Factors associated with trimethoprim-resistant bacteria isolated from urine samples.
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Urine samples with trimethoprim-resistant or trimethoprim-sensitive Gram-negative bacteria and samples with no bacterial growth (NG) were identified. Age-sex matched community controls were generated with each trimethoprim-resistant case. These four groups were evaluated for exposure. Prior trimethoprim use was significantly more common in the trimethoprim-resistant group when compared with the trimethoprim-sensitive or the NG group. Prior hospitalization was significantly less common in the trimethoprim-resistant than the trimethoprim-sensitive group, but not with the NG group. Prior oestrogen exposure was associated with trimethoprim resistance. There were no associations found for diabetes or prior corticosteroid exposure. Community controls were found to be inappropriate controls for the study of trimethoprim-resistant bacteria in urine samples. (+info)
Analysis of functional regions of YPM, a superantigen derived from gram-negative bacteria.
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The bacterial superantigens, staphylococcal enterotoxins and streptococcal pyrogenic exotoxins, are grouped in a family by the conservation of amino acid sequence and polypeptide folding patterns. In the case of Yersinia pseudotuberculosis-derived mitogen (YPM), however, there is no noticeable homology with this family, although many of the in vitro functional features conform to the criteria for a superantigen. To study the mode of action of YPM at the molecular level, we first generated a number of YPM point mutants with reduced T-cell proliferative activity using random mutagenesis and localized the amino acid positions involved in either major histocompatibility complex class II or T-cell receptor Vbeta-interaction. Plotting the elucidated positions on the hydrophilicity profile suggested that they reside mostly on the outer portion of the molecule. We also report that the two cysteines positioned almost at opposing ends of the YPM molecule are connected by an S-S bond the destruction of which causes fatal damage. Finally, we obtained evidence that YPM partially competes with staphylococcal enterotoxin E for human leukocyte antigen-DR binding. This raises the question of whether these different types of superantigens have acquired the same function by genetic convergence or originated from a common ancestral gene. (+info)
A role for coenzyme M (2-mercaptoethanesulfonic acid) in a bacterial pathway of aliphatic epoxide carboxylation.
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The bacterial metabolism of short-chain aliphatic alkenes occurs via oxidation to epoxyalkanes followed by carboxylation to beta-ketoacids. Epoxyalkane carboxylation requires four enzymes (components I-IV), NADPH, NAD(+), and a previously unidentified nucleophilic thiol. In the present work, coenzyme M (2-mercaptoethanesulfonic acid), a compound previously found only in the methanogenic Archaea where it serves as a methyl group carrier and activator, has been identified as the thiol and central cofactor of aliphatic epoxide carboxylation in the Gram-negative bacterium Xanthobacter strain Py2. Component I catalyzed the addition of coenzyme M to epoxypropane to form a beta-hydroxythioether, 2-(2-hydroxypropylthio)ethanesulfonate. Components III and IV catalyzed the NAD(+)-dependent stereoselective dehydrogenation of R- and S-enantiomers of 2-(2-hydroxypropylthio)ethanesulfonate to form 2-(2-ketopropylthio)ethanesulfonate. Component II catalyzed the NADPH-dependent cleavage and carboxylation of the beta-ketothioether to form acetoacetate and coenzyme M. These findings evince a newfound versatility for coenzyme M as a carrier and activator of alkyl groups longer in chain-length than methane, a function for coenzyme M in a catabolic pathway of hydrocarbon oxidation, and the presence of coenzyme M in the bacterial domain of the phylogenetic tree. These results serve to unify bacterial and Archaeal metabolism further and showcase diverse biological functions for an elegantly simple organic molecule. (+info)
Purification and properties of proline-rich antimicrobial peptides from sheep and goat leukocytes.
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We purified three proline-rich antimicrobial peptides from elastase-treated extracts of sheep and goat leukocytes and subjected two of them, OaBac5alpha and ChBac5, to detailed analysis. OaBac5alpha and ChBac5 were homologous to each other and to bovine Bac5. Both exhibited potent, broad-spectrum antimicrobial activity under low-concentration salt conditions. While the peptides remained active against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Listeria monocytogenes in 100 mM NaCl, they lost activity against Staphylococcus aureus and Candida albicans under these conditions. ChBac5 was shown to bind lipopolysaccharide, a property that could enhance its ability to kill gram-negative bacteria. Proline-rich Bac5 peptides are highly conserved in ruminants and may contribute significantly to their innate host defense mechanisms. (+info)
Fermentative bacteria from estuarine mud: phylogenetic position of Acidaminobacter hydrogenoformans and description of a new type of gram-negative, propionigenic bacterium as Propionibacter pelophilus gen. nov., sp. nov.
