fixation on the early mouth-opening movement of an intracapsular fracture involving the condylar process. MATERIALS AND METHODS: In this study, patients who underwent mandibular condylar intracapsular fracture surgery in our hospital from 2012 to 2020 were selected as research subjects. A total of 44 patients received steel wire internal fixation treatment, 32 patients received titanium plate-and-nail rigid internal fixation, and 28 patients underwent conservative non-surgical treatment. RESULTS: For the patients in the stainless-steel wire group, the degree of mouth opening reached normal levels of 3.7 cm approximately 10 days after surgery. The recovery time for the patients in the titanium plate-and-nail rigid internal-fixation group was 21 days, while the patients in the conservative treatment group needed 60 days to recover. CONCLUSION: The treatment of fixation with a stainless-steel wire for intracapsular condylar fracture reduced the time taken to perform mouth-opening exercises and improved the recovery rate of patients.

OBJETIVO: Explorar el efecto clínico de la fijación de alambre de acero inoxidable en el movimiento temprano de apertura de la boca en la fractura interna del cóndilo. MÉTODO: Este estudio seleccionó a pacientes que se sometieron a cirugía de fractura intracapsular de cóndilo en nuestro hospital de 2012 a 2020 como sujetos de investigación. Un total de 44 pacientes recibieron tratamiento de fijación interna de alambre de acero, 32 recibieron placa de titanio y fijación interna con clavos, y 28 recibieron tratamiento conservador no quirúrgico. RESULTADOS: En los pacientes del grupo de alambre de acero inoxidable, alrededor de 10 días después de la cirugía el grado de apertura de la boca alcanzó un valor normal de 3.7 cm. El tiempo de recuperación de los pacientes en el grupo de fijación interna con clavos y placa de titanio fue de 21 días, mientras que los pacientes en el grupo de tratamiento conservador tardaron 60 días en recuperarse. CONCLUSIONES: La fijación con alambre de acero inoxidable para el tratamiento de la fractura intracapsular del cóndilo acorta el tiempo hasta la apertura de la boca y mejora la tasa de recuperación de los pacientes.

Asunto(s)

RESUMEN

Pathogenic bacterial biofilms present significant challenges, particularly in food safety and material deterioration. Therefore, using Enterococcus mundtii A2, known for its antagonistic activity against pathogen adhesion, could serve as a novel strategy to reduce pathogenic colonization within the food sector. This study aimed to investigate the biofilm-forming ability of E. mundtii A2, isolated from camel milk, on two widely used stainless steels within the agri-food domain and to assess its anti-adhesive properties against various pathogens, especially on stainless steel 316L. Additionally, investigations into auto-aggregation and co-aggregation were also conducted. Plate count methodologies revealed increased biofilm formation by E. mundtii A2 on 316L, followed by 304L. Scanning electron microscopy (SEM) analysis revealed a dense yet thin biofilm layer, playing a critical role in reducing the adhesion of L. monocytogenes CECT 4032 and Staphylococcus aureus CECT 976, with a significant reduction of ≈ 2 Log CFU/cm2. However, Gram-negative strains, P. aeruginosa ATCC 27853 and E. coli ATCC 25922, exhibit modest adhesion reduction (~ 0.7 Log CFU/cm2). The findings demonstrate the potential of applying E. mundtii A2 biofilms as an effective strategy to reduce the adhesion and propagation of potentially pathogenic bacterial species on stainless steel 316L.

Asunto(s)

RESUMEN

Objective: The aim was to evaluate the difference in the heat generated between zirconia (Zr) and steel (SS) drills, during implant site preparation. Material and methods: This systematic review followed the PRISMA methodology criteria and used the JBI Critical Assessment Guidelines for Quasi-Experimental Studies for quality assessment. The electronic search was conducted by using the PubMed/MEDLINE, Embase, and Cochrane Library databases to January 2023. The formulated population, intervention, comparison, outcome (PICO) question was "Do zirconia drills generate less heat than steel drills during implant site preparation?". The meta-analysis was based on an inverse variance (IV) method. Results: This review included 10 studies in vitro that used zirconia drills compared to steel drills with or without coatings. The meta-analysis indicated a significant difference between Zr drills and SS drills, with a lower bone temperature variation with Zr drills. Conclusions: Despite the limitations of this review, it was concluded that Zr drills had significantly less temperature variation than SS drills.

