Effect of antibiotic administration on the structure of the larval microbiota of Genypterus chilensis in culture and the occurrence of genes coding for antimicrobial resistance
The cultivation of Genypterus chilensis is currently considered a priority in national aquaculture and is within the Chilean Aquaculture Diversification Program (PDACh). But low larval survival rates have led to the need for continued use of antibacterials mainly with florfenicol or oxytetracycline,...
| Autor: | |
|---|---|
| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2020 |
| País: | Chile |
| OAI Identifier: | oai:repositorio.anid.cl:10533/42591 |
| Acceso en línea: | https://hdl.handle.net/10533/42591 |
| Access Level: | acceso abierto |
| Palabra clave: | Ciencias Naturales Ciencias de la Tierra y del Medio Ambiente Microbiología |
| Sumario: | The cultivation of Genypterus chilensis is currently considered a priority in national aquaculture and is within the Chilean Aquaculture Diversification Program (PDACh). But low larval survival rates have led to the need for continued use of antibacterials mainly with florfenicol or oxytetracycline, the two most widely used antimicrobial agents (AAM) in marine fish aquaculture in Chile. This study determined the effect of the use of these AAM in the microbiota of living feed (rotifers and Artemia) and on the larvae of G. chilensis, in addition to the presence of bacterial resistance and antibacterial resistance genes (ARGs) associated with it. When treating live feed with florfenicol (FFC) or oxytetracycline (OTC), no significant decrease in levels of TCB (total culturable bacteria) levels in rotifers, Artemia and G chilensis larvae were obtained, in addition high levels of FRB (florfenicol resistant bacteria) and ORB (oxytetracycline resistant bacteria) were observed in all experiences. The composition of the microbiota (using the mass sequencing technique) was determined in treated rotifers and control which in the case of both antibiotics was composed of the phyla Proteobacteria and Bacteroidetes and the genera Vibrio, Cohesibacter and Aliiroseovarius which had different abundances depending on the origin of the sample. In the case of Artemia treated and not treated with both antibiotics the predominant phyla were Proteobacteria, Bacteroidetes and Epsilonbacteraeota whose relative abundances varied according to the origin of the sample, the most abundant genus in laboratory experience was Halomonas and in the experiences in mass cultivation the most abundant genera were Arcobacter and Pseudomonas in Artemia control and Psychrobacter in those treated with oxytetracycline. For the experience with florfenicol the most abundant genera in control Artemia were Neptunemonas and Pseudoalteromonas and in the treated Arcobacter and Neptunemonas. In the case of the predominant phyla in conger eel larvae were Actinobacteria, Proteobacteria and Firmicutes with Glutamicibacter as the predominant genus in the control larvae and treated with oxytetracycline. For the experience with florfenicol the predominant phyla in the control and treated larvae were Proteobacteria and Firmicutes and the predominant genera Alloiococcus, Dialister and Neptuneomonas in control and Psychrobacter, Piscirickettsia and Methylobacterium in the treated larvae in all experiences performed the use of antibiotics changed the taxonomic composition of the crops despite not changing their beta diversity. Finally, 167 resistant strains were selected from the cultures of live feeds and red conger eel larvae treated and not treated with AAM, which turned out to have a high proportion of multiresistance to antimicrobials and a high co-resistance to florfenicol and oxytetracycline. In addition, a high percentage of the resistant strains turned out to be carriers of floR and fexA ARGs with floR as the most prevalent for florfenicol and for oxytetracycline tet(A) and tet(D) were the most prevalent in the strains analyzed. Finally, a high level of plasmid carriage was detected in the resistant strains and the resistance to FFC, OTC, S and SXT was transferred by conjugation to a E. coli strain. These results suggest that Artemia, rotifers and G. chilensis larvae cultures should be monitored as there is a high risk that the microbiota of these organisms will become a reservoir for these ARGs, which could be transferred to pathogens making antibiotic therapies ineffective in the future. |
|---|