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Invasive properties of south Indian strains of Streptococcus pyogenes in a HEp-2 cell model
P Gladstone1, M V Jesudason, G Sridharan
1Department of Clinical Microbiology, Christian Medical College & Hospital, Vellore, 632004, India.
Abstract:
The objective of this study was to consider the invasive properties of Streptococcus pyogenes in human pharyngeal epithelial cells, and to correlate these with their clinical significance. Clinical isolates of S. pyogenes obtained from blood cultures over a period of 10 years, and throat and skin isolates from a community-based study, were used in this investigation. The S. pyogenes isolates were inoculated in HEp-2 cells and subsequently treated with antibiotics to kill the extracellular bacteria. The cells were then lyzed, and a colony count was carried out to check for invasion. The throat and skin isolates had 45.7%, 25.7% and 28.5% of low, intermediate and high invasion efficiencies, respectively, while 80%, 8.6% and 11.4% of the blood isolates had low, intermediate and high invasion efficiencies. We concluded that the throat and the skin isolates from superficial infections were more invasive than the blood isolates, which is an interesting and paradoxical feature.
Insights
Streptococcus pyogenes from superficial infections showed higher invasion of human cells than those from blood. This paradoxical finding challenges typical understandings of bacterial virulence factors.
Area of Science:
- Microbiology
- Infectious Diseases
- Cell Biology
Background:
- Streptococcus pyogenes is a significant human pathogen.
- Understanding bacterial invasion mechanisms is crucial for disease pathogenesis.
- Invasive properties of S. pyogenes isolates vary depending on infection source.
Purpose of the Study:
- To investigate the invasive potential of Streptococcus pyogenes in human pharyngeal epithelial cells.
- To correlate the invasive properties of S. pyogenes with their clinical significance.
- To compare invasion efficiencies between blood, throat, and skin isolates.
Main Methods:
- Utilized HEp-2 cells to model human pharyngeal epithelial cells.
- Inoculated HEp-2 cells with clinical isolates of S. pyogenes.
- Quantified bacterial invasion by lysing cells and performing colony counts after antibiotic treatment to eliminate extracellular bacteria.
Main Results:
- Throat and skin isolates exhibited higher invasion efficiencies compared to blood isolates.
- Low invasion efficiency was observed in 45.7% of throat/skin isolates versus 80% of blood isolates.
- High invasion efficiency was noted in 28.5% of throat/skin isolates versus 11.4% of blood isolates.
Conclusions:
- Superficial infection isolates (throat and skin) of S. pyogenes demonstrate greater invasiveness than blood isolates.
- This finding presents a paradox, as blood isolates are typically associated with more severe, systemic infections.
- Further research is needed to elucidate the mechanisms behind this observed difference in invasiveness.
