Fig. 5

a Cell culture assay for cytotoxicity. HeLa cells were treated with E. coli at a multiplicity of infection (MOI) between 1 and 100 for 4 h followed by a 72 h incubation in gentamicin-containing media. Cells infected with the novel rhesus macaque isolates encoding pks (S1, S2, S4, S5, S13, and S14) displayed megalocytosis (enlargement of the cell body and nucleus) similar to the pks+ E. coli controls (NC101 mouse isolate and V27 human urosepsis isolate). Isolates pks−/cnf1+ (S3, S9, and S10) did not induce megalocytosis, but caused elongated cell morphologies. No cytotoxicity was observed for cells treated with novel isolates pks−/cnf1− (S7, S8, and S12), the E. coli negative controls (media control and K12 non-pathogenic laboratory strain) as well as NC101 Δpks. Images were taken at 20× magnification. b Cell culture assay for cytotoxicity. HeLa cells were treated for 72 h with E. coli sonicate at a dose of 40 μg/mL total protein. Only treatment with sonicate from the cnf1-encoding novel rhesus macaque isolates (S1, S2, S3, S9, S10, and S14) caused cell body enlargement and multi-nucleation. No cytotoxicity was observed after sonicate treatment with the other novel isolates. Images were taken at 20× magnification