RESUMEN

Objetivo: Analizar la resistencia a la corrosión por picaduras de aceros inoxidables AISI 304 y AISI 420 en un medio que contiene cloruros (solu-ción de NaCl al 0,9 y 3,5%, en masa), así como su citotoxicidad, in vitro, en muestras con y sin corrosión por picaduras. Método: Estudio experimental. Se utilizaron técnicas de polarización potenciodinámica cíclica (PPC) para caracterizar el alcance y la forma del ataque corrosivo a las muestras. Se utilizó el método de difusión en agar y evaluación de la viabilidad de la línea celular NCTC clon 929 (CCIAL 020) para evaluar la citotoxicidad de las muestras de acero con y sin picaduras. Resultados: El acero AISI 304 presentó una resistencia a la corrosión superior al acero AISI 420. Los valores de potencial de picadura disminuyeron para ambos aceros cuando aumentó la concentración de cloruros en la solución agresiva. Hubo toxicidad celular moderada (grado 3 ­ ISO 10993-5) en todas las muestras. Conclusión: Los resultados corroboraron las recomendaciones para evitar la inmersión innecesaria de instrumentos en soluciones salinas. La citotoxicidad moderada de estos aceros desaconseja su uso en dispositivos implantables, reservándolos solo para instrumentos quirúrgicos. (AU)

Objective: To analyze the pitting corrosion resistance of AISI 304 and AISI 420 stainless steels in chloride-containing medium (0.9 and 3.5% NaCl solution, by weight), as well as their cytotoxicity,in vitro, in samples with and without pitting corrosion. Method: This is an experimental study. Cyclic potentiodynamic polarization (CPP) techniques were used to characterize the extent and shape of the corrosive attack on the samples. The agar diffusion and viability evaluation method of the NCTC clone 929 cell line (CCIAL 020) was used to evaluate the cytotoxicity of samples of steels with and without pitting. Results: The AISI 304 steel showed superior corrosion resistance to the AISI 420 steel. The values of the pitting potentials decreased for both steels when the chloride concentration in the aggressive solution was increased. There was moderate cell toxicity (grade 3 ­ ISO 10993-5) in all samples. Conclusions: The results corroborated the recommendations to avoid unnecessary immersion of the instruments in saline solutions. Moderate cytotoxicity to these steels contraindicates their use in implantable devices, only in surgical instruments. (AU)

Objetivo: Analisar a resistência à corrosão por pites dos aços inoxidáveis AISI 304 e AISI 420 em meio contendo cloretos (solução de NaCl a 0,9 e 3,5%, em massa), assim como sua citotoxicidade,in vitro, em amostras com e sem corrosão por pites. Método: Estudo experimental. Utilizaram-se téc-nicas de polarização potenciodinâmica cíclica (PPC) para caracterizar extensão e forma do ataque corrosivo nas amostras. O método de difusão em ágar e avaliação da viabilidade da linhagem celular NCTC clone 929 (CCIAL 020) foi empregado para avaliar a citotoxicidade de amostras dos aços com e sem pites. Resultados: O aço AISI 304 apresentou resistência à corrosão superior ao aço AISI 420. Os valores dos potenciais de pite caíram para ambos os aços quando se aumentou a concentração de cloretos na solução agressiva. Houve moderada toxicidade celular (grau 3 ­ ISO 10993-5) em todas as amostras. Conclusão: Os resultados corroboraram as recomendações para evitar a imersão desnecessária dos instrumentais em soluções salinas. A citotoxicidade moderada para esses aços contraindica seu uso em dispositivos implantáveis, apenas em instrumentos cirúrgicos. (AU)

Asunto(s)

RESUMEN

ABSTRACT Objectives: To identify the characteristics of patients and femur fractures treated with a stainless steel intramedullary nail (ESIN) in children under 15 years of age. Know the results of using the ESIN of related steel in the service. Methods: Retrospective study with review of hospital records and organization of data in spreadsheets. Result: 24 cases were identified, 17 male cases and 7 female cases. A minimum age of 4 years and a maximum of 11 years were observed (average of 7 years). The 3 most common trauma mechanisms were being run over (n:8, 33%) and falling from a height (n:8, 3%). The most common location of the fractures was in the mid-diaphyseal region (n: 20, 88%), only one case presented a bilateral femur fracture. The most common associated trauma was traumatic brain injury. The observation period observed several months between 2 and 5. With regard to complications, 3 cases were observed (12.5%) being bursitis, vicious construction and loss of reduction. Conclusion: Steel HIF shows similar good results. As the study includes the retrospective profile, the absence of a group and the small sample size. Level of Evidence IV, Case series.

