Abstract
Background and Objective:Poly-γ-glutamic acid (γ-PGA) is a constituent of theBacillus anthraciscapsule and a potential virulence factor ofS. epidermidis. In this study, a methodology for the isolation, purification and quantification of γ-PGA in the isolates was adapted. In addition, the fate of the produced γ-PGA and its antiphagocytic activity were investigated.Methods:ThecapBgene was investigated by the PCR method in 50 isolates ofS. epidermidis. A modified methodology was used for the extraction, purification, and quantification of γ-PGA using Cetyltrimethylammonium Bromide (CTAB) solution. The fate of γ-PGA was determined in Tryptic Soy Broth (TSB) medium, as well as the effect of ethanol, NaCl and KCl on the induction of the polymer production. The ability of neutrophils to phagocyte both FITC-labeled latex particles in the presence of free γ-PGA andS. epidermidiswith and without anchored γ-PGA was evaluated by cytometry.Results:The production of γ-PGA was detected in 40 isolates; all of them werecapBgene carriers. Free γ-PGA was detected and in the strain, the amount of released γ-PGA in the supernatant was 67% greater than the cell anchored γ-PGA. Phagocytosis tests performed with one γ-PGA producer isolate showed a significant reduction in neutrophil internalization.Conclusion:The adapted methodology was able to detect γ-PGA in the isolates studied. In addition to being found attached to the cell wall, it was demonstrated in this study that γ-PGA can also be found in the culture supernatant. Free γ-PGA did not determine a reduction in the internalization of latex by neutrophils, but cells with anchored γ-PGA showed significant protection against phagocytosis.
Highlights
S. epidermidis was long considered a typically commensal bacterium in humans
The first described mechanism related to the pathogenicity of S. epidermidis was the ability to produce biofilm
The main component detected in the matrix of this biofilm was the Polysaccharide Intercellular Adhesin (PIA)
Summary
In the last decades, this species has been progressively recognized as an important opportunistic pathogen, as it is currently the main cause of healthcareassociated infections, as well as infections associated with implanted medical devices [1]. The first described mechanism related to the pathogenicity of S. epidermidis was the ability to produce biofilm. Biofilm protects the bacterium against the components of immune defense and antimicrobial drugs and explains the close correlation of S. epidermidis with infections associated with internal medical. The awareness of the virulence potential of S. epidermidis was amplified with the detection of the capBCAE operon in this species, which is responsible for the production of poly-γ-glutamic acid (γ-PGA) [4]. Poly-γ-glutamic acid (γ-PGA) is a constituent of the Bacillus anthracis capsule and a potential virulence factor of S. epidermidis. The fate of the produced γ-PGA and its antiphagocytic activity were investigated
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