Susceptibilidade in vitro e eficÃcia da terapia com oxitetraciclina em infecÃÃes por Streptococcus agalactiae em tilÃpia do Nilo / Susceptibility in vitro and efficiency of therapy with oxytetracycline in infections by Streptococcus agalactiae in Nile tilapia

AUTOR(ES)

Flaviane Castro de Faria

DATA DE PUBLICAÇÃO

2009

RESUMO

The aims of this work were to determine the in vitro sensitivity of different isolates of Streptococcus agalactiae to oxytetracycline (OTC) and verify the effectiveness of antibiotic therapy in the treatment of streptococcal disease in Nile tilapia (Oreochromis niloticus). To determine the diameter of the halo of inhibition and minimum inhibitory concentration (MIC) of OTC were used 29 S. agalactiae strains isolates from outbreaks of meningoencephalitis and septicemia in the Nile tilapia. The isolates were classified as sensitive (wild-type - WT) or resistant (non-wild-type - NWT) according to the frequency distributions of the values of MIC and diameter of the zone of inhibition. The strains were divided into two groups: sensitive to OTC diameter of the zone of inhibition of Â28 mm and the MIC value of <1.95 mg/mL composed of 27 isolates, and resistant to OTC, composed of only two isolated, with the diameter of the zone of inhibition equal to 12 mm and MIC value of equal to 31.25 mg/mL. The therapeutic efficiency of OTC was determined by experimental infection in Nile tilapia with S. agalactiae and treatment with OTC (medicated feed) before or after the challenge. The dose of OTC used was 100 mg per kg body weight for ten days. Three therapeutic models were tested: 1 - treatment with OTC initiated 24 hours before the challenge; 2 - treatment with OTC started 1h after the challenge and 3 - treatment with OTC started 24h after the challenge. The use of OTC in the treatment of infections by S. agalactiae in Nile tilapia was effective in reducing mortality, but it can collaborate in the maintenance of the agent in the breeding because of asymptomatic carriers.

ASSUNTO(S)

medicina veterinaria oxitetraciclina nile tilapia terapia antimicrobiana testes of susceptibility antimicrobial therapy testes de susceptibilidade tilÃpia do nilo oxytetracycline streptococcus agalactiae streptococcus agalactiae

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