Bacterial Spectra Research Articles

Multivariate statistical analysis of mutational spectra of alkylating agents

A series of multivariate statistical methods were used to explore the current knowledge on the mutational spectra of alkylating agents (AA) in bacterial and mammalian cells. The data relative to lac I and gpt genes of Escherichia coli were considered. The analysis focused on the distribution of GC to AT transitions, which account for the majority of AA-induced mutations. The statistical analysis of 15 different mutational spectra obtained by various laboratories pointed to a number of biological factors involved in the mutational process. First of all, factor and cluster analyses demonstrated that the mutational profiles obtained in mammalian cells form a homogeneous cluster different from the cluster formed by the bacterial cell mutational spectra. S N1-type AAs give rise to classes of mutational spectra statistically different from the spectra induced by the S N2-type AAs. The analysis of the mutated sequences of both genes pointed to a correlation between mutation induction by S N1 AAs, which react through a positively charged alkylating intermediate, and the occurrence of mutations at guanines preceded 5′ by a purine. Moreover, our statistical analysis showed that the distribution of AA-induced mutations is not affected by the transcriptional activity of the target gene, but is strongly determined by the sequence specificity of AA-induced mutagenesis and by the structure of the target proteins. The agreement of our results with the findings of previous studies indicates that the multivariate data analysis methods are a sensitive and reliable tool for exploring the mechanisms underlying complex biological processes. The novelty of the present results lies in their quantitative character, and in the clarity of the graphical displays. We propose the use of this methodological approach to large bulk of information available on mutational spectra.

The gastropulmonary route of infection—Fact or fiction?

Published studies relating to whether medicinal stress-bleeding prophylaxis leading to an increase of gastric pH favors the development of bronchopulmonary infections are reviewed. Results from studies in healthy humans, patients with ulcer disease, and patients in the intensive care unit (ICU) clearly show that the risk of gastric bacterial colonization significantly increases relative to increasing gastric pH. Moreover, a drug-induced increase of gastric pH leads directly to gastric bacterial colonization also in patients in the ICU, above all with bacteria typical of the gastrointestinal tract. Comparing the different bacterial spectra of the oropharynx, stomach, and upper small intestine, it becomes clear that the stomach is a reservoir of bacteria independent of the oropharynx and also subject to retrograde colonization due to the duodenogastric reflux. Both by means of microbiological and in particular direct detection procedures, it can be demonstrated that in at least 30–40% of intubated patients a gastropulmonary route of colonization occurs. In patient groups without a medication-induced increase of gastric pH the number of bacteria detected in the tracheal secretion is about 33% less than in the case of conventional stress-bleeding prophylaxis. These findings make it understandable that a highly significant increase in the pneumonia rate is seen in patients receiving pH-increasing stress-bleeding prophylaxis versus control groups without therapy essentially influencing gastric pH. A risk score was developed that allows an easy description of those patients who are at an increased risk of pulmonary infections due to the gastropulmonary route of colonization.

UV-B-Inducible and Temperature-Sensitive Photoreactivation of Cyclobutane Pyrimidine Dimers in Arabidopsis thaliana

Removal of cyclobutane pyrimidine dimers (CBPDs) in vivo from the DNA of UV-irradiated eight-leaf seedlings of Arabidopsis thaliana was rapid in the presence of visible light (half-life about 1 hour); removal of CBPDs in the dark, presumably via excision repair, was an order of magnitude slower. Extracts of plants contained significant photolyase in vitro, as assayed by restoration of transforming activity to UV-irradiated Escherichia coli plasmids; activity was maximal from four-leaf to 12-leaf stages. UV-B treatment of seedlings for 6 hours increased photolyase specific activity in extracts twofold. Arabidopsis photolyase was markedly temperature-sensitive, both in vitro (half-life at 30 degrees C about 12 minutes) and in vivo (half-life at 30 degrees C, 30 to 45 minutes). The wavelength dependency of the photoreactivation cross-section showed a broad peak at 375 to 400 nm, and is thus similar to that for maize pollen; it overlaps bacterial and yeast photolyase action spectra.

Resonance Raman Spectra of Aqueous Pollen Suspensions with 222.5–242.4-nm Pulsed Laser Excitation

Excitation of resonance Raman spectra with wavelengths shorter than 257 nm, i.e., deep UV-excited resonance Raman spectroscopy, has been shown to have major advantages. This has been most apparent in the study of relatively simple biologically important molecules which have electronic transitions in the deep UV. Recently, such techniques have been extended in order to study much more complex systems such as whole bacterial cells and viruses. A variety of molecular components can be excited selectively and sensitively to a degree dependent upon the exciting wavelength. In this laboratory our primary emphasis has been on the investigation of the bases for the development of analytical methods aiding the rapid detection and identification of bacteria. A variety of taxonomic markers have been detected which allow rapid bacterial identification at the genus and perhaps even the species level. Most recently, it has been shown to be possible to determine bacterial G+C/A+T base pair molar ratios from bacterial spectra independent of cultural conditions or growth rates.

