Table 1.
Bacterial strains used in this study.
Figure 1.
The rfb gene clusters of E. coli serotypes O1, O2, O18 and O78 strains.
The black arrows correspond to gnd and galF genes. Grey arrows correspond to rfb gene cluster and the gene names are italic indicated. The length of rfb gene cluster was also shown. In the PCR reaction system, the universal forward primer was used for all the sero-typing amplification with specific reverse primers. The bold lines below the gnd gene indicate the size of the PCR products for different E. coli serotype strains, which allow the differentiation of the O types. Primers and their locations were also indicated.
Table 2.
Primers used in this study.
Figure 2.
The product profiles of E. coli serotypes O1, O2, O18 and O78 strains amplified using the allele-specific PCR.
Lane M: DL2000 DNA Marker; O1, O2, O18 and O78 represent PCR products for O1, O2, O18 and O78 strains respectively. Lane 1: APEC O1 strain; Lane 2: APEC strain DE47; Lane 3: APEC strain DE14; Lane 4: APEC strain DE17; Lane 5: APEC strain RS218; Lane 6: APEC strain CE66; Lane 7: APEC strain DE48; Lane 8: APEC strain DE65; Lane 9: Negative control.
Table 3.
Comparison of PCR and serum agglutination assays for differentiating the serotypes of APEC isolates and clinical infected samples.
Figure 3.
Sensitivity analysis of the allele-specific PCR assay.
(A) Sensitivity analysis using the bacterial genomic DNA. The detection limit was determined as 10 pg of bacterial DNA for E. coli serotypes O2 and O18 strains, and 500 pg of bacterial DNA for E. coli serotypes O1 and O78 strains, respectively. (B) Sensitivity analysis using the bacterial culture. The detection limit was determined as 10 CFUs of E. coli serotypes O2 and O18 strains, and 1,000 CFUs of E. coli serotypes O1 and O78 strains, respectively. Lane M: DL2000 Marker.