title: Impact of antibiotic treatments on the expression of the R plasmid tra genes and on the host innate immune activity during pRAS1 bearing Aeromonas hydrophila infection in zebrafish (Danio rerio).
abstract: BACKGROUND
  The transfer of R plasmids between bacteria has been well studied under laboratory conditions and the transfer frequency has been found to vary between plasmids and under various physical conditions. For the first time, we here study the expression of the selected plasmid mobility genes traD, virB11 and virD4 in the 45 kb IncU plasmid, pRAS1, conferring resistance to tetracycline, trimethoprim and sulphonamide, using an in vivo zebrafish infection- treatment model.
  
  
  RESULTS
  Three days after oral infection of adult zebrafish with Aeromonas hydrophila harboring pRAS1, elevated expression of pro-inflammatory cytokine (TNF α, IL-1β and IL-8) and complement C3 genes in the intestine coincided with disease symptoms. Tetracycline, trimethoprim and an ineffective concentration of flumequine given 48 h prior to sampling, strongly increased expression of plasmid mobility genes, whereas an effective dosage of flumequine resulted in lower levels of mRNA copies of these genes relative to placebo treatment. Following effective treatment with flumequine, and ineffective treatments with a low concentration of flumequine, with trimethoprim or with sulphonamide, the intestinal expression of immune genes was strongly induced compared to placebo treated control fish.
  
  
  CONCLUSIONS
  Treatment of zebrafish infected with an antibiotic resistant (TcR, TmR, SuR) A. hydrophila with ineffective concentrations of flumequine or the ineffective antimicrobials tetracycline and trimethoprim strongly induced expression of genes mediating conjugative transfer of the R-plasmid pRAS1. Simultaneously, there was a strong induction of selected inflammatory and immune response genes, which was again evident in fish subjected to ineffective treatment protocols. Our findings point to the essential role of therapeutic practices in escalation or control of antibiotic resistance transfer, and suggest that antibiotic substances, even in sub-inhibitory concentrations, may stimulate innate defenses against bacterial infections.
authors.affiliation: Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, Ullevålsveien 72, PO 8146, 0033 Oslo, Norway. Leon.Cantas@nvh.no
authors.forename: Leon
authors.initials: L
authors.lastname: Cantas
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Midtlyng
authors.forename: Henning
authors.initials: H
authors.lastname: Sørum
mesh_terms: D016980:Aeromonas hydrophila / Q000187:drug effects* / Q000235:genetics; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003227:Conjugation, Genetic; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D005260:Female; D005393:Fish Diseases / Q000276:immunology / Q000382:microbiology; D024841:Fluoroquinolones / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial; D022761:Gene Transfer, Horizontal; D016905:Gram-Negative Bacterial Infections / Q000276:immunology / Q000382:microbiology / Q000662:veterinary; D007113:Immunity, Innate; D007422:Intestines / Q000276:immunology / Q000382:microbiology; D008297:Male; D054892:Metagenome; D011815:R Factors; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013752:Tetracycline / Q000494:pharmacology; D014295:Trimethoprim / Q000494:pharmacology; D015027:Zebrafish / Q000276:immunology* / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D012336:RNA, Ribosomal, 16S; D014295:Trimethoprim; D013752:Tetracycline; C012976:flumequine