Classification and identification of bacteria by Fourier-transform infrared spectroscopy

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.

Evaluation of infrared spectroscopy as a bacterial identification method.

A study motivated by the recent revival of interest in the use of IR spectroscopy to identify bacteria is reported. A library of FT-IR spectra of dried bacterial films was complied using 16 different strains. A test set was compiled from spectra of the same strains grown several months later. The test set was quantitatively compared with the library on the basis of spectral similarity in the region 980-1190 cm-1. Six of the strains in the test set were not matched with the correct strain in the library despite efforts to reproduce the conditions under which cells were grown and prepared. The results suggest that reproducibility of the bacterial spectra is a potential difficulty that must be addressed by any attempts to develop FT-IR spectroscopy as a bacterial identification method.

UV resonance Raman spectra of bacteria, bacterial spores, protoplasts and calcium dipicolinate

Resonance Raman spectra have been obtained with 222.65, 230.72, 242.39 and 250.96 nm excitation for Bacillus subtilis, Enterobacter cloacae, Pseudomonas fluorescens and Staphylococcus epidermids. Endospores of Bacillus cereus and protoplasts of Bacillus megaterium have been studied also. With 251 nm excitation, bacterial nucleic acid spectra are obtained selectively. Nucleic acid also strongly excited by 242 nm light while at that wavelength aromatic amino acid spectra just begin to be detected. Aromatic amino acid spectra are observed exclusively at 231 nm and appear along with some new strong nucleic acid peaks with 222 nm excitation. Calcium dipicolinate has been excited selectively in Bacillus spores at 242 nm. Large characteristic spectral differences can be explained as due to the selective excitation of various UV-absorbing cell components. Large intensity differences seen in the tryptophan-associated 1556 cm −1 peak excited at 222 and 231 nm appear to be strongly correlated with Gram type. Results suggest that UV-absorbing bacterial taxonomic markers can be selectively excited to give rise to characteristics resonance Raman bacterial spectral fingerprints which have the potential to be used as the basis for methods of rapid identification.

Ultraviolet Resonance Raman Spectra of Escherichia Coli with 222.5–251.0 nm Pulsed Laser Excitation

Resonance Raman spectra of the gram-negative organism, Escherichia coli, have been obtained with 222.5-, 230.6-, and 251.0-nm excitation, and the results have been compared with those reported earlier for 242.4-nm excitation. Major changes in bacterial spectra have been observed with changes in exciting wavelength. The origins of the major peaks in each spectrum have been explained primarily in terms of contributions of nucleic acid bases and aromatic amino acids. As an aid in making assignments, spectra of aromatic amino acids, nucleosides, and mixtures of the two have been obtained at each wavelength used to excite bacterial spectra. Background fluorescence has been observed to be negligible below 251 nm. Selective excitation of bacterial nucleic acid and protein components has been done with ease. Results suggest that an extension of the exciting wavelength range to 190–220 nm will allow the selective excitation of additional cell components.

Infectious disease management with oral antibiotics

This paper has reviewed the bacterial etiologies and therapeis for commonly seen infections in the out-patient clinic or physician's office. The use of oral antibiotics for the treatment of pharyngitis, otitis media, sinusitis, bronchitis, certain pneumonias, cellulitis, urinary tract infections and as follow-up therapy to systemic administration is discussed. Emphasis on the decreasing bacterial spectra of the tetracyclines is noted as well as a discussion of therapy of infections due to beta-lactamase-producing Staphylococcus aureus and Haemophilus influenzae.

Aramycin, a Streptothricin-like Antibiotic, Produced by a Local Strain of Streptomyces MYS-20A

One strain of actinomycetes, designated as MYS-20 A, was isolated from the Egyptian soil. The organism produces a substance that appears to be different from previously described antibiotics. The substance was named "Aramycin". A description of the strain of actinomyces MYS 20 A is given as well as conditions of growth for maximum production of the antibiotic substance. The bacterial and fungal spectra of aramycin are given. The substance appears to exhibit a very significant cytotoxic effect. The antibiotic was toxic to mice, the lethal dose being, however, about 15 times higher than the curative dose.

