Capsule Independent Antimicrobial Activity Induced by Nanochitosan against Streptococcus pneumoniae

Abstract

Background: Streptococcus pneumoniae remains a major cause of community-acquired pneumonia, meningitis, and other diseases, contributing significantly to high morbidity and mortality worldwide. Although it responds to antibiotics, their use is becoming limited due to the rise in antibiotic resistance, which necessitates the development of new therapeutics. Nanotechnology is used to counteract antimicrobial resistance. In this regard, polymeric nanoparticles (NPs) made of natural, biodegradable, biocompatible, and cationic polymers such as Chitosan (CNPs) exhibit wide-spectrum antimicrobial activity. Therefore, this study aimed to prepare CNPs, characterize their physiochemical characteristics: particle size (PZ), polydispersity index (PDI), and zeta potential (ZP), and investigate their antimicrobial activity against Streptococcus pneumoniae TIGR4 (virulent serotype 4) and its capsular mutant (∆cps). Methods: CNPs were prepared at 1, 2.5, and 5 mg/mL concentrations using the ion gelation method. Then, PZ, PDI, and ZP were characterized using a Zetasizer. Transmission electron microscopy (TEM) was used to visualize the CNP’s morphology. Broth and agar dilution methods were used to assess their antimicrobial activity. Cytotoxicity of prepared NPs on A549 cells and their effect on pneumococcal hemolysis were also investigated. Results: Spherical CNPs were produced with PZ ranging from 133.3 nm ± 0.57 to 423 nm ± 12.93 PDI < 0.35, and ZP from 19 ± 0.115 to 27 ± 0.819. The prepared CNPs exhibited antibacterial activity against TIGR4 and its capsule mutant with a minimum inhibitory concentration (MIC90) of 0.5 to 2.5 mg/mL in a non-acidic environment. The hemolysis assay results revealed that CNPs reduced bacterial hemolysis in a concentration-dependent manner. Their mammalian cytotoxicity results indicated that CNPs formed from low concentrations of Chitosan (Cs) were cytocompatible. Conclusion: Nanochitosan particles showed anti-pneumococcal activity regardless of the presence of capsules. They resulted in a concentration-dependent reduction in bacterial hemolysis and were cytocompatible at a lower concentration of Cs. These findings highlight the potential of CNPs in the treatment of pneumococcal diseases.

Chitosan loaded RNA polymerase inhibitor nanoparticles increased attenuation in toxin release from Streptococcus pneumonia

“…The effect of empty CNPs on the hemolysis activity of pneumococcal culture supernatants was reported previously ( Alqahtani et al, 2021 ). Therefore, the influence of C3-005 and C3-CNPs on the hemolytic activity of S. pneumonia were evaluated utilizing a hemolysis assay.…”

“…In the current study, CNPs were successfully generated in this research using the ion gelation method, which is depends on crosslinking between cationic Cs and anionic TPP and has been reported in previous reports ( Calvo et al, 1997 , Aleanizy et al, 2018 , Alqahtani et al, 2021 ). The PS, PDI, ZP and EE% of prepared empty CNPs and C3-005 loaded CNPs were presented in Table 1 .…”

“…Thus, alternative antimicrobial approaches must be developed, and design of novel antimicrobials with new targets, such as compound C3-005 ( Hinsberger et al, 2013 , Ma et al, 2013 , Murakami, 2015 , Ye et al, 2019 ), and use of nanoparticles (NPs) are among these strategies ( Czaplewski et al, 2016 ). In our previous study, NPs formulated from Cs found to exhibited antipneumococcal activity and reduced bacterial hemolysis ( Alqahtani et al, 2021 ). Therefore, our study aims to formulate C3-005 loaded CNPs and evaluate their antibacterial activity and effect on bacterial hemolysis.…”

“…As previously reported, hemolytic activity was carried out with some modifications ( Alqahtani et al, 2021 ). In THYB, TIGR4 strain were sub-cultured from overnight culture till reaching an OD600 of 0.5.…”

“…The integrity of the bacterial membrane has compromised as a result of this interaction, leading to the release of intracellular components and cell killing ( Rabea et al, 2003 , Kong et al, 2010 , Ke et al, 2021 ). From previous study, CNPs exhibited greater antibacterial effect than chitosan against diverse range of fungal ( Ing et al, 2012 ), Gram-positive including S. pneumonia ( Chávez de Paz et al, 2011 , Alqahtani et al, 2021 ), and Gram-negative bacteria ( Qi et al, 2004 , Aleanizy et al, 2018 , Alqahtani et al, 2020 ). Given the superior anti-pnumococcal activity of C3-005 and CNPs, thus, this research purposed to develop CNPs loaded with C3-005 and characterize their antimicrobial properties against S. pneumonia .…”