Significance: Persisters represent a bacterial subpopulation that survive high antibiotic concentrations without being resistant. Their role in clinics in persistent infections and their molecular and functional landscape is not fully established. Staphylococcus aureus is a pathobiont that causes severe invasive infections often difficult to treat. Here, we assessed S. aureus recovered directly from persistent infections and show that host-mediated stress and antibiotic exposure promoted persister formation. Using a multiomics approach and enrichment of persisters, we were able to draw a molecular atlas of persisters, to correlate accumulation of insoluble proteins and ATP depletion with dormancy and persistence. Our results give insights into the molecular profile of bacterial persisters and provide a guide for therapy optimization for persistent S. aureus infections.

COVID-19 displays diverse disease severities and symptoms including acute systemic inflammation and hypercytokinemia, with subsequent dysregulation of immune cells. Bacterial superinfections in COVID-19 can further complicate the disease course and are associated with increased mortality. However, there is limited understanding of how SARS-CoV-2 pathogenesis and hypercytokinemia impede the innate immune function against bacterial superinfections. We assessed the influence of COVID-19 plasma hypercytokinemia on the functional responses of myeloid immune cells upon bacterial challenges from acute-phase COVID-19 patients and their corresponding recovery-phase. We show that a severe hypercytokinemia status in COVID-19 patients correlates with the development of bacterial superinfections. Neutrophils and monocytes derived from COVID-19 patients in their acute-phase showed an impaired intracellular microbicidal capacity upon bacterial challenges. The impaired microbicidal capacity was reflected by abrogated MPO and reduced NETs production in neutrophils along with reduced ROS production in both neutrophils and monocytes. Moreover, we observed a distinct pattern of cell surface receptor expression on both neutrophils and monocytes, in line with suppressed autocrine and paracrine cytokine signaling. This phenotype was characterized by a high expression of CD66b, CXCR4 and low expression of CXCR1, CXCR2 and CD15 in neutrophils and low expression of HLA-DR, CD86 and high expression of CD163 and CD11b in monocytes. Furthermore, the impaired antibacterial effector function was mediated by synergistic effect of the cytokines TNF-α, IFN-γ and IL-4. COVID-19 patients receiving dexamethasone showed a significant reduction of overall inflammatory markers in the plasma as well as exhibited an enhanced immune response towards bacterial challengeex vivo. Finally, broad anti-inflammatory treatment was associated with a reduction in CRP, IL-6 levels as well as length of ICU stay and ventilation-days in critically ill COVID-19 patients. Our data provides insights into the transient functional dysregulation of myeloid immune cells against subsequent bacterial infections in COVID-19 patients and describe a beneficial role for the use of dexamethasone in these patients.

To evaluate changes in reproductive fitness of bacteria, e.g., after acquisition of antimicrobial resistance, a low-cost high-throughput method to analyze bacterial growth on agar is desirable for broad usability. In our bacterial quantitative fitness analysis (BaQFA), arrayed cultures are spotted on agar and photographed sequentially while growing. These time-lapse images are analyzed using a purpose-built open-source software to derive normalized image intensity (NI) values for each culture spot. Subsequently, a Gompertz growth model is fitted to NI values, and fitness is calculated from model parameters. To represent a range of clinically important pathogenic bacteria, we used different strains of Enterococcus faecium, Escherichia coli, and Staphylococcus aureus, with and without antimicrobial resistance. Relative competitive fitness (RCF) was defined as the mean fitness ratio of two strains growing competitively on one plate.BaQFA permitted the accurate construction of growth curves from bacteria grown on semisolid agar plates and fitting of Gompertz models. Normalized image intensity values showed a strong association with the total CFU/ml count per spotted culture (P < 0.001) for all strains of the three species. BaQFA showed relevant reproductive fitness differences between individual strains, suggesting substantially higher fitness of methicillin-resistant S. aureus JE2 than Cowan (RCF, 1.58; P < 0.001). Similarly, the vancomycin-resistant E. faecium ST172b showed higher competitive fitness than susceptible E. faecium ST172 (RCF, 1.59; P < 0.001). Our BaQFA method allows detection of fitness differences between bacterial strains and may help to estimate epidemiological antimicrobial persistence or contribute to the prediction of clinical outcomes in severe infections. IMPORTANCE Reproductive fitness of bacteria is a major factor in the evolution and persistence of antimicrobial resistance and may play an important role in severe infections. With a computational approach to quantify fitness in bacteria growing competitively on agar plates, our high-throughput method has been designed to obtain additional phenotypic data for antimicrobial resistance analysis at a low cost. Furthermore, our bacterial quantitative fitness analysis (BaQFA) enables the investigation of a link between bacterial fitness and clinical outcomes in severe invasive bacterial infections. This may allow future use of our method for patient management and risk stratification of clinical outcomes. Our proposed method uses open-source software and a hardware setup that can utilize consumer electronics. This will enable a wider community of researchers, including those from low-resource countries, where the burden of antimicrobial resistance is highest, to obtain valuable information about emerging bacterial strains.

