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Published on: March 9, 2019
Inclusion bodies and pH lowering: as an effect of gold nanoparticles in Streptococcus pneumoniae
Edgar Augusto Ortiz-Benitez1, Mariana Carrillo-Morales, Norma Velázquez-Guadarrama
1Posgrado en Ciencias Genómicas, Universidad Autónoma de la Ciudad de México, San Lorenzo 290, C.P. 03100, Ciudad de México, Mexico. olivarestrejo@yahoo.com.
Abstract:
Streptococcus pneumoniae is a human pathogen whose principal virulence factor is its capsule. This structure allows the bacterium to evade the human immune system. Treatment of infections caused by this bacterium is based on antibiotics; however, the emergence of antibiotic-resistant strains makes this task increasingly difficult. Therefore, it is necessary to investigate new therapies, such as those based on gold nanoparticles, for which unfortunately the mechanisms involved have not yet been investigated. As far as we know, this study is the first that attempts to explain how gold nanoparticles destroy the bacterium Streptococcus pneumoniae. We found that the mean particle size was an important issue, and that the effect on the bacterium was dose-dependent. Cellular growth was inhibited by the presence of the nanoparticles, as was cell viability. The pH of the bacterial growth media was acidified, but interestingly the reactive species were not affected. A transmission electron microscopy analysis revealed the presence of inclusion bodies of gold nanoparticles within the bacterium. We present the first findings that attempt to explain how gold nanoparticles lyse Gram-positive bacteria.
Insights
Gold nanoparticles show promise in combating antibiotic-resistant Streptococcus pneumoniae. This study reveals how these nanoparticles inhibit bacterial growth and viability, offering new therapeutic strategies.
Area of Science:
- Nanotechnology
- Microbiology
- Infectious Diseases
Background:
- Streptococcus pneumoniae is a major human pathogen, with its capsule aiding immune evasion.
- Antibiotic resistance in S. pneumoniae necessitates novel therapeutic approaches.
- Gold nanoparticles (AuNPs) are being explored for antimicrobial applications, but their mechanisms are unclear.
Purpose of the Study:
- To elucidate the mechanisms by which gold nanoparticles exert their bactericidal effects on Streptococcus pneumoniae.
- To investigate the influence of gold nanoparticle characteristics, such as size and dose, on antimicrobial activity.
- To provide the first detailed explanation of gold nanoparticle-mediated lysis in Gram-positive bacteria.
Main Methods:
- Investigated the dose-dependent effects of gold nanoparticles on bacterial growth and viability.
- Monitored changes in the pH of the bacterial growth media.
- Utilized transmission electron microscopy (TEM) to visualize nanoparticle-bacterium interactions.
Main Results:
- Gold nanoparticle efficacy was dependent on particle size and applied dose.
- Nanoparticles significantly inhibited bacterial growth and reduced cell viability.
- TEM revealed intracellular accumulation of gold nanoparticles within S. pneumoniae.
- Bacterial media pH decreased, but reactive oxygen species levels remained unaffected.
Conclusions:
- Gold nanoparticles effectively inhibit Streptococcus pneumoniae growth and viability.
- Intracellular accumulation of gold nanoparticles is a key factor in their bactericidal mechanism.
- This study provides the foundational understanding of gold nanoparticle-mediated bacterial lysis in Gram-positive pathogens.
