Abstract
The initial aim of this study was to investigate the potential of oxygen releasing compounds as an antimicrobial treatment to reduce the transmission of C. jejuni. C. jejuni was highly sensitive to MgO2, CaO2 and 2Na2CO3. 3H2O2 when exposed to these compounds in Maximum Recovery Diluent (MRD), Ultra Heat Treated (UHT) skimmed milk and soil microcosms. In MRD, initial counts of 1 x 107 colony forming units per ml fell to undetectable levels in 32, 8 and 4 hours in the presence of 0.26, 2.6 and 5.2 mM MgO2 respectively. The same reduction in viability of C. jejuni was seen within 10 minutes and 30 minutes in the presence of 5.2 mM, 2.6 mM and CaO2 respectively. When C. jejuni cells were exposed to 2.6 mM and 5.2 mM 2Na2CO3. 3H2O2, viable counts fell by 7-logs in 15 minutes. The survival of C. jejuni when exposed to H2O2 was similar to that seen with MgO2 but when catalase was added, Mg02 had little impact on C. jejuni killing, suggesting that H2O2 formation via this metal peroxide is important in the killing process. Electron microscope observations revealed an irregular cell morphology and loss of cell wall integrity as well as loss of polar flagella. CorA (Cj0726C), the main magnesium transporter of C. jejuni, was inactivated by allelic exchange to determine whether magnesium transport was necessary for the oxidative killing seen with magnesium peroxide. The corA mutant did not grow without Mg2+ supplementation (20 mM), indicating that Mg2+ acquisition by corA is essential for C. jejuni growth in vitro that might be important in adaptation to low-Mg2+ conditions. However, CorA was not essential in magnesium peroxide killing. Whilst a corA mutant showed a reduced ability to kill the larvae of Galleria mellonella, CorA did not appear to be required for chicken colonisation by oral gavage or for intracellular survival within Caco-2 cells.