Prediction model for early diagnosis of late-onset sepsis in preterm newborns.

AIM: Late-onset neonatal sepsis has a high mortality rate in premature infants. To date, no single test in the evaluation of neonatal sepsis has been demonstrated to be both sensitive and specific enough to assist in timely decision making. The aim of our study is to develop a predictive model that can be applied to all premature babies, using clinical and laboratory findings in premature babies, to recognize late-onset neonatal sepsis. STUDY DESIGN: 65 premature patients diagnosed with culture-proven late-onset neonatal sepsis and hospitalized in Dr. Behcet Uz Pediatric Diseases and Surgery Training and Research Hospital neonatal intensive care unit between January 2018 and December 2020, and 65 premature newborns of similar age and gender who did not have sepsis were included in the study retrospectively. RESULTS: In our study, feeding difficulties, worsening in clinical appearance and fever were found to be significant among clinical findings, while thrombocytopenia and high C-reactive protein among laboratory findings are the strongest data supporting late-onset neonatal sepsis. In multiple regression analysis, thrombocytopenia, mean platelet volume, C-reactive protein, lymphocyte count and feeding difficulties had the highest odds ratio (p < 0.05). By converting these data into a scoring system, a nomogram was created that can be easily used by all clinicians. CONCLUSION: In our study, we developed a scoring system that can be easily applied to all premature patients by evaluating the clinical and laboratory findings in late-onset neonatal sepsis. We think that it will help in recognizing late-onset neonatal sepsis and strengthening the treatment decision. Predicting the individual probability of sepsis in preterm newborns may provide benefits for uninfected newborns to be exposed to less antibiotics, not to be separated from mother and baby, and to reduce healthcare system expenditures. The nomogram can be used to assess the likelihood of sepsis and guide treatment decision.

Comparison of "IN-REC-SUR-E" and LISA in preterm neonates with respiratory distress syndrome: a randomized controlled trial (IN-REC-LISA trial).

BACKGROUND: Surfactant is a well-established therapy for preterm neonates affected by respiratory distress syndrome (RDS). The goals of different methods of surfactant administration are to reduce the duration of mechanical ventilation and the severity of bronchopulmonary dysplasia (BPD); however, the optimal administration method remains unknown. This study compares the effectiveness of the INtubate-RECruit-SURfactant-Extubate (IN-REC-SUR-E) technique with the less-invasive surfactant administration (LISA) technique, in increasing BPD-free survival of preterm infants. This is an international unblinded multicenter randomized controlled study in which preterm infants will be randomized into two groups to receive IN-REC-SUR-E or LISA surfactant administration. METHODS: In this study, 382 infants born at 24+0-27+6 weeks' gestation, not intubated in the delivery room and failing nasal continuous positive airway pressure (nCPAP) or nasal intermittent positive pressure ventilation (NIPPV) during the first 24 h of life, will be randomized 1:1 to receive IN-REC-SUR-E or LISA surfactant administration. The primary outcome is a composite outcome of death or BPD at 36 weeks' postmenstrual age. The secondary outcomes are BPD at 36 weeks' postmenstrual age; death; pulse oximetry/fraction of inspired oxygen; severe intraventricular hemorrhage; pneumothorax; duration of respiratory support and oxygen therapy; pulmonary hemorrhage; patent ductus arteriosus undergoing treatment; percentage of infants receiving more doses of surfactant; periventricular leukomalacia, severe retinopathy of prematurity, necrotizing enterocolitis, sepsis; total in-hospital stay; systemic postnatal steroids; neurodevelopmental outcomes; and respiratory function testing at 24 months of age. Randomization will be centrally provided using both stratification and permuted blocks with random block sizes and block order. Stratification factors will include center and gestational age (24+0 to 25+6 weeks or 26+0 to 27+6 weeks). Analyses will be conducted in both intention-to-treat and per-protocol populations, utilizing a log-binomial regression model that corrects for stratification factors to estimate the adjusted relative risk (RR). DISCUSSION: This trial is designed to provide robust data on the best method of surfactant administration in spontaneously breathing preterm infants born at 24+0-27+6 weeks' gestation affected by RDS and failing nCPAP or NIPPV during the first 24 h of life, comparing IN-REC-SUR-E to LISA technique, in increasing BPD-free survival at 36 weeks' postmenstrual age of life. TRIAL REGISTRATION: ClinicalTrials.gov NCT05711966. Registered on February 3, 2023.

