A Broad-Spectrum Infection Diagnostic that Detects Pathogen-Associated Molecular Patterns (PAMPs) in Whole Blood

Recombinant mannan-binding lectin magnetic beads increase pathogen detection in immunocompromised patients

The microbiological diagnosis of infection for hematological malignancy patients receiving chemotherapy or allogeneic hematopoietic stem cell transplantation (allo-HSCT) patients relies primarily on standard microbial culture, especially blood culture, which has many shortcomings, such as having low positive rates, being time-consuming and having a limited pathogenic spectrum. In this prospective observational self-controlled test accuracy study, blood, cerebrospinal fluid (CSF), and bronchoalveolar lavage fluid (BALF) samples were collected from chemotherapy or allo-HSCT patients with clinical symptoms of infections who were hospitalized at Peking University First Hospital. Possible pathogens were detected by the method based on recombinant mannan-binding lectin (MBL) magnetic bead enrichment (M1 method) and simultaneously by a standard method. The analytical sensitivity of M1 method was close to that of standard culture method. Besides, the turn-around time of M1-method was significantly shorter than that of standard culture method. Moreover, the M1 method also added diagnostic value through the detection of some clinically relevant microbes missed by the standard method. M1 method could significantly increase the detection efficiency of pathogens (including bacteria and fungi) in immunocompromised patients. KEY POINTS: • The detection results of M1-method had a high coincidence rate with that of standard method • M1 method detected many pathogens which had not been found by standard clinic method.

S9.6-based hybrid capture immunoassay for pathogen detection

The detection of pathogens is critical for clinical diagnosis and public health surveillance. Detection is usually done with nucleic acid-based tests (NATs) and rapid antigen tests (e.g., lateral flow assays [LFAs]). Although NATs are more sensitive and specific, their use is often limited in resource-poor settings due to specialized requirements. To address this limitation, we developed a rapid DNA-RNA Hybrid Capture immunoassay (HC) that specifically detects RNA from pathogens. This assay utilizes a unique monoclonal antibody, S9.6, which binds DNA-RNA hybrids. Biotinylated single-stranded DNA probes are hybridized to target RNAs, followed by hybrid capture on streptavidin and detection with S9.6. The HC-ELISA assay can detect as few as 104 RNA molecules that are 2.2 kb in length. We also adapted this assay into a LFA format, where captured Bacillus anthracis rpoB RNA of 3.5 kb length was detectable from a bacterial load equivalent to 107 CFU per 100 mg of mouse tissue using either HC-ELISA or HC-LFA. Importantly, we also demonstrated the versatility of HC by detecting other pathogens, including SARS-CoV-2 and Toxoplasma gondii, showing its potential for broad pathogen detection. Notably, HC does not require amplification of the target nucleic acid and utilizes economical formats like ELISA and LFA, making it suitable for use in sentinel labs for pathogen detection or as a molecular tool in basic research laboratories. Our study highlights the potential of HC as a sensitive and versatile method for RNA-based pathogen detection.

Labeled TEMPO-Oxidized Mannan Differentiates Binding Profiles within the Collectin Families

Establishing the rapid and accurate diagnosis of sepsis is a key component to the improvement of clinical outcomes. The ability of analytical platforms to rapidly detect pathogen-associated molecular patterns (PAMP) in blood could provide a powerful host-independent biomarker of sepsis. A novel concept was investigated based on the idea that a pre-bound and fluorescent ligand could be released from lectins in contact with high-affinity ligands (such as PAMPs). To create fluorescent ligands with precise avidity, the kinetically followed TEMPO oxidation of yeast mannan and carbodiimide coupling were used. The chemical modifications led to decreases in avidity between mannan and human collectins, such as the mannan-binding lectin (MBL) and human surfactant protein D (SP-D), but not in porcine SP-D. Despite this effect, these fluorescent derivatives were captured by human lectins using highly concentrated solutions. The resulting fluorescent beads were exposed to different solutions, and the results showed that displacements occur in contact with higher affinity ligands, proving that two-stage competition processes can occur in collectin carbohydrate recognition mechanisms. Moreover, the fluorescence loss depends on the discrepancy between the respective avidities of the recognized ligand and the fluorescent mannan. Chemically modulated fluorescent ligands associated with a diversity of collectins may lead to the creation of diagnostic tools suitable for multiplex array assays and the identification of high-avidity ligands.

