A Prophage in Diabetic Foot Ulcer-Colonizing Staphylococcus aureus Impairs Invasiveness by Limiting Intracellular Growth

Advances in the targeted theragnostics of osteomyelitis caused by Staphylococcus aureus

Bone infections caused by Staphylococcus aureus may lead to an inflammatory condition called osteomyelitis, which results in progressive bone loss. Biofilm formation, intracellular survival, and the ability of S. aureus to evade the immune response result in recurrent and persistent infections that present significant challenges in treating osteomyelitis. Moreover, people with diabetes are prone to osteomyelitis due to their compromised immune system, and in life-threatening cases, this may lead to amputation of the affected limbs. In most cases, bone infections are localized; thus, early detection and targeted therapy may prove fruitful in treating S. aureus-related bone infections and preventing the spread of the infection. Specific S. aureus components or overexpressed tissue biomarkers in bone infections could be targeted to deliver active therapeutics, thereby reducing drug dosage and systemic toxicity. Compounds like peptides and antibodies can specifically bind to S. aureus or overexpressed disease markers and combining these with therapeutics or imaging agents can facilitate targeted delivery to the site of infection. The effectiveness of photodynamic therapy and hyperthermia therapy can be increased by the addition of targeting molecules to these therapies enabling site-specific therapy delivery. Strategies like host-directed therapy focus on modulating the host immune mechanisms or signaling pathways utilized by S. aureus for therapeutic efficacy. Targeted therapeutic strategies in conjunction with standard surgical care could be potential treatment strategies for S. aureus-associated osteomyelitis to overcome antibiotic resistance and disease recurrence. This review paper presents information about the targeting strategies and agents for the therapy and diagnostic imaging of S. aureus bone infections.

The ROSA-Like Prophage Colonizing Staphylococcus aureus Promotes Intracellular Survival, Biofilm Formation, and Virulence in a Chronic Wound Environment

BACKGROUND

The transition from colonization to invasion is critical in diabetic foot ulcer (DFU). Staphylococcus aureus can colonize DFU, or invade the underlying tissues, causing serious infections. The ROSA-like prophage has previously been implicated in strain colonization characteristics of S aureus isolates in uninfected ulcers.

METHODS

In this study, we investigated this prophage in the S aureus-colonizing strain using an in vitro chronic wound medium mimicking the chronic wound environment.

RESULTS

Chronic wound medium reduced bacterial growth and increased biofilm formation and virulence in a zebrafish model.

CONCLUSIONS

The ROSA-like prophage promoted intracellular survival of S aureus-colonizing strain in macrophages, keratinocytes, and osteoblasts.

Preclinical study of diabetic foot ulcers: From pathogenesis to vivo/vitro models and clinical therapeutic transformation

Diabetic foot ulcer (DFU), a common intractable chronic complication of diabetes mellitus (DM), has a prevalence of up to 25%, with more than 17% of the affected patients at risk of amputation or even death. Vascular risk factors, including vascular stenosis or occlusion, dyslipidemia, impaired neurosensory and motor function, and skin infection caused by trauma, all increase the risk of DFU in patients with diabetes. Therefore, diabetic foot is not a single pathogenesis. Preclinical studies have contributed greatly to the pathogenesis determination and efficacy evaluation of DFU. Many therapeutic tools are currently being investigated using DFU animal models for effective clinical translation. However, preclinical animal models that completely mimic the pathogenesis of DFU remain unexplored. Therefore, in this review, the preparation methods and evaluation criteria of DFU animal models with three major pathological mechanisms: neuropathy, angiopathy and DFU infection were discussed in detail. And the advantages and disadvantages of various DFU animal models for clinical sign simulation. Furthermore, the current status of vitro models of DFU and some preclinical studies have been transformed into clinical treatment programs, such as medical dressings, growth factor therapy, 3D bioprinting and pre-vascularization, Traditional Chinese Medicine treatment. However, because of the complexity of the pathological mechanism of DFU, the clinical transformation of DFU model still faces many challenges. We need to further optimize the existing preclinical studies of DFU to provide an effective animal platform for the future study of pathophysiology and clinical treatment of DFU.

Colonizing microbiota is associated with clinical outcomes in diabetic wound healing

With the development of society and the improvement of life quality, more than 500 million people are affected by diabetes. More than 10 % of people with diabetes will suffer from diabetic wounds, and 80 % of diabetic wounds will reoccur, so the development of new diabetic wound treatments is of great importance. The development of skin microbe research technology has gradually drawn people's attention to the complex relationship between microbes and diabetic wounds. Many studies have shown that skin microbes are associated with the outcome of diabetic wounds and can even be used as one of the indicators of wound prognosis. Skin microbes have also been found to have the potential to treat diabetic wounds. The wound colonization of different bacteria can exert opposing therapeutic effects. It is necessary to fully understand the skin microbes in diabetic wounds, which can provide valuable guidance for clinical diabetic wound treatment.

