The microbiological characteristics of Staphylococcus aureus isolated from patients with native valve infective endocarditis

Evaluation of the 2023 Duke-ISCVID and 2023 Duke-ESC Clinical Criteria for the Diagnosis of Infective Endocarditis in a Multicenter Cohort of Patients With Staphylococcus aureus Bacteremia

BACKGROUND

The Duke criteria for infective endocarditis (IE) diagnosis underwent revisions in 2023 by the European Society of Cardiology (ESC) and the International Society for Cardiovascular Infectious Diseases (ISCVID). This study aims to assess the diagnostic accuracy of these criteria, focusing on patients with Staphylococcus aureus bacteremia (SAB).

METHODS

This Swiss multicenter study conducted between 2014 and 2023 pooled data from three cohorts. It evaluated the performance of each iteration of the Duke criteria by assessing the degree of concordance between definite S. aureus IE (SAIE) and the diagnoses made by the Endocarditis Team (2018-23) or IE expert clinicians (2014-17).

RESULTS

Among 1344 SAB episodes analyzed, 486 (36%) were identified as cases of SAIE. The 2023 Duke-ISCVID and 2023 Duke-ESC criteria demonstrated improved sensitivity for SAIE diagnosis (81% and 82%, respectively) compared to the 2015 Duke-ESC criteria (75%). However, the new criteria exhibited reduced specificity for SAIE (96% for both) compared to the 2015 criteria (99%). Spondylodiscitis was more prevalent among patients with SAIE compared to those with SAB alone (10% vs 7%, P = .026). However, when patients meeting the minor 2015 Duke-ESC vascular criterion were excluded, the incidence of spondylodiscitis was similar between SAIE and SAB patients (6% vs 5%, P = .461).

CONCLUSIONS

The 2023 Duke-ISCVID and 2023 Duke-ESC clinical criteria show improved sensitivity for SAIE diagnosis compared to 2015 Duke-ESC criteria. However, this increase in sensitivity comes at the expense of reduced specificity. Future research should aim at evaluating the impact of each component introduced within these criteria.

Draft genome sequence of Staphylococcus aureus sequence type 5 SA01 isolated from bloodstream infection and comparative analysis with reference strains

A Staphylococcus aureus isolate (SA01) obtained from bloodstream infection exhibited a remarkable drug resistance profile. In this study, we report the draft genome sequence of S. aureus ST 5 SA01, a multidrug-resistant isolate, and analyzed the genes associated with drug resistance and virulence. The genome sketch of S. aureus ST5 SA01 was sequenced with Illumina and annotated using the Prokka software. Rapid Annotation Subsystem Technology (RAST) was used to verify the gene functions in the genome subsystems. The Comprehensive Antibiotic Resistance Database (CARD) and Virulence Factor Database (VFDB) were used in the analysis. The RAST indicated a contribution of 25 proteins to host adenine, fibronectin-binding protein A (FnbA), and biofilm formation as an intercellular polysaccharide adhesive system (PIA). The MLST indicated that S. aureus ST 5 SA01 belongs to ST5 (CC5). In silico analyses also showed an extensive repertoire of genes associated with toxins, such as LukGH leukocidin, enterotoxins, and superantigen staphylococcal classes (SSL). The 11 genes for antimicrobial resistance in S. aureus ST 5 SA01 showed similarity and identity above ≥ 99% with nucleotide sequences deposited in GenBank. Although studies on ST5 clones in Brazil are scarce, monitoring the clone of S. aureus ST 5 SA01 is essential, as it has become a problem in pediatrics in several countries.

Ultrasonic irradiation enhanced the efficacy of antimicrobial photodynamic therapy against methicillin-resistant Staphylococcus aureus biofilm

Antimicrobial photodynamic therapy (aPDT) is a non-pharmacological antimicrobial regimen based on light, photosensitizer and oxygen. It has become a potential method to inactivate multidrug-resistant bacteria. However, limited by the delivery of photosensitizer (PS) in biofilm, eradicating biofilm-associated infections by aPDT remains challenging. This study aimed to explore the feasibility of combining ultrasonic irradiation with aPDT to enhance the efficacy of aPDT against methicillin-resistant staphylococcus aureus (MRSA) biofilm. A cationic benzylidene cyclopentanone photosensitizer with much higher selectivity to bacterial cells than mammalian cells were applied at the concentration of 10 μM. 532 nm laser (40 mW/cm², 10 min) and 1 MHz ultrasound (500 mW/cm², 10 min, simultaneously with aPDT) were employed against MRSA biofilms in vitro. In addition to combined with ultrasonic irradiation and aPDT, MRSA biofilms were treated with laser irradiation only, photosensitizer only, ultrasonic irradiation only, ultrasonic irradiation and photosensitizer, and aPDT respectively. The antibacterial efficacy was determined by XTT assay, and the penetration depth of PS in biofilm was observed using a photoluminescence spectrometer and a confocal laser scanning microscopy (CLSM). In addition, the viability of human dermal fibroblasts (WS-1 cells) after the same treatments mentioned above and the uptake of P3 by WS-1 cells after ultrasonic irradiation were detected by CCK-8 and CLSM in vitro. Results showed that the percent decrease in metabolic activity resulting from the US + aPDT group (75.76%) was higher than the sum of the aPDT group (44.14%) and the US group (9.88%), suggesting synergistic effects. Meanwhile, the diffusion of PS in the biofilm of MRSA was significantly increased by 1 MHz ultrasonic irradiation. Ultrasonic irradiation neither induced the PS uptake by WS-1 cells nor reduced the viability of WS-1 cells. These results suggested that 1 MHz ultrasonic irradiation significantly enhanced the efficacy of aPDT against MRSA biofilm by increasing the penetration depth of PS. In addition, the antibacterial efficacy of aPDT can be enhanced by ultrasonic irradiation, the US + aPDT treatment demonstrated encouraging in vivo antibacterial efficacy (1.73 log₁₀ CFU/mL reduction). In conclusion, the combination of aPDT and 1 MHz ultrasound is a potential and promising strategy to eradicate biofilm-associated infections of MRSA.

Photodynamic therapy for treatment of Staphylococcus aureus infections

BACKGROUND

Staphylococcus aureus is a Gram-positive spherical bacterium that commonly causes various infections which can range from superficial to life-threatening. Hospital strains of S. aureus are often resistant to antibiotics, which has made their treatment difficult in recent decades. Other therapeutic alternatives have been postulated to overcome the drawbacks of antibiotic multi-resistance. Of these, photodynamic therapy (PDT) is a promising approach to address the notable shortage of new active antibiotics against multidrug-resistant S. aureus. PDT combines the use of a photosensitizer agent, light, and oxygen to eradicate pathogenic microorganisms. Through a systematic analysis of published results, this work aims to verify the usefulness of applying PDT in treating multidrug-resistant S.aureus infections.

METHODS

This review was based on a bibliographic search in various databases and the analysis of relevant publications.

RESULTS

There is currently a large body of evidence demonstrating the efficacy of photodynamic therapy in eliminating S.aureus strains. Both biofilm-producing strains, as well as multidrug-resistant strains.

CONCLUSION

We conclude that there is sufficient scientific evidence that PDT is a useful adjunct to traditional antibiotic therapy for treating S. aureus infections. Clinical application through appropriate trials should be introduced to further define optimal treatment protocols, safety and efficay.