The concentration of microplastics (MPs) in two important Hungarian freshwater habitats was determined in the size range of 50 μm–1 mm. Lake Balaton (LB) is the largest shallow lake in Central Europe, with a significant role in recreation and tourism. Its main inflow, the Zala River, enters the lake through an artificially constructed wetland, the Kis-Balaton Water Protection System and its catchment area (KB), which helps preserve the water quality of the lake. From these two areas, 15 samples were taken with an in situ filtration sampling method. After preparation, the samples were analyzed automatically by FT-IR microscopy. All samples, from both areas, contained MPs; the dominant microplastic (MP) shape was the fragment, while the most frequently polymer types were polyethylene, polypropylene and alkyd. Small MPs were dominant in both areas; around 90% of the MPs were smaller than 500 μm. On average, LB contained more MPs (21.0 ± 12.5 MPs/m³) compared to the KB, which presented an average concentration of MPs of 7.8 ± 5.9 MPs/m³. In the examined areas, two potential MP sources were determined, i.e., treated wastewater and road traffic. The importance of tourism should also be further investigated.

Recent studies have identified microplastics (MPs) in wastewater as surfaces that facilitate microbial colonization and act as vectors for the dissemination of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARBs). Their presence throughout the wastewater treatment process highlights the importance of investigating the microbial communities associated with MPs in wastewater treatment plants (WWTPs) and their potential implications for environmental and human health. This study investigates microbial colonization on MPs in wastewater by sampling six types of MPs deployed at various phases of wastewater treatment in three different WWTPs across Hungary, between June 2024 and March 2025. MPs were incubated in plastic colonizers submerged in treated and untreated wastewater. Post-retrieval, MPs were processed using selective media to ARBs, using Chromatic agar plates and selective medium for Pseudomonas aeruginosa. Strains were identified by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) at the genus level. Based on our results, Stenotrophomonas, Aeromonas genera, and members of the Enterobacteriaceae family were the dominant antibiotic-resistant bacterial taxa associated with MPs.