Colonies which varied in opacity were isolated from the four strains of Vibrio vulnificus. Opaque and translucent colonial types of the strains were distinguished from the corresponding parent strains. Variation in the opacity of colonies formed by each strain was accompanied by variation of capsular material formation, which was clarified by electron microscopy of the organisms stained with ruthenium red. The opaque-type colonies of the strains had capsular materials. On the other hand, three translucent-type colonies had no observable capsular materials, and one had incomplete capsular materials, in contrast to the corresponding opaque type. The corresponding opaque and translucent types of the strains were compared for points of virulence in mice and guinea pigs. By having capsular materials, the bacterial strains acquired resistance to serum bactericidal action, antiphagocytic activity, high lethality for mice, and strong invasiveness in the subcutaneous tissue of guinea pigs. Capsular materials of V. vulnificus were considered to be important for the expression of virulence. Vibrio vulnificus, a halophilic marine vibrio, is an occa

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Lecithin-dependent haemolysin (LDH) of Vibrio puruhuemolyticus was purified from Escherichia coli C600 transformed with a plasmid (pHL591) ligated with a 1.5 kb DNA fragment of V. puruhuemolyticus. The final preparation comprised two LDH proteins with different molecular masses which were immunologically crossreactive and had the same enzymic activity. The LDH was a phospholipase hydrolysing both fatty acid esters of phospholipid, i.e. it hydrolysed phosphatidylcholine (PC) to lysophosphatidylcholine (LPC) and then LPC to glycerophosphorylcholine (GPC). From this point of view, LDH should be classified as a phospholipase B.Phospholipase B, however, does not usually show haemolytic activity, because the intermediate (LPC), which is the actual haemolytic agent, is immediately hydrolysed to the final product (GPC). On the other hand, LPC formed by LDH action was comparatively stable, because the rates of the two reactions catalysed by LDH, PC to LPC and LPC to GPC, are almost the same. This is the reason that LDH shows haemolytic activity. Therefore, LDH of V. parahuemolyticus is an atypical phospholipase to be designated as phospholipase A2/lysophospholipase.

We examined the molecular mechanisms of resistance to kanamycin and viomycin in Mycobacterium smegmatis. All of the M. smegmatis strains with high-level kanamycin resistance had a nucleotide substitution from A to G at position 1389 of the 16S rRNA gene (rrs). This position is equivalent to position 1408 of Escherichia coli, and mutation at this position is known to cause aminoglycoside resistance. Mutations from G to A or G to T at position 1473 of the M. smegmatis rrs gene were found in viomycin-resistant mutants which had been designated vicB mutants in our earlier studies. Using the M. smegmatis conjugation system, we confirmed that these mutations indeed contributed to kanamycin and viomycin resistance, and kanamycin susceptibility was dominant over resistance in a heterogenomic strain. Additional experiments showed that three of four Mycobacterium tuberculosis strains with high-level kanamycin resistance had a mutation from A to G at position 1400, which was equivalent to position 1389 of M. smegmatis.

h Cryptococcosis due to a highly virulent fungus, Cryptococcus gattii, emerged as an infectious disease on Vancouver Island in Canada and surrounding areas in 1999, causing deaths among immunocompetent individuals. Previous studies indicated that C. gattii strain R265 isolated from the Canadian outbreak had immune avoidance or immune suppression capabilities. However, protective immunity against C. gattii has not been identified. In this study, we used a gain-of-function approach to investigate the protective immunity against C. gattii infection using a dendritic cell (DC)-based vaccine. Bone marrow-derived dendritic cells (BMDCs) efficiently engulfed acapsular C. gattii (⌬cap60 strain), which resulted in their expression of costimulatory molecules and inflammatory cytokines. This was not observed for BMDCs that were cultured with encapsulated strains. When ⌬cap60 strain-pulsed BMDCs were transferred to mice prior to intratracheal R265 infection, significant amelioration of pathology, fungal burden, and the survival rate resulted compared with those in controls. Inhalation of the airborne fungal pathogens Cryptococcus neoformans and Cryptococcus gattii causes life-threatening infectious diseases despite treatment with antifungal drugs. These two species are genetically close, although they have some distinct features. C. neoformans typically causes fatal infections, such as meningitis, in immunocompromised hosts, whereas C. gattii causes similar infections in immunocompetent hosts. Although cryptococcosis caused by C. gattii is endemic in tropical areas, such as Australia and Papua New Guinea, outbreaks of C. gattii, including fatalities among healthy individuals, were reported on Vancouver Island and surrounding areas beginning in 1999 (1, 2). In response to this, the Centers for Disease Control and Prevention (CDC) of the United States and British Columbia organized a public health working group to promote awareness of this outbreak (3-5).Using mouse pulmonary infection models, two groups independently showed that C. gattii strain R265, which was clinically isolated during the Canadian outbreak, was more virulent than C. neoformans strain H99, which is frequently studied (6, 7). Although the mechanisms for its hypervirulence remain unknown, there is evidence that C. gattii induces a less severe inflammatory response than that induced by C. neoformans infection. Histological and flow cytometry analyses showed reduced migration of inflammatory cells into the lungs of mice infected with R265 compared with those infected with H99 (7-9). Additionally, a smaller amount of inflammatory cytokines was found in the lungs of mice infected with C. gattii (9) and in the cerebrospinal fluid of humans infected with C. gattii (10,11). These findings suggest that C. gattii has a superior ability to suppress or evade the inflammatory response.Previous studies indicated that one of the capsular components of C. gattii may have been involved in immune avoidance or immune suppression and was required for the complete virulence of...