A comparative analysis of chronic inducible urticaria in 423 patients: Clinical and laboratory features and comorbid conditions.

BACKGROUND: Chronic inducible urticaria (CIndU) is a subtype of chronic urticaria (CU) which require specific physical or non-physical triggers to occur. They may be isolated or may coexist with chronic spontaneous urticaria (CSU). Despite their frequent appearance in dermatology clinics, there is scarce information on the distinguishing features among the most common subtypes of CIndU as well as isolated CIndU versus CSU plus CIndU. OBJECTIVES: To compare clinical and laboratory characteristics, and comorbid conditions among the most common CIndU types and isolated CIndU versus CSU plus CIndU. METHODS: We retrospectively analysed CIndU patients and compared patients' demographic, clinical and laboratory characteristics across isolated CIndU, CSU plus CIndU, symptomatic dermographism (SD), cold urticaria (ColdU) and cholinergic urticaria (ChoU). RESULTS: A total of 423 patients (~70% isolated CIndU, ~30% CSU plus CIndU, ~5% mixed CIndU subtypes) were included in the study. The most frequent CIndU subtypes were SD (68.6%; 290/423), ColdU (11.4%; 48/423) and ChoU (10.9%; 46/423). Isolated CIndU patients were younger than CSU plus CIndU (33.74 ± 12.72 vs. 37.06 ± 11.84, p = 0.010). Angioedema, emergency referrals, need for systemic steroids, comorbid systemic disorders were more frequent and baseline urticaria control test scores were lower in CSU plus CIndU patients (vs. CIndU, p < 0.001, p = 0.008, p < 0.001, p = 0.031, p = 0.036, respectively). Among CIndU subtypes, ChoU patients were younger (24.9 ± 12.2 vs. 34.47 ± 12.12 vs. 31.38 ± 14.95; p < 0.001) and had male predominance (p < 0.001) while SD patients had no angioedema (p < 0.001) and had higher frequency of increased total IgE levels (p = 0.006). CONCLUSIONS: Isolated CIndU and CSU plus CIndU seems to be different endotypes of CU where CSU plus CIndU presents a more severe and refractory course. There are distinctive features of each CIndU subtype. These suggest involvement of different pathomechanistic pathways in these subtypes that need to be clarified in future studies.

Relationship between platelet indices in acute cholecystitis: A case-control study.

INTRODUCTION AND AIMS: We aimed to investigate changes in initial platelet indices in patients arriving at the emergency department with acute cholecystitis. MATERIAL AND METHODS: A retrospective case-control study was conducted at a tertiary care teaching hospital. Demographics, comorbidities, laboratory data, length of hospital stay, and mortality data for the acute cholecystitis group were retrospectively obtained from the hospital digital database. Platelet count, mean platelet volume, plateletcrit, platelet distribution width, and platelet mass index were collected. RESULTS: A total of 553 patients with acute cholecystitis were the study cases, and 541 hospital employees were the study controls. According to the results of the multivariate analysis of the platelet indices studied, only mean platelet volume and platelet distribution width showed significant differences between the two groups (adjusted odds ratio: 2, 95% confidence interval: 1.4-2.7, p < 0.001 and adjusted odds ratio: 5.88, 95% confidence interval: 2.44-14.4, p < 0.001, respectively). The multivariate regression model created had an area under the curve of 0.969 in the prediction of acute cholecystitis (accuracy: 0.917, sensitivity: 89%, and specificity: 94.5%). CONCLUSION: The study results indicate that the initial mean platelet volume and platelet distribution width were independent predictors of acute cholecystitis.

