Differences were considered significant at (*) p < 0.05, (**) p < 0.01 and (*** p < 0.001). Results Clinical symptoms and re-isolation of A. hydrophila No fish died within 3 days of the intubation challenge. All A. hydrophila inoculated zebrafish showed changes in external body color (pale, reddish coloration around gill covers), abnormal positioning in the aquarium (at the surface or near the bottom), increased gill H 89 solubility dmso ventilation frequency or lack of appetite within 24 h, while no such symptoms were seen in the uninfected

control group. On termination of the experiment after 3 days, macroscopically visible ascites was observed in both the placebo treated fish and groups treated with ineffective antibiotics, whereas reduced clinical symptoms were noted in the group that had received effective treatment. Moderate to heavy growth of A. hydrophila in pure culture was detected from kidney samples of groups receiving placebo or ineffective treatments, whereas very low levels of A. hydrophila were isolated from groups of zebrafish exposed to effective antibiotic treatment [Figure 1]. Figure 1 Growth level median BV-6 supplier counts of A. hydrophila isolated from kidney samples of experimentally

infected zebrafish, 48 h post antibiotic treatment (6 different treatment groups). Axis scale: absent = 0, very few = 1, few = 2, moderate = 3, rich = 4 and Histone demethylase very rich = 5. Error bars represent ± SEM (6 adults per treatment group). Differences were considered significant at (**) p < 0.01 for total growth degree of placebo vs. other antibiotic treated zebrafish in each intestinal tissue analyzed. Immune response of zebrafish to A. hydrophila Compared to uninfected fish the transcription patterns of the innate immune response genes in placebo treated fish [Figure 2] were clearly raised and the transcription patterns of IL-1β (108

fold) and IL-8 (45 fold) genes were found to be substantially higher than TNF α (8 fold) and C3 (3 fold). Figure 2 Relative pro-inflammatory cytokine and complement C3 genes Selleck Inhibitor Library expression levels across the entire intestine of A. hydrophila infected and placebo treated adult zebrafish after harvesting 3 days post-challenge. Expression levels are reported as fold change compared to average expression levels of uninfected (sterile physiological saline solution inoculated) control groups. Error bars represent ± SEM (based on variation between 6 adults per treatment group). Comparing the gut microbiota related 16S rRNA gene copy number under different antibiotic treatments The copy numbers of 16S rRNA genes in the digestive tract significantly decreased following treatment with inhibitory doses of flumequine. The copy numbers obtained from ineffective antibiotic treatment groups were similar to those observed in the placebo treated group [Figure 3].