As P. aeruginosa might act cytotoxic to eukaryotic cells we chose to use only conditioned medium instead of direct bacterial infection and we also controlled viability by annexin V and propidium iodide staining. Even though we observed some cytotoxic effects at 14 h we did not detect differences in viability of epithelial cells conditioned with medium from either of the two P. aeruginosa strains up to 10 h (viability was 96 ± 1.7% for Boston vs. 96 ± 2.7% for PAO1 after hRV infection and 95 ± 2% and 96 ± 3% after RSV infection, respectively). Therefore, cytotoxic effects can be excluded as an explanation why only PAO1 inhibited the antiviral response. Of note, we did not observe any differences by any CM treatment with respect to the viral load of the primary infected cells indicating that the first infection of the cells was not affected by soluble P. aeruginosa factors (Figure S1). Yet, we speculated that the inhibition of the antiviral response by CM-PAO1 (as indicated by reduced ISG induction) may facilitate spread of the virus infection. To analyze the functional relevance of the decreased antiviral response, we therefore challenged another batch of BEAS2B cells with the supernatant of CM-pretreated and RSV infected cells (Figure 1A). In line with a decrease of the antiviral response in CM-PAO1 treated BEAS2B cells, we observed increases in RSV-RNA and RSV-specific cytopathic effects in cells challenged with the supernatant of CM-PAO1 treated cells as compared to control or CM-Boston treated cells (Figure 1C). These results indicate that the repression of the antiviral response by PAO1 leads to an increase in virus spreading and is therefore of functional relevance. To confirm the effects in primary cells we repeated the main experiment in primary human bronchial epithelial cells (hBrEpC). In line with our observations in BEAS2B cells, PAO1 was also able to repress RSV induced antiviral responses in hBrEpC (Figure 1D). It is known that P. aeruginosa can be classified into three different phylogenetic groups (25), represented by PA14, PAO1, and PA7 for group 1, 2, and 3, respectively. Like PAO1 PA14 but not PA7 was also able to repress the antiviral response toward RSV (Figure 1E) indicating that the inhibition of an antiviral response is not restricted to a specific phylogenetic group.