Bacterial Interactions in the Context of Chronic Wound Biofilm: A Review

Chronic wounds, defined by their resistance to care after four weeks, are a major concern, affecting millions of patients every year. They can be divided into three types of lesions: diabetic foot ulcers (DFU), pressure ulcers (PU), and venous/arterial ulcers. Once established, the classical treatment for chronic wounds includes tissue debridement at regular intervals to decrease biofilm mass constituted by microorganisms physiologically colonizing the wound. This particular niche hosts a dynamic bacterial population constituting the bed of interaction between the various microorganisms. The temporal reshuffle of biofilm relies on an organized architecture. Microbial community turnover is mainly associated with debridement (allowing transitioning from one major representant to another), but also with microbial competition and/or collaboration within wounds. This complex network of species and interactions has the potential, through diversity in antagonist and/or synergistic crosstalk, to accelerate, delay, or worsen wound healing. Understanding these interactions between microorganisms encountered in this clinical situation is essential to improve the management of chronic wounds.

Genotypic Characterization and Biofilm Production of Group B Streptococcus Strains Isolated from Bone and Joint Infections

Bone and joint infections (BJI) represent the second cause of invasive Group B Streptococcus (GBS) infections. Biofilm formation plays a major role in BJI. This study's aim was to analyze the genetic features and biofilm production of GBS strains. In six French laboratories, 77 GBS strains isolated from BJI and 57 strains from vaginal human colonization (Hcol) were characterized and compared by Multi-Locus Sequence Typing (MLST). PCR was used to search for the adhesins (bsaB, lmb, scpB, fbsA, fbsB, hvgA, bibA, bca, srr-1, and srr-2) and Pilus Islands (PI) related genes (PI-1, PI-2a, PI-2b). Biofilm production was studied by crystal violet assay. Strains were categorized into three groups, based on Specific Biofilm Formation (SBF) values defined as: weak, moderate, or strong producers. Molecular study revealed three major clonal complexes (CC) in BJI strains: CC1 (42%), CC23 (22%) and CC10 (14%). Several associations between CC and adhesin/pili were identified: CC1 with srr2, PI-1 + 2a; CC10 with srr-1, bca, PI-1 + 2a; CC17 with fbsB, hvgA, srr-2, PI-1+PI-2b; CC19 with bibA, srr-1, PI-1 + 2a; CC23 with fbsB, bibA, srr-1, PI-2a. The biofilm production was significantly different according to CC, adhesins and pili gene detection. CC10, CC23 and strains harboring fbsB produce more biofilm than CC1, PI-1 + 2a (independently). Finally, SBF values were significantly stronger for Hcol strains rather than for BJI strains (76% versus 40%). This study revealed that Hcol strains appeared to produce stronger biofilm than BJI strains, though they belonged to similar CCs and had the same adhesin and pili content. IMPORTANCE Bone and joint infections (BJI) are pathologies that can be life-threatening and result in compromised functional prognosis for patients. Relapses are common and often related to biofilm formation. Group B streptococci (GBS) BJI increased since the last decade. However, few data are available on this subject in the literature. Our study aims to highlight genotype and biofilm production of GBS isolates from BJI. Seventy-seven GBS strains isolated from BJI and 57 from asymptomatic human vaginal colonization were characterized by multilocus sequence typing (MLST), adhesins content, nature of the pili and the ability to form biofilm. Our results revealed that vaginal human colonization strains produced stronger biofilm than BJI strains, despite belonging to the same phylogenetic lineage and having the same adhesin and pili content.

Long-Term Intrahost Evolution of Staphylococcus aureus Among Diabetic Patients With Foot Infections

Staphylococcus aureus is one of the main pathogens isolated from diabetic foot infections (DFI). The purpose of this study was to evaluate the importance of the persistence of S. aureus in this environment and the possible modifications of the bacterial genome content over time. Molecular typing of S. aureus isolates cultured from patients with the same DFI over a 7-year study revealed a 25% rate of persistence of this species in 48 patients, with a short median persistence time of 12weeks (range: 4-52weeks). Non-specific clonal complexes were linked to this persistence. During the follow-up, bla genes were acquired in three cases, whereas some virulence markers were lost in all cases after a long period of colonization (21.5weeks). Only one patient (2%) had a long-term persistence of 48weeks. The genome sequencing of a clonal pair of early/late strains isolated in this patient showed mutations in genes encoding bacterial defence and two-component signal transduction systems. Although, this study suggests that the long-term persistence of S. aureus in DFI is a rare event, genomic evolution is observed, highlighting the low adaptive ability of S. aureus to the specific environment and stressful conditions of diabetic foot ulcers. These results provide the basis for better understanding of S. aureus dynamics during persistent colonization in chronic wounds.

Microbial Diversity of Chronic Wound and Successful Management of Traditional Chinese Medicine

Chronic ulcer, including diabetic ulcer, varicose ulcer, and pressure ulcer, negatively affects patients' quality of life. As microbiology plays an important role in the mechanism of pathology for chronic wound healing, this study concentrates on microecology environment of the wound and how Traditional Chinese Medicine (TCM) regulates wound bacteria. Method. The study took wound samples from 35 patients and analyzed bacteria variation before and after TCM treatment by 16s rRNA sequencing. All samples were evaluated from aspects of α-diversity, β-diversity, and Simpson's Diversity index. Result. After total DNA extraction, PCR, and 16S rRNA sequencing of wound bacteria from 35 individuals, it was discovered that younger patients with shorter course of disease have a higher microbial diversity and were easier to recover from ulcers. Additionally, gender also played a vital role in wound healing, and a significant microbial diversity existed between male and female patients. Conclusion. Patients with chronic ulcers achieved a positive effect after TCM treatment (skin-producing ointment). Mechanistically, TCM helped promote wound healing by regulating the wound microbiota.