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PubMedDate not supplied

Ceftriaxone: a beta-lactamase-stable, broad-spectrum cephalosporin with an extended half-life.

Ceftriaxone is an aminothiazolyl-oxyimino cephalosporin. It possesses the typical in vitro activity of a third-generation cephalosporin with excellent activity against many gram-negative aerobic bacilli: Escherichia coli; species of Proteus, Klebsiella, Morganella, Providencia and Citrobacter; and Enterobacter agglomerans. Ceftriaxone also has outstanding bactericidal action against pneumococci, group B streptococci, meningococci, gonococci and Hemophilus influenzae. In healthy volunteers, it has an exceptionally long serum half-life of 5.8-8.7 (mean 6.5) hours. It distributes well throughout all body spaces, including cerebrospinal fluid in the presence of inflammation. Dosage modification is necessary only when there is combined hepatic and renal dysfunction. Adverse reactions characteristic of cephalosporins have been observed with the administration of ceftriaxone. No unique toxicities have been identified, and hypoprothrombinemic bleeding is not part of the adverse reaction profile. Ceftriaxone has been used to treat serious bacterial infections in neonates, infants, children and adults. Bacteriologic and clinical success rates have consistently exceeded 90%. The drug has also been used as single-dose chemoprophylaxis in coronary artery bypass, biliary tract, vaginal hysterectomy and prostatic surgery. Efficacy and safety were similar to multiple-dose cefazolin. Ceftriaxone warrants special consideration because its extended half-life allows for less frequent dosing than other antimicrobials. Significant cost savings can be realized with proper use of this antibiotic.

Bacteria↗
PubMed2006

Identification of nif genes in N2-fixing bacterial strains isolated from rice fields along the Yangtze River Plain.

The aim of this research was to identify nifH and nifHDKYE ' genes in twenty strains of N2-fixing heterotrophic bacteria isolated from rice fields in the Yangtze River Plain. Southern hybridization of the total DNA from each strain was performed with the Klebsiella pneumoniae nifHDKYE ' gene probe (6.2 kb Eco RI fragment from pSA30) and the Azospirillum brasilense nifH gene probe (0.6 kb Eco RI-Hin dIII fragment from pHU8). We found that Eco RI fragments of total DNA from Aeromonas hydrophila HY2, Bacillus azotoformans FD, Bacillus licheniformis NCH1, NCH5, WH4, Bacillus brevis NC2, Bacillus pumilus NC12, Bacillus cereus NCH2, Citrobacter freundii HY5, HY9, Derxia gummosa HZ5, Pseudomonas mendocina HZ1 and Pseudomonas pseudoalcaligenes WH3 were positively hybridized with both of the probes. Agrobacterium radiobacter HY17, Corynebacterium sp. HY12, YZ and Pseudomonas sp. HY11 had Eco RI fragments hybridized with the K. pneumoniae nifHDKYE ' gene probe. An Eco RI fragment of total DNA from Bacillus megaterium YY4 was positively hybridized to the A. brasilense nifH gene probe. No hybridization sign was found in the total DNA fragments from Alcaligenes cupidus YY6 and Corynebacterium sp. NC11 hybridized with either of the gene probes. The data provide the number and size of EcoRI fragments of the total DNA hybridized with the nif gene probes for these strains of rarely studied species, suggesting additional evidence for N2 fixing and nif gene diversity of N2-fixing bacteria in rice fields along the Yangtze River Plain.

Bacteria↗
PubMed2005

(1)H NMR spectroscopy in the diagnosis of Pseudomonas aeruginosa-induced urinary tract infection.

The utility of (1)H NMR spectroscopy is suggested and demonstrated for the diagnosis of Pseudomonas aeruginosa in urinary tract infection (UTI). The specific property of P. aeruginosa of metabolizing nicotinic acid to 6-hydroxynicotinic acid (6-OHNA) is exploited. The quantity of 6-OHNA produced correlates well with the viable bacterial count. Other common bacteria causing UTI such as Escherichia coli, Klebsiella pneumonia, Enterobacter aerogenes, Acinetobacter baumanii, Proteus mirabilis, Citrobacter frundii, Enterococcus faecalis, Streptococcus gp B and Staphylococcus aureus do not metabolize nicotinic acid under similar conditions. The method provides a single-step documentation of P. aeruginosa qualitatively as well as quantitatively. The NMR method is demonstrated on urine samples from 30 patients with UTI caused by P. aeruginosa.

Biomarkers↗
PubMed1997

Binding of monoclonal antibody 4B1 to homologs of the lactose permease of Escherichia coli.

