Use of an Electrochemical Split Cell Technique to Evaluate the Influence of Shewanella oneidensis Activities on Corrosion of Carbon Steel

Microbially induced corrosion (MIC) is a complex problem that affects various industries. Several techniques have been developed to monitor corrosion and elucidate corrosion mechanisms, including microbiological processes that induce metal deterioration. We used zero resistance ammetry (ZRA) in a split chamber configuration to evaluate the effects of the facultatively anaerobic Fe(III) reducing bacterium Shewanella oneidensis MR-1 on the corrosion of UNS G10180 carbon steel. We show that activities of S. oneidensis inhibit corrosion of steel with which that organism has direct contact. However, when a carbon steel coupon in contact with S. oneidensis was electrically connected to a second coupon that was free of biofilm (in separate chambers of the split chamber assembly), ZRA-based measurements indicated that current moved from the S. oneidensis-containing chamber to the cell-free chamber. This electron transfer enhanced the O2 reduction reaction on the coupon deployed in the cell free chamber, and consequently, enhanced oxidation and corrosion of that electrode. Our results illustrate a novel mechanism for MIC in cases where metal surfaces are heterogeneously covered by biofilms

Fatality rate and predictors of mortality in an Italian cohort of hospitalized COVID-19 patients

Clinical features and natural history of coronavirus disease 2019 (COVID-19) differ widely among different countries and during different phases of the pandemia. Here, we aimed to evaluate the case fatality rate (CFR) and to identify predictors of mortality in a cohort of COVID-19 patients admitted to three hospitals of Northern Italy between March 1 and April 28, 2020. All these patients had a confirmed diagnosis of SARS-CoV-2 infection by molecular methods. During the study period 504/1697 patients died; thus, overall CFR was 29.7%. We looked for predictors of mortality in a subgroup of 486 patients (239 males, 59%; median age 71 years) for whom sufficient clinical data were available at data cut-off. Among the demographic and clinical variables considered, age, a diagnosis of cancer, obesity and current smoking independently predicted mortality. When laboratory data were added to the model in a further subgroup of patients, age, the diagnosis of cancer, and the baseline PaO2/FiO2 ratio were identified as independent predictors of mortality. In conclusion, the CFR of hospitalized patients in Northern Italy during the ascending phase of the COVID-19 pandemic approached 30%. The identification of mortality predictors might contribute to better stratification of individual patient risk

Efficacy of Sterilization Methods and Their Influence on the Electrochemical Behavior of Plain Carbon Steel

Minimizing contamination of control treatments in microbiologically influenced corrosion (MIC) studies is of critical importance. Metal sterilization procedures should not alter the surface nor affect the inherent susceptibility of the metal to corrosion while adequately deactivating biological activity. However, there is no consensus in the literature regarding such procedures due to, in part, the lack of a universally accepted methodology. This investigation evaluates various sterilization methods for carbon steel concerning practicality, efficacy, and effects on the electrochemical response of the metal. Three sterilization procedures using i) dry heat, ii) ethanol, or iii) glutaraldehyde as sterilizing agents were evaluated. Even though all sterilization approaches were equally effective in eliminating microorganisms and spores from the metal surface, dry heating at 170°C in an inert atmosphere was identified as the most convenient sterilization method regarding practicality and consistency in the electrochemical response of the metal. Sterilization of carbon steels in 75 vol% ethanol and glutaraldehyde, as well as alcohol followed by flaming, is discouraged given the large dispersion in corrosion response caused by the exposure to the sterilization media

Galvanic current, lactate concentrations, and Fe(II) concentrations (panels A-C, respectively) measured in split-chamber incubations.

<p>Lactate and Fe(II) concentrations in WE1 (which received <i>S</i>. <i>oneidensis</i> and lactate amendments) and WE2 chambers are depicted with ■ and ●, respectively.</p

Summary of split-chamber ZRA experimental conditions and electrochemical and corrosion characteristics during the incubations.

<p>Summary of split-chamber ZRA experimental conditions and electrochemical and corrosion characteristics during the incubations.</p

Mass loss from carbon steel coupons (A), lactate concentration (B), dissolved Fe(II) concentration (C), and pH (D) in incubations that contained growth medium and steel coupons, and were (■) inoculated with <i>S</i>. <i>oneidensis</i> immediately, (●) inoculated with <i>S</i>. <i>oneidensis</i> after 2 day preincubation of the coupon, or (▲) in uninoculated medium.

<p>Error bars represent one standard deviation of triplicate incubations.</p

Confocal laser scanning micrographs of Bac-Light-stained <i>S</i>. <i>oneidensis</i> incubated for 72 h on carbon steel coupons in medium without (A) and with (B) lactate.

<p>Confocal laser scanning micrographs of Bac-Light-stained <i>S</i>. <i>oneidensis</i> incubated for 72 h on carbon steel coupons in medium without (A) and with (B) lactate.</p

Galvanic current, lactate concentrations, and Fe(II) concentrations measured in split-chamber incubations.

<p>Env. 1 indicates incubations that received <i>S</i>. <i>oneidensis</i> in the WE1 chamber after 2 d of preincubation, and Control 3 indicates incubations that did not receive inoculation. Lactate and dissolved Fe(II) concentrations are shown in both the WE1 and WE2 chambers. Panels A-C illustrate configuration of split-chamber incubations and ZRA measurements, as well the proposed redox processes that are hypothesized to occur during different phases (A-C) of the incubations.</p

SARS-CoV-2 in myelodysplastic syndromes: a snapshot from early Italian experience

Myelodysplastic syndrome patients are subjects of advanced age, vulnerable and frail, whose outcome is heavily influenced by pre-existing comorbidities worsening the hematologic condition. Infections are a rather common cause of death (around 30%), especially, but not only, for IPSS-R higher risk patients.1–3 In MDS there is a significant impairment of lymphopoiesis, resulting in lymphopenia (ALC&lt;1.0109 /l) in around 38% of MDS patients and poor prognosis.4 Data on innate and adoptive immune systems (either disease related or due to immunosenescence) and the subsequent supposed susceptibility and incidence of viral infections in MDS are scarce.