Biofilm Formation by Pseudomonas aeruginosa in a Novel Septic Arthritis Model

Exploring the Microbial Landscape of Bone and Joint Infections: An Analysis Using 16S rRNA Metagenome Sequencing

Background

Bone and joint infections (BJIs) are challenging to diagnose. This study evaluated the utility of 16S rRNA gene sequencing in diagnosing BJIs, comparing it with conventional bacterial culture to explore microbial diversity in orthopedic infections.

Methods

Thirty patients with BJIs were enrolled from January 2019 to September 2020 at a single orthopedic center. Diagnoses were based on the Musculoskeletal Infection Society standards. DNA extraction, 16S rRNA sequencing, and microbial composition analysis were performed. Conventional bacterial culture results were compared with metagenomics detection, and associations with blood routine and biochemical test factors were analyzed.

Results

The study enrolled 30 patients with BJIs. Traditional bacterial culture successfully identified pathogens in 60% (18/30) of cases, predominantly Staphylococcus aureus. In contrast, 16S rRNA metagenomics sequencing revealed distinct microorganisms in all cases, it unveiled a diverse microbial landscape. The correlation between bacterial culture and metagenomics detection showcased both concordance and discrepancies. Consistency of detection between the two methods showed that metagenomics detection detected the same genus or species in 14 (87.5%) of the 16 samples identified as species by bacterial culture. In nearly half of the patients with negative cultures, pathogenic microorganisms were detected, highlighting the capability of 16S rRNA sequencing to identify microorganisms, even in samples with negative or unidentified culture results. Moreover, no significant correlation was observed between bacterial culture, metagenomics detection and the factors of blood routine and biochemical test.

Conclusion

This study deepens our understanding of the microbial complexity in BJIs. While traditional culture methods are cost-effective and practical, 16S rRNA gene sequencing proves valuable for complementary microbial analysis, particularly when traditional methods fail or rapid identification is critical. This emerging diagnostic approach can enhance the accuracy and speed of pathogen identification, enabling more effective interventions in the management of BJIs.

The role of extracellular structures in Clostridioides difficile biofilm formation

C. difficile infection (CDI) is a costly and increasing burden on the healthcare systems of many developed countries due to the high rates of nosocomial infections. Despite the availability of several antibiotics with high response rates, effective treatment is hampered by recurrent infections. One potential mechanism for recurrence is the existence of C. difficile biofilms in the gut which persist through the course of antibiotics. In this review, we describe current developments in understanding the molecular mechanisms by which C. difficile biofilms form and are stabilized through extracellular biomolecular interactions.

Genome characterization of a uropathogenic Pseudomonas aeruginosa isolate PA_HN002 with cyclic di-GMP-dependent hyper-biofilm production

Pseudomonas aeruginosa can cause various types of infections and is one of the most ubiquitous antibiotic-resistant pathogens found in healthcare settings. It is capable of adapting to adverse conditions by transforming its motile lifestyle to a sessile biofilm lifestyle, which induces a steady state of chronic infection. However, mechanisms triggering the lifestyle transition of P. aeruginosa strains with clinical significance are not very clear. In this study, we reported a recently isolated uropathogenic hyper-biofilm producer PA_HN002 and characterized its genome to explore genetic factors that may promote its transition into the biofilm lifestyle. We first showed that high intracellular c-di-GMP content in PA_HN002 gave rise to its attenuated motilities and extraordinary strong biofilm. Reducing the intracellular c-di-GMP content by overexpressing phosphodiesterases (PDEs) such as BifA or W909_14950 converted the biofilm and motility phenotypes. Whole genome sequencing and comprehensive analysis of all the c-di-GMP metabolizing enzymes led to the identification of multiple mutations within PDEs. Gene expression assays further indicated that the shifted expression profile of c-di-GMP metabolizing enzymes in PA_HN002 might mainly contribute to its elevated production of intracellular c-di-GMP and enhanced biofilm formation. Moreover, mobile genetic elements which might interfere the endogenous regulatory network of c-di-GMP metabolism in PA_HN002 were analyzed. This study showed a reprogrammed expression profile of c-di-GMP metabolizing enzymes which may promote the pathoadaption of clinical P. aeruginosa into biofilm producers.

Decellularized Avian Cartilage, a Promising Alternative for Human Cartilage Tissue Regeneration

Articular cartilage defects, and subsequent degeneration, are prevalent and account for the poor quality of life of most elderly persons; they are also one of the main predisposing factors to osteoarthritis. Articular cartilage is an avascular tissue and, thus, has limited capacity for healing and self-repair. Damage to the articular cartilage by trauma or pathological causes is irreversible. Many approaches to repair cartilage have been attempted with some potential; however, there is no consensus on any ideal therapy. Tissue engineering holds promise as an approach to regenerate damaged cartilage. Since cell adhesion is a critical step in tissue engineering, providing a 3D microenvironment that recapitulates the cartilage tissue is vital to inducing cartilage regeneration. Decellularized materials have emerged as promising scaffolds for tissue engineering, since this procedure produces scaffolds from native tissues that possess structural and chemical natures that are mimetic of the extracellular matrix (ECM) of the native tissue. In this work, we present, for the first time, a study of decellularized scaffolds, produced from avian articular cartilage (extracted from Gallus Gallus domesticus), reseeded with human chondrocytes, and we demonstrate for the first time that human chondrocytes survived, proliferated and interacted with the scaffolds. Morphological studies of the decellularized scaffolds revealed an interconnected, porous architecture, ideal for cell growth. Mechanical characterization showed that the decellularized scaffolds registered stiffness comparable to the native cartilage tissues. Cell growth inhibition and immunocytochemical analyses showed that the decellularized scaffolds are suitable for cartilage regeneration.