| 英文摘要 |
In this study, four commercially available kits specific for Escherichia coli O157 and one PCR method were evaluated for their performance while applied to detect E. coli O157:H7 in foods. Using 69 pure strains, the specificity and sensitivity rates were both 100% as determined on the base of O157-antigen. While targeted on both O157 and H7 antigens, all tested kits showed 100% sensitivity rates, but specificity rates decreased to 89.6%. The detection limits of the four kits ranged from 103 to 104 CFU/mL. Both the specificity rate and sensitivity rate of the PCR method were 100%, with a detection limit of 103 CFU/test. This study indicated that these four commercial kits were designed only for O157 antigen of E. coli, suggesting that these kits are only useful for prescreening of O157 antigen of E. coli. Positive samples tested by the kits should be confirmed by other appropriate methods following isolation of suspect colonies. Inoculation tests revealed that one E. coli O157 cell in one gram sample could be detected following enrichment procedures. When the four kits were applied to examine market food samples, all gave different degrees of false-positive results. Hence, these kits can only be used for screening. No false-positive results were obtained by the PCR method.
本研究選用四種E. coli O157商業化檢測套組及PCR方法，進行食品中E. coli O157:H7檢測方法評估。以69株菌之純菌培養測試套組之專一度、敏感度，其結果針對O157抗原，專一度及敏感度皆為100%，若同時針對O157及H7抗原，全部測試套組之敏感度均為100%，專一度則降為89.6%，四種套組之最低檢測量為103至104 CFU／mL。PCR方法之專一度、敏感度則均為100%，最低檢測量為103 CFU／test。由本實驗得知，此四種商業化套組乃針對E. coli O157抗原設計之套組，僅能初步測試檢體是否污染O157血清型之E. coli，至於最後確認呈陽性反應結果之檢體，必須再配合其他方法做進一步菌株分離及確認。純菌添加檢體試驗，每克檢體中僅污染單一E. coli O157菌量，即可經由增菌步驟檢測出。四種套組實際應用於市售檢體之檢測，均出現不同比率之偽陽性反應，故祇能作為食品檢體之初篩方法， PCR方法則皆未出現偽陽性。 |
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