CRP/CD11b ratio: a novel parameter for detecting gram-positive sepsis

Biomarkers of sepsis: time for a reappraisal

INTRODUCTION

Sepsis biomarkers can have important diagnostic, therapeutic, and prognostic functions. In a previous review, we identified 3370 references reporting on 178 different biomarkers related to sepsis. In the present review, we evaluate the progress in the research of sepsis biomarkers.

METHODS

Using the same methodology as in our previous review, we searched the PubMed database from 2009 until September 2019 using the terms "Biomarker" AND "Sepsis." There were no restrictions by age or language, and all studies, clinical and experimental, were included.

RESULTS

We retrieved a total of 5367 new references since our previous review. We identified 258 biomarkers, 80 of which were new compared to our previous list. The majority of biomarkers have been evaluated in fewer than 5 studies, with 81 (31%) being assessed in just a single study. Apart from studies of C-reactive protein (CRP) or procalcitonin (PCT), only 26 biomarkers have been assessed in clinical studies with more than 300 participants. Forty biomarkers have been compared to PCT and/or CRP for their diagnostic value; 9 were shown to have a better diagnostic value for sepsis than either or both of these biomarkers. Forty-four biomarkers have been evaluated for a role in answering a specific clinical question rather than for their general diagnostic or prognostic properties in sepsis.

CONCLUSIONS

The number of biomarkers being identified is still increasing although at a slower rate than in the past. Most of the biomarkers have not been well-studied; in particular, the clinical role of these biomarkers needs to be better evaluated.

Neutrophil CD64, C-reactive protein, and procalcitonin in the identification of sepsis in the ICU - Post-test probabilities

PURPOSE

We were interested in whether C-reactive protein (CRP) and procalcitonin (PCT) distinguish sepsis from non-septic controls and whether a combination of CRP, PCT, and neutrophil CD64 improves identification of sepsis in the intensive care unit (ICU).

MATERIALS AND METHODS

We analyzed the CRP and PCT concentrations from 27 patients with sepsis and 15 ICU controls. In addition, CD64 on neutrophils was measured using quantitative flow cytometry. We present a multiple marker analysis for sepsis diagnostics combining neutrophil CD64, CRP, and PCT using post-test analysis.

RESULTS

The CRP and PCT values separated sepsis and non-septic ICU patients. In post-test analysis, CRP provided a positive probability of 0.48 and a negative probability of 0.053 for sepsis in the ICU; while, the corresponding values were 0.35 and 0.0059, respectively, for PCT and 0.62 and 0.0013, respectively, for neutrophil CD64. When neutrophil CD64 was analyzed with PCT and CRP, the probabilities were 0.98 and <0.001, respectively.

CONCLUSIONS

Neutrophil CD64 expression was superior to PCT and CRP for the identification of sepsis in ICU. Positive post-test probability for any combinations of simultaneously analyzed CRP, PCT and CD64 showed improved diagnostic accuracy for sepsis. This approach may be useful for guiding antibiotic treatment in ICU.

Variation of Circulating Inflammatory Mediators in Staphylococcus aureus and Escherichia coli Bloodstream Infection

Background

The aim of this study was to examine the behavior of circulating inflammatory mediators and to exclude gram-positive from gram-negative bloodstream infections. Results may be helpful in selection of optimal specific antibiotic therapies.

Material/Methods

Mice (25–27 g) were randomized to 3 groups infected with Staphylococcus aureus (S. aureus) ATCC 25923, Escherichia coli (E. coli) ATCC 25922, or phosphate-buffered saline (PBS). The white blood cell count (WBC) and the concentrations of serum C-reactive protein (CRP), procalcitonin (PCT), interleukin (IL)-1α, IL-1β, IL-6, IL-10, monocyte chemotactic protein-1 (MCP-1), and macrophage inflammatory protein-1α (MIP-1α) were detected in blood samples at different time intervals after intravenous tail injection.

Results

The results showed that compared to the control mice, infected animals exhibited significantly higher levels of all mediators after bacterial infection. Moreover, compared to the mice that received S. aureus, animals with E. coli infection showed significantly greater increases in serum IL-1α, IL-1β, IL-6, MCP-1, and MIP-1α levels.

Conclusions

These results suggest that the use of the analyzed serum markers at an early stage of bloodstream infection may give useful information for the clinician to distinguish gram-negative from gram-positive infections.

Kinetics of leukocyte CD11b and CD64 expression in severe sepsis and non-infectious critical care patients

BACKGROUND

Leukocyte surface molecules may improve sepsis diagnostics. Our aim was to study whether monocyte and neutrophil CD11b and CD64 expression differs between patients with severe sepsis (including septic shock) and intensive care unit (ICU) controls, and also to investigate the expression kinetics in patient groups.

METHODS

Monocyte and neutrophil CD11b and CD64 expression was analyzed in 27 patients with severe sepsis, 7 off-pump coronary artery bypass (OPCAB) patients, and 8 ICU patients without systemic inflammation in the beginning of the treatment using quantitative flow cytometry. Blood samples were collected within 48 h of the beginning of severe sepsis, at admission to the ICU for non-systemic inflammatory response syndrome patients, and on the day of surgery before the skin incision for OPCAB patients, and on 2 consecutive days for all patients. Ten healthy individuals served as controls.

RESULTS

Monocyte and neutrophil CD11b and neutrophil CD64 expression was higher in severe sepsis patients compared with the other groups (P < 0.05). In severe sepsis, the expression decreased over time (P < 0.05). In OPCAB patients, the monocyte and neutrophil CD64 expression increased after surgery (P < 0.05). Neutrophil CD64 expression had the highest and statistically significant area under curves (AUC) values for identification of severe sepsis during 3 consecutive days, the highest AUC being 0.990 on D0.

