RESUMEN
A total of 43 A. baumannii strains, isolated from 43 patients affected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and by bacterial sepsis, were analyzed by antimicrobial susceptibility testing. All strains were resistant to almost three different classes of antibiotics, including carbapenems and colistin. The whole-genome sequencing (WGS) of eight selected A. baumannii isolates showed the presence of different insertion sequences (ISs), such as ISAba13, ISAba26, IS26, ISVsa3, ISEc29, IS6100 and IS17, giving to A. baumannii a high ability to capture and mobilize antibiotic resistance genes. Resistance to carbapenems is mainly mediated by the presence of OXA-23, OXA-66 and OXA-82 oxacillinases belonging to OXA-51-like enzymes. The presence of AmpC cephalosporinase, ADC-25, was identified in all A. baumannii. The pathogenicity of A. baumannii was exacerbated by the presence of several virulence factors. The multi-locus sequence typing (MLST) analysis showed that all strains belong to sequence type 2 (ST) international clone.
RESUMEN
The study investigated the inhibitory activity of protocetraric and salazinic acids against SARS-CoV-2 3CLpro. The kinetic parameters were determined by microtiter plate-reading fluorimeter using a fluorogenic substrate. The cytotoxic activity was tested on murine Sertoli TM4 cells. In silico analysis was performed to ascertain the nature of the binding with the 3CLpro. The compounds are slow-binding inactivators of 3CLpro with a Ki of 3.95 µM and 3.77 µM for protocetraric and salazinic acid, respectively, and inhibitory efficiency kinact/Ki at about 3 × 10-5 s-1µM-1. The mechanism of inhibition shows that both compounds act as competitive inhibitors with the formation of a stable covalent adduct. The viability assay on epithelial cells revealed that none of them shows cytotoxicity up to 80 µM, which is well below the Ki values. By molecular modelling, we predicted that the catalytic Cys145 makes a nucleophilic attack on the carbonyl carbon of the cyclic ester common to both inhibitors, forming a stably acyl-enzyme complex. The computational and kinetic analyses confirm the formation of a stable acyl-enzyme complex with 3CLpro. The results obtained enrich the knowledge of the already numerous biological activities exhibited by lichen secondary metabolites, paving the way for developing promising scaffolds for the design of cysteine enzyme inhibitors.
RESUMEN
Although lymphopenia is currently considered a good predictor for the prognosis of COVID-19, it must be critically evaluated in patients with CLL, where other clinical markers should be considered to define the prognosis and treatment.