An in vitro co-culture model of SCp2 mammary epithelial cells and Escherichia coli strains was established in bacterial non-CO2 incubators. Co-culturing SCp2 cells with either the rod-shaped W3110 or spherical-shaped GC7378Tn10 strains of Escherichia coli led to an increase in interleukin-6 (IL-6) levels by SCp2 cells after 9 h. At a ratio of 1:100 (epithelial:bacterial), the rod-shaped W3110 strain induced almost double the amount of IL-6 induced by the spherical-shaped GC7378Tn10 strain. The effect of Escherichia coli morphology (rod versus spherical) on IL-6 production by SCp2 cells was further investigated by shifting GC7378Tn10 morphology to rod through introducing the pbpA gene by transduction and transformation. In both approaches, the generated rod strains elicited higher IL-6 levels in SCp2 cells compared to the spherical ones at 1:50 and 1:100 ratios (epithelial:bacterial). Our findings demonstrate the significance of cell shape in bacterial-host interactions with potential implications in bacterial pathogenesis in general.