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Differences in the susceptibility of Streptococcus pyogenes to rokitamycin and erythromycin A revealed by
Pier Carlo Braga1, Davide Ricci
1Centre of Respiratory Pharmacology, Department of Pharmacology, School of Medicine, University of Milan, Via Vanvitelli 32, 20129 Milano, Italy. piercarlo.braga@unimi.it
Abstract:
The aim of this study was to use atomic force microscopy (AFM), an innovative type of microscopy, to investigate the different behaviours of erythromycin A (a 14-membered ring) and rokitamycin (a 16-membered ring) in disrupting the morphology of Streptococcus pyogenes with the M phenotype. AFM scanning and sensing of the topography of a sample makes it possible to obtain simultaneous high-resolution digital measurements of the x, y and z coordinates at any point on the bacteria surface. The images obtained before and 2, 4 and 6 h after incubation with erythromycin A (32 mg/L) and rokitamycin (2 mg/L) clearly show that not even high concentrations of erythromycin A interfere with the M phenotype of S. pyogenes, whereas rokitamycin has a progressive action that leads to the formation of abnormally large cells, the loosening of chain structure and the formation of clusters.
Insights
Rokitamycin effectively disrupts Streptococcus pyogenes morphology, causing cell enlargement and clustering. Erythromycin A, however, shows no significant effect on this M phenotype bacteria, even at high concentrations.
Area of Science:
- Microbiology
- Microscopy
- Pharmacology
Background:
- Streptococcus pyogenes is a significant human pathogen.
- Macrolide antibiotics like erythromycin A and rokitamycin are used to treat S. pyogenes infections.
- Understanding the morphological effects of these antibiotics is crucial for treatment efficacy.
Purpose of the Study:
- To investigate the differential effects of erythromycin A and rokitamycin on the M phenotype of Streptococcus pyogenes.
- To utilize atomic force microscopy (AFM) for high-resolution morphological analysis.
Main Methods:
- Atomic Force Microscopy (AFM) was employed to scan and sense the topography of S. pyogenes.
- Bacteria were incubated with erythromycin A (32 mg/L) and rokitamycin (2 mg/L) for 2, 4, and 6 hours.
- Morphological changes were analyzed by comparing AFM images taken at different time points.
Main Results:
- Erythromycin A did not interfere with the M phenotype of S. pyogenes, even at high concentrations.
- Rokitamycin demonstrated a progressive action, leading to abnormally enlarged cells.
- Rokitamycin also caused loosening of the bacterial chain structure and the formation of clusters.
Conclusions:
- Rokitamycin is effective in disrupting the M phenotype of S. pyogenes, inducing significant morphological alterations.
- Erythromycin A lacks efficacy against this specific phenotype of S. pyogenes.
- AFM is a valuable tool for visualizing antibiotic-induced bacterial morphological changes at high resolution.