Functional Research Of Pfs And Target Treatment Of Infection Of Staphylococcus Aureus

Staphylococcus aureus is a major cause of infectious morbidity and mortality in community and hospital settings. This bacterium has the ability to cause a variety of infections in numerous ecological niches within the host, ranging from cutaneous infections to deep-seated infections such as pneumonia, endocarditis, septicaemia, osteomyelitis, and other metastatic complications. Nowadays, the universal biofilm formation and the incessant emergence of antibiotic resistant strains have created new challenges in the treatment of S. aureus infection. It highlights the urgent need for new agents for the treatment of S. aureus infection. It is a central goal and key challenge to develop an anti-infection agent capable of attenuation the virulence and biofilm formation ability of bacteria at the same time without killing them. In this way, the emergence of antibiotic resistant strains is assumed to be less significant, and the intrinsic resistance of biofilm-associated infections should be overcome. As an integral component of the S-adenosylmethionine pathway, methylthioadenosine/S-adenosylhomocysteine nucleosidase (Pfs) is predicted to be involved in methylation reactions, polyamine synthesis, vitamin synthesis, quorum sensing pathways, and so on. For the first time, we demonstrate a role of Pfs in biofilm formation and virulence of S. aureus. The pfs mutation decreases the biofilm formation ability of S. aureus, and correspondingly the pfs mutation decreases Triton X-100induced autolysis, clumping ability in liquid culture, and extracellular DNA level in biofilm. It is suspected that the decreased biofilm formation of the pfs mutant is associated with the decreased extracellular DNA level in biofilm, which is released through autolysis. Compared to the isogenic wild type strain, the pfs mutant strain displayed a decreased production of extracellular proteases. Through the zyogram analysis of extracellular protease and the transcription analysis along the growth phases, it is shown that the decreased extracellular protease activity was correlated with a dramatic decrease in the expression of the sspABC operon. Finally, mouse infection models were constructed to investigate the significance of these observations in vitro to disease pathogenesis. The mouse models of sepsis and subcutaneous abscesses indicated the pfs mutant strain displayed highly impaired virulence. The decreased virulence of the pfs mutant strain is correspondence with decreased proliferation in vivo. Our data suggested that Pfs is a potential novel target for anti-infection therapy capable of attenuation the virulence and biofilm formation of S. aureus at the same time.Besides the emergence of antibiotic resistant strains and the biofilm related infection, there are other issues in S. aureus infection treatment. The unselected killing of antibacterial agent makes destructions to the commensal microflora of the human body, which is crucial for maintaining stability of the body external environment. The destruction of commensal microflora is proved to be harmful, and would decrease the resistant ability of the human body to pathogenic microorganism. The side effects of antibiotics also include the ototoxicity, renal toxicity and so on. Another issue is that the antibiotics exhibit poor penetration into cells. The intracellular bacteria can evade from the bactericidal action of antibiotics, leading to infection recurrence and chronic infection. Vancomycin has become the last defence of anti-infection therapy of the resistant strains of5. aureus. Here we report a new strategy for differential delivery of antibiotics to bacterial infection sites for decreasing the side effects and increasing the penetration ability into cells of antibiotics. The unique micro environment of the infection site was utilized for the design of microenviroment-response nanoparticles, enabling the on-demand release of antibiotics. As an important virulence factor, lipases are wildly distributed in bacteria. We designed the lipase-sensitive polymeric triple-layered nanogel (TLN) as the carrier of antibiotics. The TLN contains lipase-senstive poly (ε-caprolactone)(PCL) interlayer between the cross-linked polyphosphoester core and the shell of poly (ethylene glycol). The hydrophilic antibiotics can reside in the polyphosphoester core. The hydrophobic PCL segments collapsed and surrounded the polyphosphoester core, forming a hydrophobic and compact molecular fence in aqueous solution which prevented antibiotic release from the polyphosphoester core prior to reaching bacterial infection sites. However, once the TLN sensed the lipase or lipase-secreting bacteria, the PCL fence of the TLN degraded to release the antibiotic and kill the bacteria. The TLN further delivered the drug into bacteria-infected cells and efficiently released the drug to kill intracellular bacteria. This technique can be generalized to selectively deliver a variety of antibiotics for the treatment of various infections caused by lipase-secreting bacteria and thus provides a new, safe, effective, and universal approach for the treatment of extracellular and intracellular bacterial infections.