Activation of the Type III Secretion System of Enteropathogenic Escherichia coli Leads to Remodeling of Its Membrane Composition and Function.

The cell envelope of Gram-negative bacteria is a complex structure, essential for bacterial survival and for resistance to many antibiotics. Channels that cross the bacterial envelope and the host cell membrane form secretion systems that are activated upon attachment to host, enabling bacteria to inject effector molecules into the host cell, required for bacterium-host interaction. The type III secretion system (T3SS) is critical for the virulence of several pathogenic bacteria, including enteropathogenic Escherichia coli (EPEC). EPEC T3SS activation is associated with repression of carbon storage regulator (CsrA), resulting in gene expression remodeling, which is known to affect EPEC central carbon metabolism and contributes to the adaptation to a cell-adherent lifestyle in a poorly understood manner. We reasoned that the changes in the bacterial envelope upon attachment to the host and the activation of a secretion system may involve a modification of the lipid composition of bacterial envelope. Accordingly, we performed a lipidomics analysis on mutant strains that simulate T3SS activation. We saw a shift in glycerophospholipid metabolism toward the formation of lysophospholipids, attributed to corresponding upregulation of the phospholipase gene pldA and the acyltransferase gene ygiH upon T3SS activation in EPEC. We also detected a shift from menaquinones and ubiquinones to undecaprenyl lipids, concomitant with abnormal synthesis of O antigen. The remodeling of lipid metabolism is mediated by CsrA and associated with increased bacterial cell size and zeta potential and a corresponding alteration in EPEC permeability to vancomycin, increasing the sensitivity of T3SS-activated strains and of adherent wild-type EPEC to the antibiotic. IMPORTANCE The characterization of EPEC membrane lipid metabolism upon attachment to the host is an important step toward a better understanding the shift of EPEC, a notable human pathogen, from a planktonic to adherent lifestyle. It may also apply to other pathogenic bacteria that use this secretion system. We predict that upon attachment to host cells, the lipid remodeling upon T3SS activation contributes to bacterial fitness and promotes host colonization, and we show that it is associated with increased cell permeability and higher sensitivity to vancomycin. To the best of our knowledge, this is the first demonstration of a bacterial lipid remodeling due to activation of a secretion system.

THE PREDICTIVE VALUE OF SOME RECENT PARAMETERS FOR DIAGNOSIS OF SPONTANEOUS BACTERIAL PERITONITIS.

Spontaneous Bacterial Peritonitis (SBP) is a frequent and severe complication in patient with cirrhosis and ascites due to CLD with high mortality rate (20%-40%). SBP causes an inflammatory reaction resulting in an increased number of PMNs in ascitic fluid. It was reported that diagnosis of SBP is established when the ascitic fluid PMN count is greater than 250 cells/mm3 Lysis of the PMNs during transport to the laboratory, may occur which may lead to false negative results. This study evaluated the*usefulness of some recent parameters for diagnosis of SBP that can be used for future development of a rapid bedside test. Identifying a sensitive marker that can be used for rapid diagnosis of SBP in cirrhotic patients will have important clinical and economic consequences for this group of patients and also for clinicians involved in their cares. This study was conducted on 100 patients with ascites admitted to Tropical Medicine department, Al-Azhar University.Hospitals in the period from January 2015 to August 2015. The results showed that there was a highly significant positive correlation between ascetic fluid LAF level and neutrophils in ascitic fluid in cases of SBP, Also there wasopositive correlation between ascetic fluid LAF and ascetic fluid LDH (p value<0.001).

The antihyperlipidemic activities of 4(3H) quinazolinone and two halogenated derivatives in rats.

In the present study, the effects of subchronic treatments (4 weeks) of hypercholesterolemic (single) and diabetic-hypercholesterolemic (combined) rats with 4 (3H) quinazolinone and 2 halogenated derivatives (6, 8-dibromo-2-methy-4 (3H) quinazolinone and 6-iodo-2-methyl-4(3H) quinazolinone) at a sublethal dose level (2 mg/Kg) on cholesterol metabolism were investigated. Bezafibrate, a hypolipidemic drug was used as a reference compound for data comparison. Treatment of rats with single and combined hypercholesterolemia with quinazolinone compounds gave rise to highly significant reductions in serum total cholesterol and cholesterol ester levels, whereas serum triacylglycerol level was significantly reduced only after treatment with halogen-substituted quinazolinones in single hyper-cholesterolemia, compared to the control group. The effects of different quinazolinones and bezafibrate on reduction of serum LDL-C level were comparable in single hypercholesterolemia but significantly different in combined hypercholesterolemia. Results obtained from this study suggest that the antihyperlipidemic effect of quinazolinone compounds was brought about by inhibition of dietary cholesterol absorption and / or intestinal ACAT activity.

Evaluation of the available anti-HCV antibody detection tests and RT-PCR assay in the diagnosis of hepatitis C virus infection.

The aim of the present work is to evaluate the commercially available antibody tests in the diagnosis of hepatitis C virus (HCV) infection by comparing their results with the RT-PCR test. The study included 316 serum samples from three groups: blood donors, patients on maintenance hemodialysis (HD) and patients infected with the human immunodeficiency virus (HIV). Samples were subjected to HCV-antibody detection by ELISA and RIBA tests and HCV-RNA detection by RT-PCR assay. The percentage of infectivity for blood donors was 18.9% by ELISA, 20.8% by RIBA and 23.6% by RT-PCR test. For patients on HD and those positive for HIV, the test positivity was respectively 59.3% and 5.3% by ELISA, 64% and 10.5% by RIBA and, 66.3% and 21% by PCR test. The percentage of false negativity of HCV-Ab by ELISA and RIBA when compared with RT-PCR test was 3.5 and 8.1% for samples blood donors, 17.1 and 25.7% for HD patients and 5.6 and 16.7% for HIV-infected samples, respectively. The false positivity of HCV-Ab by ELISA and RIBA, when compared with RT-PCR, was 5%, 3.9% and zero for blood donors, HD patients and HIV-HCV co-infected cases, respectively. While comparing ELISA with RT-PCR, the false positivity was 10%, 5.9% and zero respectively for blood donors, HD patients and HIV-HCV co-infected cases. Thus, it is very important to screen blood donors, HD patients and HIV-infected patients by using the RT-PCR for HCV-RNA to avoid false negative results.