FcMBL magnetic bead-based MALDI-TOF MS rapidly identifies paediatric blood stream infections from positive blood cultures

Rapid identification of potentially life-threatening blood stream infections (BSI) improves clinical outcomes, yet conventional blood culture (BC) identification methods require ~24-72 hours of liquid culture, plus 24-48 hours to generate single colonies on solid media suitable for identification by mass spectrometry (MS). Newer rapid centrifugation techniques, such as the Bruker MBT-Sepsityper® IVD, replace culturing on solid media and expedite the diagnosis of BCs but frequently demonstrate reduced sensitivity for identifying clinically significant Gram-positive bacterial or fungal infections. This study introduces a protocol that utilises the broad-range binding properties of an engineered version of mannose-binding lectin linked to the Fc portion of immunoglobulin (FcMBL) to capture and enrich pathogens combined with matrix-assisted laser desorption-ionisation time-of-flight (MALDI-TOF) MS for enhanced infection identification in BCs. The FcMBL method identified 94.1% (64 of 68) of clinical BCs processed, with a high sensitivity for both Gram-negative and Gram-positive bacteria (94.7 and 93.2%, respectively). The FcMBL method identified more patient positive BCs than the Sepsityper® (25 of 25 vs 17 of 25), notably with 100% (3/3) sensitivity for clinical candidemia, compared to only 33% (1/3) for the Sepsityper®. Additionally, during inoculation experiments, the FcMBL method demonstrated a greater sensitivity, identifying 100% (24/24) of candida to genus level and 9/24 (37.5%) top species level compared to 70.8% (17/24) to genus and 6/24 to species (25%) using the Sepsityper®. This study demonstrates that capture and enrichment of samples using magnetic FcMBL-conjugated beads is superior to rapid centrifugation methods for identification of BCs by MALDI-TOF MS. Deploying the FcMBL method therefore offers potential clinical benefits in sensitivity and reduced turnaround times for BC diagnosis compared to the standard Sepsityper® kit, especially for fungal diagnosis.

Biomarkers for the Prediction and Judgement of Sepsis and Sepsis Complications: A Step towards precision medicine?

Sepsis and septic shock are a major public health concern and are still associated with high rates of morbidity and mortality. Whilst there is growing understanding of different phenotypes and endotypes of sepsis, all too often treatment strategies still only employ a “one-size-fits-all” approach. Biomarkers offer a unique opportunity to close this gap to more precise treatment approaches by providing insight into clinically hidden, yet complex, pathophysiology, or by individualizing treatment pathways. Predicting and evaluating systemic inflammation, sepsis or septic shock are essential to improve outcomes for these patients. Besides opportunities to improve patient care, employing biomarkers offers a unique opportunity to improve clinical research in patients with sepsis. The high rate of negative clinical trials in this field may partly be explained by a high degree of heterogeneity in patient cohorts and a lack of understanding of specific endotypes or phenotypes. Moving forward, biomarkers can support the selection of more homogeneous cohorts, thereby potentially improving study conditions of clinical trials. This may finally pave the way to a precision medicine approach to sepsis, septic shock and complication of sepsis in the future.

Materials‐based vaccines for infectious diseases

Infectious diseases that result from pathogen infection are among the leading causes of human death, with pathogens such as human immunodeficiency virus, malaria, influenza, and ongoing SARS‐COV‐2 viruses constantly threatening the global population. While the mechanisms behind various infectious diseases are not entirely clear and thus retard the development of effective therapeutics, vaccines have served as a universal approach to containing infectious diseases. However, conventional vaccines that solely consist of antigens or simply mix antigens and adjuvants have failed to control various highly infective or deadly pathogens. Biomaterials‐based vaccines have provided a promising solution due to their ability to synergize the function of antigens and adjuvants, troubleshoot delivery issues, home and manipulate immune cells in situ. In this review, we will summarize different types of materials‐based vaccines for generating cellular and humoral responses against pathogens and discuss the design criteria for amplifying the efficacy of materials‐based vaccines against infectious diseases.

