OPRD1 and susceptibility to pneumonia measurement: Another study obtained slightly different results by showing that the deletion of OprD was associated with an attenuated virulence compared to its parental strain (PAO1) in a murine pneumonia model (at day 2, there was 100% of lethality in the group infected with the WT strain vs almost 50% of lethality in the group infected with the strain lacking OprD) [125].