Effect of Particulate Matter of Natural and Anthropogenic Origin on Growth Indicators and Sensitivity to Antibiotics of Escherichia coli B906

Abstract

Particulate matter (PM), which is among the main components of polluted air, can contribute to the development of gastrointestinal diseases and alter the composition of gut microbiota and its metabolic properties. Objective. The study focuses on analyzing the influence of different concentrations of PM derived from the combustion of cottonwood (PMC) and medical masks (PMM) on the growth intensity, biofilm formation capability, and antibiotic susceptibility of lactose-positive Escherichia coli strain B906. Methods. The MPA medium was inoculated with a culture of E. coli B906 at a concentration of 105 CFU/mL, followed by the addition of PMC and PMM at concentrations of 18 μg/mL, 36 μg/mL, or 72 μg/mL. The growth intensity was determined by measuring the optical density using a spectrophotometer over a period of 72 h. To determine the number of viable cells and their ability to ferment lactose, seeding on the Endo medium was performed. The biofilm-forming ability was determined on polystyrene plates using a staining and desorption method. The antibiotic susceptibility (ampicillin, levomycetin, meropenem, norfloxacin, and ceftriaxone) was determined using the disc-diffusion method for 24, 48, and 72 h of cultivation. Results. Both PMC and PMM exerted suppressive effects on the growth of E. coli B906: at a concentration of 72 μg/mL, the biomass increase was virtually absent. The number of viable cells on the medium with PMC decreased by 1—2 orders of magnitude at concentrations of 18 μg/mL and 36 μg/mL compared to the control and by 6 orders of magnitude at a concentration of 72 μg/mL. At this concentration, no growth was observed at 48 and 72 h. PMM exerted bacteriostatic effects: when seeded on the Endo medium, the number of viable cells decreased by 1—2 orders of magnitude at concentrations of 18 μg/mL and 36 μg/mL from 24 to 72 h, and by 3—4 orders of magnitude at a concentration of 72 μg/mL. At 48 h cultivation, PMC stimulated biofilm formation at concentrations of 18 μg/mL and 36 μg/mL, while inhibiting it at a concentration of 72 μg/mL. In contrast, PMM reduced the biofilm density at all concentrations. Both types of PM induced resistance to ampicillin, but the effect was stronger for PMM, which also led to resistance to norfloxacin. Conclusions. This study demonstrates that both PMC and PMM have a direct impact on lactose-positive E. coli strain B906, reflected in decreased growth intensity at moderate and high concentrations (36 μg/mL and 72 μg/mL) and increased aggressiveness through reduced enzymatic activity, enhanced biofilm formation, and the emergence of resistance to ampicillin, ceftriaxone, and norfloxacin.