Guntram Seltmann

Application of physico-chemical typing methods for the epidemiological analysis of Salmonella enteritidis strains of phage type 25/17.

Eighty-nine Salmonella enteritidis phage type 25/17 strains isolated from a localized outbreak in the German state Nordrhein-Westfalen (outbreak NWI) could not be further differentiated by biochemotyping and plasmid pattern analysis. They were submitted to a complex typing system consisting of modern physico-chemical analytical procedures. In lipopolysaccharide pattern analysis the strains proved to be homogeneous. In multilocus enzyme electrophoresis, outer membrane and whole cell protein pattern (WCPP) analysis, and Fourier-transform infrared (FT-IR) spectroscopy (increasing extent of differentiation in the given order) strains deviating from each basal pattern were found. The extent of correspondence in these deviations was satisfactory. Forty-six strains of the same sero- and phage type, however, obtained from different outbreaks, were additionally typed. The results obtained with them indicate that the data of the first group were not restricted to strains from outbreak NWI, but of general validity. It was found that both WCPP and FT-IR represent valuable methods for the sub-grouping of bacteria.

Comparative classification of Acinetobacter baumannii strains using seven different typing methods

A group of 49 Acinetobacter baumannii strains obtained from several hospital outbreaks and some sporadic cases were typed by biotyping, antimicrobial susceptibility testing, pulsed-field gel electrophoresis (PFGE), plasmid typing, multilocus enzyme electrophoresis, whole-cell protein profile, and Fourier-transform infrared (FT-IR) spectroscopy. All these methods have shown a high degree of reproducibility and are capable of recognising strains from the same epidemiological event. However, their power to discriminate between epidemiologically unrelated strains varies, with PFGE being superior to the other methods investigated. FT-IR spectroscopy, which has not yet been used for typing of Acinetobacter strains, proved to be a very rapid and highly reproducible method, but was somewhat limited in its discriminating power.

NMR investigation of the 6-deoxy-l-talose-containing O45, O45-related (O45rel), and O66 polysaccharides of Escherichia coli

The structures of the 6-deoxytalose-containing O-specific polysaccharides from the O45 antigen, an O45-related antigen (O45rel), and the O66 antigen (lipopolysaccharides, LPSs) of Escherichia coli were elucidated by chemical characterization and by one- and two-dimensional 1H and 13C NMR spectroscopy. The O45 and O45-related polysaccharides have the following general structure: [formula: see text] For the O45 antigen, X is alpha-D-FucpNAc and for the O45-related antigen, X is beta-D-GlcpNAc. The structure of the O66 polysaccharide is [formula: see text]

Characterization of nosocomial Serratia marcescens isolates: Comparison Of Fouriertransform Infrared Spectroscopy With Pulsed-Field Gel Electrophoresis of Genomic Dna Fragments and Multilocus Enzyme Electrophoresis

A total of 66 Serratia marcescens isolates from 46 patients was investigated by macrorestriction using XbaI followed by pulsed-field gel electrophoresis. 7 restriction fragment patterns attributable to more than one patient and 9 individual patterns were identified. The isolates were additionally characterized by multilocus enzyme electrophoresis and Fourier-transform infrared spectroscopy. The macrorestriction patterns and the multilocus enzyme electrophoresis patterns corresponded fairly well while the classifications derived from these methods were not completely congruent. The grouping achieved by Fourier-transform infrared spectroscopy on the basis of high (> 1000) and moderately high heterogeneity values (300) was consistent with the macrorestriction results. Grouping on a lower heterogeneity level did not contribute to further discrimination. In general, Fourier-transform infrared spectroscopy was less discriminatory than the two other methods, but easier to perform. Therefore, laboratories equipped with the necessary devices may use it to rapidly select bacterial isolates for macrorestriction or other well established characterization procedures.

The Outer Membrane of the Gram-Negative Bacteria and their Components

Unlike proteins and polysaccharides, the lipids are not characterised by similarities in structure but by a commonly high hydrophobicity: they are therefore more or less insoluble in water, but exhibit good solubilities in hydrophobic organic solvents such as benzene, chloroform or ether. Thus, significant structural differences exist between the individual lipid groups.

