양식(養殖) 넙치의 연쇄구균증(連鎖球菌症)

A streptococcal Disease of Cultured Flounder, Paralichthys olivaceus

1. 1991년(年) 8월(月)부터 10일(日)까지 제주도내(濟州道內) 넙치양식장 4개소(個所)의 병어에서 연쇄구균을 분리하였다. 2. 분리균(分離菌)은 $10^{\circ}C$, $45^{\circ}C$, 6.5% Nacl, pH 9.6 및 0.1% methylene blue milk 에서는 발육(發育)되지 않았고 또한 Indole 및 $H_2S$도 생성하지 못하였으며 $\beta$ 용혈성(溶血性)을 나타내었다. 3. 이상(以上)의 성상(性狀)에서 분리균(分離菌)은 Bergey's Manual of Determinative Bacteriology 및 Bergey's Manual os Systematic Bacteriology I 및 II에 근거(根據)를 두어 검색(檢索)한 결과(結果) Streptococcus pyogenes 및 Streptococcus epuisimilis와 유사하지만 약간의 차이(差異)가 있으므로 Streptococcus sp.로 하였다. 4. 분리균(分離菌)의 약제(藥劑) 감수성(感受性) 시험결과(試驗結果) Spiramycin 및 Erythromycin에 높은 감수성(感受性)을 나타냈으나 Penicillin에는 내성(耐性)을 나타냈다. 5. 분리균(分離菌)의 병원성(病原性) 시험결과(試驗結果) $1.1{\times}10^3cells$/100g 어체중 이상(以上) 접종(接種)하였을 때는 폐사(斃死) 미수(尾數)가 발생(發生)하였으나 그 이하(以下)의 접종(接種) 농도(濃度)에서는 폐사(斃死)가 발생(發生)하지 않았다.

From August to October of 1991, a bacterial disease occurred in cultured flounder, of 0 age Paralichthys olivaceus, in Cheju-do. Typical symptoms of the diseased fish were the hemorrage of the opercle, discoloration of the body, exophthalmus and hemorrhage of the eyes. The causative organism isolated from diseased fish was identified as a $\beta$-hemolytic Streptococcus. This bacterium was not identical with any known Streptococcus species listed in Bergey's Manual of Determinative Bacteriology 8th edition. However there was a close similarity between this species and Streptococcus sp. isolated from flounder and reported by Tashio (1983). The isolated bacteria streptococcus sp. showed very high sensitivity to the SM and EM, however, it resisted to the high concentration of Penicillin. In the pathagenicity analysis, about $1.1{\times}10^9$, $1.1{\times}10^7$, $1.1{\times}10^5$, $1.1{\times}10^3$, $1.1{\times}10^1cells$/100g B.W of isolated bacteria were injected percutaneouly. The results showed that this inoculation size $1.1{\times}10^3cells$/100g B.W was the threshold for the induction of mortality in pathogenicity analysis.