Characterization of Microbiota Composition and Presence of Selected Antibiotic Resistance Genes in Carriage Water of Ornamental Fish

Abstract

<div><p>International trade with ornamental fish is gradually recognized as an important source of a wide range of different antibiotic resistant bacteria. In this study we therefore characterized the prevalence of selected antibiotic resistance genes in the microbiota found in the carriage water of ornamental fish originating from 3 different continents. Real-time PCR quantification showed that the <i>sul1</i> gene was present in 11 out of 100 bacteria. <i>tet(A)</i> was present in 6 out of 100 bacteria and <i>strA</i>, <i>tet(G)</i>, <i>sul2</i> and <i>aadA</i> were present in 1–2 copies per 100 bacteria. Class I integrons were quite common in carriage water microbiota, however, pyrosequencing showed that only 12 different antibiotic gene cassettes were present in class I integrons. The microbiota characterized by pyrosequencing of the V3/V4 variable region of 16S rRNA genes consisted of <i>Proteobacteria</i> (48%), <i>Bacteroidetes</i> (29.5%), <i>Firmicutes</i> (17.8%), <i>Actinobacteria</i> (2.1%) and <i>Fusobacteria</i> (1.6%). Correlation analysis between antibiotic resistance gene prevalence and microbiota composition verified by bacterial culture showed that major reservoirs of <i>sul1 sul2, tet(A)</i>, <i>tet(B) tet(G)</i>, <i>cat</i>, <i>cml</i>, <i>bla</i>, <i>strA</i>, <i>aacA</i>, <i>aph</i> and <i>aadA</i> could be found among <i>Alpha-, Beta-</i> and <i>Gammaproteobacteria</i> with representatives of <i>Enterobacteriaceae, Pseudomonadaceae, Rhizobiaceae</i> and <i>Comamonadaceae</i> being those most positively associated with the tested antibiotic resistance genes.</p></div