Feasibility of Continuous Infusion of Cefiderocol in Conjunction with the Establishment of Therapeutic Drug Monitoring in Patients with Extensively Drug-Resistant Gram-Negative Bacteria.

BACKGROUND AND OBJECTIVE: Resistance to antibacterial substances is a huge and still emerging issue, especially with regard to Gram-negative bacteria and in critically ill patients. We report a study in six patients infected with extensively drug-resistant Gram-negative bacteria in a limited outbreak who were successfully managed with a quasi-continuous infusion of cefiderocol. METHODS: Patients were initially treated with prolonged infusions of cefiderocol over 3 h every 8 h, and the application mode was then switched to a quasi-continuous infusion of 2 g over 8 h, i.e. 6 g in 24 h. Therapeutic drug monitoring (TDM) was established using an in-house liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. RESULTS: Determined trough plasma concentrations were a median of 50.00 mg/L [95% confidence interval (CI) 27.20, 74.60] and steady-state plasma concentrations were a median of 90.96 mg/L [95% CI 37.80, 124]. No significant differences were detected with respect to acute kidney injury/continuous renal replacement therapy. Plasma concentrations determined from different modes of storage were almost equal when frozen or cooled, but markedly reduced when stored at room temperature. CONCLUSIONS: (Quasi) continuous application of cefiderocol 6 g/24 h in conjunction with TDM is a feasible mode of application; the sample for TDM should either be immediately analyzed, cooled, or frozen prior to analysis.

Comparison and Harmonization of Different Semi-Automated and Automated qRT-PCR Assays in the Assessment of SARS-CoV-2.

In SARS-CoV-2 diagnostics, cycle threshold (Ct) values from qRT-PCRs semi-quantitatively estimate a patient's viral load. However, relevant analytical differences between qRT-PCR assays are often neglected. This study was designed (i) to identify such differences between five commonly used assays and (ii) to demonstrate a straightforward strategy to harmonize them. QRT-PCRs for SARS-CoV-2 were carried out in 85 oropharyngeal swab samples using three fully automated (Alinity m, cobas®6800 and GeneXpert) and two semi-automated (genesig® and RIDA®GENE) assays. Qualitative results (positive/negative) showed excellent comparability between the fully automated assays, but not between the Alinity m and semi-automated methods. Ct values significantly varied between all the methods, with the median values ranging from 22.76 (Alinity m) to 30.89 (RIDA®GENE) and 31.50 (genesig®), indicating the lowest sensitivity for semi-automated methods. Passing-Bablok analysis further revealed systemic biases. Assay-specific viral load concentration calculations-based on generated individual standard curves-resulted in much better comparability between the assays. Applying these calculations, significant differences were no longer detectable. This study highlights relevant analytical differences between SARS-CoV-2 qRT-PCR assays, leading to divergent decisions about the mandatory isolation of infected individuals. Secondly, we propose a strategy to harmonize qRT-PCR assays to achieve better comparability. Our findings are of particular interest for laboratories utilizing different assays.

Interdependencies of cellular and humoral immune responses in heterologous and homologous SARS-CoV-2 vaccination.

BACKGROUND: Homologous and heterologous SARS-CoV-2 vaccinations yield different spike protein-directed humoral and cellular immune responses. This study aimed to explore their currently unknown interdependencies. METHODS: COV-ADAPT is a prospective, observational cohort study of 417 healthcare workers who received vaccination with homologous ChAdOx1 nCoV-19, homologous BNT162b2 or with heterologous ChAdOx1 nCoV-19/BNT162b2. We assessed humoral (anti-spike-RBD-IgG, neutralizing antibodies, and avidity) and cellular (spike-induced T-cell interferon-γ release) immune responses in blood samples up to 2 weeks before (T1) and 2-12 weeks following secondary immunization (T2). RESULTS: Initial vaccination with ChAdOx1 nCoV-19 resulted in lower anti-spike-RBD-IgG compared with BNT162b2 (70 ± 114 vs. 226 ± 279 BAU/ml, p < .01) at T1. Booster vaccination with BNT162b2 proved superior to ChAdOx1 nCoV-19 at T2 (anti-spike-RBD-IgG: ChAdOx1 nCoV-19/BNT162b2 2387 ± 1627 and homologous BNT162b2 3202 ± 2184 vs. homologous ChAdOx1 nCoV-19 413 ± 461 BAU/ml, both p < .001; spike-induced T-cell interferon-γ release: ChAdOx1 nCoV-19/BNT162b2 5069 ± 6733 and homologous BNT162b2 4880 ± 7570 vs. homologous ChAdOx1 nCoV-19 1152 ± 2243 mIU/ml, both p < .001). No significant differences were detected between BNT162b2-boostered groups at T2. For ChAdOx1 nCoV-19, no booster effect on T-cell activation could be observed. We found associations between anti-spike-RBD-IgG levels (ChAdOx1 nCoV-19/BNT162b2 and homologous BNT162b2) and T-cell responses (homologous ChAdOx1 nCoV-19 and ChAdOx1 nCoV-19/BNT162b2) from T1 to T2. Additionally, anti-spike-RBD-IgG and T-cell response were linked at both time points (all groups combined). All regimes yielded neutralizing antibodies and increased antibody avidity at T2. CONCLUSIONS: Interdependencies between humoral and cellular immune responses differ between common SARS-CoV-2 vaccination regimes. T-cell activation is unlikely to compensate for poor humoral responses.

