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Figure 1A shows the typical aggregative adherence pattern of the EAEC prototype strain E. coli 042 on SW-480 cells (human colon adenocarcinoma cell line) as well as on the glass coverslip. In this adhesion pattern, aggregates of bacteria assumed a hallmark "stacked-brick" or "honeycomb" pattern on the surface of the cells, as well as on the glass coverslip. E. coli ATCC 25922, which is unable to adhere to both the glass slide and the SW-480 cells, was used as a negative control (Fig. 1B). The adhesion assay was performed with monolayers of SW-480 cells grown on circular coverslips in wells of 24-well tissue culture plates. Thereafter, the carcinogenic cells were infected for 3 hours at 37°C with 107 to 108 bacteria/ml, previously plated overnight at 37°C in 1% tryptone broth with 1% D-mannose. After the infection period, the coverslips were washed 3 times with phosphate-buffered saline, fixed with 70% methanol, and stained with 10% Giemsa (3). The stained coverslips were examined with a light microscope under oil immersion microscopy (total magnification 1,000X).

Figure 2 depicts an electrophoretic profile of three plasmid-borne genes of the same prototype EAEC strain, amplified by an mPCR reaction using three primer sets (aap, aggR, and AA probe genes). Lanes: 1, 100-bp DNA ladder (molecular weight marker); 2, no PCR products obtained from DNA of E. coli ATCC 25922 (negative control);  3, PCR products obtained from the E. coli 042 strain; 4 to 6, PCR products obtained with 042 strain and primers for the AA probe, aggR, and aap genes, respectively. All PCR reactions were prepared according to Cerna, et al (1). The amplicons were separated by electrophoresis on 2.5% agarose gel in Tris-acetate-EDTA buffer and visualized under a UV-transilluminator after staining with 0.5 mg/ml of ethidium bromide solution. The picture was obtained using a Canon-EOS Rebel T2i camera.

Figure 1: Enteroaggregative Escherichia coli Adherence to SW-480 Cells. Enteroaggregative Escherichia coli strain 042 adhering to both the glass slide and the SW-480 cells.

Figure 2: Enteroaggregative Escherichia coli Adherence to SW-480 cells (Labeled view)

Figure 3: Enteroaggregative Escherichia coli Not Adhering to SW-480 Cells. Escherichia coli ATCC 25922 is unable to adhere to both the glass slide and the SW-480 cells.

Figure 4: Enteroaggregative Escherichia coli Not Adhering to SW-480 Cells (Labeled view)

Figure 5: PCR Products from Enteroaggregative Escherichia coli. Diagnostic tools for enteroaggregative Escherichia coli.

Figure 6: PCR Products from Enteroaggregative Escherichia coli (Labeled view)