The increasing use of antibiotics has led to a dramatic increase in the number of resistant microorganisms. Many microorganisms are not only resistant to one antibiotic, but to a variety of different substances. This makes it particularly difficult to treat infections.
Michael Schloter, Helmholtz Zentrum Munich, Neuherberg, and Technical University of Munich, Freising, Germany, and colleagues have studied the transmission mechanisms of antibiotic resistance between bacteria. The team used Piaractus mesopotamicus as a model, a fish species from South America known as Pacu that is often kept in aquacultures. The animals received the antibiotic florfenicol with their food. The team took samples from the fishes’ digestive tract and searched for genetic changes in the bacteria living there.
As expected, the administration of the antibiotic led to an increase in genes responsible for resistance (antibiotic resistance genes or ARGs), e.g., genes for pump proteins, which transport the active ingredient out of the bacteria. In addition, an increase in so-called mobile genetic elements (MGEs) in the vicinity of these resistance genes was found. This suggests that the bacteria exchange resistances with each other. Further investigations confirmed that these MGEs jump across the genome. They tear away parts of the genome, including ARGs, and insert them elsewhere.
The researchers conclude that the oral administration of antibiotics increases the potential for MGE-mediated exchange of ARGs in the gut of fish. This could contribute to the enrichment and dispersion of ARGs in aquaculture systems. According to the team, the study highlights the risk of using in-feed antibiotic during aquaculture production.
- Oral administration of antibiotics increased the potential mobility of bacterial resistance genes in the gut of the fish Piaractus mesopotamicus,
Johan S. Sáenz, Tamires Valim Marques, Rafael Simões Coelho Barone, José Eurico Possebon Cyrino, Susanne Kublik, Joseph Nesme, Michael Schloter, Susanne Rath, Gisle Vestergaard,