Diphtheria is an acute, communicable disease caused by Corynebacterium diphtheriae. The disease is generally characterized by local growth of the bacterium in the pharynx with pseudomembrane formation or, less commonly, in the stomach or lungs; systemic dissemination of toxin then invokes lesions in distant organs. Acute disease of the upper respiratory tract usually involves one or more of the following: tonsillar zones, larynx, soft palate, uvula, and nasal cavities. A recent epidemic in Russia emphasized the role of vaccination in reducing disease in children and adults.

Brucellae are gram-negative intracellular pathogens which can survive and multiply within the phagocytic cells of their hosts and are resistant to the bactericidal action of serum. Brucella melitensis is considered the principal cause of human brucellosis (40,41) and is more virulent than B. abortus (42). These species may occur as either smooth or rough variants depending on the expression of O-polysaccharides (OPS) as a component of the bacterial outer membrane lipopolysaccharide (LPS). In rough strains expression of OPS is limited or absent and attenuation in virulence is generally observed (1,4,19,26,31,35). Our previous studies demonstrated that smooth B. melitensis and B. abortus strains bind fewer complement components on their surface than their corresponding roughmutant organisms (13) obtained by disruption or deletion of the wboA gene (13,26,37,40). However, OPS-deficient strains derived from smooth, virulent B. melitensis 16M are as resistant as the wild type to the bactericidal action of nonimmune human serum (HS) and bind less complement than OPS-deficient strains derived from B. abortus 2308 (13). Since rough mutants of B. melitensis are protected from extracellular complement-mediated killing, we decided to investigate whether the attenuation in virulence previously observed in these strains was associated with differences in their interaction with macrophages.The green fluorescent protein (GFP) from the jellyfish Aequorea victoria is a self-fluorescing protein that requires no substrates and emits bright green fluorescence at 509 nm (3). We took advantage of the properties of the GFP to study the interaction of fluorescent rough and smooth B. melitensis strains with human mononuclear phagocytes and to evaluate the importance of the presence of OPS in the pathogenesis of brucellosis. We introduced plasmid pBBR1MCS-6Y (29) expressing GFP into 16M, OPS-deficient ⌬wboA B. melitensis strain WRR51, and WRR51 complemented with wboA and examined interactions of the fluorescent bacteria with human and murine macrophages by fluorescent and electron microscopy, flow cytometry, and release of lactate dehydrogenase (LDH). We found that infection of mononuclear phagocytes with WRR51 was followed by host cell apoptosis and bacterial death. In contrast, infection with either 16M or wboA-complemented WRR51 led to intracellular bacterial replication but not host cell apoptosis. Moreover, infection with the latter

Vegetative valvular endocarditis involving the aortic and, to a lesser extent, mitral valves was diagnosed echocardiographically in a 3-year-old spayed female Labrador retriever. Historically, the dog had been treated with tetracycline hydrochloride and prednisolone for positive seroreactivity to Ehrlichia canis and antinuclear antigens. Although three aerobic and anaerobic blood cultures failed to grow bacteria, blood cultured simultaneously by the lysis centrifugation technique grew a fastidious, gram-negative organism. Despite an initial therapeutic response, the owner elected euthanasia 17 days later. Necropsy confirmed aortic and mitral valvular endocarditis. Bacteria phenotypically similar to Bartonella species were visualized in the heart valve by light and electron microscopy, and Bartonella DNA from a frozen heart valve was amplified by PCR. Subsequent phenotypic and genotypic characterization of the isolate, including biochemical testing, cellular fatty acid analysis, DNA hybridization, and sequencing of the 16S rRNA gene indicated that this organism, which can induce endocarditis in dogs, is a novel Bartonella subspecies containing an insertion sequence unique among currently recognized Bartonella species. The name Bartonella vinsonii subsp. berkoffii subsp. nov. will be proposed for this organism.

Histopathologic examination of lymph nodes from 39 patients with clinical and pathological criteria for cat scratch disease revealed delicate pleomorphic Gram-negative bacilli in 34 of the 39 nodes. They were within the walls of capillaries in or near areas of follicular hyperplasia and within microabscesses. They were best seen with the Warthin-Starry silver impregnation stain. Organisms in lymph node sections exposed to convalescent serum from three patients and to immunoperoxidase stained equally well with all three samples. The organisms did not react with hyperimmune sera to Legionella pneumophila nor to several species of Rickettsia. These bacilli appear to be the causative agents of cat scratch disease.

Shortly after adopting a 6-week-old cat, a veterinarian was bitten on the left index finger. Within 3 weeks, he developed headache, fever, and left axillary lymphadenopathy. Initial blood cultures from the cat and veterinarian were sterile. Repeat cultures from the cat grew Bartonella-like organisms with lophotrichous flagella. Sera from the veterinarian were not reactive against Bartonella henselae, B. quintana, or B. elizabethae antigens but were seroreactive (reciprocal titer, 1,024) against the feline isolate. Sequential serum samples from the cat were reactive against antigens of B. henselae (titer, 1,024), B. quintana (titer, 128), and the feline isolate (titer, 2,048). Phenotypic and genotypic characterization of this and six additional feline isolates, including microscopic evaluation, biochemical analysis, 16S rRNA gene sequencing, DNA-DNA hybridization, and PCR-restriction fragment length polymorphism of the 16S gene, 16S-23S intergenic spacer region, and citrate synthase gene identified the isolates as B. clarridgeiae. This is the first report of cat scratch disease associated with B. clarridgeiae.