| Summary: | 碩士 === 國立中興大學 === 獸醫研究所 === 81 === Several samples, including the feces collected from pig farm, the tonsils of slaughtered pigs and the necropsied pigs infected with erysipelas, were collected for isolation and serotyping of Erysipelothrix rhusiopathiae from March 1992 through February 1993.
In the farms, the isolation rate was 9.02% (22/244), and mostly distributed in spring (27.62%) and summer (10.22%) seasons. In slaughtered pigs, the isolation rate of the tonsils was 21.3% (32/150) which were sampled in the period of August and September, the more popular seasons present the occurance of swine erysipelas.
A total of 114 isolates were identified their serotypes as type 1a, 1b, 2, 4, 6, 12 or 20, except 18 isolates were untypable strains. Among them 74.6% belongs to type 1a, 1bor2.Results of the toxcity test showed that 67.5% (77/114) of the isolated strains were toxicto the pig,of these, 93.62% (44/47) type 1a and 72% (18/25) type 2 were the high virulent strains. All the 47 strains isolated from necropsied cases were identified as high virulent type 1a or 2.
The strains identified as serotype 2 had higher isolation rates either in pig farm (17.4%) or in slaughtered pigs (45.2%). These type 2 strains were proven toxic and might also be associated with the disease in pig farms.
Three types of colonies as globoid, rhizoid and dense ramiform were observed. In type 1, the globoid type of colony was proven to be avirulent. The other two types were virulent, the rhizoid type was more toxic than the dense ramiform. On the contrary, these 3 types were proven to be toxic in type 2. The virulent abilities were demonstrated as dense ramiform >rhizoid >globoid. The results indicated that the colonied types of pure gelatin plate cultre can be a indicator to indentify the virulence of E. rhusiopathiae strains.
The drug sensitivity tests showed all the isolates were sensitve to penicillin series antibiotics. Among them. Ampicillin was the most sensitive one. Most of the isolated strains had more or less resistent to Oxytetracyclin, Chlortetracyclin and Chloramphenicol, but the vaccine strains still showed sensitive to them.
Tests of cross immunity had been done in this study. The mice vaccinated by type 1a living bacterin double doses had a complete protection against high or low virulent type 1a strain challenged, but incomplete protection was shown in the mice vaccinated by only one dose. Arthritis was visible in this incomplete protection mice. No matter vaccinated with one or double doses of the 1a living bacterin , incomplete protection was shown after challenged by various serotypes other than type 1a.
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