Co-Infections in Critically Ill Patients with or without COVID-19: A Comparison of Clinical Microbial Culture Findings

Co-infections in critically ill patients hospitalized for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection have an important impact on the outcome of coronavirus disease 2019 (COVID-19). We compared the microbial isolations found in COVID-19 patients hospitalized in an intensive care unit (ICU) with those in a non-COVID-19 ICU from 22 February to 30 April 2020 and in the same period of 2019. We considered blood, urine or respiratory specimens obtained with bronchoalveolar lavage (BAL) or bronchial aspirate (BASP), collected from all patients admitted in ICUs with or without COVID-19 infection. We found a higher frequency of infections due to methicillin-resistant (MR) staphylococci, vancomycin-resistant Enterococcus faecium, carbapenem-resistant Acinetobacter baumannii and Candida parapsilosis in COVID-19-positive patients admitted in ICUs compared to those who were COVID-19 negative. Carbapenem-resistant Pseudomonas aeruginosa was more frequently isolated from patients admitted in non-COVID-19 ICUs. Several conditions favor the increased frequency of these infections by antibiotic-resistant microorganisms. Among all, the severity of the respiratory tracts was definitely decisive, which required assisted ventilation with invasive procedures. The turnover in the ICU of a large number of patients in a very short time requiring urgent invasive interventions has favored the not always suitable execution of assistance procedures. No less important is the increased exposure to infectious risk from bacteria and fungi in patients with severe impairment due to ventilation. The highest costs for antifungal drugs were shown in the ICU-COVID group.

Accelerated elimination from the circulation of homologous aged red blood cells in rats bearing anti-spectrin antibodies

In order to analyse a possible role of anti-spectrin antibodies in the clearance of aged red blood cells (RBC), a homologous system was employed, whereby a population of aged RBC, obtained by hypertransfusion, was injected into rats bearing a high level of anti-spectrin antibodies, following immunization with spectrin. The aged RBC bound the anti-spectrin antibodies 'in vitro' and were eliminated from circulation in spectrin-treated rats at a faster rate than in control rats with naturally occurring antibodies. The analysis of the clearance curves revealed aged RBC of heterogeneous lifespans: two principal populations of short- and longer-living could be identified. In rats with anti-spectrin antibodies, the survival of the short-living population was further reduced. However, the similar kinetics of elimination of aged RBC in the two groups (with naturally-occurring and induced antibodies, respectively) suggest that anti-spectrin antibodies strengthened the intervention of the naturally-occurring ones. On the basis of these results, we assume that during their aging in circulation, RBC can accumulate surface alterations to make spectrin accessible to antibodies so that, in addition to anti-band 3 antibodies, anti-spectrin antibodies may contribute to their elimination.

Rabbit IgG antibodies against cord red blood cell membranes bind to complement receptor 1 (CD35)

We have previously shown that a subpopulation of cord/fetal red blood cells (RBC) binds rabbit IgG antibodies raised against cord RBC and absorbed on adult RBC (F-IgG), while control IgG, raised against and absorbed on adult RBC (A-IgG), fails to do so. In the present study, F-IgG maintained its binding to cord RBC surface antigens following absorption on spectrin but not after absorption on skeleton-stripped RBC membranes. Spectrin-absorbed F-IgG- but not A-IgG-affinity-purified material from cord RBC contained polypeptides with apparent MW of complement receptor 1 (CR1) allotypes. Moreover, on immunoblotting these polypeptides reacted with 125I-F-IgG as well as with 125I-anti-CR1 mAb, and binding of 125I-anti-CR1 mAb was inhibited by unlabelled F-IgG. In addition, cord RBC incubated with F-IgG prior to reaction with anti-CR1 showed decreased fluorescence intensity on flow cytometry. Taken together the results suggest that F-IgG binds to CR1 which shows increased expression/accessibility on a subpopulation of cord/fetal RBC.