RESUMO Objetivos: Identificar as características dos pacientes e das fraturas de fêmur tratadas com haste intramedular flexível (HIF) de aço inoxidável em menores de 15 anos. A partir disso, conhecer os resultados relacionados ao uso da HIF de aço inoxidável no serviço. Métodos: Estudo retrospectivo, com revisão de prontuários hospitalares e organização dos dados em planilhas. Resultado: Identificados 24 casos, sendo 17 do gênero masculino e sete do gênero feminino. Foram observadas idade mínima de 4 anos e máxima de 11 anos (média de 7 anos). Os mecanismos de trauma mais comuns foram atropelamento (n: 8, 33%) e queda de altura (n: 8, 33%). A localização mais comum das fraturas foi na região médio diafisária (n: 20, 88%), apenas um caso apresentou fratura de fêmur bilateral. O trauma associado mais comum foi traumatismo crânio-encefálico. O período de consolidação observado variou entre 2 e 5 meses. No que se refere a complicações, foram observados três casos (12,5%), sendo estes: bursite, consolidação viciosa e perda de redução. Conclusão: A HIF de aço apresenta bons resultados, semelhantes aos das hastes de titânio. As limitações do estudo incluem o perfil retrospectivo, a ausência de grupo controle e o número pequeno da amostra. Nível de evidência IV, Série de casos.

RESUMEN

ABSTRACT Objective: This study aimed to compare the insertion torque (IT), flexural strength (FS) and surface alterations between stainless steel (SS-MIs) and titanium alloy (Ti-MIs) orthodontic mini-implants. Methods: Twenty-four MIs (2 x 10 mm; SS-MIs, n = 12; Ti-MIs, n = 12) were inserted on artificial bone blocks of 20 lb/ft3 (20 PCF) and 40 lb/ft3 (40 PCF) density. The maximum IT was recorded using a digital torque meter. FS was evaluated at 2, 3 and 4 mm-deflection. Surface topography and chemical composition of MIs were assessed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). General linear and mixed models were used to assess the effect of the MI type, bone density and deflection on the evaluated outcomes. Results: The IT of Ti-MIs was 1.1 Ncm greater than that obtained for the SS-MIs (p= 0.018). The IT for MIs inserted in 40 PCF test blocks was 5.4 Ncm greater than that for those inserted in 20 PCF test blocks (p < 0.001). SS-MIs inserted in higher density bone (40 PCF) had significantly higher flexural strength than the other groups, at 2 mm (98.7 ± 5.1 Ncm), 3 mm (112.0 ± 3.9 Ncm) and 4 mm (120.0 ± 3.4 Ncm) of deflection (p< 0.001). SEM evidenced fractures in the Ti-MIs. EDS revealed incorporation of 18% of C and 2.06% of O in the loaded SS-MIs, and 3.91% of C in the loaded Ti-MIs. Conclusions: Based on the findings of this in vitro study, it seems that SS-MIs offer sufficient stability and exhibit greater mechanical strength, compared to Ti-MIs when inserted into higher density bone.

RESUMO Objetivo: O objetivo deste estudo foi comparar o torque de inserção (TI), a resistência flexural (RF) e as alterações de superfície em mini-implantes ortodônticos de aço inoxidável (MIs-Ai) e de liga de titânio (MIs-Ti). Métodos: Vinte e quatro MIs (2 x 10 mm; MIs-Ai, n = 12; MIs-Ti, n = 12) foram inseridos em blocos de osso artificial de densidades de 20 lb/ft3 (20 PCF) e 40 lb/ft3 (40 PCF). O torque máximo de inserção foi registrado por meio de um torquímetro digital. A resistência flexural foi avaliada nas deflexões de 2, 3 e 4 mm. Topografia de superfície e composição química dos MIs foram avaliadas por Microscopia Eletrônica de Varredura (MEV) e Espectroscopia de Energia Dispersiva de Raios X (EDS). Modelos lineares gerais e mistos foram utilizados para avaliar o efeito do tipo de MI, da densidade óssea e da deflexão nos desfechos avaliados. Resultados: O TI dos MIs-Ti foi 1,1 Ncm maior do que o obtido para os MIs-Ai (P = 0,018). O TI para MIs inseridos em blocos de teste de 40 PCF foi 5,4 Ncm maior do que para aqueles inseridos em blocos de teste 20 PCF (p < 0,001). MIs-Ai inseridos em osso de maior densidade (40 PCF) apresentaram resistência flexural significativamente maior do que outros grupos, em deflexões de 2 mm (98,7 ± 5,1 Ncm), 3 mm (112,0 ± 3,9 Ncm) e 4 mm (120,0 ± 3,4 Ncm) (p < 0,001). A MEV evidenciou fraturas nos MIs-Ti. A EDS revelou incorporação de 18% de C e 2,06% de O nos MIs-Ai e 3,91% de C nos MIs-Ti, ambos submetidos a testes mecânicos. Conclusões: Com base nos resultados desse estudo in vitro, os MIs-Ai aparentam oferecer adequada estabilidade e maior resistência mecânica, em comparação aos MIs-Ti, quando inseridos em osso de maior densidade.