This article is categorized under:

Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease

Biomolecules capturing live bacteria from clinical samples

Rapid phenotypic antimicrobial susceptibility testing (AST) requires the enrichment of live bacteria from patient samples, which is particularly challenging in the context of life-threatening bloodstream infections (BSIs) due to low bacterial titers. Over two decades, an extensive array of pathogen-specific biomolecules has been identified to capture live bacteria. The prevailing biomolecules are immune proteins of the complement system, antibodies, aptamers, phage proteins, and antimicrobial peptides. These biomolecules differ by their binder generation technologies and exhibit highly variable specificities, ranging from bacterial strains to most pathogenic bacteria. Here, we summarize how these diverse biomolecules were identified, list examples of successfully reported capture assays, and provide an outlook on the use of nanobodies raised against conserved surface-accessible proteins as promising biomolecules for pathogen capture.

Rapid Detection of Gram-Positive and -Negative Bacteria in Water Samples Using Mannan-Binding Lectin-Based Visual Biosensor

Waterborne bacterial infection is a health threat worldwide, making accurate and timely bacteria detection crucial to prevent waterborne disease outbreaks. Inspired by the intrinsic capability of mannan-binding lectin (MBL) in recognizing the pathogen-associated molecular patterns (PAMPs), a visual biosensor is developed here for the on-site detection of both Gram-positive and -negative bacteria. The biosensor was synthesized by immobilization of the MBL protein onto the blue carboxyl-functionalized polystyrene microparticles (PSM), which is then used in a two-step assay to detect bacterial cells in water samples. The first step involved a 20 min incubation following the MBL-PSM and calcium chloride solution addition to the samples. The second step was to add ethanol to the resultant blue mixture and observe the color change with the naked eye after 15 min. The biosensor had a binary (all-or-none) response, which in the presence of bacterial cells kept its blue color, while in their absence the color changed from blue to colorless. Testing the water samples spiked with four Gram-negative bacteria including Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa and two Gram-positive bacteria of Enterococcus faecalis and Staphylococcus aureus showed that the biosensor could detect all tested bacteria with a concentration as low as 10^1.5 CFU/ml. The performance of biosensor using the water samples from a water treatment plant also confirmed its capability to detect the pathogens in real-life water samples without the need for instrumentation.

Biomaterial vaccines capturing pathogen-associated molecular patterns protect against bacterial infections and septic shock

Most bacterial vaccines work for a subset of bacterial strains or require the modification of the antigen or isolation of the pathogen before vaccine development. Here we report injectable biomaterial vaccines that trigger potent humoral and T-cell responses to bacterial antigens by recruiting, reprogramming and releasing dendritic cells. The vaccines are assembled from regulatorily approved products and consist of a scaffold with absorbed granulocyte-macrophage colony-stimulating factor and CpG-rich oligonucleotides incorporating superparamagnetic microbeads coated with the broad-spectrum opsonin Fc-mannose-binding lectin for the magnetic capture of pathogen-associated molecular patterns from inactivated bacterial-cell-wall lysates. The vaccines protect mice against skin infection with methicillin-resistant Staphylococcus aureus, mice and pigs against septic shock from a lethal Escherichia coli challenge and, when loaded with pathogen-associated molecular patterns isolated from infected animals, uninfected animals against a challenge with different E. coli serotypes. The strong immunogenicity and low incidence of adverse events, a modular manufacturing process, and the use of components compatible with current good manufacturing practice could make this vaccine technology suitable for responding to bacterial pandemics and biothreats.

Novel Diagnostics and Therapeutics in Sepsis

Sepsis management demands early diagnosis and timely treatment that includes source control, antimicrobial therapy, and resuscitation. Currently employed diagnostic tools are ill-equipped to rapidly diagnose sepsis and isolate the offending pathogen, which limits the ability to offer targeted and lowest-toxicity treatment. Cutting edge diagnostics and therapeutics in development may improve time to diagnosis and address two broad management principles: (1) source control by removing the molecular infectious stimulus of sepsis, and (2) attenuation of the pathological immune response allowing the body to heal. This review addresses novel diagnostics and therapeutics and their role in the management of sepsis.

