Biomedical subjects
Publications and source records attributed to D Naumann.
Infrared signals of microorganisms are highly specific fingerprint-like patterns that can be used for probing the identity of microorganisms. The simplicity and versatility of Fourier-transform infrared spectroscopy (FT-IR) makes it a versatile technique for rapid differentiation, classification, identification and large-scale screening at the subspecies level.
This study describes a computer-based technique for classifying and identifying bacterial samples using Fourier-transform infrared spectroscopy (FT-IR) patterns. Classification schemes were tested for selected series of bacterial strains and species from a variety of different genera. Dissimilarities between bacterial IR spectra were calculated using modified correlation coefficients. Dissimilarity matrices were used for cluster analysis, which yielded dendrograms broadly equated with conventional taxonomic classification schemes. Analyses were performed with selected strains of the taxa Staphylococcus, Streptococcus, Clostridium, Legionella and Escherichia coli in particular, and with a database containing 139 bacterial reference spectra. The latter covered a wide range of Gram-negative and Gram-positive bacteria. Unknown specimens could be identified when included in an established cluster analysis. Thirty-six clinical isolates of Staphylococcus aureus and 24 of Streptococcus faecalis were tested and all were assigned to the correct species cluster. It is concluded that: (1) FT-IR patterns can be used to type bacteria; (2) FT-IR provides data which can be treated such that classifications are similar and/or complementary to conventional classification schemes; and (3) FT-IR can be used as an easy and safe method for the rapid identification of clinical isolates.
The valency of the Sokolow-index for the proof of a left-ventricular hypertrophy was investigated in 179 hypertensives with for the most part mild hypertension and 31 borderline hypertensives in comparison to 55 normotensives. Though in a part of the test persons an enlargement of the left-ventricular muscle bulk could be made evident by means of echocardiography, the Sokolow-index is fully insensitive and partly controversial.
179 male hypertensives with predominantly mild hypertension were in comparison to 55 male normotensives investigated by means of a 2-D-regulated M-mode echocardiogram in order to prove the interrelations between blood pressure, age, body mass and left-ventricular muscle mass of the heart. The thicknesses of the wall of the left ventricle, the left-ventricular muscle mass and the left-ventricular muscle mass index were significantly larger in the hypertensives. Univariate calculations of correlation did not show any significant relations of the left-ventricular muscle mass to the height of the blood pressure but significantly positive relations with a small measure of distinctness to the body mass in the hypertensives and normotensives and to the age in the hypertensives. Conclusions for the valuation of echocardiographic findings in left-ventricular hypertrophy were derived.
179 male hypertensives with above all mild arterial hypertension were in comparison to 55 male normotensives investigated by means of a two-dimensionally regulated M-mode echocardiogram for the recognition of left-ventricular functional disturbances. Thereby the hypertensives showed a significantly higher mean value for the left-ventricular ejection time as well as a significantly more frequent number (11.2%) of cases with a frequency-normed average circumferent shortening speed of the fibres below 0.82 circ/s and thus a beginning reduction of the contractility of the left ventricle. Stroke volume, ejection fraction and increase of the thickness of the left-ventricular walls of the heart did not show any significant differences between hypertensives and normotensives. With the calculation of these parameters the M-mode echocardiogram is apparently overcharged.
In 179 hypertensives with above all mild hypertension, 31 borderline hypertensives and 55 normotensives of male sex for the proof of a left-ventricular hypertrophy were determined the type of position and the index RI + SIII from the bipolar limb-ECG after Einthoven and compared with the left-ventricular muscle mass established in a 2-D-regulated M-mode echocardiogram. Thereby in the not very much distinct cases of hypertrophy the index RI + SIII of more than 2.5 mV given by Gubner and Ungerleider has proven itself fully insensitive, whereas an index of more than 1.1 mV resulted in a sensitivity of 50% and a specificity of 73.5% for a left-ventricular hypertrophy which was made evident by means of echocardiography. In the total spectre of the diagnostics of hypertrophy the Einthoven-ECG has further its full justification.
