Inhibition Of Biofilm Formation And Exploration Of Key Factors Among Differnent Virulence Isolates By Cronobacter Spp.

Cronobacter is a group of important foodborne pathogens that have been implicated in meningitis, sepsis and necrotizing enterocolitis, especially in neonates through consumption of contaminated powdered infant formula (PIF). The prevalence of contamination by Cronobacter spp. in dried edible macrofungi and frozen food samples was firstly carried out and 31 Cronobacter isolates isolated these food samples were characterized using the antibiotics susceptibility test, osmotic and desiccation resistance. To date, virulence factors involved in virulence of Cronobacter spp. are still not discerned. Based on the determination of virulence differences of Cronobacter sakazakii isolates (virulent G362 and attenuated L3101) through animal experiment and histologic analysis, three organs in suckling mouse (small intestine, liver and kidney) revealed significant pathological changes than control group. Furthermore, proteins differently expressed between virulent and attenuated isolates were identified by using two-dimension electrophoresis (2-DE) coupled with MALDI/TOP/TOF mass spectrometry. These specific proteins might play important roles in virulence of C. sakazakii and provided important information for exploration of pathogenic mechanism of C. sakazakii. Additionally, the bacterial biofilm development of foodborne pathogenic C. sakazakii on the surface of equipment and environments may be a constant concern to food safety. Based on the preliminary analysis of inhibitory effects of D/L-AAs (glutamic, tyrosine, tryptophan, lysine, leucine, and alanine) on biofilm formation, significant inhibitory influences of D-Try was determined, which also suggested that it could effectively trigger disassembly of existing biofilm in C. sakazakii. Furthermore, comparative proteomics technology was also used to study the differential expression between biofilm and corresponding planktonic modes in C. sakazakii isolate. The findings presented in the dissertation showed some relevant factors implicated in the biofilm development.