In vitro and in vivo activities of drugs against Mycobacterium marinum in yellowtail Seriola quinqueradiata

Abstract

Mycobacterium marinum (NJB 0419, MY 0401) isolated from yellowtail Seriola quinqueradiata showed drug susceptibility to rifampin, streptomycin (SM), ethambutol, kanamycin, sulfamethoxazole, amikacin, ciprofloxacin and ofloxacin by the broth dilution method. Furthermore, SM, kanamycin and sulfamonomethoxine activities were tested using the proportion method, and M. marinum was most susceptible to SM. Therefore, SM was used for the treatment of yellowtail (mean body weight 236 g) intramuscularly injected with NJB 0419 at a dose of 5.6 × 104 CFU/fish. The diet medicated with SM was orally administered at doses of 25 and 50 mg/kg body weight/day for 7 consecutive days after 4 h or 10 days following injection. Fish receiving 50 mg SM had lower mortality than the controls when medication started 4 h after injection. Therefore, SM may be an effective drug to control M. marinum infection. The timing for initiating oral medication with SM requires further study. © 2008 The Japanese Society of Fish Pathology.