Study On Susceptibility Testing And Analysis Virulence Factors Of LIPI-1Gene Cluster From Listeria Monocytogenes

Listeria monocytogenes (Lm) is an important food-born pathogen that can cause septicaemia, encephalitis, meningitis and gastroenteritis in human with the mortality about25%. Listeria monocytogenes encompasses a diversity of strains with varping pathogenic potential. While many Listeria monocytogenes strains could be of high pathogenicity, others are less virolent or even avirulent. Contamination to food by Listeria monocytogenes and its serious consequence have gained considerable attention in the worldwild.The discovery of antibiotics and development made great contribution to human health. Nearly20years, however. Accumulating evidences indicate that the use of antimicrobial agents in livestock breeding is also an important contributing factor in the emergence of resistant bacteria and dissemination of resistant genes. Listeria considered sensitive to all antibiotics also showed the trend of the development of the multiple drug resistance.Listeriosis are relatively rare, but the case fatality rate is very high.It is so difficult to treat a infections of drug-resistant strains that treatment period has been extended and medical expenses burden has been increasing,so that early diagnosis accurately and timely and reasonable antibiotic treatment is particularly importantFor the study of analyze the expression level of Lm virulence gene. GyrB gene clusters from two LM isolates with different virulence were amplified by PCR and subsequently cloned, and setted up Real-time fluorescent quantitative PCR standard curve of Six LIPI-1genes, prfA、 plcA、hly、mpl、actA、plcB.It showed that the detection method was established successfully and verified,all the standard curve correlation coefficient (r2) was between0.99-1, all the amplification efficiency was between0.8and1.2, indicating that the Q-PCR had system stability, the result had high credibility, so we could analysis dates by double standard curve methods.Results show that in the weak strain, mRNA expression level of LIPI-1significantly higher than the strong strain. Besides that, Drug sensitive experiment has been done between two Lm, aimed at estimating virulence from the result, and than analyzed whether the level of gene expression related to drug sensitivity.14kinds of antibiotics was selected to do Antimicrobial susceptibility test. The results show that Ciprofloxacin bacteriostatic ring diameter are16mm and17mm, in the scope of mediation, that is moderately susceptible; inhibition zone to Ampicillin Trihydrate are16mm and20mm, less than Resistance value;Zones of inhibition to Penicillin are26mm and27mm, both under the Drug resistance line. Ampicillin Trihydrate and Penicillin are drug-fast. The two kinds of Lm are sensitive to the other antibiotics.By anglicizing Lmo0686and N21gene expression level, we knew that Listeria virulence is related to expression level of LIPI-1, lay a foundation for proven its weak poison mechanism. Compared the result of drug sensitive test in the same antibiotic, judgment with the relationship between the gene expression level, at the same time provides a reference for clinical medication...