A single-tube sample preparation method based on a dual-electrostatic interaction strategy for molecular diagnosis of gram-negative bacteria

A single-tube method based on a dual-electrostatic interaction (EI) strategy for bacteria capture and DNA extraction was designed to enable the highly sensitive detection of nucleic acids. Specially designed magnetic nanoparticles were developed to meet the opposing requirements of a single-tube method, which exist between the strong EI required for efficient bacteria capture and the weak EI required for DNA extraction with minimal DNA adsorption. A dual-EI strategy for the single-tube (DESIGN) method was thus developed to integrate bacteria enrichment, bacteria cell lysis, and DNA recovery in a single tube, thereby minimizing precious sample loss and reducing handling time. Subsequently, we evaluated the performance with a variety of concentrations from 5 to 100 colony-forming units (CFU)/10 mL human urine and milk samples. The DESIGN method achieved the simple and sensitive detection of Salmonella enterica serovar Typhimurium in 10 mL of human urine and milk samples up to 5 CFU by quantitative PCR. Furthermore, the DESIGN method detected Brucella ovis and Escherichia coli from 10 mL of human urine with a detection limit up to 5 CFU/10 mL. Graphical abstract.

Innovative optofluidics and microscopy-based rapid analysis of pathogens

The timely knowledge and prescription of the most suitable antibiotic to treat bacterial infections is critical for the recovery of patients battling life-threatening bacterial infections. Unfortunately, current standard-of-care approaches relies on the empiric prescription of an antibiotic, as determination of the most effective antibiotic requires multiple time-consuming steps. These steps often include culturing of the bacterium responsible for infection and subsequent antibiotic susceptibility testing. Here we introduce an optofluidic technology that allows us to capture bacterial cells efficiently and rapidly from different biological samples and use the captured cells for rapid antibiotic selection thereby bypassing the need to culture the bacterium.

The challenge of recognising sepsis: Future nanotechnology solutions

The urgent need to start anti-infective therapeutic interventions in suspected sepsis, and the lack of specific time-critical diagnostic information often lead to the widespread administration of broad-spectrum antimicrobial therapies, increasing the risk of unwanted patient harms and contributing to rising pathogen antimicrobial resistance. Nanotechnology, which involves engineering at the nanoscale, allows for the bespoke development of diagnostic solutions with multi-functionality and high sensitivity that has the potential to help provide time-critical information to make more accurate diagnoses and treatment decisions for sepsis. Nanotechnologies also have the potential to improve upon the current strategies used for novel biomarker discovery. Here we describe some of the current limitations to identifying sepsis and explore the potential role for nanotechnology solutions.

Click-to-Capture: A method for enriching viable Staphylococcus aureus using bio-orthogonal labeling of surface proteins

Staphylococcus aureus is one of the principal causative agents of bacteremia which can progress to sepsis. Rapid diagnostic tests for identification and antibiotic resistance profiling of S. aureus would improve patient outcomes and antibiotic stewardship, but existing methods require a lengthy culture step to obtain enough material for testing. Complexity of the host matrix, where pathogenic microbes are often present, also interferes with many diagnostic methods. Here, we describe a straightforward and rapid method for enriching viable S. aureus using bio-orthogonal, or “click,” chemistry methods. Bacteria labeled in this manner can potentially be cultured, interrogated using molecular methods for pathogen identification, or used to test antibiotic susceptibility.

Odontogenic infection by Porphyromonas gingivalis exacerbates fibrosis in NASH via hepatic stellate cell activation