The conformationally sensitive epitope for monoclonal antibody (mAb) 4B1, which uncouples lactose from H+ translocation in the lactose permease of Escherichia coli, is localized in the periplasmic loop between helices VII and VIII (loop VII/VIII) on one face of a short helical segment (Sun J, et al., 1996, Biochemistry 35;990-998). Comparison of sequences in the region corresponding to loop VII/VIII in members of Cluster 5 of the Major Facilitator Superfamily (MFS), which includes five homologous oligosaccharide/H+ symporters, reveals interesting variations. 4B1 binds to the Citrobacter freundii lactose permease or E. coli raffinose permease with resultant inhibition of transport activity. Because E. coli raffinose permease contains a Pro residue at position 254 rather than Gly, it is unlikely that the mAb recognizes the peptide backbone at this position. Consistently, E. coli lactose permease with Pro in place of Gly254 also binds 4B1. In contrast, 4B1 binding is not observed with either Klebsiella pneumoniae lactose permease or E. coli sucrose permease. When the epitope is transferred from E. coli lactose permease (residues 245-259) to the sucrose permease, the modified protein binds 4B1, but the mAb has no significant effect on sucrose transport. The studies provide further evidence that the 4B1 epitope is restricted to loop VII/VIII, and that 4B1 binding induces a highly specific conformational change that uncouples substrate and H+ translocation.

Amino Acid Sequence↗
PubMed1997

An homogeneous fluorescence polymerase chain reaction assay to identify Salmonella.

We have developed a semiquantitative homogeneous fluorescence assay that combines polymerase chain reaction (PCR) amplification with direct fluorescence detection (HF-PCR). The assay eliminates the need to perform gel electrophoresis on test samples. Using a set of Salmonella-specific primers, this system was used to verify suspect colonies from culture plates as Salmonella. The fluorescence signal is generated by a nucleic acid dye, YO-PRO-1, that is included in the amplification reaction. This homogeneous PCR assay was used to test 84 Salmonella strains picked from selective culture plates. All data indicated positive results when compared with 17 non-Salmonella strains (in general, Citrobacter, Hafnia, Proteus, and Escherichia). The HF-PCR assay is a sensitive, simple, accurate, and reproducible method that correlates well with size-exclusion high-performance liquid chromatography and gel electrophoresis techniques as a means to monitor PCR-mediated DNA amplification. This assay can confirm suspect colonies within 2.5 h.

Bacterial Typing Techniques↗
PubMed2000

Molecular beacons: a real-time polymerase chain reaction assay for detecting Salmonella.

Molecular beacons are oligonucleotide probes that become fluorescent upon hybridization. We developed a real-time PCR assay to detect the presence of Salmonella species using these fluorogenic reporter molecules. A 122-base-pair section of the himA was used as the amplification target. Molecular beacons were designed to recognize a 16-base-pair region on the amplicon. As few as 2 colony-forming unit (CFU) per PCR reaction could be detected. We also demonstrated the ability of the molecular beacons to discriminate between amplicons obtained from similar species such as Escherichia coli and Citrobacter freundii in real-time PCR assays. These assays could be carried out entirely in sealed PCR tubes, enabling fast and direct detection of Salmonella in a semiautomated format.

Bacterial Proteins↗
PubMed1995

Polyphosphate accumulation among denitrifying bacteria in activated sludge.

Bacterial polyphosphate accumulation and denitrification are important processes in biological removal of nutrients from wastewater. It has been suggested that phosphorus accumulators are able to denitrify. However, the bacteria known as the most important phosphorus accumulators, belonging to the genus Acinetobacter are generally not known to denitrify. To clarify how commonly both physiological traits are present in the same organism, we screened 165 isolates from activated sludge and wastewater for their ability to denitrify, and the ability of the denitrifying isolates to accumulate polyphosphate. Of the 165 isolates, 149 were from acetate mineral medium (87 of these identified as Acinetobacter by the API 20 NE identification system) and 16 were from nutrient broth and nitrate medium. Only 15 of 165 isolates tested showed true respiratory denitrification activity. In the presence of acetylene they converted more than 80% of 5mM NO3- to N2O in 6 days. None of the Acinetobacter isolates were among the 15 respiratory denitrifiers. The denitrifying isolates were identified as species of Pseudomonas, Agrobacterium, Pasteurella, Sphingomonas or could not be identified by the API 20 NE identification system. According to the BIOLOG identification system the denitrifiers were species of Pseudomonas, Hydrogenophaga, Citrobacter, Xanthomonas or they could not be identified. The ability of confirmed denitrifiers to accumulate phosphate was measured in experiments where cells pregrown under phosphorus limitation were exposed to phosphate (8 mg P/L) under aerobic conditions. The rates of excess phosphate uptake varied from 0.3 to more than 23 mg P/g dry matter/h. Rates for four isolates were higher than those reported for Acinetobacter strains. These results show that polyphosphate accumulation and denitrification in activated sludge can be carried out by the same organisms.