Enhancement of Quantum Heat Engine by Encircling a Liouvillian Exceptional Point.

Quantum heat engines are expected to outperform the classical counterparts due to quantum coherences involved. Here we experimentally execute a single-ion quantum heat engine and demonstrate, for the first time, the dynamics and the enhanced performance of the heat engine originating from the Liouvillian exceptional points (LEPs). In addition to the topological effects related to LEPs, we focus on thermodynamic effects, which can be understood by the Landau-Zener-Stückelberg process under decoherence. We witness a positive net work from the quantum heat engine if the heat engine cycle dynamically encircles a LEP. Further investigation reveals that a larger net work is done when the system is operated closer to the LEP. We attribute the enhanced performance of the quantum heat engine to the Landau-Zener-Stückelberg process, enabled by the eigenenergy landscape in the vicinity of the LEP, and the exceptional point-induced topological transition. Therefore, our results open new possibilities toward LEP-enabled control of quantum heat engines and of thermodynamic processes in open quantum systems.

Neonatal outcomes and long-term neurodevelopmental evaluations of hospitalized early term infants: prospective case-control study.

BACKGROUNDS: It was intended to compare early term babies to term babies by reviewing short-term issues and long-term neurodevelopmental evaluations. METHODS: It was planned as a prospective case-control study. Of the 4263 infants admitted to the neonatal intensive care unit, 109 infants born at early term by elective cesarean section and hospitalized within the first 10 postnatal days were included in the study. As the control group, 109 babies born at term were enrolled. Nutrition status of infants, reasons for hospitalization in the first postnatal week were recorded. When the babies were 18-24 months old, an appointment was made for neurodevelopmental evaluation. RESULTS: In the early term group, the time of breastfeeding was later than the control group, with a statistically significant difference. Similarly, breastfeeding difficulty, need for formula in the first week postpartum and hospitalization were found to be significantly higher in the early term group. Considering the short-term results; pathological weight loss, hyperbilirubinemia requiring phototherapy and feeding difficulties were statistically significantly higher in the early term group. Neurodevelopmental delay did not statistically differ across the groups, but the early term group's MDI and PDI scores were found to be statistically lower than those of the term group. CONCLUSION: Early term infants are thought to be like term infants in many ways. Although these babies are similar to term babies, they are still physiologically immature. The short and long-term negative consequences of early term birth are obvious, non-medical elective early term births should be prevented.

The effect of standard, ketogenic, and Western-type diets applied to rats in pressure wound therapy.

OBJECTIVE: This study aimed at investigating the effect of ketogenic and Western diets on pressure wounds. MATERIALS AND METHODS: This randomized controlled study used 33 male Sprague-Dawley rats. They were randomly divided into the control, ketogenic, and Western diet groups. Pressure wounds were created on the rats' backs. RESULTS: Wound healing of the Western diet group on day 42 was better than the ketogenic and standard groups. In the microscopic examinations, wound closure, damaged muscle tissue repair, angiogenesis, vascularization, granulation, and collagenization in the Western diet group were faster than in the ketogenic and standard groups. CONCLUSIONS: The Western diet was potentially effective for pressure wound healing. Future research should be conducted to clarify how this affects the wound-healing process.

Dynamical control of quantum heat engines using exceptional points.

