Polysaccharides of type 6 Klebsiella

Development and Application of a High-Throughput Method for the Purification and Analysis of Surface Carbohydrates from Klebsiella pneumoniae

Klebsiella pneumoniae (Kp) is a Gram-negative bacterium, and a leading cause of neonatal sepsis in low- and middle-income countries, often associated with anti-microbial resistance. Two types of polysaccharides are expressed on the Kp cell surface and have been proposed as key antigens for vaccine design: capsular polysaccharides (known as K-antigens, K-Ags) and O-antigens (O-Ags). Historically, Kp has been classified using capsule serotyping and although 186 distinct genotypes have been predicted so far based on sequence analysis, many structures are still unknown. In contrast, only 11 distinct OAg serotypes have been described. The characterization of emerging strains requires the development of a high-throughput purification method to obtain sufficient K- and O-Ag material to characterize the large collection of serotypes and gain insight on structural features and potential cross-reactivity that could allow vaccine simplification. Here, this was achieved by adapting our established method for the simple purification of O-Ags, using mild acetic acid hydrolysis performed directly on bacterial cells, followed by filtration and precipitation steps. The method was successfully applied to purify the surface carbohydrates from different Kp strains, thereby demonstrating the robustness and general applicability of the purification method developed. Further, antigen characterization showed that the purification method had no impact on the structural integrity of the polysaccharides and preserved labile substituents such as O-acetyl and pyruvyl groups. This method can be further optimized for scaling up and manufacturing to support the development of high-valency saccharide-based vaccines against Kp.

Significance of circulating capsular antigen in Klebsiella infections

Klebsiella capsular antigen (KCA) was detected in serum by counterimmunoelectrophoresis in 8 of 31 patients with klebsiella bacteremia, in two nonbacteremic patients with pneumonia and meningitis, respectively, and in the cerebrospinal fluid only of 1 of the 31 bacteremic patients. It was also detected in cerebrospinal fluid, urine (two patients each) empyema fluid, and abscess drainage (one patient each). Patients whose bacteremias were associated with a discernible tissue focus (e.g., pneumonia) tended to have detectable serum KCA more often than those with "primary bacteremia." A fatal outcome occurred in six of nine bacteremia patients with detectable serum KCA compared with 4 of 22 without demonstrable antigen (P < 0.05). Persistent antigenemia and antigenuria aided in the diagnosis of perinephric abscess in one patient, and increasing levels of serum KCA anticipated treatment failure in another patient with pneumonia. The presence of detectable KCA in the serum of patients infected with klebsiella thus appeared to correlate with severity of infection, with persistence of active foci, and with a poorer prognosis than in those patients who had no detectable antigen. Whether the presence of this antigen itself plays any pathogenic role needs to be further clarified.

Progress in immunization against Klebsiella infections

Nosocomial infections with Klebsiella spp. are a leading cause of morbidity and mortality. The ability of Klebsiella spp. readily to colonize hospitalized patients, complications in treatment of infections due to R-factor-acquired antibiotic resistance, and the high mortality rate in certain patient populations, point to the need for immunoprophylactic/immunotherapeutic agents for disease control. The potential for vaccination against Klebsiella spp. is discussed in light of recent developments concerning the pathogenesis of Klebsiella infections as relates to the identification of protective antigens as possible vaccine candidates.

Further Studies of the polysaccharide of Klebsiella pneumoniae possessing strong adjuvanticity. I. Production of the adjuvant polysaccharide by noncapsulated mutant

In culture fluid, Klebsiella pneumoniae type 1 Kasuya strain produces polysaccharide exhibiting a strong adjuvant effect. The active substance responsible for the strong adjuvant effect of the polysaccharide isn ot its acidic polysaccharide fraction (the type-specific capsular antigen) but the neutral polysaccharide fraction. In the present study, a mutant which did not produce the type-specific capsular polysaccharide was isolated from ultraviolet-irradiated cells of K. pneumoniae type 1 Kasuya strain which had been labeled with leucine-requiring marker by selecting unagglutinable cells with the antiserum to he type-specific capsular polysaccharide. Serological tests showed that the type-specific acidic capsular polysaccharide was present neither on the cells surface nor in the culture fluid of the mutant. Electron microscopically, the mutant did not possess any capsular material. On the other hand, nearly an equal amount of neutral polysaccharide antigen as produced in culture fluids of the noncapsulated mutant polysaccharide antigen was produced in culture fluids of te noncapsulated mutant and the parent strain. The neutral polysaccharide antigen produced by the noncapsulated mutant exhibited the same degree of strong adjuvant effect on antibody response to bovine gammaglobulin in mice as that produced by the parent strain. The relationship between the neutral polysaccharide antigen in culture fluid and the O antigen of K. pneumoniae was discussed.

Isolation and characterization of a bacteriophage specific for the lipopolysaccharide of rough derivatives of Pseudomonas aeruginosa strain PAO

A lipopolysaccharide (LPS)-defective (rough) mutant of Pseudomonas aeruginosa PAO was isolated by selection for resistance to the LPS-specific phage E79. The LPS of this mutant, AK-1012, lacked the O-antigenic side chain-specific amino sugar fucosamine as well as the core-specific sugars glucose and rhamnose. Using this strain, we isolated and characterized a phage, phi PLS27, which is specifically inactivated upon incubation with LPS extracted from rough mutants of P. aeruginosa PAO. phi PLS27 was found to be a Bradley type C phage and was very similar to coliphage T7 in a number of properties, including size, buoyant density, mass, and the number of structural proteins.