Journal Article↗
PubMed1993

Characterization of the replicon from plasmid pAC1 from Acetobacter pasteurianus.

A panel of recombinant plasmids pACK5 and pACT7 was prepared by introducing kanamycin and tetracycline resistance into the partially split plasmid pAC1 which contained replicon isolated from Acetobacter pasteurianus. The replicon in plasmid pAC1 is compatible with the ColE1 replicon. Compared to pBR322, the plasmid had more than 30 copies per chromosome in Escherichia coli cells. Plasmids were transformed into E. coli DH1, Acetobacter pasteurianus 3614, Acetobacter aceti 3620, Shigella, Citrobacter, and Brevibacterium flavum cells, and the stability of plasmid DNA was tested after cultivation in nonselective conditions.

Acetobacter↗
PubMed1996

Mutational analysis of the CitA citrate transporter from Salmonella typhimurium: altered substrate specificity.

The CitA citrate transporter in Salmonella typhimurium is encoded by the citA gene and consists of 434 amino acid residues that probably include 12 membrane-spanning segments [Shimamoto. T., et al. (1991) J. Biochem. 110, 22-28]. CitA mutants with altered substrate specificities were isolated by in vitro mutagenesis using nitrous acid. The mutants could grow on isocitrate as a sole carbon source which normally cannot be transported well by the CitA transporter of S. typhimurium. The mutation sites in the citA gene of the nine mutants were determined to involve single residues at seven sites (one mutation per mutant). The original amino acid residues at these sites (Arg-19, Ala-38, Glu-51, Gly-132, Ala-169, Pro-262 and Leu-271) were identified to be responsible for the altered substrate specificity. All these amino acid residues were conserved in four other homologous citrate transporters from Escherichia coli, Citrobacter amalonaticus and Klebsiella pneumoniae and are suggested to be involved in substrate recognition by the CitA transporter.

Amino Acid Sequence↗
PubMed1998

The entericidin locus of Escherichia coli and its implications for programmed bacterial cell death.

Antidote/toxin gene pairs known as "addiction modules" can maintain plasmids in bacterial populations by means of post-segregational killing. However, several chromosome-encoded addiction modules may provide an entirely distinct function in the programmed cell death of moribund subpopulations under starvation conditions. We now report a novel chromosomal bacteriolytic module of Escherichia coli called the entericidin locus, which is activated in stationary phase under high osmolarity conditions by sigmaS and simultaneously repressed by the osmoregulatory EnvZ/OmpR signal transduction pathway. The entericidin locus encodes tandem paralogous genes (ecnAB) and directs the synthesis of two small cell-envelope lipoproteins. An attenuator precedes ecnA and an ompR-sensitive sigmaS promoter governs expression of ecnB. The entericidin A lipoprotein is an antidote to the bacteriolytic lipoprotein entericidin B. The entericidins are predicted to adopt amphipathic alpha-helical structures and to reciprocally modulate membrane stability. The entericidin locus is not present on any known plasmids, but is conserved in the homologous region of the Citrobacter freundii chromosome. Although the cloned C. freundii entericidin locus is expressed in E. coli independently of ompR, it carries an additional ompR-like gene called ecnR. The organization of the entericidin locus as a chromosomal antidote/toxin gene pair, which is regulated by both positive and negative osmotic signals during starvation, is consistent with an emerging paradigm of programmed bacterial cell death.

Amino Acid Sequence↗
PubMed1993

Oligonucleotide probe determination of tetracycline-resistant bacteria isolated from catfish ponds.

Oligonucleotide probes for class A, B and C tetracycline resistance determinants were synthesized and tested individually and in combination for hybridization with Gram-negative isolates previously characterized by restriction fragment DNA probes. Similar hybridization patterns were observed with either probe type. Gram-negative catfish pond bacteria were characterized by these oligonucleotide probes. The most common bacteria were Plesiomonas shigelloides (47.7%), Aeromonas hydrophila (28.8%) and Citrobacter freundii (13.3%). The class A (46.4%) tetracycline resistance determinant was more prevalent than B (19.8%) and C (0.3%). Some tetracycline-resistant isolates of each species, including most A. hydrophila (62.1%) isolates, failed to hybridize with any of the probes.

