oxytetracycline--anhydrous and Flavobacteriaceae-Infections

Topics: Animals; Anti-Bacterial Agents; Chile; Fish Diseases; Fisheries; Flavobacteriaceae Infections; Oxytetracycline; Salmonidae; Tenacibaculum; Thiamphenicol

Leakage of medical residues into the environment can significantly impact natural communities. For example, antibiotic contamination from agriculture and aquaculture can directly influence targeted pathogens, but also other non-targeted taxa of commensals and parasites that regularly co-occur and co-infect the same host. Consequently, antibiotics could significantly alter interspecific interactions and epidemiology of the co-infecting parasite community. We studied how minor environmental concentrations of antibiotic affects the co-infection of two parasites, the bacterium Flavobacterium columnare and the fluke Diplostomum pseudospathaceum, in their fish host. We found that antibiotic in feed, and particularly the minute concentration in water, significantly decreased bacterial virulence and changed the infection success of the flukes. These effects depended on the level of antibiotic resistance of the bacterial strains. Antibiotic, however, did not compensate for the higher virulence of co-infections. Our results demonstrate that even very low environmental concentrations of antibiotic can influence ecology and epidemiology of diseases in co-infection with non-targeted parasites. Leakage of antibiotics into the environment may thus have more complex effects on disease ecology than previously anticipated.

Topics: Animals; Anti-Bacterial Agents; Aquaculture; Coinfection; Drug Resistance, Bacterial; Fish Diseases; Flavobacteriaceae Infections; Flavobacterium; Oncorhynchus mykiss; Oxytetracycline; Trematoda; Trematode Infections; Virulence; Water Pollution, Chemical

Topics: Animals; Anti-Bacterial Agents; DNA, Bacterial; Fish Diseases; Flavobacteriaceae Infections; Flavobacterium; Oncorhynchus mykiss; Oxytetracycline; Polymerase Chain Reaction; Scotland; Water Microbiology

Columnaris disease was induced in channel catfish, Ictalurus punctatus (Rafinesque), by bath exposure to four highly virulent isolates of Flavobacterium columnare. In untreated controls, mortality began 20 h after exposure and reached 100% by 48 h. Mortality in channel catfish given antibiotic treatments with oxytetracycline or a combination of sulphadimethoxine and ormetoprim in feed prior to bacterial challenge was zero with all four strains of F. columnare. Diquat (Zeneca Agricultural Products, Wilmington, DE, USA) was the most effective bath treatment; mortality with all four strains was zero. With potassium permanganate, chloramine-T, hydrogen peroxide and copper sulphate, bath treatment efficacy varied significantly among strains (P = 0.0346) and among treatments (P = 0.0033). Bath treatments with chloramine-T and potassium permanganate significantly reduced (P < 0.05) mortality from 100 to 75 and 69%, respectively, but copper sulphate and hydrogen peroxide treatments were not effective. Based on our results, oral antibiotics prevented columnaris disease but, of the bath treatments, only Diquat produced a dramatic reduction in the mortality of acutely infected fish. Diquat is labelled for aquatic use as an herbicide in the USA but in large ponds it is prohibitively expensive.

Topics: Animals; Anti-Bacterial Agents; Aquaculture; Catfishes; Chloramines; Copper Sulfate; Fish Diseases; Flavobacteriaceae Infections; Flavobacterium; Oxytetracycline; Potassium Permanganate; Pyrimidines; Sulfadimethoxine; Tosyl Compounds