MPO and bacterial infectious disease: Ishikawa et al. reported that susceptibility to 2° bacterial infection after influenza was secondary to neutrophil dysfunction when mice were infected with Pseudomonas aeruginosa4 days after PR8 infection due to a decrease in granulocyte colony-stimulating factor activity (25), accompanied by decreased myeloperoxidase (MPO) activity, in the bronchoalveolar lavage fluids of mice infected with PR8 and then P. aeruginosa (25).