Comparison of Detection of Escherichia coli O157 Between Culture After Acid Treatment and Polymerase Chain Reaction After Enrichment.
- Author:
In Ki PAIK
1
;
Tae Hee HAN
Author Information
1. Department of Laboratory Medicine, Inje University Sanggye Paik Hospital, Seoul, Korea. ikpaik@sanggyepaik.ac.kr
- Publication Type:Original Article
- Keywords:
Escherichia coli O157;
Culture;
PCR;
Acid treatment
- MeSH:
Adult;
Agar;
Diagnosis;
DNA;
Escherichia coli O157*;
Escherichia coli*;
Escherichia*;
Humans;
Limit of Detection;
Polymerase Chain Reaction*;
Shiga Toxin;
Shiga-Toxigenic Escherichia coli;
Stem Cells
- From:The Korean Journal of Laboratory Medicine
2002;22(5):331-335
- CountryRepublic of Korea
- Language:Korean
-
Abstract:
BACKGROUND: The Polymerase Chain Reaction (PCR) for the Shiga toxin has been widely used for diagnosis of Shiga toxin-producing Escherichia coli (STEC) infection including Escherichia coli O157 (O157) instead of using a culture. However, bacteriological isolation must be followed for final diagnosis. Our study was aimed to compare the detection limit between the culture after the acid treatment and the PCR after enrichment. METHODS: The standard strain of O157 was cultured, diluted and mixed with the stool of normal adult in order to make a final concentration of the 10(1)-10(5) colony forming unit (CFU)/g of stool. Each concentration of samples was enriched in a trypticase soy broth for 6 hours at 42degrees C and treated with acid to suppress normal flora. Then it was streaked on cefixime-tellurite-sorbitol MacConkey (CT-SMAC) agar evenly and cultured for 18 hours at 37degrees C. The same concentrations of bacterial suspension in the stool were enriched in a Luria-Bertani (LB) broth overnight at 37degrees C. The centrifuged pellets from 1 mL of each concentration of the samples were boiled and DNA was extracted using the resin method and PCR was performed to amplify stx2. RESULTS: The detection limit for the culture after acid treatment was 10(3) CFU/g of the stool and that for PCR after enrichment was 101 CFU/g of the stool. CONCLUSIONS: Culture after acid treatment for O157 would be an effective method for isolation of O157 from a patient's stool. However, this method is less sensitive than the PCR after enrichment as far as detection limit is concerned. A combination of both methods would be an effective method for detecting O157 from patient stools.