Odontogenic infection of Porphyromonas gingivalis (P.g.), a major periodontal pathogen, exacerbates pathological progression of non-alcoholic steatohepatitis (NASH). In this study, we aimed to clarify the detailed mechanism in which P.g. induced hepatic stellate cells (HSCs; key effector cells in liver fibrosis) activation. In the liver of high fat diet-induced NASH mouse model with P.g. odontogenic infection, immunolocalization of P.g. was detected. The number of hepatic crown-like structure, which was macrophage aggregation and related to liver fibrosis, was drastically increased and fibrosis area was also increased through upregulating immunoexpression of Phosphorylated Smad2 (key signaling molecule of TGF-β1) and Galectin-3. P.g.-secreted trypsin-like enzyme [gingipain; an activator of protease-activated receptor 2 (PAR2)] stimulated HSC proliferation and differentiation through Smad and ERK signaling induced by TGF-β1 produced from HSCs with P.g.-infection. Further, Galectin-3 produced from HSCs with P.g. infection and P.g.-derived LPS/lipoprotein stimulation stabilized TGFβ-receptor II resulting in increasing sensitivity for TGF-β1, finally leading to HSC differentiation via activating Smad and ERK signaling. In addition to them, hepatocytes (main component cells of liver) contributed to HSC activation through TGF-β1 and Galectin-3 production in paracrine manner. Collectively, P.g.-odontogenic infection exacerbates fibrosis of NASH by HSC activation through TGF-β1 and Gal-3 production from HSCs and hepatocytes.

Fluorescent Sensor Arrays Can Predict and Quantify the Composition of Multicomponent Bacterial Samples

Fast and reliable identification of infectious disease agents is among the most important challenges for the healthcare system. The discrimination of individual components of mixed infections represents a particularly difficult task. In the current study we further expand the functionality of a ratiometric sensor array technology based on small-molecule environmentally-sensitive organic dyes, which can be successfully applied for the analysis of mixed bacterial samples. Using pattern recognition methods and data from pure bacterial species, we demonstrate that this approach can be used to quantify the composition of mixtures, as well as to predict their components with the accuracy of ~80% without the need to acquire additional reference data. The described approach significantly expands the functionality of sensor arrays and provides important insights into data processing for the analysis of other complex samples.

Gastrointestinal Failure in Critically Ill Patients With Cirrhosis

Gastrointestinal failure (GIF) is frequent in patients managed in the intensive care units and manifests as gut paralysis or ileus. GIF is often associated with sepsis or multiorgan failure. In critically ill patients, the precipitating causes of GIF include inflammation, sepsis, electrolyte abnormalities, and acidosis. It is possible that GIF is associated with an increase in bacterial translocation, especially in those with cirrhosis and portal hypertension, and this may play a significant pathogenic or prognostic role in acute-on-chronic liver failure (ACLF). The critical care literature suggests that GIF is associated with a higher mortality risk. In this review, we summarize the evidence for a potential association between GIF and ACLF and propose treatment options for the management of GIF. Moreover, we suggest GIF to be considered as another organ failure when the severity of ACLF is assessed.

Activation of multiple Toll-like receptors serves different roles in sepsis-induced acute lung injury

The activation of Toll-like receptors (TLRs) is involved in the innate immune response and the acute inflammatory response following sepsis-induced acute lung injury (ALI). Increasing evidence has demonstrated that sepsis-induced ALI may be closely associated with several abnormal TLRs, activated by components of microorganisms. However, the number of TLRs involved in this process and the extent of their involvement has not been fully elucidated. The current study examined the simultaneous activation of four TLRs closely associated with sepsis-induced ALI. The results demonstrated that in contrast to the sham-operated group, the mRNA and protein expression levels of TLR2/4/9 were significantly increased in the cecal ligation and puncture (CLP)-operated group. In addition, TLR2^-/-, TLR3^-/-, TLR4^-/- and TLR9^-/- C57BL/6 mice were used to establish a CLP-induced ALI animal model and measure the expression levels of TNF-α and IL-6 in plasma and lung tissue samples. The expression of both TNF-α and IL-6 were significantly decreased in TLR2^-/-, TLR4^-/- and TLR9^-/- mice compared with WT mice. In addition, the results revealed that knockdown of TLR2, 4 or 9 decreased immune cell infiltration and therefore may attenuate lung injury. Furthermore, the overall survival was significantly increased in TLR2^-/-, 4^-/- and 9^-/- CLP-induced ALI mice compared with the WT CLP-induced ALI mice. However, there was no statistical significance between TLR3^-/- CLP-induced ALI and WT CLP-induced ALI in the current study. Taken together, these results suggest that in the sepsis-induced ALI model, several TLRs are upregulated and participate in the inflammatory response. Therefore, inhibition of multiple TLRs including TLR2, 9, and especially TLR4 simultaneously, but not TLR3, may be a potential therapeutic target for the treatment of sepsis-induced ALI.

