Rapid identification of Staphylococcus aureus, Vibrio parahaemolyticus and Shigella sonnei in foods by solid phase microextraction coupled with gas chromatography-mass spectrometry.

A novel approach for rapid identification of three foodborne pathogens including Staphylococcus aureus, Vibrio parahaemolyticus and Shigella sonnei in foods by solid phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was established. After cultivation 24, 18 and 20 h for Staphylococcus aureus, Vibrio parahaemolyticus and Shigella sonnei, respectively, the microbial volatile organic compounds (MVOCs) were extracted with a SPME device equipped with divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) coated fibers. The DB-1701P column was applied for separation of MVOCs. A total of 17, 13 and 14 volatile organic compounds were identified as characteristic MVOCs of Staphylococcus aureus, Vibrio parahaemolyticus and Shigella sonnei, respectively. Similarity of the MVOC chromatographic fingerprints for the bacteria were calculated and compared, and the results showed that the established method is stable, reproducible, accurate and has the potential to identify the three bacteria in food samples.

Listeria ivanovii Infection in Mice: Restricted to the Liver and Lung with Limited Replication in the Spleen.

Listeria monocytogenes (LM) vectors have shown much promise in delivery of viral and tumor antigens for the development of vaccines. L. ivanovii (LI) is a closely related bacterium with a similar intracellular life cycle that may offer advantages over LM because it is not a human pathogen, but can infect other animal species. Recent studies show that recombinant LI expressing Mycobacterium tuberculosis antigens is effective in inducing protective immunity in mouse models, demonstrating the potential of LI as a live vaccine vector. However, a key barrier in the development of LI into a live vaccine vector is that its pathogenic and immunogenic characteristics have yet to be fully understood. Therefore, in this research, C57BL/6J mice were inoculated with LM or LI intravenously or intranasally, and bacterial loads, histopathologic changes, and cytokine production were determined at indicated days post inoculation. Results showed that after intravenous infection with LM or LI, bacteria were found proliferating in the liver, spleen, and lung. However, LI could only reach a heavy burden in the liver and its ability to multiply and to resist host immunity seemed limited in the spleen and lung. After intranasal inoculation with LI, bacteria were mainly localized in the lung and failed to infect liver or spleen, while LM could. In organs with heavy LI burden, lesions were isolated, localized and densely packed, compared to lesions caused by LM, which were invasive. In the liver of intravenously inoculated mice and lung of intranasally inoculate mice, LI was able to elicit comparable cytokine production with LM and cause less severe histopathologic damages, and thus could be considered as a vector for treating or preventing hepatic or pulmonary diseases.