31 male patients (average age 44.0 +/- 8.5 years) suffering from borderline hypertension for many years were examined in comparison with 55 male patients (average age 44.2 +/- 10.1 years) having normotension. We used a conventional electrocardiogram and a two-dimensionally controlled M-mode echocardiogram to diagnose left ventricular hypertrophy of the heart (LVH). Electrocardiographic examinations did not clearly reveal LVH. Septal and posterior wall thicknesses measured by echocardiography as well as the calculated left ventricular muscular mass showed significantly higher mean values in patients suffering from borderline hypertension. An end-diastolic septum thickness equal to or larger than 11 mm and/or a left ventricular muscular mass larger than 155 g showed an LVH prevalence of 26 to 32 per cent in patients with borderline hypertension compared with 13 to 15 per cent in patients having normal blood pressure values. After the relativation of the values measured by the echocardiogram with respect to the body surface, there was no more evidence of significant values. Positive correlations were particularly found between the body weight and the echocardiogram parameters and not so much between the body weight and the blood pressure or the blood pressure and the measured echocardiogram values. No correlation was found concerning the duration of the borderline hypertension of our subjects.
By using the X-ray and infrared spectroscopic characteristics of various synthetic analogues and partial structures of lipid A in the dried state, a comparison of these compounds with their natural counterparts was undertaken. As judged by their X-ray diffraction and infrared spectroscopic features, the compounds tested could be divided into two main groups. The first group covered those samples synthesized in accordance with a previously assumed structure, while those synthesized in accordance with present knowledge on the lipid-A primary structure formed the second group. Members of the first group were characterized by a liquid-like, alpha-type arrangement of their fatty acyl chains in a non-lamellar supramolecular structure, while all members of the second group formed bilayered phases with a much more ordered, beta-type conformation of their fatty acyl chains. Synthetic Escherichia coli-type lipid A (compound 506), proved to be essentially identical to its natural counterpart with respect to those conformational properties accessible by our methods. The synthetic hepta-acyl species of Salmonella minnesota lipid A (compound 516) revealed an unexpected conformational behaviour, whereby a fatty-acyl-chain packing could be detected which was different from the hexagonal arrangement found for all other compounds of the second group.
Simultaneous infections with different Legionella spp. have rarely been described in the literature. We now report on seven sporadic cases of legionellosis of which three were simultaneous infections caused by multiple Legionella pneumophila serogroups. Four different legionellae were involved. L. pneumophila serogroup 1, two different types of L. pneumophila serogroup 4, and L. pneumophila serogroup 10 have been identified simultaneously from a lung tissue specimen of one patient. Specimens from two other patients each revealed two different legionellae of serogroups 1 and 4. The existence of different L. pneumophila serogroups in simultaneous infections has not only been documented by identifying the incriminated Legionella spp. by classical methods. In addition, preliminary results of Legionella spp. identification with the novel physical procedure of Fourier transform infrared spectroscopy have been presented to evaluate its possible applicability for routine diagnostic procedures.
