Resistance and Biodegradation of Triclosan and Propylparaben by Isolated Bacteria from Greywater

We investigated the relationship between antibiotic-resistance genes and the antimicrobial agents, triclosan (TCS) and propylparaben (PPB). The greywater microbiome was repeatedly exposed to triclosan and propylparaben and the effect was analyzed using a combination of PCR, Etest, Biolog, 16S rRNA sequencing, and liquid chromatography. The taxonomic identification points to very similar or even identical isolates, however, the phenotypic analysis suggests that their metabolic potential is different, likely due to genomic variation or differences in the expression of the substrate utilization pathways. For both triclosan and propylparaben, the antibiotic resistance levels among isolates remain consistent regardless of the exposure duration. This suggests that antibiotic-resistance genes are acquired rapidly and that their presence is not directly proportional to the level of micropollutant exposure. In a biodegradation test, TCS was reduced by 50% after 7 h, while PPB decreased only after 75 h. For TCS, the minimal inhibition concentration (MIC) ranged from 64 to above 256 mg/mL. Conversely, for PPB the MIC for the tested strains ranged between 512 and 800 mg/mL. This study highlights the complex interaction between household xenobiotics, greywater microorganisms, and the emergence of antibiotic resistance.