Staphylococcus aureus can cause infections that are often chronic and difficult to treat, even when the bacteria are not antibiotic resistant because most antibiotics act only on metabolically active cells. Subpopulations of persister cells are metabolically quiescent, a state associated with delayed growth, reduced protein synthesis, and increased tolerance to antibiotics. Serine-threonine kinases and phosphatases similar to those found in eukaryotes can fine-tune essential bacterial cellular processes, such as metabolism and stress signaling. We found that acid stress–mimicking conditions that S. aureus experiences in host tissues delayed growth, globally altered the serine and threonine phosphoproteome, and increased threonine phosphorylation of the activation loop of the serine-threonine protein kinase B (PknB). The deletion of stp , which encodes the only annotated functional serine-threonine phosphatase in S. aureus , increased the growth delay and phenotypic heterogeneity under different stress challenges, including growth in acidic conditions, the intracellular milieu of human cells, and abscesses in mice. This growth delay was associated with reduced protein translation and intracellular ATP concentrations and increased antibiotic tolerance. Using phosphopeptide enrichment and mass spectrometry–based proteomics, we identified targets of serine-threonine phosphorylation that may regulate bacterial growth and metabolism. Together, our findings highlight the importance of phosphoregulation in mediating bacterial quiescence and antibiotic tolerance and suggest that targeting PknB or Stp might offer a future therapeutic strategy to prevent persister formation during S. aureus infections.

Background: Nasal microbiota composition of patients with diffuse type 2 chronic rhinosinusitis with nasal polyps (CRSwNP) is altered compared to healthy individuals. Dupilumab, an anti‐IL‐4Rα‐mAb, modulates type 2 inflammation, but the effect on microbiota composition in CRSwNP is unknown. The aim of this study was to investigate longitudinal effects of dupilumab on the nasal passage and gastrointestinal microbiota in patients with diffuse type 2 CRSwNP.Methods: Twenty‐seven patients with diffuse type 2 CRSwNP treated with dupilumab 300 mg subcutaneously every 2 weeks, 10 untreated patients with CRSwNP, and 11 healthy controls were included. Nasal and stool samples were collected at Days 0, 28, 90, and 180 posttreatment of the treated CRSwNP group and at Days 0 and 28 of untreated CRSwNP and healthy controls. The samples were analyzed using 16S rRNA gene amplicon sequencing (V3/V4).Results: In CRSwNP patients, the most abundant genera in nasal passage microbiota were Corynebacterium and Staphylococcus. Cutibacterium and Lawsonella were less abundant in CRSwNP at baseline compared to healthy controls. Dupilumab treatment was associated with increased relative abundances in the nasal passage of genera such as Lawsonella, Corynebacterium, and Dolosigranulum. Microbial diversity of the gastrointestinal microbiota in CRSwNP at baseline was significantly higher than in healthy controls. There were no changes in gastrointestinal microbiota during dupilumab treatment.Conclusion: Dupilumab treatment was associated with a shift in the nasal passage bacterial microbiota toward that of healthy controls, whereas the composition of gastrointestinal microbiota did not change. These findings suggest that nasal passage microbiota composition is influenced by the underlying inflammatory endotype.

S. aureus is a major pathogen of humans, causing a wide range of diseases. The difficulty to develop a vaccine and antibiotic treatment failure warrant the exploration of novel treatment strategies.