Direct detection of bacteremia by exploiting host-pathogen interactions of lipoteichoic acid and lipopolysaccharide

Bacteremia is a leading cause of death in sub-Saharan Africa where childhood mortality rates are the highest in the world. The early diagnosis of bacteremia and initiation of treatment saves lives, especially in high-disease burden areas. However, diagnosing bacteremia is challenging for clinicians, especially in children presenting with co-infections such as malaria and HIV. There is an urgent need for a rapid method for detecting bacteremia in pediatric patients with co-morbidities to inform treatment. In this manuscript, we have developed and clinically validated a novel method for the direct detection of amphiphilic pathogen biomarkers indicative of bacteremia, directly in aqueous blood, by mimicking innate immune recognition. Specifically, we have exploited the interaction of amphiphilic pathogen biomarkers such as lipopolysaccharides (LPS) from Gram-negative bacteria and lipoteichoic acids (LTA) from Gram-positive bacteria with host lipoprotein carriers in blood, in order to develop two tailored assays – lipoprotein capture and membrane insertion – for their direct detection. Our assays demonstrate a sensitivity of detection of 4 ng/mL for LPS and 2 ng/mL for LTA using a waveguide-based optical biosensor platform that was developed at LANL. In this manuscript, we also demonstrate the application of these methods for the detection of LPS in serum from pediatric patients with invasive Salmonella Typhimurium bacteremia (n = 7) and those with Staphylococcal bacteremia (n = 7) with 100% correlation with confirmatory culture. Taken together, these results demonstrate the significance of biochemistry in both our understanding of host-pathogen biology, and development of assay methodology, as well as demonstrate a potential new approach for the rapid, sensitive and accurate diagnosis of bacteremia at the point of need.

Broad-spectrum capture of clinical pathogens using engineered Fc-mannose-binding lectin enhanced by antibiotic treatment

Background: Fc-mannose-binding lectin (FcMBL), an engineered version of the blood opsonin MBL that contains the carbohydrate recognition domain (CRD) and flexible neck regions of MBL fused to the Fc portion of human IgG1, has been shown to bind various microbes and pathogen-associated molecular patterns (PAMPs). FcMBL has also been used to create an enzyme-linked lectin sorbent assay (ELLecSA) for use as a rapid (<1 h) diagnostic of bloodstream infections. Methods: Here we extended this work by using the ELLecSA to test FcMBL's ability to bind to more than 190 different isolates from over 95 different pathogen species. Results: FcMBL bound to 85% of the isolates and 97 of the 112 (87%) different pathogen species tested, including bacteria, fungi, viral antigens and parasites. FcMBL also bound to PAMPs including, lipopolysaccharide endotoxin (LPS) and lipoteichoic acid (LTA) from Gram-negative and Gram-positive bacteria, as well as lipoarabinomannan (LAM) and phosphatidylinositol mannoside 6 (PIM 6) from Mycobacterium tuberculosis. Conclusions: The efficiency of pathogen detection and variation between binding of different strains of the same species could be improved by treating the bacteria with antibiotics, or mechanical disruption using a bead mill, prior to FcMBL capture to reveal previously concealed binding sites within the bacterial cell wall. As FcMBL can bind to pathogens and PAMPs in urine as well as blood, its broad-binding capability could be leveraged to develop a variety of clinically relevant technologies, including infectious disease diagnostics, therapeutics, and vaccines.

A plasma ion bombardment process enabling reagent-free covalent binding of multiple functional molecules onto magnetic particles

We report a plasma immersion ion implantation process for functionalizing polymer coated magnetic particles, converting them into a universal covalent binding platform for the simultaneous binding of multiple molecular agents without the need for specialised chemical linking groups. As an example, we demonstrate the improvement of wettability and the control of surface charge of polystyrene coated magnetic particles, enhancing biomolecule attachment density with strong covalent binding. We demonstrate the preparation of multifunctional magnetic particles where two or more types of molecule are co-immobilized. This enables a platform technology with simultaneous multiple covalent binding of molecules drawn from oligonucleotides, antibodies and enzymes suitable for targeted nanoparticle diagnostic and therapies.

