Erythromycin and florfenicol treatment of rainbow trout Oncorhynchus mykiss (Walbaum) experimentally infected with Flavobacterium psychrophilum

Abstract

Flavobacterium psychrophilum is responsible for significant economic losses in rainbow trout aquaculture. Antimicrobial treatment remains the primary means of control; however, there are limited choices available for use. The objectives of the study were therefore to determine the minimum inhibitory concentrations for erythromycin and florfenicol in selected F. psychrophilum isolates and to evaluate their clinical treatment efficacy in experimentally infected rainbow trout. All isolates tested had moderate susceptibility to florfenicol and erythromycin except one isolate, which had low susceptibility to erythromycin. Two isolates (one with moderate and one with low susceptibility to erythromycin) were used in an experimental infection trial. Rainbow trout juveniles were injected intraperitoneally with 108 cfu/fish and after mortality had begun, fish were given erythromycin‐ and florfenicol‐medicated feed at a rate of 75 mg kg−1 day−1 and 10 mg kg−1 day−1 fish body weight, respectively, for 10 consecutive days. The splenic F. psychrophilum load was determined using an rpoC quantitative PCR throughout the 30‐day trial. Relative to antibiotic‐free controls, erythromycin treatment significantly (p < 0.05) reduced mortality of rainbow trout juveniles infected with FPG101, even when treatment was initiated after clinical signs developed.

A global analysis on the systemic effects of antibiotics in cultured fish and their potential human health risk: a review

“…1997; Wise & Johnson 1998; Jarau et al . 2019) increased the survival rate of treated fish due to effective killing or inhibition of pathogenic bacteria (Inglis et al . 1991; Johnson & Smith 1994; Jarau et al .…”

“…1991; Johnson & Smith 1994; Jarau et al . 2019). In general, distinct antibiotics induce controversial effects on fish survival rate based on exposure methods (Hustvedt et al .…”

“…1991; Johnson & Smith 1994; Jarau et al . 2019). Future studies linking the observed body malformation to nutrients, physiology and metabolism in cultured fish are needed.…”

“…This may reduce aquaculture fingerlings production required to perpetuate the industry. On the other hand, various doses of dietary antibiotics (Hustvedt et al 1991;Inglis et al 1991;Thune & Johnson 1992;Johnson & Smith 1994;Rawles et al 1997;Wise & Johnson 1998;Jarau et al 2019) increased the survival rate of treated fish due to effective killing or inhibition of pathogenic bacteria (Inglis et al 1991;Johnson & Smith 1994;Jarau et al 2019). In general, distinct antibiotics induce controversial effects on fish survival rate based on exposure methods (Hustvedt et al 1991;Rodrigues et al 2018c) and doses and time (Topic Popovic et al 2012;Reda et al 2013;Limbu et al 2018) as observed on growth performance ( Table 2).…”

New Copper(I) Complex with a Coumarin as Ligand with Antibacterial Activity against Flavobacterium psychrophilum

“…The antibiotics used in Chile are mainly florfenicol and oxytetracycline [ 4 , 5 ]. However, the indiscriminate antibiotic use produces alterations of the bacteria flora in the aquatic environment inducing the appearance of resistant bacteria [ 4 ], and potentially transfer resistance to pathogens terrestrial animals and humans [ 6 ]. Identifying novel antibacterial drugs is therefore of critical importance and natural products are an excellent source for such discoveries.…”