Case Report: Interferon- γ Rescues Monocytic Human Leukocyte Antigen Receptor (mHLA-DR) Function in a COVID-19 Patient With ARDS and Superinfection With Multiple MDR 4MRGN Bacterial Strains.

Background: CD14+ monocytes present antigens to adaptive immune cells via monocytic human leukocyte antigen receptor (mHLA-DR), which is described as an immunological synapse. Reduced levels of mHLA-DR can display an acquired immune defect, which is often found in sepsis and predisposes for secondary infections and fatal outcomes. Monocytic HLA-DR expression is reliably induced by interferon- γ (IFNγ) therapy. Case Report: We report a case of multidrug-resistant superinfected COVID-19 acute respiratory distress syndrome (ARDS) on extracorporeal membrane oxygenation (ECMO) support. The resistance profiles of the detected Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii and Citrobacter freundii isolates were equipped with resistance to all four antibiotic classes including carbapenems (4MRGN) and Cefiderocol in the case of K. pneumoniae. A causal therapeutic antibiotic strategy was not available. Therefore, we measured the immune status of the patient aiming to identify a potential acquired immune deficiency. Monocyte HLA-DR expression identified by FACS analysis revealed an expression level of 34% positive monocytes and suggested severe immunosuppression. We indicated IFNγ therapy, which resulted in a rapid increase in mHLA-DR expression (96%), rapid resolution of invasive bloodstream infection, and discharge from the hospital on day 70. Discussion: Superinfection is a dangerous complication of COVID-19 pneumonia, and sepsis-induced immunosuppression is a risk factor for it. Immunosuppression is expressed by a disturbed antigen presentation of monocytes to cells of the adaptive immune system. The case presented here is remarkable as no validated antibiotic regimen existed against the detected bacterial pathogens causing bloodstream infection and severe pneumonia in a patient suffering from COVID-19 ARDS. Possible restoration of the patient's own immunity by IFNγ was a plausible option to boost the patient's immune system, eliminate the identified 4MRGNs, and allow for lung recovery. This led to the conclusion that immune status monitoring is useful in complicated COVID-19-ARDS and that concomitant IFNγ therapy may support antibiotic strategies. Conclusion: After a compromised immune system has been detected by suppressed mHLA-DR levels, the immune system can be safely reactivated by IFNγ.

Case Report: Interferon-γ Restores Monocytic Human Leukocyte Antigen Receptor (mHLA-DR) in Severe COVID-19 With Acquired Immunosuppression Syndrome.

Background: The major histocompatibility complex (MHC) class II characterized by monocytes CD14+ expression of human leukocyte antigen receptors (HLA-DR), is essential for the synapse between innate and adaptive immune response in infectious disease. Its reduced expression is associated with a high risk of secondary infections in septic patients and can be safely corrected by Interferon-y (IFNy) injection. Coronavirus disease (COVID-19) induces an alteration of Interferon (IFN) genes expression potentially responsible for the observed low HLA-DR expression in circulating monocytes (mHLA-DR). Methods: We report a case of one-time INFy injection (100 mcg s.c.) in a superinfected 61-year-old man with COVID-19-associated acute respiratory distress syndrome (ARDS), with monitoring of mHLA-DR expression and clinical tolerance. Observations: Low mHLA-DR pretreatment expression (26.7%) was observed. IFNy therapy leading to a rapid increase in mHLA-DR expression (83.1%). Conclusions: Severe ARDS in a COVID-19 patient has a deep reduction in mHLA-DR expression concomitantly with secondary infections. The unique IFNy injection was safe and led to a sharp increase in the expression of mHLA-DR. Based on immune and infection monitoring, more cases of severe COVID-19 patients with low mHLA-DR should be treated by IFNy to test the clinical effectiveness.