Response of Escherichia coli to Prolonged Berberine Exposure.

Berberine is a plant-derived alkaloid possessing antimicrobial activity; unfortunately, its efflux through multidrug resistance pumps reduces its efficacy. Cellular life span of Escherichia coli is generally shorter with prolonged berberine exposure; nevertheless, about 30% of the cells still remain robust following this treatment. To elucidate its mechanism of action and to identify proteins that could be involved in development of antimicrobial resistance, protein profiles of E. coli cells treated with berberine for 4.5 and 8 hours were compared with control cells. A total of 42 proteins were differentially expressed in cells treated with berberine for 8 hours when compared to control cells. In both 4.5 and 8 hours of berberine-treated cells, carbohydrate and peptide uptake regimens remained unchanged, although amino acid maintenance regimen switched from transport to synthesis. Defect in cell division persisted and this condition was confirmed by images obtained from scanning electron microscopy. Universal stress proteins were not involved in stress response. The significant increase in the abundance of elongation factors could suggest the involvement of these proteins in protection by exhibiting chaperone activities. Furthermore, the involvement of the outer membrane protein OmpW could receive special attention as a protein involved in response to antimicrobial agents, since the expression of only this porin protein was upregulated after 8 hours of exposure.

Detection of drug-resistance mechanism of Pseudomonas aeruginosa developing from a sensitive strain to a persister during carbapenem treatment.

We explored the mechanism of the development from sensitivity to resistance to carbapenem in Pseudomonas aeruginosa. Two P. aeruginosa strains were collected during treatment with carbapenem. Strain homology was investigated using pulsed-field gel electrophoresis. Porin oprD2 expression was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The minimum inhibitory concentrations (MICs) of imipenem and meropenem with or without MC207110 were determined using the agar dilution method. The expression level of efflux pump mRNA was tested using real-time polymerase chain reaction. Metallo-lactamases (MBLs) were screened using the EDTA-disk synergy test. Genes encoding MBLs were amplified and then analyzed by DNA sequencing. The two treated strains belonged to the same pulsed-field gel electrophoresis type. The SDS-PAGE profile of the P. aeruginosa strains revealed that the 46-kDa membrane protein OprD2 of IMP(R)MEM(R) type strains was lost, whereas OprD2 of 1 IMP(S)MEM(S) strain was normal. With or without MC207110 treatment, the MIC of carbapenem-resistant P. aeruginosa decreased by 4-fold, while the MIC of carbapenem-sensitive P. aeruginosa did not. Compared with the carbapenem-sensitive strain, MexX mRNA expression in the carbapenem-resistant strain increased by 102.5-fold, while the mRNA expression of other efflux pumps did not markedly increase. Neither carbapenem-resistant nor carbapenem-sensitive P. aeruginosa produced MBL. The mechanism of development from sensitivity to resistance of P. aeruginosa to carbapenem during carbapenem treatment is due to porin oprD2 loss and an increased expression level of MexXY-OprM.

OspC is potent plasminogen receptor on surface of Borrelia burgdorferi.

Host-derived proteases are crucial for the successful infection of vertebrates by several pathogens, including the Lyme disease spirochete bacterium, Borrelia burgdorferi. B. burgdorferi must traverse tissue barriers in the tick vector during transmission to the host and during dissemination within the host, and it must disrupt immune challenges to successfully complete its infectious cycle. It has been proposed that B. burgdorferi can accomplish these tasks without an endogenous extra-cytoplasmic protease by commandeering plasminogen, the highly abundant precursor of the vertebrate protease plasmin. However, the molecular mechanism by which B. burgdorferi immobilizes plasminogen to its surface remains obscure. The data presented here demonstrate that the outer surface protein C (OspC) of B. burgdorferi is a potent plasminogen receptor on the outer membrane of the bacterium. OspC-expressing spirochetes readily bind plasminogen, whereas only background levels of plasminogen are detectable on OspC-deficient strains. Furthermore, plasminogen binding by OspC-expressing spirochetes can be significantly reduced using anti-OspC antibodies. Co-immunofluorescence staining assays demonstrate that wild-type bacteria immobilize plasminogen only if they are actively expressing OspC regardless of the expression of other surface proteins. The co-localization of plasminogen and OspC on OspC-expressing spirochetes further implicates OspC as a biologically relevant plasminogen receptor on the surface of live B. burgdorferi.

Molecular mimicry in Lyme arthritis demonstrated at the single cell level: LFA-1 alpha L is a partial agonist for outer surface protein A-reactive T cells.

Antibiotic treatment-resistant Lyme arthritis is a chronic inflammatory joint disease that follows infection with Borrelia burgdorferi (BB:). A marked Ab and T cell response to BB: outer surface protein A (OspA) often develops during prolonged episodes of arthritis. Furthermore, cross-reaction between the bacterial OspA and human LFA-1alpha(L) at the T cell level and the inability to detect BB: in the joint implicate an autoimmune mechanism. To analyze the nature of response to OspA and LFA-1alpha(L), we used OspA-specific T cell hybrids from DR4 transgenic mice, as well as cloned human cells specific for OspA(165-184), the immunodominant epitope, from five DRB1*0401(+) patients, using OspA-MHC class II tetramers. Although OspA(165-184) stimulated nearly all OspA-specific human T cell clones tested to proliferate and secrete IFN-gamma and IL-13, LFA-1alpha(L326-345) stimulated approximately 10% of these clones to proliferate and a greater percentage to secrete IL-13. Assays with LFA- or OspA-DR4 monomers revealed that higher concentrations of LFA-DR4 were needed to stimulate dual-reactive T cell hybrids. Our analysis at the clonal level demonstrates that human LFA-1alpha(L326-345) behaves as a partial agonist, perhaps playing a role in perpetuating symptoms of arthritis.