FIG 4.

HM56 and HM86 uniquely exhibit alpha-hemolysis and can kill uroepithelial cells in culture. (A and B) To determine the ability of clinical UPEC strains to lyse epithelial cells, monolayers of T24 bladder (A) or HK2 kidney (B) cell lines were treated with UPEC for 5 h. The MTT cell viability kit was used to measure monolayer viability pre- and posttreatment with UPEC. Cellular respiration causes a color change, which can be measured via absorbance. These data were normalized, and mean values of the results of four biological replicates are represented by bars, with error bars indicating the SEM. RPMI cell culture medium with no bacteria (PBS mock) served as a negative control, and 0.4% Triton X-100 served as a positive control for cell death. One-way ANOVA was performed using Dunnett’s multiple-test correction in comparison to PBS mock infection. ***, P < 0.005; ****, P < 0.0001. (C) UPEC strains were spotted onto blood agar plates and incubated overnight at 37°C. The lysis of red blood cells leads to a zone of clearance (black arrowheads) around isolated bacterial colonies. CFT073 was used as a positive control for hemolysis. The chart describes the type of hemolysis detected by each strain. Alpha-hemolysis is partial hemolysis indicated by an opaque zone. Beta-hemolysis is completed hemolysis indicated by a transparent zone.