The Emergence of Tetracycline Resistance in Rumen Bacteria

The emergence of antibiotic-resistant bacteria is a major concern for human health because current antibiotics have become ineffective in treating diseases caused by the antibiotic-resistant pathogenic bacteria. The objective of this study was to test the hypothesis that exposing rumen bacteria to tetracycline will gradually lead to the development of tetracycline-resistant bacteria, some of which will become multidrug resistant bacteria. To achieve this objective, rumen fluid containing bacteria were cultured on agar plates containing tetracycline to select for tetracycline-resistant bacteria, which were then cultured on Tryptic Soy Broth (TSB) agar containing chloramphenicol, ampicillin, and kanamycin antibiotics. The results showed that, of the ten tetracycline-resistant bacteria that were previously isolated as resistant to tetracycline at 12 µg/mL, eight isolates were still able to survive in TSB agar supplemented with 25 µg/mL tetracycline. All but one bacterial isolate also grew on TSB agars supplemented with chloramphenicol, ampicillin, and kanamycin. PCR results of 16S rRNA suggest that isolates consisted of the Sphingobacterium, Stenotrophomonas, and Microbacterium genuses. These results are significant because they show that some rumen bacteria are capable of developing resistance to tetracycline and may subsequently cause untreatable diseases in humans.