Pathogen enrichment from human whole blood for the diagnosis of bloodstream infection: Prospects and limitations

Blood culture represents the current reference method for the detection of bacteria or fungi in the circulation. To accelerate pathogen identification, molecular diagnostic methods, mainly based on polymerase chain reaction (PCR), have been introduced to ensure early and targeted antibiotic treatment of patients suffering from bloodstream infection. Still, these approaches suffer from a lack of sensitivity and from inhibition of PCR in a number of clinical samples, leading to false negative results. To overcome these limitations, various approaches aiming at the enrichment of pathogens from larger blood volumes prior to the extraction of pathogen DNA, thereby also depleting factors interfering with PCR, have been developed. Here, we provide an overview of current systems for diagnosing bloodstream infection, with a focus on approaches for pre-analytical pathogen enrichment, and highlight emerging applications of pathogen depletion for therapeutic purposes as a potential adjunctive treatment of sepsis patients.

Comparison of the Performance Between Sepsis-1 and Sepsis-3 in ICUs in China: A Retrospective Multicenter Study

The definition of sepsis was updated to sepsis-3 in February 2016. However, the performance of the previous and new definition of sepsis remains unclear in China. This was a retrospective multicenter study in six intensive care unit (ICUs) from five university-affiliated hospitals to compare the performance between sepsis-1 and sepsis-3 in China. From May 1, 2016 to June 1, 2016, 496 patients were enrolled consecutively. Data were extracted from the electronic clinical records. We evaluated the performance of sepsis-1 and sepsis-3 by measuring the area under the receiver operating characteristic curves (AUROC) to predict 28-day mortality rates. Of 496 enrolled patients, 186 (37.5%) were diagnosed with sepsis according to sepsis-1, while 175 (35.3%) fulfilled the criteria of sepsis-3. The AUROC of systemic inflammatory response syndrome (SIRS) is significantly smaller than that of sequential organ failure assessment (SOFA) (0.55 [95% confidence interval, 0.46–0.64] vs. 0.69 (95% confidence interval, 0.61–0.77], P = 0.008) to predict 28-day mortality rates of infected patients. Moreover, 5.9% infected patients (11 patients) were diagnosed as sepsis according to sepsis-1 but not to sepsis-3. The APACHE II, SOFA scores, and mortality rate of the 11 patients were significantly lower than of patients whose sepsis was defined by both the previous and new criteria (8.6±3.5 vs. 16.3±6.2, P =  < 0.001; 1 (0–1) vs. 6 (4–8), P = <0.001; 0.0 vs. 33.1%, P = 0.019). In addition, the APACHE II, length of stay in ICU, and 28-day mortality rate of septic patients rose gradually corresponding with the raise in SOFA score (but not the SIRS score). Sepsis-3 performed better than sepsis-1 in the study samples in ICUs in China.

Emerging Microtechnologies and Automated Systems for Rapid Bacterial Identification and Antibiotic Susceptibility Testing

Rapid bacterial identification (ID) and antibiotic susceptibility testing (AST) are in great demand due to the rise of drug-resistant bacteria. Conventional culture-based AST methods suffer from a long turnaround time. By necessity, physicians often have to treat patients empirically with antibiotics, which has led to an inappropriate use of antibiotics, an elevated mortality rate and healthcare costs, and antibiotic resistance. Recent advances in miniaturization and automation provide promising solutions for rapid bacterial ID/AST profiling, which will potentially make a significant impact in the clinical management of infectious diseases and antibiotic stewardship in the coming years. In this review, we summarize and analyze representative emerging micro- and nanotechnologies, as well as automated systems for bacterial ID/AST, including both phenotypic (e.g., microfluidic-based bacterial culture, and digital imaging of single cells) and molecular (e.g., multiplex PCR, hybridization probes, nanoparticles, synthetic biology tools, mass spectrometry, and sequencing technologies) methods. We also discuss representative point-of-care (POC) systems that integrate sample processing, fluid handling, and detection for rapid bacterial ID/AST. Finally, we highlight major remaining challenges and discuss potential future endeavors toward improving clinical outcomes with rapid bacterial ID/AST technologies.