Structural and serological characterisation of the O-specific polysaccharide of the lipopolysaccharide from proposed new serotype 029 of Serratia marcescens

The structure of the repeating unit of the O-antigenic polysaccharide from the lipopolysaccharide (LPS) of Serratia marcescens strain 111 was determined by compositional and methylation analyses and NMR spectroscopy as →6)-α-D-Glcp-(1→2)-α-L-Rhap-(1→2)-α-L-Rha p-(1→2)-α-L-Rhap-(1→ (Rha, rhamnose) which represents a new O-antigenic structure in LPS of S. marcescens but is similar to the structure of the repeating unit of the O-antigen of S. marcescens 018 →6)-α-D-GlcpNAc-(1→2)-α-L-Rhap-(1→2)-α-L-Rha p-(1→2)-α-L-Rhap-(1→ (Oxley D., Wilkinson S.G. Structure of a neutral polymer isolated from the lipopolysaccharide of the reference strain for S. marcescens serogroup 018. Carbohydr Res 1989; 195: 111-115). Serological investigations using S. marcescens O- and K-specific ELISA tests and immunoblotting showed that S111 reacted with anti-O18 and anti-K4 sera, and that the anti-S111 serum reacted with serotype strain 018. The K4 reaction was confirmed as capsular by the Quellung reaction. After absorption with the heterologous strain, S. marcescens 018 and strain 111 were shown to be immunologically distinct, probably because of the presence of the GlcNAc residue in 018. We propose to add S111 to the O-serotype strains of S. marcescens as 029.

Periplasmic Space and Rigid Layer

The region between cytoplasmic and outer membrane of the Gram-negative bacteria is called the periplasmic space. It contains a concentrated gel-like matrix, the periplasm. Embedded in it is a rigid layer (peptidoglycan). Its width has been electron microscopically determined as 13–25 nm, a variation range that may be explained by differences in cultivation or preparation conditions. The total volume of the periplasmic space has been determined as 20–40% of the whole cell; this value, however, is not identical with that calculated from the width, which would allow a volume of only 8–16%. Because of its great importance for the vital processes of the bacteria, the existence of a space at least similar to the periplasmic is also thought to be present in Gram-positive bacteria (Dijkstra and Keck 1996).

Further Cell Wall Components of Gram-Positive Bacteria

In addition to peptidoglycan, the cell walls of Gram-positive bacteria contain mainly proteins and polysaccharides. With the exception of mycolata and similar bacteria they are generally poor in lipids and lack the outer membrane. The lipid moiety of the lipoteichoic acids is not a constituent of the cell wall, but embedded in the cytoplasmic membrane.

Genomic and Biochemical Relatedness Between Vibrio Cholerae Serovar 0139 and Serovar 01 Eltor Strains

Vibrio cholerae O139 (Bengal) the new pandemic cholera strain emerging on the Indian subcontinent has revealed considerable homology to Vibrio cholerae O1 EL Tor (strain of the seventh pandemic cholera) in terms of genetic and biochemical properties. Apart from capsule and O139 LPS formation, all strains of V. cholerae O139 were found to be identical to V. cholerae O1 EL Tor strains with respect to genomic restriction fragment length polymorphism, genomic distribution of the pathogenic island, pattern of OMP and multilocus enzymes. However, the analysis of a nonpathogenic V. cholerae O139 isolate from Sri Lanka with a totally different pattern of genetic properties underline that horizontal gene transfer of a piece of DNA encoding biosynthesis of the Vibrio cholerae O139-specific LPS and capsule formation to an O1 El Tor precursor strains must have occurred giving rise to a kind of hybrid V. cholerae O1 El Tor encoding the new serovar-specific O139 antigens.

Cell Wall Models

The composition and structure of cell walls are not invariable even under in vitro conditions. They do vary in dependence on cell age, composition of the cultivation medium, pH, redoxpotential, and other parameters. Under in vivo conditions such relationships are even more expressed, especially with regard to colonisation sites in the host and to the phase of progressive infection. Bacterial response to variations in the environment is partially regulated by switch-on/switch-off processes which serve the adaptation of the microorganisms to changing environmental conditions during the course of infection.