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The phylogenetic positions of two strains of fermentative bacteria that had been isolated from the highest positive tubes inoculated with serial dilutions of estuarine mud in agar media with either glutamate or aspartate as substrate were determined by comparative sequence analysis of their 16S rRNA genes. The strain isolated with glutamate (glu 65) utilized several substrates, including a number of amino acids but no sugars. The degradation of certain substrates was enhanced by or dependent upon co-cultivation with a hydrogen-utilizing partner. In earlier work this strain was assigned to the new genus and species Acidaminobacter hydrogenoformans. On the basis of its 16S rRNA gene sequence Acidaminobacter hydrogenoformans has now been identified as a member of cluster XI of the Clostridium subphylum with Clostridium halophilum as its closest relative. The aspartate-fermenting strain asp 66T was a Gram-negative, rather aerotolerant anaerobe which utilized a wide range of substrates in a propionic fermentation and had the ability to fix molecular nitrogen. Strain asp 66T was shown to be a new member of the beta-subclass of the Proteobacteria with Azoarcus sp. strain 6a3 and Rhodocyclus tenuis as its closest relatives. It is described as Propionibacter pelophilus gen. nov., sp. nov., with the type strain asp 66T (= DSM 12018T). (+info)
Taxonomic characterization of denitrifying bacteria that degrade aromatic compounds and description of Azoarcus toluvorans sp. nov. and Azoarcus toluclasticus sp. nov.
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A taxonomic characterization of twenty-one strains capable of degrading aromatic compounds under denitrifying conditions, isolated from ten different geographical locations, was performed on the basis of general morphological and physiological characteristics, cellular fatty acids, DNA base composition, small ribosomal (16S) subunit DNA sequences, whole-cell protein patterns and genomic DNA fragmentation analysis, in addition to DNA similarity estimations using hybridization methods. The collection of strains was subdivided into a number of different groups. A first group, consisting of four strains, could be assigned to the previously described species Azoarcus tolulyticus. A second group (five strains) had DNA which reannealed highly to that of strains of the first group, and it is considered to represent a genomovar of A. tolulyticus. The third and fourth groups, composed of a total of five strains, represent a new species of Azoarcus, Azoarcus toluclasticus (group 3) and a genomovar of this species (group 4), respectively. Finally, the fifth group, with two strains, corresponds to another new species of the genus Azoarcus, Azoarcus toluvorans. In addition to these five groups, the collection includes five individual strains perhaps representing as many different new species. The above classification is partially consistent with the results of approaches other than DNA-DNA hybridization (electrophoretic patterns of whole-cell proteins and of the fragments obtained after digestion of total DNA with infrequently cutting restriction enzymes). On the other hand, no correlation of these groupings was found in terms of the cellular fatty acid composition. It is also unfortunate that no simple sets of easily determinable phenotypic properties could be defined as being characteristic of each of the groups. (+info)
Sulfurospirillum barnesii sp. nov. and Sulfurospirillum arsenophilum sp. nov., new members of the Sulfurospirillum clade of the epsilon Proteobacteria.
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Two strains of dissimilatory arsenate-reducing vibrio-shaped bacteria are assigned to the genus Sulfurospirillum. These two new species, Sulfurospirillum barnesii strain SES-3T and Sulfurospirillum arsenophilum strain MIT-13T, in addition to Sulfurospirillum sp. SM-5, two strains of Sulfurospirillum deleyianum, and Sulfurospirillum arcachonense, form a distinct clade within the epsilon subclass of the Proteobacteria based on 16S rRNA analysis. (+info)
Studies on the phylogenetic relationships of melanogenic marine bacteria: proposal of Marinomonas mediterranea sp. nov.
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The polyphenol oxidase (PPO) activities of the marine melanogenic strains MMB-1T and 2-40 were compared. Both contained a multifunctional PPO able to oxidize a wide range of substrates. In spite of this similarity, phylogenetic studies based on 16S rRNA sequences showed that these strains are not closely related. Strain 2-40 is not related to any previously described genus. On the basis of these studies and morphological and physiological characteristics, it is proposed that strain MMB-1T (= CECT 4803T = ATCC 700492T) represents a new species in the genus Marinomonas, Marinomonas mediterranea sp. nov. (+info)