A quantum thermal machine is an open quantum system coupled to hot and cold thermal baths. Thus, its dynamics can be well understood using the concepts and tools from non-Hermitian quantum systems. A hallmark of non-Hermiticity is the existence of exceptional points where the eigenvalues of a non-Hermitian Hamiltonian or a Liouvillian superoperator and their associated eigenvectors coalesce. Here, we report the experimental realization of a single-ion heat engine and demonstrate the effect of Liouvillian exceptional points on the dynamics and the performance of a quantum heat engine. Our experiments have revealed that operating the engine in the exact- and broken-phases, separated by a Liouvillian exceptional point, respectively during the isochoric heating and cooling strokes of an Otto cycle produces more work and output power and achieves higher efficiency than executing the Otto cycle completely in the exact phase where the system has an oscillatory dynamics and higher coherence. This result opens interesting possibilities for the control of quantum heat engines and will be of interest to other research areas that are concerned with the role of coherence and exceptional points in quantum processes and in work extraction by thermal machines.

Linear response theory of open systems with exceptional points.

Understanding the linear response of any system is the first step towards analyzing its linear and nonlinear dynamics, stability properties, as well as its behavior in the presence of noise. In non-Hermitian Hamiltonian systems, calculating the linear response is complicated due to the non-orthogonality of their eigenmodes, and the presence of exceptional points (EPs). Here, we derive a closed form series expansion of the resolvent associated with an arbitrary non-Hermitian system in terms of the ordinary and generalized eigenfunctions of the underlying Hamiltonian. This in turn reveals an interesting and previously overlooked feature of non-Hermitian systems, namely that their lineshape scaling is dictated by how the input (excitation) and output (collection) profiles are chosen. In particular, we demonstrate that a configuration with an EP of order M can exhibit a Lorentzian response or a super-Lorentzian response of order Ms with Ms = 2, 3, …, M, depending on the choice of input and output channels.

Stem cell-based therapies for temporomandibular joint osteoarthritis and regeneration of cartilage/osteochondral defects: a systematic review of preclinical experiments.

OBJECTIVES: The aim of this systematic review was to assess the effects of stem cell-based therapies on the treatment of Temporomandibular Joint Osteoarthritis (TMJ-OA) and the regeneration of cartilage/osteochondral defects. METHODS: Data on preclinical studies evaluating the effectiveness of stem cell-based therapies for treating Temporomandibular Disorders (TMDs) were extracted from PubMed, Web of Science, and Cochrane Library and the grey literature by three independent reviewers. A manual search was performed in the databases, the reference list of review studies, and relevant journals in the field. Compliance with the ARRIVE guidelines was evaluated for quality assessment. SYRCLE's risk of bias tool for animal experimental studies was assessed to define internal validity. RESULTS: After applying the inclusion and exclusion criteria, 10 studies were included in the qualitative synthesis. Regardless of cell origin, stem cell-based therapeutic approaches induced protective, anti-inflammatory, and chondroregenerative potential in the treatment of TMJ-OA. Regeneration of the cartilage layer on the surface of the condyle was achieved when stem cells were directly flushed into the defect or when delivered within a carrier. CONCLUSION: Stem cell-based therapies may be considered a promising approach for the treatment of TMJ-OA and for the regeneration of full-thickness cartilage and osteochondral defects in the TMJ. Human studies shall be performed to validate these results found in animals.

The effect of erosive beverages and polishing systems on the surface properties of nanohybrid composite resin.

Aims and Background: The aim of this study is to evaluate the surface microhardness and roughness of composites treated with three different polishing systems exposed to two different corrosive beverages. Material and Methods: Ninety-six composite resin disks were randomly divided into four groups, one of which was the control group. The surface roughness and microhardness values were measured after 24 h in the polishing process. The samples were divided into three subgroups and kept in distilled water, cola, and ice tea for 20 min a day for 14 days. Then, the roughness and microhardness measurements of the samples were taken again. Two samples randomly selected from each group were examined using a scanning electron microscope (SEM) and analyzed statistically using the two way anova (ANOVA) and Duncan tests. Results: A statistically significant difference was found between the roughness and hardness values at the end of 24 h and 14 days. Onegloss (OG), Dentoflex (DF), and Super-snap (SNP) polish systems showed the highest roughness in the cola group, respectively. Microhardness values: The unpolished group had the lowest significant microhardness in the coke group (P < 0.05). Conclusion: In this study, it was seen that the lowest success rate was the OG polishing system.

