BACKGROUND. Coronavirus disease 19 (COVID-19) is an emerging infectious disease caused by SARS-CoV-2. Antiviral immune response is crucial to achieve pathogen clearance; however, in some patients an excessive and aberrant host immune response can lead to an acute respiratory distress syndrome. The comprehension of the mechanisms that regulate pathogen elimination, immunity, and pathology is essential to better characterize disease progression and widen the spectrum of therapeutic options. METHODS. We performed a flow cytometric characterization of immune cell subsets from 30 patients with COVID-19 and correlated these data with clinical outcomes. RESULTS. Patients with COVID-19 showed decreased numbers of circulating T, B, and NK cells and exhibited a skewing of CD8⁺ T cells toward a terminally differentiated/senescent phenotype. In agreement, CD4⁺ T and CD8⁺ T, but also NK cells, displayed reduced antiviral cytokine production capability. Moreover, a reduced cytotoxic potential was identified in patients with COVID-19, particularly in those who required intensive care. The latter group of patients also showed increased serum IL-6 levels that inversely correlated to the frequency of granzyme A–expressing NK cells. Off-label treatment with tocilizumab restored the cytotoxic potential of NK cells. CONCLUSION. The association between IL-6 serum levels and the impairment of cytotoxic activity suggests the possibility that targeting this cytokine may restore antiviral mechanisms. FUNDING. This study was supported by funds from the Department of Experimental and Clinical Medicine of University of Florence (the ex-60% fund and the “Excellence Departments 2018–2022 Project”) derived from Ministero dell’Istruzione, dell’Università e della Ricerca (Italy).

To characterize a novel phenicol–oxazolidinone–tetracycline resistance gene, named poxtA, identified in a previously described MRSA strain that was highly resistant to linezolid and also carried the cfr gene. The poxtA gene was identified by bioinformatic analysis of the whole genome sequence of Staphylococcus aureus AOUC-0915. The poxtA gene was cloned in a shuttle plasmid vector and expressed in Escherichia coli, S. aureus and Enterococcus faecalis to investigate the protein function. Comparative sequence analyses at the protein and genetic levels were carried out using standard procedures. The poxtA gene encodes a protein that is 32% identical to OptrA and exhibits structural features typical of the F lineage of the ATP-binding cassette (ABC) protein superfamily that cause antibiotic resistance by ribosomal protection. Expression of poxtA in E. coli, S. aureus and E. faecalis was able to decrease susceptibility to phenicols, oxazolidinones and tetracyclines. A database search identified the presence of poxtA in E. faecalis, Enterococcus faecium and Pediococcus acidilactici strains, mostly of animal origin, and revealed the presence of poxtA homologues in the genomes of some Clostridiales. Analysis of the genetic context revealed that poxtA was located in a composite transposon-like structure containing two IS1216 elements. A novel resistance gene, named poxtA, encoding a protein of the antibiotic resistance (ARE) ABC-F lineage, was identified in the genome of an MRSA of clinical origin. PoxtA can confer decreased susceptibility to phenicols, oxazolidinones and tetracyclines and is associated with a putative mobile element that could contribute to its horizontal dissemination.

Background: Previous studies showed that the epidemic of carbapenem-resistant Klebsiella pneumoniae (CR-KP) observed in Italy since 2010 was sustained mostly by strains of clonal group (CG) 258 producing KPC-type carbapenemases. In the framework of the National Antibiotic-Resistance Surveillance (AR-ISS), a countrywide survey was conducted in 2016 to explore the evolution of the phenotypic and genotypic characteristics of CR-KP isolates.Methods: From March to July 2016, hospital laboratories participating in AR-ISS were requested to provide consecutive, non-duplicated CR-KP (meropenem and/or imipenem MIC >1 mg/L) from invasive infections. Antibiotic susceptibility was determined according to EUCAST recommendations. A WGS approach was adopted to characterize the isolates by investigating phylogeny, resistome and virulome.Results: Twenty-four laboratories provided 157 CR-KP isolates, of which 156 were confirmed as K. pneumoniae sensu stricto by WGS and found to carry at least one carbapenemase-encoding gene, corresponding in most cases (96.1%) to blaKPC. MLST- and SNP-based phylogeny revealed that 87.8% of the isolates clustered in four major lineages: CG258 (47.4%), with ST512 as the most common clone, CG307 (19.9%), ST101 (15.4%) and ST395 (5.1%). A close association was identified between lineages and antibiotic resistance phenotypes and genotypes, virulence traits and capsular types. Colistin resistance, mainly associated with mgrB mutations, was common in all major lineages except ST395.Conclusions: This WGS-based survey showed that, although CG258 remained the most common CR-KP lineage in Italy, a polyclonal population has emerged with the spread of the new high-risk lineages CG307, ST101 and ST395, while KPC remained the most common carbapenemase.

Many term and preterm infants are commonly supplemented with probiotics to prevent adverse effects of antibiotic administration and necrotizing enterocolitis and they are believed to be safe. However, the supplementation with Lactobacillus rhamnosus GG has been associated with the development of sepsis with a cause–effect relationship in six newborns and children. In this study, we report two further cases and discuss the emerging issue of probiotic supplementation safety in neonates. We conclude that physicians must be aware that supplementation with L. rhamnosus GG can cause sepsis in high-risk patients on rare occasions.