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Isolation and partial characterization of polymyxin B-resistant isolates of Vibrio parahaemolyticus
Abstract:
Two polymyxin-resistant isolates V2PXR and P1R4PXR of Vibrio parahaemolyticus were spontaneously isolated and compared with the polymyxin-sensitive strains as to their chemical compositions of cell envelopes and their outer membrane protein compositions. When grown in the presence or absence of polymyxin, the cell envelopes of polymyxin-resistant isolates showed a significantly increased content of protein as compared with those of respective polymyxin-sensitive strains. Both polymyxin-resistant isolates produced the major outer membrane protein b' after growth in the presence or absence of polymyxin. A new major outer membrane protein with an apparent molecular weight of 26,000 (26 K protein) was produced by polymyxin-resistant isolates grown in the presence of polymyxin. The production of 26 K protein was also observed in the polymyxin-resistant isolates grown in the medium containing low concentrations of NaCl (0.2% and 0.5%).
Insights
Polymyxin-resistant Vibrio parahaemolyticus showed increased cell envelope protein content. A novel 26 K protein emerged in resistant strains, linked to polymyxin resistance and low salt conditions.
Area of Science:
- Microbiology
- Bacterial Physiology
- Drug Resistance
Background:
- Polymyxins are critical last-resort antibiotics against Gram-negative bacteria.
- Mechanisms of polymyxin resistance in Vibrio parahaemolyticus are not fully understood.
- Alterations in cell envelope composition are often associated with antibiotic resistance.
Purpose of the Study:
- To investigate the cell envelope and outer membrane protein composition of polymyxin-resistant Vibrio parahaemolyticus isolates.
- To identify potential molecular changes contributing to polymyxin resistance in this pathogen.
Main Methods:
- Isolation and characterization of spontaneous polymyxin-resistant Vibrio parahaemolyticus strains.
- Comparative analysis of cell envelope protein content between resistant and sensitive strains.
- Outer membrane protein profiling using SDS-PAGE.
- Growth studies in the presence/absence of polymyxin and varying NaCl concentrations.
Main Results:
- Polymyxin-resistant isolates exhibited significantly higher cell envelope protein content compared to sensitive strains.
- A novel 26,000 molecular weight (26 K) outer membrane protein was uniquely produced by resistant isolates.
- Production of the 26 K protein was induced by polymyxin exposure and also observed under low NaCl conditions (0.2-0.5%).
Conclusions:
- Increased cell envelope protein content and the novel 26 K protein are associated with polymyxin resistance in Vibrio parahaemolyticus.
- The 26 K protein may play a role in polymyxin resistance, potentially influenced by environmental factors like salinity.