FIG 4.

Adherence and invasion of HTB-9 cells as well as biofilm formation are altered in phage-resistant UPEC. (A and B) UTI89 (A) and DS566 (B) and respective phage-resistant strain adherence to HTB-9 cells after 30 min of infection; MOI of 1. HTB-9 cells were infected with UTI89 (C) or DS566 (D) and respective phage-resistant mutants (MOI of 1) for 2 h before the medium was changed to medium containing antibiotics to kill extracellular bacteria. After 2 h of antibiotic treatment, cells were lysed and intracellular bacteria enumerated. Biofilm formation of UTI89 (E) or DS566 (F) and respective phage-resistant mutants in LB, urine, or RPMI 1640 quantified by crystal violet uptake. All adherence, invasion, and biofilm assays were performed in at least technical duplicate in five to six independent experiments, with points on graphs representing mean values of each independent experiment. Bars represent median and 95% confidence intervals. Data were analyzed by Kruskal-Wallis test using Dunn’s multiple-comparison test (A to D) or repeated-measures two-way ANOVA with Geisser-Greenhouse correction and Dunnett’s multiple-comparison test (E, F). *, P < 0.05; **, P < 0.01.