OspA heterogeneity of Borrelia valaisiana confirmed by phenotypic and genotypic analyses

BACKGROUND: Although European Borrelia burgdorferi sensu lato isolates have been divided into five genospecies, specific tools for the serotype characterization of only three genospecies are available. Monoclonals antibodies (mAbs) H3TS, D6 and I17.3 identify B. burgdorferi sensu stricto (ss.), B. garinii and B. afzelii respectively, but no mAbs are available to identify B. valaisiana. In the same way, specific primers exist to amplify the OspA gene of B. burgdorferi ss., B. garinii and B. afzelii. The aim of the study was to develop species-specific mAb and PCR primers for the phenotypic and genetic identification of B. valaisiana. RESULTS: This study describes a mAb that targets OspA of B. valaisiana and primers targeting the OspA gene of this species. As the monoclonal antibody A116k did not react with strains NE231, M7, M53 and Frank and no amplification was observed with strains NE231, M7 and M53, the existence of two subgroups among European B. valaisiana species was confirmed. CONCLUSIONS: The association of both monoclonal antibody A116k and primers Bval 1F and Bval 1R allows to specific identification of the B. valaisiana isolates belonging to subgroup 1

An RND-Type Efflux System in Borrelia burgdorferi Is Involved in Virulence and Resistance to Antimicrobial Compounds

Borrelia burgdorferi is remarkable for its ability to thrive in widely different environments due to its ability to infect various organisms. In comparison to enteric Gram-negative bacteria, these spirochetes have only a few transmembrane proteins some of which are thought to play a role in solute and nutrient uptake and excretion of toxic substances. Here, we have identified an outer membrane protein, BesC, which is part of a putative export system comprising the components BesA, BesB and BesC. We show that BesC, a TolC homolog, forms channels in planar lipid bilayers and is involved in antibiotic resistance. A besC knockout was unable to establish infection in mice, signifying the importance of this outer membrane channel in the mammalian host. The biophysical properties of BesC could be explained by a model based on the channel-tunnel structure. We have also generated a structural model of the efflux apparatus showing the putative spatial orientation of BesC with respect to the AcrAB homologs BesAB. We believe that our findings will be helpful in unraveling the pathogenic mechanisms of borreliae as well as in developing novel therapeutic agents aiming to block the function of this secretion apparatus

Comparison of growth and morphology of Borrelia burgdorferi

Barbour-Stoenner-Kelly II (BSK-II) and BSK-H media were used for cultivation and isolation of fastidiousBorreliaspecies - the causative agents of Lyme borreliosis. Culture media have a limited shelf life and require adequate storage. Our goal was to assess how the growth ofBorreliawould be affected by prolonged storage of media and inadequate storage conditions (BSK-H stored at +4 degrees C for 2.5 years and BSK-II stored at -20 degrees C for 11 years). Growth of differentBorrelia afzelii,Borrelia garinii,Borrelia lusitaniaeandBorrelia valaisianastrains was assessed during 2 weeks of incubation at 33 degrees C. Monitored parameters included cell count per mL, morphology and motility. The results of this study have shown weaker growth of borrelia strains in BSK-H at +4 degrees C (median final cell number of 1.5 x 10(6)/mL) than in BSK-II at -20 degrees C (median final cell number of 7.75 x 10(6)/mL) and in fresh BSK-H media (median final cell number of 8.95 x 10(6)/mL). Duration of storage of media had no impact onBorreliamorphology and motility. Our results indicate that temperature of -20 degrees C is optimal for long-term storage of medium, BSK-II stored for 11 years provided effective support to growth ofBorreliaand may be employed for cultivation