Intravenous anti-P. aeruginosa IgY antibodies increase bacterial concentration in porcine septic shock with bacteremia

Background Bacteremia caused by Pseudomonas aeruginosa carries a high mortality rate. P. aeruginosa also possesses several resistance mechanisms to antibiotics, mandating studies of novel therapies. Specific polyclonal anti- P. aeruginosa IgY-antibodies ( Pa -IgY) have been reported to decrease P. aeruginosa concentration in the airways. In this study, we investigated the effects of intravenous Pa -IgY on P. aeruginosa septic shock. Method Pigs were anaesthetized, mechanically ventilated, and allocated to receive either intravenous P. aeruginosa only, P. aeruginosa + low dose Pa- IgY, P. aeruginosa + high dose Pa- IgY or high dose Pa- IgY only. The experiment lasted 6 h with repeated blood cultures, blood tests, monitoring of physiological parameters and postmortem organ cultures. We performed in vitro cultures of P. aeruginosa +/- porcine neutrophils and +/- Pa- IgY and flow cytometry of FITC-marked inactivated P. aeruginosa cultured with porcine blood +/- Pa- IgY. Results The pigs developed septic shock with accompanying respiratory failure as a result of the P. aeruginosa infusion. Treatment with Pa- IgY increased bacterial concentrations, both in the porcine model in blood ( p = 0.004) and when P. aeruginosa was cultured after pre-treatment with Pa- IgY +/- neutrophils in vitro ( p < 0.001). The phagocytosis of P. aeruginosa in porcine blood was similar with and without Pa- IgY. Pa- IgY had no effect on the development or severity of septic shock. Animals with high dose Pa- IgY had higher PaO 2 /FiO 2 -ratio and static compliance. The inflammatory response was similar apart from higher IL-10 in animals treated with Pa- IgY ( p = 0.007). Conclusion In pigs with P. aeruginosa septic shock, treatment with Pa- IgY was associated with higher bacterial concentration in blood without an increased inflammatory response.