Avaliação da presença de Streptococcus agalactiae através da PCR em Tilápia-do-Nilo (Oreochromis niloticus) imunizada contra estreptococose

Abstract

Streptococcosis usually damages due to the great economic losses to the world fishing industry. It is necessary to develop diagnostic techniques for the rapid identification of the pathogen. The objective was verify the presence or absence of S. agalactiae bacteria in organs (brain, cephalic kidney and spleen) of Tilapia immunized against streptococci through PCR, use of different doses of commercial vaccine. For the extraction of DNA from bacterium, was performed the phenol chloroform protocol. After the PCR, the Streptococcus agalactiae was visualized in the chosen tissue fragments, and the mortality of the vaccinated animals was analyzed compared to the control. Through DNA extraction Streptococcus DNA amplification was observed directly from tissues that were reserved for this study. The percentage probability of negative organs was in the control (T1) 0% in all the samples and in the other treatments T2 75%; 33% and 58% already in T3 100%; 85%; 69% in the brain, kidney and spleen, respectively. The mortality in the control animals was 83% aganist 69 and 63% in the treatments that received 1 dose and 2 doses of the vaccine. Through the extraction of the bacterial DNA by the chloroform phenol protocol, it was possible to obtain the genetic material and to perform a good amplification by identifying the DNA of the bacterium through PCR in the tissues of the analyzed fish.