Extracellular Vesicles: A Potential Biomarker for Quick Identification of Infectious Osteomyelitis

Abstract

Effective management of infectious osteomyelitis relies on timely microorganism identification and appropriate antibiotic therapy. Extracellular vesicles (EVs) carry protein and genetic information accumulated rapidly in the circulation upon infection. Rat osteomyelitis models infected by Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Escherichia coli were established for the present study. Serum EVs were isolated 3 days after infection. The size and number of serum EVs from infected rats were significantly higher than those from controls. In addition, bacterial aggregation assay showed that the S. aureus and E. coli formed large aggregates in response to the stimulation of serum EVs from S. aureus-infected and E. coli-infected rats, respectively. Treatment of EVs-S. epidermidis led to large aggregates of S. epidermidis and E. coli, whereas stimulation of EVs-P. aeruginosa to large aggregates of S. aureus and P. aeruginosa. To evaluate the changes in EVs in osteomyelitis patients, 28 patients including 5 S. aureus ones and 21 controls were enrolled. Results showed that the size and number of serum EVs from S. aureus osteomyelitis patients were higher than those from controls. Further analysis using receiver operating characteristic curves revealed that only the particle size might be a potential diagnostic marker for osteomyelitis. Strikingly, serum EVs from S. aureus osteomyelitis patients induced significantly stronger aggregation of S. aureus and a cross-reaction with P. aeruginosa. Together, these findings indicate that the size and number of serum EVs may help in the diagnosis of potential infection and that EVsbacteria aggregation assay may be a quick test to identify infectious microorganisms for osteomyelitis patients.

The Functional Heterogeneity of Neutrophil-Derived Extracellular Vesicles Reflects the Status of the Parent Cell

“…The EV-bacteria aggregates were characteristic for bacterial infections but were not present in non-infectious inflammation [ 131 ]. Similar results were reported in a rat osteomyelitis model and in patients with osteomyelitis, suggesting a selective aggregating ability of EVs with bacteria which were used to induce their production; however EVs showed some cross-reactivity with other bacteria as well [ 150 ]. It is also observed that alpha-2-macroglobulin positive EVs were present in higher amounts in survivors of pneumonia-related sepsis than non-survivors.…”

“…Although fMLP-induced PMN-EVs were able to bind bacteria via clusters of CR1 [ 110 ], no other receptor activation than Mac-1 resulted in antibacterial EV generation ( Figure 3 ) despite their ability to increase EV production related to spontaneous EV formation ( Figure 2 ). The aggregate forming ability of bacterial infection-induced PMN-EVs were later confirmed in septic patients [ 131 ] and in osteomyelitis patients [ 150 ]. Similar to bacteria-induced antibacterial EV formation, Shopova et al described antifungal PMN-EV release upon stimulation with opsonized A. fumigatus [ 122 ].…”

Transcriptome Profiling of Staphylococcus aureus Associated Extracellular Vesicles Reveals Presence of Small RNA-Cargo

“…In addition to eukaryotic sRNA in exosomes, circulating sRNA (ASdes) from Mycobacterium tuberculosis was found in patients suffering from active tuberculosis, implicating their role as diagnostic biomarkers (Fu et al, 2018 ). This makes us hypothesize that some of the sRNAs we have validated in EVs (RNAIII and SsrA) have a potential to be used as biomarkers for bloodstream infections (Bordeau et al, 2016 ), joint infections (osteomyelitis) (Deng et al, 2020 ), tissues infections (e.g., chronic biofilm infections) and/or bacterial persistence (Romilly et al, 2014 ; Schoenfelder et al, 2019 ). Identifying sRNAs as biomarkers should not be limited to pathogenic strains but also to nasal and other commensal strains.…”

Bacteria autoaggregation: how and why bacteria stick together

“…Organism-specific autoagglutinins eliciting visible autoaggregation can be utilized in disease diagnosis. Serum extracellular vesicles (EV) may mediate bacterial aggregation potentially specific enough to serve as a quick test to identify infection pathogens [ 71 ]. For example, serum-EVs from neutrophilic granulocytes/neutrophils isolated from osteomyelitis patients mediated aggregation of S. aureus ex vivo , albeit with weak cross-reaction with P. aeruginosa .…”