| Abstract [eng] |
Aminoglycosides, tetracyclines, macrolides, and β-lactams are among the most widely used classes of antibiotics in Lithuania and worldwide. The resistance of environmental bacteria and their ability to form biofilms can contribute to the growing problem of antibiotic resistance; there-fore, assessing these determinants is essential for a better understanding of how environmental bacteria influence the spread of genes that confer antibiotic resistance. In this study, the biofilm forming ability and antibiotic resistance of bacterial isolates from the Kazokiškės landfill were evaluated. Fourteen isolates were identified by Nanopore sequencing of their 16S rRNA genes. Biofilm formation was assessed in 96-well microplates using the crystal violet assay, and the metabolic activity of cells within the biofilm was measured by a resazurin reduction assay. The prevalence of antibiotic resistance genes (β-lactam, tetracycline, macrolide, and aminoglycoside resistance) was determined by PCR analysis. Phenotypic antibiotic susceptibility was tested by an agar well diffusion method. The cultivable isolates were predominantly from the phylum Bacillota (72%), with smaller proportions from Actinomycetota (14%) and Pseudomonadota (14%). Most (80%) of the isolates formed biofilms based on the crystal violet assay, a finding confirmed by detectable metabolic activity in the biofilm cells. However, one isolate (Lysinibacillus sp. YS112) showed a discrepancy: no biofilm was detected by the crystal violet assay, yet weak metabolic activity was observed. Several resistance genes were identified: ctx-M, oxa1, oxa2, oxa23, and shv (β-lactam resistance); tetD and tetC (tetracycline resistance); aadA1, aadB, and strB (aminoglycoside resistance); and IntI1 (class 1 integron integrase). A higher prevalence of these genes was found among biofilm forming bacteria. Four isolates were resistant to ampicillin, and this phenotypic resistance correlated with the presence of β-lactamase genes (ctx-M, oxa1, oxa23) in those iso-lates. All isolates were sensitive to the other tested antibiotics, except for one P. aeruginosa isolate, which was resistant to streptomycin and erythromycin; no corresponding aminoglycoside or macrolide resistance genes were detected in this isolate. |
