Pretreatment with colistin and Proteus sensitivity to other agents
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Abstract:
The effects of pretreatment with colistin (polymyxin E) on the sensitivity of Proteus mirabilis, P. vulgaris and P. morganii strains to tris and sodium deoxycholate (DOC) have been studied. Pretreatment of two P. mirabilis strains (NCTC 60 and 4199) with low concentrations (0.25 approximately 1 microgram/ml) of colistin rendered them sensitive to lysis by tris (0.05M) or DOC (250 approximately 1,000 microgram/ml) although DOC induced lysis of control (non-colistin-treated) suspensions also. In contrast, the other P. mirabilis strains, as well as the P. vulgaris and P. morganii strains were little affected by tris (0.2M) or DOC (10,000 microgram/ml) even after exposure of the cells to high colistin concentrations (up to 500 microgram/ml). Colistin-pretreated or control cells of P. mirabilis NCTC 60 rapidly lost viability when suspended in water but not when held in 0.16M sodium chloride solution. Ethylenediamine tetraacetate-pretreated cells of strains 60 and 4199 were fairly sensitive to tris, although the extent of the lysis was less than when colistin was used as pretreating agent. One strain of P. vulgaris (NCTC 4175) became sensitive to tris and to DOC following exposure of the cells to ampicillin.
Insights
Colistin pretreatment enhanced the sensitivity of some Proteus strains to lysis by tris and sodium deoxycholate (DOC). However, this effect was strain-specific, with other strains showing little change in susceptibility.
Area of Science:
- Microbiology
- Bacterial Physiology
- Antimicrobial Resistance
Background:
- Proteus species are Gram-negative bacteria with clinical relevance.
- Understanding bacterial membrane permeability is crucial for developing new antimicrobial strategies.
- Colistin (polymyxin E) is an antibiotic that interacts with bacterial membranes.
Purpose of the Study:
- To investigate the impact of colistin pretreatment on the susceptibility of Proteus strains to tris and sodium deoxycholate (DOC).
- To determine if colistin pretreatment alters the sensitivity of Proteus mirabilis, P. vulgaris, and P. morganii to membrane-disrupting agents.
Main Methods:
- Bacterial strains (Proteus mirabilis, P. vulgaris, P. morganii) were pretreated with varying concentrations of colistin.
- Pretreated and control bacterial cells were subsequently exposed to tris or sodium deoxycholate (DOC).
- Cell viability and lysis were assessed to determine sensitivity changes.
Main Results:
- Low-concentration colistin pretreatment sensitized two P. mirabilis strains (NCTC 60 and 4199) to lysis by tris and DOC.
- Other P. mirabilis, P. vulgaris, and P. morganii strains showed minimal sensitivity changes to tris or DOC, even after high colistin exposure.
- Ethylenediamine tetraacetate (EDTA) pretreatment also induced some tris sensitivity, but less than colistin.
- One P. vulgaris strain became sensitive to tris and DOC after ampicillin exposure.
Conclusions:
- Colistin pretreatment can selectively increase the susceptibility of certain Proteus strains to membrane-disrupting agents like tris and DOC.
- The observed effects are strain-dependent, highlighting variability within Proteus species.
- These findings suggest potential mechanisms for enhancing the efficacy of certain antimicrobial agents through combination strategies.
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