Submitted to: Journal of Clinical Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/14/2003
Publication Date: 7/20/2003
Citation: FRATAMICO, P.M., BRIGGS, C.E., NEEDLE, D., CHEN, C., DEBROY, C. Sequence of the Escherichia coli O121 O antigen gene cluster and detection of E. coli O121 by PCR amplification of the wzx and wzy genes. JOURNAL OF CLINICAL MICROBIOLOGY. Vol. 41. No. 7. pg. 3379-3383. Interpretive Summary: The bacterium, Escherichia coli, causes a variety of diseases in humans and animals, and non-harmful types, or serogroups, also exist. Traditionally, a procedure called serotyping is used to distinguish between the different E. coli types. This procedure relies on use of antisera raised in rabbits against different components of the bacteria. Serotyping, however, can generally only be performed in specialized laboratories, is labor intensive and may require several days to complete, and one antiserum can react with multiple E. coli serogroups, rendering identification difficult. Thus, due to the lack of simple and rapid methods for detection and identification of harmful and non-harmful E. coli types, the incidence of disease caused by these organisms may be underestimated, and epidemiological studies are difficult to perform. To develop a more rapid and simple method for detection and identification of the E. coli serogroups, the DNA sequence of a cluster of genes involved in production of a specific component of E. coli serogroup O121 was determined. Based on the sequence information, an assay called the polymerase chain reaction, based on amplification of specific genes in the cluster, was developed for detection and identification of E. coli O121 and was used to detect this bacterium in swine feces. This procedure can easily also be employed for the development of assays for detection and identification of the other known E. coli serogroups. Thus, use of the specific polymerase chain reaction assays enhances the ability to detect, identify, and type E. coli O121 and potentially the other E. coli serogroups, eliminating the use of the labor-intensive serotyping procedure.
Technical Abstract: The DNA sequence of the 15,155-bp O antigen gene cluster of Escherichia coli O121 was determined, and 14 open reading frames were identified with all having the same transcriptional direction. Analyses of results indicated that the wzx (O antigen flippase) and wzy (O antigen polymerase) genes were E. coli O121 specific, thus regions in these two genes were chosen for development of PCR assays. The PCR assays using DNA from 99 E. coli O121 strains, strains representative of non-O121 E. coli serogroups, strains/species of other bacterial genera, and using DNA from 7 enrichments of swine fecal samples, naturally contaminated with E. coli O121, showed specificity for E. coli O121. Thus, the PCR assay can be employed to reliably identify E. coli O121 and to potentially detect the organism in food, fecal, or environmental samples