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Development of a UPLC-MS/MS Method for Tracking Polymyxin B Dynamics in Soil Inoculated with Paenibacillus polymyxa
Siyu Huang1, Xiaorui Li1, Xin Lu1
1National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing 102206, China.
Abstract:
Polymyxins, including polymyxin B (PMB), are last-resort antibiotics against multidrug-resistant Gram-negative infections in humans and livestock. Residual polymyxins from wastewater and manure can accumulate in soil, facilitating the emergence and spread of polymyxin resistance. Paenibacillus polymyxa, a natural polymyxin producer used in crop cultivation, may increase soil polymyxin burden. Since PMB strongly adsorbs to soil, its reliable quantification has been challenging. To address this, the extraction solvent and solid-phase extraction procedure were optimized to improve recovery and reduce matrix effects. We developed and validated a UPLC-MS/MS method to quantify PMB in soil. The method showed linearity (10-1000 ng/g), with a limit of detection of 0.86 ng/g and a limit of quantification of 2.12 ng/g. Method validation confirmed acceptable analytical performance. A 28-day monitoring of PMB in soil inoculated with varying P. polymyxa doses revealed a dose-dependent increase over the first 14 days, followed by a decline; PMB remained detectable on day 28. Ecological risk assessment using the risk quotient (RQ) indicated that PMB levels in the high-dose group (2 × 108 CFU/100 g) approached the high-risk threshold (RQ ≥ 1) on day 14, while lower doses posed low to medium risk. This work provides a soil PMB quantification method and insight into the ecological risk of P. polymyxa application.
Insights
Polymyxin B (PMB) in soil can be accurately measured using a new UPLC-MS/MS method. Applying the bacterium Paenibacillus polymyxa increases soil PMB, potentially posing ecological risks.
Area of Science:
- Environmental Chemistry
- Microbiology
- Analytical Chemistry
Background:
- Polymyxins, like polymyxin B (PMB), are crucial for treating multidrug-resistant Gram-negative infections.
- Antibiotic residues in soil, from wastewater and manure, can drive the emergence of resistance.
- The bacterium Paenibacillus polymyxa, used in agriculture, may contribute to soil polymyxin levels.
Purpose of the Study:
- To develop and validate a reliable method for quantifying polymyxin B (PMB) in soil.
- To investigate the impact of Paenibacillus polymyxa application on soil PMB concentrations.
- To assess the ecological risk associated with soil PMB accumulation.
Main Methods:
- Optimized solvent extraction and solid-phase extraction for improved PMB recovery from soil.
- Developed and validated a UPLC-MS/MS method for sensitive and accurate PMB quantification.
- Monitored soil PMB levels over 28 days following inoculation with varying doses of P. polymyxa.
Main Results:
- The UPLC-MS/MS method demonstrated good linearity, low detection limits (0.86 ng/g), and quantification limits (2.12 ng/g).
- Soil PMB concentrations increased in a dose-dependent manner with P. polymyxa inoculation, peaking at 14 days.
- High P. polymyxa doses led to soil PMB levels approaching the high-risk threshold (RQ ≥ 1).
Conclusions:
- A validated UPLC-MS/MS method enables accurate quantification of soil polymyxin B.
- Application of Paenibacillus polymyxa can increase soil polymyxin B burden, raising ecological concerns.
- Ecological risk assessment indicates potential risks at higher P. polymyxa application rates.
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