CONCLUSION

Neutrophil CD64 as well as neutrophil and monocyte CD11b expressions were highest in severe sepsis compared with non-infectious conditions, and thus analyses of their expression may be promising approach for sepsis diagnosis in ICU population.

Use of complement regulators, CD35, CD46, CD55, and CD59, on leukocytes as markers for diagnosis of viral and bacterial infections

Several complement regulatory proteins exist on self-cells to prevent damage by the serum complement system. In the present study, we aimed to perform quantitative analysis of membrane-bound complement regulators, CR1 (CD35), MCP (CD46), DAF (CD55), and MIRL (CD59), on peripheral blood neutrophils, monocytes, and lymphocytes from healthy controls (n=36) and febrile patients diagnosed with either bacterial (n=21) or viral (n=26) infections. Our results show that: (a) increased CD35 and CD55 levels on neutrophils and monocytes present potent markers of bacterial infection, (b) increased expression of CD46 on monocytes is an indicator of viral infection, and (c) increased CD59 expression on neutrophils and monocytes is a general infection marker. Additionally, CD19-positive B-lymphocytes represent practically the only lymphocyte population capable of expressing CD35. We further developed two novel clinical flow cytometric markers (indices), specifically, clinical mononucleosis (CM)-INDEX (incorporating CD35, CD55, and CD59 expression on lymphocytes) and clinical bacterial infection (CBI)-INDEX (incorporating CD35 and CD55 expression on neutrophils and lymphocytes), for the effective detection of viral mononucleosis and bacterial infection, respectively. In summary, bacterial and viral infections induce different expression patterns of membrane-bound complement regulators in human leukocytes, which may be effectively exploited in clinical differential diagnosis.

Modulation of acute lung injury by integrins

Acute lung injury is a common disorder with a high mortality rate, but previous efforts to develop drugs to treat this disorder have been unsuccessful. In an effort to develop more effective treatments, we have been studying the molecular pathways that regulate the dysfunction of alveolar epithelial cells and endothelial cells that serve as a final common pathway leading to alveolar flooding. Using integrin subunit knockout mice and antibodies we developed by immunizing these mice, we have found important and distinct roles for the αvβ6 integrin on epithelial cells and the αvβ5 integrin on endothelial cells in mediating increases in alveolar permeability in multiple models of acute lung injury. We have also found therapeutic effects of αvβ5 inhibition in two models of septic shock even when the antibody was administered to animals that were obviously ill. These results identify αvβ6 and αvβ5 as promising therapeutic targets for the treatment of acute lung injury and septic shock.

Bacterial infections, DNA virus infections, and RNA virus infections manifest differently in neutrophil receptor expression

Treating viral illnesses or noninfective causes of inflammation with antibiotics is ineffective and contributes to the development of antibiotic resistance, toxicity, and allergic reactions, leading to increasing medical costs. A major factor behind unnecessary use of antibiotics is, of course, incorrect diagnosis. For this reason, timely and accurate information on whether the infection is bacterial in origin would be highly beneficial. In this paper we will present our recent studies on the expression of opsonin receptors on phagocytes. The analysis of the expression levels of FcγRI, CR1, and CR3, along with CRP and ESR data, provides a novel application to the diagnosis of infectious and inflammatory diseases. The best clinical benefit will be obtained when the individual variables are combined to generate the CIS point method for a bacterial infection marker, DNAVS point for differentiating between DNA and RNA virus infections, and CRP/CD11b ratio for a marker of Gram-positive sepsis.

The real-time-based assessment of the microbial killing by the antimicrobial compounds of neutrophils

A recombinant Escherichia coli K-12 strain, transformed with a modified bacterial luciferase gene (luxABCDE) from Photorhabdus luminescens, was constructed in order to monitor the activity of various antimicrobial agents on a real-time basis. This E. coli-lux emitted, without any addition of substrate, constitutive bioluminescence (BL), which correlated to the number of viable bacterial cells. The decrease in BL signal correlated to the number of killed bacterial cells. Antimicrobial activity of hydrogen peroxide (H₂O₂) and myeloperoxidase (MPO) was assessed. In high concentrations, H₂O₂ alone had a bacteriocidic function and MPO enhanced this killing by forming hypochlorous acid (HOCl). Taurine, the known HOCl scavenger, blocked the killing by MPO. When E. coli-lux was incubated with neutrophils, similar killing kinetics was recorded as in H₂O₂/MPO experiments. The opsonization of bacteria enhanced the killing, and the maximum rate of the MPO release from lysosomes coincided with the onset of the killing.

Analysis of the temperature affects on leukocyte surface antigen expression

Flow cytometric analysis of leukocyte surface antigens has been used to characterize infectious and septic processes in patients. We wanted to investigate how the sampling and processing temperature, the anticoagulant used, and the storage of the sample influence leukocyte immunophenotyping. Four blood samples, two using acid citrate dextrose and two using heparin as an anticoagulant, were taken from five intensive-care unit patients with severe sepsis and five healthy volunteers. The samples were collected, stored, and processed either at +4°C or at room temperature (RT). The samples were processed for flow cytometric analysis within 1  hr of collection or after 6 or 24  hr storage. The surface antigens of interest were neutrophilic CD11b and CD64, monocytic CD11b, CD14, CD40, CD64, CD80 and HLA-DR, and lymphocytic CD69 (separately in CD4+ and CD8+ T cells, B cells, and natural killer cells). The fluorescence intensities were higher at RT than at +4°C. During storage the intensities increased at RT, but at +4°C there were only minor changes. The effects were similar with both anticoagulants studied. According to our results, flow cytometric analysis of leukocyte surface antigen expressions should be performed using +4°C temperature throughout the process and within 6  hr.