| Antibiotics and antibiotic resistance are emerging contaminants. Tetracyclines are common antibiotics with a well-known mode of action and multiple resistance determinants. Water column samples were collected from 22 streams in Kansas and Nebraska in conjunction with a USEPA probability-based study of perennial, wadeable streams. Tetracyclines were analyzed by enzyme-linked immunosorbent assay (ELISA), while polymerase chain reactions (PCR) were used to enumerate 16S-rRNA, tetW, tetQ, and tetO. TetW, tetQ, and tetO were highly correlated (r2 > 0.80, p < 0.001) in all streams. Observed values of genes and tetracyclines were consistent with moderately impacted areas from recent targeted studies, and were generally no different among states, reference conditions, and ecoregions. However, tetW levels were significantly lower in Kansas than Nebraska. Based on probability, approximately 20% of Kansas and Nebraska streams are predicted to have observable levels of tetracyclines, tetW, tetQ, and tetO. Findings suggest an ambient reservoir of tetracycline resistance genes and favorable conditions for resistance selection. |