Chiral and degenerate perfect absorption on exceptional surfaces.

Engineering light-matter interactions using non-Hermiticity, particularly through spectral degeneracies known as exceptional points (EPs), is an emerging field with potential applications in areas such as cavity quantum electrodynamics, spectral filtering, sensing, and thermal imaging. However, tuning and stabilizing a system to a discrete EP in parameter space is a challenging task. Here, we circumvent this challenge by operating a waveguide-coupled resonator on a surface of EPs, known as an exceptional surface (ES). We achieve this by terminating only one end of the waveguide with a tuneable symmetric reflector to induce a nonreciprocal coupling between the frequency-degenerate clockwise and counterclockwise resonator modes. By operating the system at critical coupling on the ES, we demonstrate chiral and degenerate perfect absorption with squared-Lorentzian lineshape. We expect our approach to be useful for studying quantum processes at EPs and to serve as a bridge between non-Hermitian physics and other fields that rely on radiation engineering.

Advanced Cancer Patients' Prognostic Awareness and Its Association With Anxiety, Depression and Spiritual Well-Being: A Multi-Country Study in Asia.

AIMS: The associations between prognostic awareness, acceptance of illness and psychological outcomes (anxiety, depression and spiritual well-being) remain unclear. This study examined the associations between prognostic awareness and various psychological outcomes and how they can be moderated by patient acceptance of illness (cancer). MATERIALS AND METHODS: In total, 1184 patients with stage IV solid cancer were recruited at major public hospitals across four Asian countries (China, India, Sri Lanka, Vietnam). Prognostic awareness and acceptance of illness were assessed through self-reported understanding of treatment intent and acceptance of illness, respectively. Anxiety and depression were assessed using the Hospital Anxiety and Depression Scale, whereas spiritual well-being was measured using the Functional Assessment of Chronic Illness Therapy - Spiritual Well-Being Scale. Multivariate regressions were used to estimate the associations while controlling for patient characteristics. RESULTS: Compared with being unaware of their prognosis (i.e. believing that their cancer is curable), being aware or unsure of their prognosis was associated with higher anxiety and depressive symptoms, and lower spiritual well-being scores. Acceptance of illness moderated these relationships and improved the psychological outcomes. CONCLUSIONS: The results suggest that disclosure of prognostic information should be provided in conjunction with psychological interventions that focus on acceptance of illness.

Effects of otosclerosis and stapedotomy on vestibular-evoked myogenic potentials.

OBJECTIVE: Limited data are available on the effects of otosclerosis and otosclerosis surgery on the utricle and saccule. This study aimed to determine the effect of otosclerosis and stapedotomy on vestibular-evoked myogenic potentials. METHODS: This retrospective study included 16 otosclerosis patients and 18 controls. Thirty-two ears of 16 patients with otosclerosis were divided into 2 groups based on whether the ear had been operated on or not. All patients and subjects underwent 500 Hz air- and bone-conducted ocular and cervical vestibular-evoked myogenic potentials testing. RESULTS: Overall comparison of response rates showed a significant difference among the groups. Further statistical tests showed that this difference arose from differences between both operated and unoperated groups and the control group, for air-conducted cervical and ocular vestibular-evoked myogenic potentials. CONCLUSION: Otosclerosis and stapedotomy may affect the elicitability of vestibular-evoked myogenic potentials. Otosclerosis is associated with lower response rates for air-conducted ocular and cervical vestibular-evoked myogenic potentials, regardless of whether operated on. Having been operated on does not significantly increase the response rate of air-conducted vestibular-evoked myogenic potentials.

Why Do Immigrant and Swedish Adolescents Engage in Ethnic Victimization? Common and Distinct Underlying Factors.

