High hydrostatic pressure sensitivity of virulent avian pathogenic Escherichia coli

Escherichia coli is often found as a major pathogen in both mammalian and avian species and is responsible for both intestinal and extra-intestinal diseases. Avian pathogenic E. coli (APEC) cause extra-intestinal infections, i.e. avian colibacillosis, a common respiratory tract infection that spreads to the internal organs and is responsible for large economical losses in the poultry industry. Approaches for the prevention of APEC infections include vaccination strategies with attenuated or inactivated pathogens [Barnes et al., 2003]. Evidently, vaccines or adjuvants based on inactivated pathogens are most effective when the integrity of the bacteria is well preserved. High hydrostatic pressure (HP) is a novel and promising technology in food preservation, as it can inactivate micro-organisms without compromising the sensorial quality of food the way conventional thermal processing does [Smelt and van Wely, 1993). How HP actually inactivates bacteria is still elusive and seems to depend on the pressure intensity and the bacterial strain used. While pressures above 150 MPa probably cause protein and membrane damage [Hoover, 1989; Balny et al., 1997), pressures around 100 MPa seem to activate a cryptic endonuclease (Mrr) in Escherichia coli MG1655 [Aertsen and Michiels, 2005]. In this study, we compare the HP sensitivity of two APEC strains with that of non virulent strains, and examine the potential of HP to inactivate the pathogens while leaving the cells intact and useful in vaccination strategies