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Effect of temperature on aminoglycoside binding sites in Stenotrophomonas maltophilia
A Rahmati-Bahram1, J T Magee, S K Jackson
1Department of Medical Microbiology, University of Wales College of Medicine, Cardiff, UK.
Abstract:
In this study we used strains of Stenotrophomonas maltophilia grown at 30 degrees C and 37 degrees C to investigate the role of lipopolysaccharide (LPS) in temperature-dependent variations in sensitivity (TDVS) to gentamicin. TDVS was scored as 'good' if a four-fold or greater difference in minimum inhibitory concentration (MIC) was found between the two incubation temperatures (good TDVS strains; n = 23), and otherwise as 'poor' (poor TDVS strains; n = 15). Phosphate content of isolated LPS in the strains exhibiting good TDVS grown at 37 degrees C was significantly (P < 0.001) higher than those grown at 30 degrees C. However, the phosphate content from LPS of strains exhibiting poor TDVS did not alter significantly with growth temperature. There was no significant difference in 3-deoxy-D-manno-octulosonic acid (KDO) content between the strains grown at the different incubation temperatures. Fluorescence-activated cell sorting analysis showed significant differences in binding of fluorescein Isothiocyanate conjugated gentamicin to cells grown at 30 degrees C or 37 degrees C. We conclude that the temperature-dependent variation in the aminoglycoside susceptibility of this species was not correlated with any detectable change in KDO content, but correlated well with phosphate content of LPS and that LPS phosphate is the major site of ionic interaction for aminoglycosides in S. maltophilia.
Insights
Temperature affects Stenotrophomonas maltophilia sensitivity to gentamicin, with lipopolysaccharide (LPS) phosphate content playing a key role. Higher LPS phosphate at 37°C increases gentamicin susceptibility in some strains.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Stenotrophomonas maltophilia exhibits temperature-dependent variations in sensitivity (TDVS) to gentamicin.
- Lipopolysaccharide (LPS) is a key component of the Gram-negative bacterial outer membrane and can influence antibiotic resistance.
- Understanding the molecular basis of TDVS is crucial for developing effective antimicrobial strategies.
Purpose of the Study:
- To investigate the role of lipopolysaccharide (LPS) in temperature-dependent variations in sensitivity (TDVS) to gentamicin in Stenotrophomonas maltophilia.
- To determine if changes in LPS composition, specifically phosphate and KDO content, correlate with TDVS.
- To elucidate the interaction site of gentamicin with LPS.
Main Methods:
- Culturing S. maltophilia strains at 30°C and 37°C.
- Quantifying LPS phosphate and 3-deoxy-D-manno-octulosonic acid (KDO) content.
- Assessing gentamicin sensitivity using minimum inhibitory concentration (MIC) determination.
- Analyzing gentamicin binding to bacterial cells using fluorescence-activated cell sorting (FACS).
Main Results:
- Strains with 'good' TDVS showed significantly higher LPS phosphate content at 37°C compared to 30°C (P < 0.001).
- Strains with 'poor' TDVS did not exhibit significant changes in LPS phosphate content with temperature.
- No significant difference in KDO content was observed between temperatures for either group.
- FACS analysis revealed temperature-dependent differences in gentamicin binding to bacterial cells.
Conclusions:
- Temperature-dependent variation in aminoglycoside susceptibility in S. maltophilia is strongly correlated with LPS phosphate content.
- LPS phosphate, not KDO, is the primary site for ionic interactions with aminoglycosides like gentamicin.
- These findings highlight LPS phosphate as a critical factor in S. maltophilia's response to gentamicin across different temperatures.