The polymorphism of lipid A, the endotoxic principle of the lipopolysaccharides of gram-negative bacteria, has been investigated in the fully hydrated state at temperatures between 5 degrees and 58 degrees C via Fourier-transform infrared spectroscopy. These measurements were supplemented by X-ray diffraction, fluorescence intensity techniques and differential thermal analysis. Up to three distinct phase transitions could be detected, with the main transition temperatures lying at approximately 41 degrees, 46 degrees, 44 degrees and 47 degrees C for Escherichia coli lipid A, Salmonella minnesota lipid A, and the synthetic lipid A compounds 506 and 516, respectively. 4'-Monophosphoryl-lipid A samples exhibited their main transition temperatures at considerably higher temperatures (about 52 degrees C for E. coli lipid A). The analysis of greater than CH2 stretching absorption bands as well as the wide-angle scattering behaviour of the lipid A samples showed that the main transition apparently involved the completion of hydrocarbon chain melting of lipid A, as typically observed for phospholipids. However, the phase transition behaviour was found to be much more complex than that usually observed for model phospholipid systems. Even below the main transition temperature, considerable amounts of the methylene segments of the acyl chains of lipid A were found to assume gauche conformations. These conformational changes might be related to the occurrence of up to two further transitions located at about 22 degrees, 30 degrees, 27 degrees and 25.5 degrees C (first transition) and at about 34 degrees, 42 degrees, 38.5 degrees and 40.5 degrees C (second transition) for E. coli lipid A, S. minnesota lipid A and the synthetic lipid A compounds 506 and 516, respectively. Furthermore, by the analysis of some characteristic infrared absorption bands related to the hydrophilic backbone, it could be demonstrated that the temperature-induced conformational changes occurring within the hydrocarbon chains were constantly and simultaneously accompanied by detectable rearrangements within the interfacial region and the polar head group of lipid A. The following conclusions were drawn: Up to about 30 degrees C the lipid A assemblies were supposed to adopt virtually bilayered, true lamellar arrangements, as revealed by the analysis of greater than CH2 scissoring vibrations and X-ray diffraction pattern. However, as indicated by fluorometric techniques, no stable closed vesicles seemed to be formed even under these conditions.(ABSTRACT TRUNCATED AT 400 WORDS)
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The conformational properties of the isolated S form of Salmonella sp. lipopolysaccharide (LPS), of Re mutant LPS, and of free lipid A were investigated by using X-ray diffraction and conformational energy calculations. The data obtained showed that LPS in a dried, in a hydrated, and probably also in an aqueous dispersion state is capable of forming bilayered lamellar arrangements similar to phospholipids. From the bilayer packing periodicities, a geometrical model of the extensions of the LPS regions lipid A, 2-keto-3-deoxyoctulosonic acid, and O-specific chain along the membrane normal could be calculated. Furthermore, the lipid A component was found to assume a remarkably high ordered conformation: its fatty acid chains were tightly packed in a dense hexagonal lattice with a center-to-center distance of 0.49 nm. The hydrophilic backbone of lipid A showed a strong tendency to form domains in the membrane, resulting in a more or less parallel arrangement of lipid A units. According to model calculations, the hydrophilic backbone of lipid A appears to be oriented approximately 45 degrees to the membrane surface, which would lead to a shed roof-like appearance of the surface structure in the indentations of which the 2-keto-3-deoxyoctulosonic acid moiety would fit. In contrast, the O-specific chains assume a low ordered, heavily coiled conformation. Comparison of these structural properties with those known for natural phospholipids in biological membranes indicates that the high state of order of the lipid A portion of LPS might be an important factor in the structural role and permeation barrier functions of LPS in the outer membrane of gram-negative bacteria.
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Infrared spectroscopic measurements are used to obtain insights into the three-dimensional architecture of peptidoglycan (murein), the rigid component of almost all bacterial cell walls. The infrared spectra of various types of peptidoglycans (including all chemotypes and examples of the so called A and B groups) were compared to each other and to those obtained from crystalline chitin. All peptidoglycans investigated exhibited very similar infrared spectra. In particular the conformationally sensitive amide A, I and II absorption bands were found to be constantly centered around 3300 cm-1, 1657 cm-1 and 1534 cm-1 respectively; furthermore, the spectral region between 1200 cm-1 and 800 cm-1, characterized by several strong absorption bands connected to complex sugar ring modes, proved to be remarkably uniform. Additionally the infrared spectra remained significantly constant between -175 degrees C and + 75 degrees C and turned out to be rather independent of sample preparation (solvent replacement, freeze-drying and film producing). An analysis of band half-widths revealed no high crystalline state of order of peptidoglycan. On the basis of band positions and half-widths of amide bands, regular conformations like alpha helices of beta pleated sheets could be excluded. Several distinctive, fingerprint-like spectral features of the various murein samples permitted a facile identification of individual peptidoglycans. Moreover, infrared spectroscopy seems to be very promising as an analytical tool, e.g. for tracing variations of cell wall structure, detecting conformational changes and estimating crosslinking indices in a quick and simple way. The comparative analysis of amide band positions and band half-widths yielded substantial differences between infrared spectra of chitin and murein, thus rejecting previous models based on the assumption of a nearly crystalline chitin-like structure of the glycan chains of murein.
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