Günter Schmidt

Chemistry and Biology of the Enterobacterial Common Antigen (ECA)

The classical surface antigens of Enterobacteriaceae: 0, K, and H antigens have been studied extensively in the past and have provided a basis for the taxonomy of this family (Kauffmann, 1966, 1975). In comparison to the vast knowledge accumulated on the structure, localization, genetic determination, and biologic effects of O and K antigens (Weinbaum et aI., 1971; Orskov et aI., 1977), the precise knowledge of antigens shared by various microorganisms is small. This is most probably due to the fact that the “... direction of research in the past has to a great deal been stimulated by problems and questions of taxonomy, etiology of diseases and epidemiology” (Neter and Whang, 1972).

On the primary structure of the Escherichia coli R4 cell wall lipopolysaccharide core

Abstract From Escherichia coli R4, and from some deeper rough mutants of it, the cell wall lipopolysaccharides were isolated and subjected to mild acid hydrolysis. By methylation/g.l.c./m.s. and other analyses of the core oligosaccharides thus obtained, the primary structure of the E. coli R4 core (hexose and heptose region) was elucidated:

K-Antigen Identification, Hemolysin Production, and Hemagglutination Types of Escherichia coli 06 Strains Isolated from Patients with Urinary Tract Infections

Serotyping of 1918 Escherichia coli strains isolated in significant cell numbers from the urine of patients with urinary tract infections (UTI) revealed the presence of 117 O6 strains. The K antigens were identified by means of K-specific phages and serological methods. The phages used included a K1 phage pool (phi 1, A-E) and the separate phages phi 2, phi 5, phi 7, phi 12 and phi 13. The presence of H antigens, type 1 fimbriae formation, hemolysin production and mannose-resistant hemagglutination (MRHA) ability with human A, sheep, calf and pig erythrocytes were also analyzed. Six different MRHA types were defined and discussed in relation to the O6:K:H serotype. Remarkably, E. coli O6 strains were found to possess a whole arsenal of virulence factors (K antigens, MRHA, hemolysin). The most common serotypes - O6:K2:H1/H- (26), O6:K5:H1/H- (35) and O6:K13:H1/H- (20) - differed from each other in some cases in both MRHA type and hemolysin production.

Isolation and characterization of bacteriophages specific for capsular antigens K3, K7, K12, and K13 of Escherichia coli.

Four bacteriophages recognizing the Escherichia coli capsular antigens K3, K7, K12, and K13, respectively, were isolated from pooled sewage samples. The nucleic acid of these phages was identified as double-stranded DNA of different size (phi K3, 71.3; phi K7, 32.8; phi K12, 42.9; phi K13, 43.4 kbp). Three of these phages belonged to Bradleys morphology group C and were specific for K3, K7, and K12 antigens, respectively. The phage phi K13 (Bradleys group A) attacked not only E. coli K13 strains but also E. coli producing the closely related K20 and K23 antigens. It is suggested that the common basic repeating units occurring in these capsular polysaccharides are the primary receptor of phi K13. It could be demonstrated that the four phages were able to depolymerize enzymatically the capsular polysaccharides isolated from the respective host strains.

Bacteriophages specifically recognizing the lipopolysaccharide antigens O4, O5, O6, O7 of Escherichia coli

Four bacteriophages recognizing the Escherichia coli lipopolysaccharide (LPS) antigens O4, O5, O6, and O7, respectively, were isolated from pooled sewage samples. Electron microscopic investigations revealed icosahedral phage structures. Phages phi O4, phi O5, and phi O7 belonged to Bradleys morphology group C, while phi O6 had a tail and resembles phages of group A of Bradley. The nucleic acid of the phages was identified as double-stranded DNA of different genomic sizes. Host range studies showed that only E. coli strains with homologous O antigens were attacked. No lysis of encapsulated and rough E. coli strains was observed. The phages specifically depolymerized the homologous LPS of their host strains; they may be useful for detecting respective non-capsulated E. coli strains in epidemiological studies as simple alternative to the laborious serological typing. Diagnostic application is restricted, however, as strains carrying K antigens have not been detected. The high specificity of the phage-associated enzymes provides a mild method for the preparation of oligosaccharides from the LPS for structural studies.