How penicillin works

This article describes how penicillin works at the chemical level. It should provide the endodontist some insight into bacterial resistance to and bacterial spectra of penicillins. This article describes how penicillin works at the chemical level. It should provide the endodontist some insight into bacterial resistance to and bacterial spectra of penicillins.

The use of infrared spectroscopy and artificial neural networks for detection of uropathogenic Escherichia coli strains' susceptibility to cephalothin.

Infrared spectroscopy is an increasingly common method for bacterial strains' testing. For the analysis of bacterial IR spectra, advanced mathematical methods such as artificial neural networks must be used. The combination of these two methods has been used previously to analyze taxonomic affiliation of bacteria. The aim of this study was the classification of Escherichia coli strains in terms of susceptibility/resistance to cephalothin on the basis of their infrared spectra. The infrared spectra of 109 uropathogenic E. coli strains were measured. These data are used for classification of E. coli strains by using designed artificial neural networks. The most efficient artificial neural networks classify the E. coli sensitive/resistant strains with an error of 5%. Bacteria can be classified in terms of their antibiotic susceptibility by using infrared spectroscopy and artificial neural networks.

External Otitis: A Method of Therapy and Prophylaxis

Recent investigations into the etiology and pathogenesis of external otitis have brought about a more rational method of therapy and possibly prophylaxis. Studies of the bacteriology and mycology of external otitis have been going on for many years. It has been only during the past few years, however, that interest has been directed toward explaining why this condition is so characteristically recurrent. The antibiotics and their peculiar bacterial spectra of activity have changed our mode of thinking. When we are confronted with an infectious process we now ask ourselves the following: What is the organism? Is it pathogenic, and to what antibiotic is it sensitive? Since we have been armed with this information pathogenic organisms have become an easy prey to our drugs—a far cry from the practice of medicine several years ago. All the recent investigations have uniformly reported that the vast majority of cases of external otitis are

Antibiotics—Their mechanism of action and uses as anti-infective agents

Anti-infective agents of clinical usefulness for systemic administration act by inhibition of enzymatic processes important in the metabolic scheme of the pathogenic organism. This action may occur (1) at the cell wall, preventing the uptake of an essential metabolite or (2) within the cell where it may block catabolic energy-supplying mechanisms or anabolic protein-synthesizing processes. In any case the organism loses its ability to reproduce itself. Within the body this is tantamount to the destruction of the organism and recovery from the symptoms which it has been causing. The organisms against which a given antibiotic is effective is called its bacterial spectrum. Overlapping of the bacterial spectra of different antibiotics probably indicates that the organisms have a common enzyme capable of being blocked by the antibiotic; however, the variety of enzyme systems is so great and so varied that a bacterial species is capable of producing mutant strains resistant to a given antibiotic. These mutant strains make use of alternate pathways not blocked by the antibiotic. A desirable bacterial spectrum must have a minimum or no effects on the cells of the tissues of the host. This means that it must block metabolic pathways which are peculiar to bacteria and not present in tissue cells. This property is present in penicillin and probably to a large degree in chloramphenicol, aureomycin, and terramycin, and to a definitely lesser degree in streptomycin. Other antibiotics as tyrothricin are so harmful to the tissues that in spite of desirable bacterial spectra their use is confined to topical application.

Über die Chemie des Enniatins

Judging by the physical and chemical properties and “bacterial spectra”, the antibiotic substance, Enniatin, previously isolated from a strain ofFusarium by the authors, appears to be identical with that which was recently reported byCook et al. derived from another strain and designated by them as Lateritiin-I, although the reported empirical formulæ differ. Numerous physical and chemical characteristics of Enniatin and its degradation products are given, and, further, two relatedFusarium antibiotics, here designated as Enniatin B and C, are briefly described.

A Method for Detection of Streptothricin in the Presence of Streptomycin

Streptomycin1 and streptothricin,2 two antibiotic agents having almost identical bacterial spectra,3,4 are both produced by members of the actinomycetes, namely, Actinomyces griseus and Actinomyces lavendulae respectively. Because of this close relationship and of the still existing difficulty in the identification of the various members of the actinomycetes,5 it is possible that strains of the organisms producing these 2 antibiotics might be confused. Such a confusion would be particularly undesirable when it is recognized that streptothricin is many times more toxic than streptomycin and in addition, has a distinct delayed toxicity.6,7 Streptomycin, on the other hand, because of its relative non-toxicity and its active inhibition of gram-negative bacteria both in vitro and in vivo3,8 has aroused a considerable amount of interest in the medical field. Realizing the difficulties which would be encountered if samples of streptomycin were to become contaminated with the more toxic streptothricin, it was con...