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The correlation between serology and bacteriology of Salmonella in pigs, in the central Taiwan
|摘要:||本試驗旨在分析血清ELISA檢測是否可代替豬隻糞便分離作為監控以降低豬場沙門氏桿菌污染率的檢測方法。為了提高沙門氏桿菌的分離率，首先將各種增菌及選擇性培養基做配對組合比較，最後以paired T test選定出XLT4及MSRV兩種選擇性培養基作為本試驗豬隻糞便分離用之培養基。糞便檢體之分離法皆依照ISO 6579之標準進行檢測，並將可疑菌落進行血清凝集試驗、GFB-14E生化鑑定和PCR以確定其為沙門氏桿菌；血清檢測方面則使用兩種市售的ELISA 套組 (IDEXX®和CHEKiT®) 進行檢測。試驗設計分為個體配對以及場的配對兩種予以比較並分析其效率。其中個體配對分為兩項，即從屠宰豬取得之血清與糞便個體配對檢體 (n=279) 及從豬場取得之配對檢體 (n=35) 。結果顯示豬隻血清與糞便陽性率無顯著關係，惟屠宰豬之糞便分離率 (52.7%) 遠高於血清之陽性率(IDEXX = 43.0%；CHEKiT = 29.0%)。擴大至場與場間的配對比較 (N=28) 發現糞便分離結果與IDEXX® ELISA血清陽性率有一線性關係，而Group B和C1的沙門氏桿菌則與CHEKiT® ELISA有線性關係，但是皆屬於中度相關。而將血清陽性率每10%分組進行比較時，相關係數比單一豬場配對為高，其中Group B和C1的沙門氏桿菌與CHEKiT® ELISA更高達0.951。又混合血清與個體血清平均之OD值比較，亦發現IDEXX®的相關係數極高 (>0.8)。本試驗將屠宰場以及豬場分離到的沙門氏桿菌進行藥物感受性試驗，結果顯示所有的菌株皆對大多數的藥物有感受性。從血清抗體ELISA與傳統培養法有一線性關係的結論，今後應該可以使用ELISA法進行豬場豬隻感染沙門氏桿菌之監測，以選用IDEXX® ELISA套組，利用混合血清來進行檢測，將有大幅降低成本並縮短總檢測時間之優點。|
In this study, we compared the traditional bacterial isolation method with the ELISA assay measuring antibodies in serum, for the purpose of replacing the bacterial isolation by ELISA to monitor the herd prevalence of Salmonella spp. islandwide. In order to increase the isolation rate in Salmonella spp., we first compared some selected diagnostic agars and found that XLT4 and MSRV were the most sensitive Salmonella isolation media confirmed by paired T test. All of the fecal samples were examined according to ISO 6579 standard, and every suspected Salmonella colony was further checked by GFB-14E, PCR and O antigen agglutination test. Serum samples were tested by two commercial ELISA kits (IDEXX and CHEKiT Salmonella ELISA). The data were analyzed in paired pigs and paired individual pig herds. Paired serum and fecal samples were obtained from abattoirs (n=279) and pig farms (n=35). The results indicated that there was no statistically significant correlation between Salmonella isolation rate and positive seroprevalence. The results showed that Salmonella isolation rate (52.7%) was higher than the seroprevalence either one ELISA (IDEXX = 43.0%; CHEKiT = 29.0%). We then focused on the correlation of isolation rate and seroprevalence between paired pig herds (N=28). A linear regression model was constructed for each sampling site. The results demonstrated that there was a medium correlation between IDEXX ELISA seroprevalence and the prevalence of Salmonella spp. isolated from pooled stool samples. Similar correlation was observed between CHEKiT ELISA seroloprevalence and the prevalence of Group B and C1 Salmonella. Based on the distribution of herd seroprevalences, samples were divided into subgroups with 10% interval in seroprevalence for further analysis. A good correlation coefficient of 0.951 was found between CHEKiT ELISA seroloprevalence and the prevalence of Group B and C1 Salmonella. A high correlation coefficient of >0.8 was also obtained between the averaged OD values of pooled serum and individual serum by IDEXX ELISA. Salmonella spp. isolated from abattoirs and pig farms were also subjected to drug sensitivity test. All of the Salmonella isolates were sensitive to a different degree to most drugs tested. In conclusion, in examing the prevalence of Salmonella, there was a linear association between serum ELISA assay and fecal culture. Therefore, ELISA assay might be useful in monitoring the prevalence of Salmonella in pig farms. Pooled serum samples and IDEXX ELISA assay might be the best combination to reduce the cost and testing time required in surveillance of Salmonella prevalence.
|Appears in Collections:||獸醫病理生物學所|
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