碩士 / 國立屏東科技大學 / 獸醫學系 / 93 / The present study was performed on Streptococceus iniae infection in cultured cobia ( Rachycentron canadum ) to investigate the occurrence, etiology and different routes of pathogenicity and for the purpose to know cobia infected with S. iniae from various organs of bacteria status and a wide distribution. S. iniae was frequently isolated from the brain of cultured cobia juveniles showing vertebral deformity. Morality was averaged 5 to 15% in the case examined. The diseased cobia showed exophthalmos, corneal opacity, epicarditis and congestion on the inside of the opercula and upper jaw. Histopathologically, they showed keratitis, panphthalmitis, and meningitis. S. iniae was also isolated from vertebral deformed grouper. Comparative taxonomical studies were perfomed over a total of 6 ß－hemolytic streptoccus strains isolated from diseased cultured Cobia, Grouper ( Epinephelus lancerolatus ), Greymullet ( Mugil cephalus ), Threadfin ( Polydactylus microstomus ), Bass ( Micropterus salmoides ), Tilapia ( Oreochomis sp. ) and S. iniae P1024. The phenotypic properties of the fish isolates are well agreed with each other. Considering the salt tolerance of S. iniae might have originated from terrestrial animals. Cobia were an intraperitoneal inoculated with S. iniae P1024 leaded to the occurrence of vertebral deformity become shorter period as the water temperature increased at 21-30℃. Vibable counts of S. iniae P1024 could be also isolated in the brain. Experimental infections with isolates gave gross signs and histological changes similar to those seen in naturally infected cobia. Moreover, by various different inoculated routes experiment indicates that vibable counts of S. iniae P1024 could be successfully found in various organs except brain. S. iniae isolated from cobia have been also confirmed to be deaded to mice by an intraperitoneal injection.
Disk diffusion methods of 13 antimicrobial agents were tested against S. iniae P1024 strains by Mueller-Hinton agar. Amoxycillin, Ampicillin, Erythromycin, Doxycycline, Tetracycline, Florfenicol, and Lincomycin, and Enrofloxacin, highly effective against all the stains tested. Flumequine、Oxolinic acid、Sulphamethoxazole- Trimethoprim were not effective. Furthermore, effective eight antimicrobical agents were administered to cobia five days by oral ( 50mg∕kg.B.W ). Challenge by intraperitoneal inoculation S. iniae ( 2×106 CFU/mL ) after antimicrobical agents treatment and the highly effective has to protect S. iniae infection. From experimental infection with S. iniae P1024 was examined to know the recovered fish was challenged by reinfecting with S. iniae P1024 ( 1.1×107 CFU/mL ), vertebral deformity and number of viable bacteria in the blood, spleen, and kidney were decreased those of the control fish.
Formalin killed cells ( FKC ) of S. iniae P1024 were administered to cobia fingerling by immersion, oral, and an intraperitoneal injection methods. 30 days after vaccination, each group was challenged by an intraperitoneal inoculation S. iniae P1024 ( 2.4×107 CFU/mL ). After the challenge, fishes vaccinated by an intraperitoneal injection showed neither clinical signs of the disease nor they died. Furthermore, bacterial cell numbers decreased rapidly in the blood, spleen, and kidney whereas the numbers did not remained static in the brain. On the other hand, immersion and oral vaccination were ineffective, showing typical clinical signs of the disease. Results of this experiment indicate that vaccination by an intraperitoneal injection dead bacterial bacterin is the better than other two different administration routes in preventing S. iniae infection.
| Identifer | oai:union.ndltd.org:TW/093NPUST541003 |
| Date | January 2005 |
| Creators | Tseng-Fa Peng, 彭增發 |
| Contributors | Shih-Chu Chen, 陳石柱 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 76 |
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