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Bacitracin Inhibits the Oyster Pathogen Perkinsus marinus in Vitro and in Vivo
Author(s) -
Faisal Mohamed,
La Peyre Jerome F.,
Elsayed Ehab,
Wright D. Craig
Publication year - 1999
Publication title -
journal of aquatic animal health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 52
eISSN - 1548-8667
pISSN - 0899-7659
DOI - 10.1577/1548-8667(1999)011<0130:bitopp>2.0.co;2
Subject(s) - bacitracin , biology , crassostrea , oyster , ostreidae , microbiology and biotechnology , bivalvia , in vivo , eastern oyster , zoology , shellfish , veterinary medicine , mollusca , antibiotics , aquatic animal , fishery , ecology , medicine , fish <actinopterygii>
The in vitro growth rates of two isolates of Perkinsus marinus were significantly reduced by bacitracin. Upon coincubation with 1 mg bacitracin/mL, the doubling times rose from 27 ± 2.1 h to 34 ± 2.9 h for the LMTX‐1 isolate ( P < 0.001) and from 15 ± 1.9 h to 22.2 ± 2.4 h for the Perkinsus ‐1 isolate ( P < 0.001). At 10 mg bacitracin/mL, viability of both isolates was much reduced ( P < 0.0001). The sensitivity of P. marinus to bacitracin was examined in vivo in two clinical trials. In the first, individual eastern oysters Crassostrea virginica were injected with 10 7 Perkinsus ‐1 cells, then fed bacitracin at a concentration of 5 or 50 mg/mL encapsulated in lipid vesicles daily for 6 weeks. Parasite body burden was significantly reduced in oysters administered 5 mg bacitracin/mL (3.3 × 10 4 ± 2.5 × 10 4 hypnospores/g wet tissue) or 50 mg/mL (5.3 × 10 4 ± 6.4 × 10 4 hypnospores/g) as compared with control oysters (3.2 × 10 5 ± 4.7 × 10 5 hypnospores/g, P < 0.05) that received encapsulated seawater only. In the second experiment, naturally infected oysters (average, 10.9 × 10 6 ± 30.7 × 10 6 hypnospores/g) received encapsulated bacitracin at 10 mg/mL for 10 weeks. Treated oysters had significantly lower levels of infection (2.5 × 10 6 ± 3 × 10 6 hypnospores/g) than did control oysters (67.4 × 10 6 ± 144 × 10 6 hypnospores/g, P < 0.05). Despite the sharp decrease in infection intensity in the bacitracin‐treated oysters, survival rate improved by only 10%. It is possible that damage to the vital organs of infected oysters was too advanced and widespread to be reversed. The in vitro and in vivo findings of this study suggest that bacitracin has promise for use in P. marinus chemotherapy.