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Detection of agents that alter the bacterial cell surface
Abstract:
Proteus mirabilis is not killed by polymyxin B, normal serum, or sodium deoxycholate. Exposure to polymyxin B renders the cells susceptible to killing by the latter two agents. The data suggest that this synergism is due to polymyxin B-induced surface changes. The results point out an inadequacy of existing methods of screening for antibiotics; they fail to detect agents which, while showing no in vitro effect on growth, may alter a resistant organism so that it becomes more susceptible to other antimicrobials or host defense mechanisms. A method is described which can be used to detect such cell surface-modifying agents.
Insights
Polymyxin B does not kill Proteus mirabilis alone but makes it vulnerable to serum and sodium deoxycholate. This suggests polymyxin B alters bacterial surfaces, revealing new antibiotic screening methods.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Antimicrobial Resistance
Background:
- Proteus mirabilis exhibits resistance to polymyxin B, normal serum, and sodium deoxycholate independently.
- Current antibiotic screening methods may overlook agents that enhance susceptibility to other treatments or host defenses.
Purpose of the Study:
- To investigate the synergistic effect of polymyxin B on the susceptibility of Proteus mirabilis to normal serum and sodium deoxycholate.
- To highlight the limitations of conventional in vitro antibiotic screening.
- To introduce a novel method for detecting cell surface-modifying antimicrobial agents.
Main Methods:
- Exposure of Proteus mirabilis to polymyxin B.
- Assessment of bacterial susceptibility to normal serum and sodium deoxycholate post-exposure.
- Development and description of a new screening assay for cell surface-modifying agents.
Main Results:
- Proteus mirabilis, resistant to polymyxin B, normal serum, and sodium deoxycholate alone, becomes susceptible to serum and deoxycholate after polymyxin B exposure.
- This observed synergism is attributed to polymyxin B-induced alterations in the bacterial cell surface.
- Existing antibiotic screening assays failed to identify polymyxin B's potentiating effect.
Conclusions:
- Polymyxin B can induce surface changes in Proteus mirabilis, rendering it susceptible to host defense mechanisms and other antimicrobials.
- There is a critical need for improved antibiotic screening methods capable of detecting agents that modify bacterial susceptibility.
- A new method has been developed to identify such crucial cell surface-modifying agents.