Abstract

The minimum inhibitory and minimum bactericidal concentrations (MIC, MBC) of four common aquatic bacteria (Flexibacter columnaris, A. hydrophila, A. salmonicida, and Pseudomonas fluorescens) were determined for four commonly used antibiotics (tetracycline (TC), chloramphenicol sodium succinate (CH), erythromycin (ER), and Furanase (FU).  While the authors concluded TC and FU to be the most effective, they also found that the pharmacological preparation and environmental influences were crucial in the selection of an appropriate antibiotic. The need for identification and sensitivity testing previous to antibiotic administration is illustrated by resistant agents and plasmid testing.

Notes

Iatrogenic damage by antibiotics:

Chloramphenicol - High prolonged dosage -->liver damage

Sulfa - High prolonged dosage -->liver damage

Oxytetracycline -  High prolonged dosage -->liver damage

Nitrofurantoin - High prolonged dosage -->liver damage

Tetracycline resistant plasmids in bacteria decrease this drug's efficacy, however, tetracycline was effective against Pseudomonas fluorescens where furanase, chloramphenicol and erythromycin were not.  Furanase was otherwise the most efficacious drug.

Bacterial culture, along with antibiotic resistance and sensitivity, are needed to select the appropriate antibiotic for treatment.

30-50 ug/mL concentrations in water are needed to achieve therapeutic levels in fish.

Effects of environment on antibiotics:

1. Temperature - higher temperatures increase drug absorption by fish, however, high temperature also decreases antibiotic stability.
2. pH - an increase in pH will decrease oxytetracycline stability.
3. Hardness - Ca & Mg ions bind tetracyclines.