RESUMEN

Abstract The use of lactic acid bacteria (LAB) in foods as biocontrol agents against foodborne pathogens has become increasingly known. Under the premise that controlling the adhesion of microorganisms to food contact surfaces is an essential step for meeting the goals of food processing, the aim of this work was to investigate the inhibitory and anti-biofilm effectiveness of Lactobacillus rhamnosus GG (ATCC 53103) and Lactobacillus casei (ATCC 393) against Escherichia coli O157:H7, Salmonella enterica and Listeria monocytogenes. Lactobacillus strains (108UFCCFU/ml) and pathogens (104UFCCFU/ml) were evaluated to monitor LAB anti-adhesive and antibiofilm effect, in two main scenarios: (i) co-adhesion and (ii) pathogen incorporation to stainless steel surfaces with a protective biofilm of Lactobacillus cells. In (i) the predominant effect was observed in L. rhamnosus against S. enterica and L. monocytogenes, whereas in (ii) both LAB significantly reduced the number of pathogenic adherent cells. The effect of pre-established LAB biofilms was more successful in displacing the three pathogens than when they were evaluated under co-adhesion. These findings show that both LAB can be considered good candidates to prevent or inhibit the adhesion and colonization of L. monocytogenes, S. enterica and E. coli O157:H7 on surfaces and conditions of relevance for juice processing industries, offering alternatives for improving the safety and quality of fruit-based products.

Resumen Existe un creciente interés en el uso de bacterias ácido lácticas (BAL) como agentes de biocontrol frente a patógenos de transmisión alimentaria. Bajo la premisa de que el control de la adhesión de microorganismos a superficies de contacto con alimentos es el paso esencial para evitar su contaminación, el objetivo de este trabajo fue investigar la efectividad inhibitoria y antibiofilm de Lactobacillus rhamnosus GG (ATCC 53103) y Lactobacillus casei (ATCC 393) frente a Escherichia coli O157:H7, Salmonella enterica y Listeria monocytogenes. A fin de cumplir con el objetivo propuesto, las cepas de Lactobacillus (108UFCUFC/ml) y los patógenos (104UFCUFC/ml) se ensayaron en 2 escenarios: (1) coadhesión, y (2) incorporación de los patógenos a las superficies de acero inoxidable con un biofilm preformado de Lactobacillus. En (1), el efecto predominante se observó con L. rhamnosus frente a S. enterica y L. monocytogenes, mientras que en (2), ambas BAL redujeron significativamente el número de células patógenas adheridas. En función de estos resultados, concluimos que el efecto de un biofilm preformado de ambas BAL fue más exitoso en el desplazamiento de los 3 patógenos que en coadhesión. Ambas BAL pueden considerarse buenas candidatas para mitigar la adhesión y colonización de L. monocytogenes, S. enterica y E. coli O157:H7 en superficies en condiciones de relevancia para la industria procesadora de jugos, y, de esta manera, ofrecer alternativas para mejorar la seguridad y calidad de los alimentos a base de frutas.

RESUMEN

This study compared the effect of oregano essential oil versus sodium hypochlorite, hydrogen peroxide, and benzalkonium chloride against the viability of adhered Salmonella Typhimurium and Escherichia coli O157:H7 on 304 stainless steel. Oregano essential oil was effective in disrupting the biofilms of both bacteria at concentrations ranging from 0.15 to 0.52 mg mL-1. In addition, damage to stainless-steel surfaces following disinfection treatments was assessed by weight loss analysis and via visual inspection using light microscopy. Compared to the other treatments, oregano oil caused the least damage to stainless steel (~0.001% weight loss), whereas sodium hypochlorite caused the most severe damage (0.00817% weight loss) when applied at 0.5 mg mL-1. Moreover, oregano oil also had an apparent protective impact on the stainless steel as weight losses were less than for the control surfaces (distilled water only). On the other hand, sodium hypochlorite caused the most severe damage to stainless steel (0.00817% weight loss). In conclusion, oregano oil eliminated monoculture biofilms of two important foodborne pathogens on 304 stainless-steel surfaces, while at the same time minimizing damage to the surfaces compared with conventional disinfectant treatments.

