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Endocarditis, or inflammation of the lining membrane of the heart, is found among some patients whose blood is infected with the bacterium Staphylococcus aureus, and it is in these cases that the highest mortality from Staphylococcus aureus infection is seen. It has been difficult, however, to devise a blood test to distinguish those patients with endocarditis from those who simply have Staphylococcus aureus infection in their blood. It is known that capsular polysaccharides (CPs), which are a complex chain of sugars that form a protective layer over each bacterial cell, are present in S. aureus and that there are two major types: type 5 and type 8 CPs. Antibodies to these polysaccharide types have been discovered in the blood and are easily measured. Patients with endocarditis more often have measurable antibodies to CPs than those with uncomplicated Staphylococcus infection. In a study of the value of using the measured antibody levels to CP types 5 and 8 as an indication of the presence of endocarditis in patients infected with S. aureus, blood was collected from 33 infected patients and uninfected controls. Of the infected patients, 23 tested positive for antibodies to CP type 8, and five tested positive for antibodies to CP type 5. These results were significantly correlated with other diagnostic information confirming a diagnosis of endocarditis. It is therefore proposed that a blood test for antibodies to CPs types 8 and 5 is the first known to correctly diagnose patients with endocarditis. (Consumer Summary produced by Reliance Medical Information, Inc.)

ABSTRACTThe epidemic and pandemic potential of Vibrio choleraeO139 is such that a vaccine against this newly emerged serogroup ofV. choleraeis required. A conjugate made of the polysaccharide moiety (O-specific polysaccharide plus core) of the lipopolysaccharide (LPS) of V. choleraeO139 (pmLPS) was prepared by derivatization of the pmLPS with adipic acid dihydrazide and coupling to tetanus toxoid (TT) by carbodiimide-mediated condensation. The immunologic properties of the conjugate were tested using BALB/c mice injected subcutaneously three times at 2 weeks interval and then a fourth time 4 weeks later. Mice were bled 7 days after each injection and then once each month for the following 6 months. LPS and TT antibody levels were determined by enzyme-linked immunosorbent assay using immunoplates coated with either O139 LPS or TT. Both pmLPS and pmLPS-TT conjugate elicited low levels of immunoglobulin M (IgM), peaking 5 weeks after the first immunization. The conjugate elicited high levels of IgG antibodies, peaking 3 months after the first immunization and declining slowly during the following 5 months. TT alone, or as a component of conjugate, induced mostly IgG antibodies. Antibodies elicited by the conjugate recognized both capsular polysaccharide and LPS from V. choleraeO139 and were vibriocidal. They were also protective in the neonatal mouse model of cholera infection. The conjugation of the O139 pmLPS, therefore, enhanced its immunogenicity and conferred T-dependent properties to this polysaccharide.

ABSTRACTThe adherence of Staphylococcus aureusto human endothelial cells (EC) is probably an important step in the pathogenesis of systemic staphylococcal infections. We examined the influence of type 5 capsular polysaccharide (CP5) production, the global regulator agr, and the bacterial growth phase onS. aureusadherence to EC. Whereas S. aureusNewman showed maximal adherence to EC in the logarithmic phase of growth, an isogenic agrmutant showed maximal adherence in the stationary growth phase. S. aureusadherence to EC and CP5 expression were negatively correlated: a mutation in theagrlocus diminished CP5 production and led to increased adherence. Likewise, induction of CP5 expression by addition of NaCl to the growth medium resulted in reduced staphylococcal adherence to EC.S. aureusNewman cells that adhered to EC did not express CP5. A Newman cap5Omutant was acapsular and showed significantly greater adherence to EC than the parental strain did (P< 0.005). Complementation of the cap5Omutation in transrestored CP5 expression and reduced EC adherence to a level similar to that of the parental strain. The enhanced adherence shown by the cap5Omutant was similar in magnitude to that of the agrmutant or the cap5O agrdouble mutant. Cells of the cap5Omutant andcap5O agrdouble mutant harvested from stationary-phase cultures adhered significantly better than did cells harvested in the exponential growth phase. These data are consistent with the postexponential and agr-independent expression by S. aureusof at least one putative EC adhesin, whose binding domain may be masked by CP5.

Cell surface preparations and ribosomal preparations were extracted from Klebsiella pneumoniae.Agar gel diffusion with antisera to cell surface preparations or ribosomal preparations indicated common antigenic components among the preparations. Lipopolysaccharide and capsular polysaccharide were identified in the cell surface preparations. These results and the previous identification of lipopolysaccharide and capsular polysaccharide in ribosomal preparations suggest that these antigens are responsible for the immunochemical cross-reactivity observed among these two bacterial extracts. Active protection could be induced in mice by these two preparations. On a dry-weight basis, cell surface preparations provided better immunoprotective activity than did ribosomal preparations. However, the 50% protective dose of both preparations is practically the same on the basis of their capsular polysaccharide content. These results are consistent with the hypothesis that the immunoprotective moiety of ribosomal preparations is the contaminating cell surface antigens. Furthermore, the low level of nucleotidic components detected in purified cell surface preparations led us to infer that the immunoprotective activity of capsular polysaccharide may not be dependent on the adjuvant activity of ribonucleic acid. The involvement of capsular polysaccharide in the immunoprotective capacity of cell surface preparations is demonstrated either by using a degradation of this antigen by K. pneumoniaebacteriophage K2-associated glycanase or by using a preparation extracted from a noncapsulated mutant of K. pneumoniae.Nevertheless, the low protective ability of purified capsular polysaccharides is in contrast to its greater activity when induced in bacterial cell surface preparations. The protective activity of K. pneumoniaecapsular polysaccharide may be dependent on its association with other surface antigenic components present in cell surface preparations or may be dependent on its native form in the bacterial cell surface.