The Influence of Antibiotic Resistance on Innate Immune Responses to Staphylococcus aureus Infection

Staphylococcus aureus nt5 gene mutation through CRISPR RNA-guided base editing weakens bacterial virulence and immune evasion

The resistance of commonly used clinical antibiotics, such as daptomycin (DAP), has become increasingly serious in the fight against Staphylococcus aureus (S. aureus) infection. It is essential to explore key pathogenicity-driven genes/proteins in bacterial infection and antibiotics resistance, which contributes to develop novel therapeutic strategies against S. aureus infections. The nt5 gene of S. aureus, encoding 5'-nucleotidase (NT5), is nearly unknown for its function in drug resistance and bacterial infection. Herein, to reveal nt5 gene role in drug resistance and infection ability of S. aureus, we performed nt5C166T gene mutation using a clustered regulatory interspaced short palindromic repeat ribonucleic acid (RNA)-guided base editing system to investigate the lose-of-function of NT5 protein. Subsequent transcriptome sequencing of the mutant strain revealed that nt5 inactivation caused changes in cell membrane integrity and inhibited nucleotide metabolism, suggesting the nt5 gene may be involved in bacterial drug resistance and virulence. The mutant strain exhibited enhanced tolerance to DAP treatment by attenuating cell membrane potential dissipation and slowing deoxyribonucleic acid release. Moreover, the nt5 mutation alleviated abscess degree of mouse kidneys caused by S. aureus infection byreducing the expression of IL-1β, IL-6, and IL-18. The nt5 mutant strain was easily swallowed by host immune cells, resulting in weak bacterial toxicity of the S. aureus mutant in the bacterial infection process. In summary, nt5 gene mutation confers tolerance to DAP and a lower bacterial capacity to form kidney abscesses through phagocytosis of host immune cells, which indicates the targeted inhibition of NT5 protein would offer a potential new therapeutic strategy against S. aureus infection.

Roles of extracellular vesicles on macrophages in inflammatory bone diseases

Inflammatory bone disease is a general term for a series of diseases caused by chronic inflammation, which leads to the destruction of bone homeostasis, that is, the osteolytic activity of osteoclasts increases, and the osteogenic activity of osteoblasts decreases, leading to osteolysis. Macrophages are innate immune cell with plasticity, and their polarization is related to inflammatory bone diseases. The dynamic balance of macrophages between the M1 phenotype and the M2 phenotype affects the occurrence and development of diseases. In recent years, an increasing number of studies have shown that extracellular vesicles existing in the extracellular environment can act on macrophages, affecting the progress of inflammatory diseases. This process is realized by influencing the physiological activity or functional activity of macrophages, inducing macrophages to secrete cytokines, and playing an anti-inflammatory or pro-inflammatory role. In addition, by modifying and editing extracellular vesicles, the potential of targeting macrophages can be used to provide new ideas for developing new drug carriers for inflammatory bone diseases.

Plectasin: from evolution to truncation, expression, and better druggability

Non-computational classical evolution analysis of plectasin and its functional relatives can especially contribute tool value during access to meet requirements for their better druggability in clinical use. Staphylococcus aureus is a zoonotic pathogen that can infect the skin, blood, and other tissues of humans and animals. The impact of pathogens on humans is exacerbated by the crisis of drug resistance caused by the misuse of antibiotics. In this study, we analyzed the evolution of anti-Staphylococcus target functional sequences, designed a series of plectasin derivatives by truncation, and recombinantly expressed them in Pichia pastoris X-33, from which the best recombinant Ple-AB was selected for the druggability study. The amount of total protein reached 2.9 g/L following 120 h of high-density expression in a 5-L fermenter. Ple-AB was found to have good bactericidal activity against gram-positive bacteria, with minimum inhibitory concentration (MIC) values ranging between 2 and 16 μg/mL. It showed good stability and maintained its bactericidal activity during high temperatures, strong acid and alkali environments. Notably, Ple-AB exhibited better druggability, including excellent trypsin resistance, and still possessed approximately 50% of its initial activity following exposure to simulated intestinal fluids for 1 h. In vitro safety testing of Ple-AB revealed low hemolytic activity against mouse erythrocytes and cytotoxicity against murine-derived macrophages. This study successfully realized the high expression of a new antimicrobial peptide (AMP), Ple-AB, in P. pastoris and the establishment of its oral administration as an additive form with high trypsin resistance; the study also revealed its antibacterial properties, indicating that truncation design is a valuable tool for improving druggability and that the candidate Ple-AB may be a novel promising antimicrobial agent.

Patterns, Cost, and Immunological Response of MDR vs. Non MDR-Bacteremia: A Prospective Cohort Study

BACKGROUND

Antimicrobial resistance (AMR) is a significant global health concern, posing a critical challenge for the effective management of infectious diseases. This study aimed to compare the immunological response, clinical outcomes, and associated costs in patients with bacteremia due to antibiotic-resistant vs. susceptible bacterial microorganisms.

METHODS

This study was a single-center, prospective cohort study conducted from May 2017 to November 2019. The study population consisted of patients admitted with a confirmed diagnosis of bacteremia.

RESULTS

A total of 116 patients were included, with 53 (45.7%) harboring non-multidrug-resistant (non-MDR) bacterial isolates and 63 (54.3%) harboring multidrug-resistant (MDR) bacterial isolates. Patients with MDR bacteremia had more severe clinical presentations, as indicated by higher SOFA and APACHE II scores. Results revealed higher all-cause mortality rates (39.7% vs. 17%) and median healthcare costs (€4791 vs. €2843.5) in the MDR bacteremia group. Moreover, MDR bacteremia was linked to higher levels of TNF-a, indicating a differential immune response. Furthermore, MDR bacteremia was found to be an independent predictor of mortality (OR = 3.216, 95% CI: 1.338-7.730, p = 0.009) and increased healthcare costs (effect size of approximately 27.4%).

CONCLUSION

These findings underscore the significant impact of antimicrobial resistance in healthcare settings, highlighting the urgency of addressing the challenges posed by MDR microorganisms.