RESUMEN

The aim of this study was to evaluate the stress distribution in cortical and cancellous bones and within the screw when a stainless steel extra-alveolar screw (EA-S) is inserted into the retromolar region of the mandible using the finite element method (FEM). The stress values in the EA-S were highest at 60° with horizontal (shear) force and lowest at 90° with axial force. In the bones (cortical and cancellous), the stress value was greatest at 90° with horizontal force. Greater stability of the screw may be achieved by tilting it to the force when horizontal loads are applied.

RESUMEN

Stainless steel SS430 and carbon steel B450C were exposed for 30 days to the aqueous extract of sodium silicate-modified limestone-Portland cement as an alternative for the partial replacement of the Portland cement clinker. The initial pH of 12.60 was lowered and maintained at an average of 9.60, associated with air CO2 dissolution and acidification. As a result, the carbon steel lost its passive state, and the corrosion potential (OCP) reached a negative value of up to 296 mV, forming the corrosion layer of FeO, and FeOOH. In the meaning time, on the stainless steel SS430 surface, a passive layer of Cr2O3 grew in the presence of FeO, Fe2O3 and Cr(OH)3 corrosion products; thus, the OCP shifted to more positive values of +150 mV. It is suggested that a self-repassivation process took place on the SS430 surface due to the accumulation of alkaline sulfates on the interface. Because of the chloride attack, SS430 presented isolated pits, while on B450C, their area was extended. The quantitative analysis of EIS Nyquist and Bode diagrams revealed that the Rp of the corrosion process for SS430 was 2500 kΩcm2, ≈32 times lower in magnitude than on B450C, for which the passive layer tended to disappear, while that on SS430 was ≈0.82 nm.

RESUMEN

Poultry products are recognized as the main source of Salmonella and Campylobacter jejuni infections in humans, while avian pathogenic Escherichia coli may have zoonotic potential and can be transmitted from chicken meat to humans. Biofilm formation contributes to their spread through the food chain. This study aimed to compare the adhesion of Salmonella Enteritidis, E. coli, and C. jejuni strains isolated from poultry, food implicated in outbreaks, and poultry slaughterhouses on three surfaces widely used in poultry production (polystyrene, stainless steel, and polyethylene). S. Enteritidis and E. coli adhesion on the three surfaces tested were not significantly different (p > 0.05). Interestingly, the number of C. jejuni cells on stainless steel (4.51-4.67 log10 CFU/cm.-2) was significantly higher (p = 0.0004) than that on polystyrene (3.80-4.25 log10 CFU/cm.-2), but similar (p > 0.05) to that on polyethylene (4.03-4.36 log10 CFU/cm.-2). However, C. jejuni adhesion was significantly lower (p < 0.05) than S. Enteritidis and E. coli adhesion, regardless of the surface evaluated. In addition, scanning electron microscopy analyses have shown an increased irregularity of the stainless steel surface when compared to polyethylene and polystyrene. These irregularities form small spaces ideal for microbial adhesion.

Asunto(s)

RESUMEN

The use of lactic acid bacteria (LAB) in foods as biocontrol agents against foodborne pathogens has become increasingly known. Under the premise that controlling the adhesion of microorganisms to food contact surfaces is an essential step for meeting the goals of food processing, the aim of this work was to investigate the inhibitory and anti-biofilm effectiveness of Lactobacillus rhamnosus GG (ATCC 53103) and Lactobacillus casei (ATCC 393) against Escherichia coli O157:H7, Salmonella enterica and Listeria monocytogenes. Lactobacillus strains (108CFU/ml) and pathogens (104CFU/ml) were evaluated to monitor LAB anti-adhesive and antibiofilm effect, in two main scenarios: (i) co-adhesion and (ii) pathogen incorporation to stainless steel surfaces with a protective biofilm of Lactobacillus cells. In (i) the predominant effect was observed in L. rhamnosus against S. enterica and L. monocytogenes, whereas in (ii) both LAB significantly reduced the number of pathogenic adherent cells. The effect of pre-established LAB biofilms was more successful in displacing the three pathogens than when they were evaluated under co-adhesion. These findings show that both LAB can be considered good candidates to prevent or inhibit the adhesion and colonization of L. monocytogenes, S. enterica and E. coli O157:H7 on surfaces and conditions of relevance for juice processing industries, offering alternatives for improving the safety and quality of fruit-based products.

Asunto(s)