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Inhibition of K88ab-mediated haemagglutination by polymyxin B nonapeptide
A M Matranga1, B Moore, P M Bennett
1Department of Microbiology, School of Medicine Sciences, University of Bristol, UK.
Abstract:
The ability of the cyclic peptide polymyxin B nonapeptide (PMBN) to inhibit haemagglutination of erythrocytes by Escherichia coli bearing K88ab, K99 or F41 fimbriae was examined. The agent strongly inhibited K88ab-mediated haemagglutination, but had little or no effect on haemagglutination mediated by K99 or F41 fimbriae. Inhibition of K88ab-mediated haemagglutination did not result from release of fimbrial adhesins from the bacterial cell surface, nor from solubilization of K88ab receptors in erythrocytes. Since PMBN also prevented haemagglutination mediated by partially-purified K88ab fimbriae, the agent may directly obstruct access of fimbriae to their mammalian receptor binding sites.
Insights
Polymyxin B nonapeptide (PMBN) effectively blocks *Escherichia coli* K88ab fimbriae-mediated red blood cell agglutination. However, PMBN shows minimal impact on K99 or F41 fimbriae-mediated agglutination, suggesting a specific inhibitory mechanism.
Area of Science:
- Microbiology
- Biochemistry
- Immunology
Background:
- *Escherichia coli* fimbriae mediate bacterial adhesion to host cells, contributing to infections.
- Haemagglutination assays are used to study bacterial fimbriae-host cell interactions.
- Polymyxin B nonapeptide (PMBN) is a cyclic peptide with known antimicrobial properties.
Purpose of the Study:
- To investigate the inhibitory effect of PMBN on haemagglutination mediated by different *E. coli* fimbrial types (K88ab, K99, F41).
- To elucidate the mechanism by which PMBN affects fimbriae-mediated haemagglutination.
Main Methods:
- Haemagglutination assays using erythrocytes and *E. coli* strains expressing K88ab, K99, or F41 fimbriae.
- Testing the effect of PMBN on bacterial cells, fimbrial adhesins, and erythrocyte receptors.
- Assessing PMBN's inhibition of haemagglutination mediated by partially purified K88ab fimbriae.
Main Results:
- PMBN strongly inhibited haemagglutination mediated by K88ab fimbriae.
- PMBN had minimal to no inhibitory effect on haemagglutination mediated by K99 and F41 fimbriae.
- Inhibition was not due to the release of fimbrial adhesins or solubilization of erythrocyte receptors.
Conclusions:
- PMBN specifically inhibits K88ab fimbriae-mediated haemagglutination.
- The mechanism of inhibition likely involves PMBN directly blocking the interaction between K88ab fimbriae and their mammalian receptors.
- PMBN's specificity suggests potential for targeted therapeutic interventions against K88ab-expressing *E. coli*.