Production of Bacterial Ghosts from Gram-Positive PathogenListeria monocytogenes

Introduction: The Gram-positive bacterium Listeria monocytogenes is a ubiquitous intracellular pathogen, which has been implicated within the past decade as the causative organism in several outbreaks of foodborne disease. Bacterial ghosts (BGs) are nonliving and vacant cell envelopes of bacteria generated by releasing the bacterial cytoplasm through a channel in the cell envelope. This study attempted to produce Gram-positive pathogenic L. monocytogenes ghosts (LMGs) with simple chemicals. Materials and Methods: The generation of LMGs was based on minimum inhibition concentrations of 1.10 mg/mL NaOH, 0.0675 mg/mL SDS, and 0.035% (v/v) H2O2. The potential efficacy of LMGs as vaccines and their ability to induce protective immune responses against virulent L. monocytogenes challenge through multipoint subcutaneous injection were also evaluated. Results: The detected activity and viability of LMGs showed that nonliving LMGs could be induced. The detected LMG DNA and protein, as well as its morphological features, indicated that the produced LMGs were empty cells with the correct morphological structure. The subcutaneous vaccination of LMGs through multipoint injection conferred effective protection, with an antibody titer that reached 104 U. Conclusions: These findings strongly suggested that this chemical method can be used to produce LMGs and could be useful in future vaccine development against this foodborne pathogen.