Youth of immigrant background are at risk of experiencing victimization due to their ethnic or cultural background. However, limited knowledge is available regarding why youth victimize their immigrant peers, and whether the factors associated with engagement in ethnic victimization vary across adolescents of different background. To address this gap in knowledge, the present study aimed to elucidate the common or differential factors associated with engagement in ethnic victimization among immigrant and native youth. The analytical sample included seventh grade students residing in Sweden from 55 classrooms (N = 963, Mage = 13.11, SD = 0.41; 46% girls; 38% youth of immigrant background). The results showed that being morally disengaged and engaging in general victimization are the common denominators of engagement in ethnic victimization for immigrant and Swedish youth. Low levels of positive attitudes toward immigrants provide a foundation for ethnic victimization among Swedish youth, but not youth of immigrant background. Classroom ethnic composition was not significantly related to engagement in ethnic victimization in either group. Predictors of engagement in ethnic victimization seem to have similarities and differences among immigrant and Swedish youth. The factors involved require further attention in developing strategies to combat bias-based hostile behaviors in diverse school settings.

Experiences of cultural clashes at home and ethnic victimization in school: "I live between two cultures, and neither of them understands me".

The present study aims to examine the extent to which adolescents of immigrant background experience acculturative stress (i.e., cultural clashes with parents and ethnic victimization in school) in multiple contexts, and the reasons why such stress takes a toll on their psychological functioning and views of themselves. The analytic sample includes adolescents of immigrant background residing in Sweden (N = 423, Mage = 13.19, SD = 0.51). Cluster analysis revealed five distinct groups of adolescents, based on their reports of cultural clashes with parents and ethnic victimization in school: (1) low on both acculturative stressors, (2) average on both acculturative stressors, (3) high on cultural clashes only, (4) high on ethnic victimization only, and (5) high on both acculturative stressors. Mediation analysis showed that adolescents who experienced cultural clashes at home and who were also victimized by their peers in school reported higher levels of feeling in between cultures than adolescents in all the other clusters (except those high on cultural clashes only), and in turn reported higher levels of depressive symptoms and lower levels of self-esteem. The present study highlights the importance of understanding immigrant youth's experiences across multiple contexts simultaneously in order to develop a holistic perspective on their adjustment and integration processes.

Acute effect of thymoquinone on action potential and ionic currents of rat cardiac myocytes.

OBJECTIVES: This study aims to investigate the acute effects of thymoquinone (TQ) which has been suggested to be a cardioprotective agent, on ventricular myocytes. METHODS: Freshly isolated rat ventricular myocytes were exposed to TQ and using standard whole-cell patch-clamp technique action potential (AP), sodium current (INa), L-type calcium current (ICaL) and transient outward potassium current (Ito) were measured. RESULTS: TQ prolonged the duration of AP and decreased the peak value compared to that of control myocytes. Consistently, it inhibited INa in a concentration-dependent manner and shifted the channel kinetics to more hyperpolarized voltages. Besides, TQ not only inhibited Ito and ICaL but also significantly attenuated the isoproterenol-induced increase in ICaL. CONCLUSION: The effect of TQ on cardiomyocytes has been demonstrated for the first time. TQ changes AP morphology along with ionic currents and alleviates ß-adrenergic response in adult ventricular myocytes. These results indicate that TQ may be considered as a therapeutic agent in cases such as diabetic cardiomyopathy and cardiac hypertrophy, wherein the ß-adrenergic system is over-activated (Tab. 2, Fig. 6, Ref. 30).

The relevance between graft preservation solutions and QTc interval during living donor kidney transplantation and rat cardiomyocytes sampling.

