Hello! I have been through your question. According the infection in an open wound from Pseudomonas aeruginosa usually can happen in the persons consider with weakened immune system from different reasons,as it is and pregnancy. In my experience the infection from pseudomonas aeruginosa is difficult to treat because Pseudomonas infections can often develop resistance to multiple types of antibiotics. In your wife case, it is important before starting the antibiotic to meet an infectious diseases specialist, to see antibiogram result(after a specimen test) to determine which antibiotic will work best and to choose the right antibiotic for pregnancy, because you know that not all antibiotics are allow to use during pregnancy. Usually what I suggest in these conditions is ceftazidime or cefepime or ticarcillini if they aren t resistant and if your wife isn t allergic, for best result in IV route (in hospital) for 7-10 days(depends on the severity of infection). I hope my answer help you. I wish your wife a quick recovery.