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Structural changes induced by subinhibitory concentrations of fosfomycin on Staphylococcus aureus and Bacillus cereus
Abstract:
Exposure of Staphylococcus aureus ATCC 6538 and Bacillus cereus ATCC 11778 to 1/2 MIC fosfomycin for 3 and 6 h was studied by transmission and scanning electron microscopy. After 3 h, a loss of density and irregularity of shape in the septum was noted, while after 6 h a delayed separation of newly formed cells was observed in both species. In Staphylococcus aureus this resulted in the formation of chains of intact cells and cells in lysis. In Bacillus cereus, it produced filamentous forms with multiple septa. the differences between the effects observed at 3 h and 6 h may be due to time-related variations in cell permeability to fosfomycin, or to the existence of indirect mechanisms enabling fosfomycin to interfere with the enzymatic activity regulating the normal separation of cells, or to a combination of these factors.
Insights
Fosfomycin exposure disrupts cell division in Staphylococcus aureus and Bacillus cereus. This antibiotic causes cell shape changes and delayed separation, leading to abnormal cell structures like chains or filaments.
Area of Science:
- Microbiology
- Cell Biology
- Antibiotic Research
Background:
- Staphylococcus aureus and Bacillus cereus are significant bacterial pathogens.
- Fosfomycin is a broad-spectrum antibiotic with a unique mechanism of action.
- Understanding fosfomycin's effects on bacterial cell division is crucial for combating resistance.
Purpose of the Study:
- To investigate the ultrastructural effects of sub-inhibitory concentrations of fosfomycin on Staphylococcus aureus and Bacillus cereus.
- To analyze the time-dependent morphological changes induced by fosfomycin exposure.
Main Methods:
- Transmission and scanning electron microscopy were used to examine bacterial morphology.
- Staphylococcus aureus ATCC 6538 and Bacillus cereus ATCC 11778 were exposed to 1/2 MIC of fosfomycin.
- Microscopy was performed after 3 and 6 hours of antibiotic exposure.
Main Results:
- After 3 hours, both species showed loss of septum density and irregular shapes.
- After 6 hours, delayed cell separation was observed, leading to cell chains in S. aureus and filamentous forms in B. cereus.
- S. aureus exhibited both intact cell chains and lysis, while B. cereus formed filamentous structures with multiple septa.
Conclusions:
- Fosfomycin significantly interferes with bacterial cell division and septum formation in both Gram-positive species.
- Observed morphological changes suggest potential time-dependent alterations in cell permeability or indirect interference with cell separation enzymes.
- These findings highlight fosfomycin's impact on bacterial cell wall synthesis and division, offering insights into its antimicrobial activity.