BACKGROUND: The purpose of the retrospective study was to identify the impacts of different solutions on the electrocardiogram and cardiovascular changes. Moreover, the differences between these solutions were analyzed by examining their impacts on rat ventricular cardiomyocytes. METHODS: Eighty renal transplant patients were evaluated retrospectively. The patients were divided into two groups: Group UW (n =40) used the University of Wisconsin solution, and Group HTK (n =40) used the Histidine-Tryptophan-Ketoglutarate solution. Electrocardiograms of the subjects were obtained three times at different periods; during the pre-perfusion, intraoperative kidney reperfusion, and postperfusion phase at the end of the surgery. Any Electrocardiogram or cardiovascular alterations were noted and analyzed. Adult male Wistar rats were used for in vitro experiments. Myocyte contractility, action potentials, and membrane current were recorded in enzymatically isolated ventricular myocytes. RESULTS: Sinus bradycardia was detected in 19 patients of Group UW, while there was short-term asystole in eight patients. However, no cardiac changes were observed in Group HTK patients. In both Groups, reperfusion and postperfusion corrected QT (QTc) intervals were different from pre-perfusion QTc intervals. Group UW patients' reperfusion and postperfusion QTc's values were higher than those of the Group HTK patients. In rat myocytes, prominent asystole episodes were observed at specific concentrations of the UW solution compared to the HTK solution. The UW solution depolarized the resting membrane potential significantly and decreased the peak value of action potential, whereas the HTK solution did not elicit a significant change in those parameters. Accordingly, the UW solution elicited a significant inward current at -70 mV, while the HTK solution activated only a modest current, which may not change the membrane potential. CONCLUSION: Prolongation of QTc intervals was detected with reperfusion in both groups according to electrocardiography analysis. However, the QTc interval was observed to be longer in cases using the UW solution and required intervention intraoperatively. HIPPOKRATIA 2021, 25 (1):22-30.

Hierarchical Construction of Higher-Order Exceptional Points.

The realization of higher-order exceptional points (HOEPs) can lead to orders of magnitude enhancement in light-matter interactions beyond the current fundamental limits. Unfortunately, implementing HOEPs in the existing schemes is a rather difficult task, due to the complexity and sensitivity to fabrication imperfections. Here we introduce a hierarchical approach for engineering photonic structures having HOEPs that are easier to build and more resilient to experimental uncertainties. We demonstrate our technique by an example that involves parity-time symmetric optical microring resonators with chiral coupling among the internal optical modes of each resonator. Interestingly, we find that the uniform coupling profile is not required to achieve HOEPs in this system-a feature that implies the emergence of HOEPs from disorder and provides resilience against some fabrication errors. Our results are confirmed by using full-wave simulations based on Maxwell's equation in realistic optical material systems.

Impact of commonly used Ag-Cu ion doses on Desulfovibrio sp.: growth and microbiologically induced corrosion against stainless steel.

Ag-Cu ions in cooling water may inhibit the activity of sulfate-reducing bacteria and therefore provide solutions to microbiologically induced corrosion (MIC) problems, mainly caused by Desulfovibrio sp. To investigate this, the MIC behavior of Desulfovibrio sp. on 316L stainless steel in terms of growth and extracellular polymeric substances (EPS) production was investigated in the presence of Ag-Cu ions. Laboratory-scale systems were set up with final concentrations of 0.13 ppm Ag and 0.3 ppm Cu ions, as they are the frequently used doses for cooling waters, and operated over 720 hours. The corrosion rate was evaluated by gravimetric assay, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyses. The growth of Desulfovibrio sp. was assessed by bacterial counting and EPS production. Ag-Cu ions in the biofilm were assessed by inductively coupled plasma - optical emission spectrometry (ICP-OES) and EDS-elemental mapping analyses. It was concluded that the ion concentrations used caused an increase in EPS production, especially of protein. The corrosion rate of the metal by Desulfovibrio sp. in the presence of ions was detected as being 29 times higher than that in the sterile medium with the ions after 720 hours. The results suggested that Desulfovibrio sp. exhibited more corrosive behavior in the presence of non-toxic concentrations of Ag-Cu ions.