Animals↗
PubMed1999

Use of PNA oligonucleotides for the in situ detection of Escherichia coli in water.

A species-specific Peptide Nucleic Acid (PNA) oligonucleotide probe directed against the V(1)region of the 16S rRNA molecule was synthesized for the detection of Escherichia coli in water. The specificity of the probe was tested in dot blot hybridizations against a number of environmental isolates including those from the genera Escherichia, Klebsiella, Enterobacter and Citrobacter. In situ hybridization experiments were performed with biotinylated PNA oligonucleotide probes with subsequent detection of the biotin label using a combination of Streptavidin-Horseradish Peroxidase and a tyramide signal amplification system. The results obtained enabled the specific detection of E. coli in under 3 h. Hybridizations were also performed on cells which were treated with chlorine (1.5 mg l(-1)) for up to 30 min. Escherichia coli cells were still detected after storage for 14 days at room temperature. No cells were detected by conventional plate count or the < > assay, a method currently used for the routine detection of E. coli and coliforms in the water industry. Cell viability was assessed by the ability of cells to reduce 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) to highly fluorescent formazan crystals through bacterial respiration. Only cells that had not been chlorinated were detected. These results confirm that ribosomal RNA exists within the cell long after cell death has occurred and that rRNA cannot be used to assess the viability of individual cells. However rRNA probes in combination with viability markers should enable the specific detection of viable cells in situ. Hybridization experiments were also performed successfully on seeded tap water samples. The number of fluorescent cells detected correlated well with those obtained by plate count analysis. This represents the first reported use of PNA oligonucleotides for in situ detection of micro-organisms and offers a fast efficient alternative to conventional DNA approaches.

Chlorine↗
PubMed1993

Phylogenetic tree and sequence similarity of beta-lactamases.

beta-Lactamases are the main cause of beta-lactam resistance in many pathogenic bacteria. These enzymes can be detected in a variety of pathogenic as well as non-pathogenic bacteria. The cyanobacteria are also known to produce a beta-lactamase. Recently, the amino acid sequences and the three-dimensional structures of some of these beta-lactamases have been clarified. On the basis of the amino acid sequences of 47 beta-lactamases and the computer-aided analysis, a phylogenetic tree is proposed in this paper. According to the tree, beta-lactamases are classified into six groups. Group 1 beta-lactamases are mainly composed of plasmid-mediated enzymes from gram-negative bacteria. However, chromosome-derived beta-lactamases from Klebsiella pneumoniae and Rhodopseudomonas capsulata take part in this group. Group 2 enzymes consist of a part of the chromosome-encoded beta-lactamases from Streptomyces, and chromosome-mediated enzymes from Yersinia enterocolitica, Citrobacter diversus, and Klebsiella oxytoca. Chromosome-encoded beta-lactamases from gram-negative bacteria form group 3. Group 4 is composed of metalloenzymes, whereas group 5 consists of OXA type beta-lactamases. Chromosome-encoded beta-lactamases from gram-positive bacteria form group 6. Comparison of the amino acid sequences among these groups confirmed the phylogenetic tree and the classification: the beta-lactamases in each group have its particular conserved amino acid sequences. In addition, the tree provides more detailed classification and time-scale mutual relationships and predicts new types of beta-lactamases that may be found. Furthermore, the classification deduced from the tree is generally in accord with the one based on the amino acid sequences reported previously. However, the class A beta-lactamases are clearly divided into three groups: groups 1, 2, and 6. RDF2 analysis shows that some combinations between beta-lactamases and beta-lactam-interacting proteins as well as eukaryotic proteins have a low but significant evolutionary relatedness.

Amino Acid Sequence↗
PubMed1997

Small cryptic plasmids of multiplasmid, clinical Escherichia coli.

Clinical isolates of Escherichia coli were found to host a multiplicity of plasmids. These were resolved from plasmid gel profiles, from the properties of various transconjugants and transformants of E. coli DH1, by the topoisomerase I relaxation of covalently closed circle plasmid DNA, by electron microscopy, and by the determination of their compatibilities. The majority of these were unusually small, cryptic plasmids (SCPs). From one strain, KL4, 13 electrophoretic bands were resolved to five plasmids, three of which were SCPs. SCPs were phenotypically barren, and the smallest of these, pKL1, contained barely enough information for self-replication. A derivative of pKL1, pKL1Km, in which the transposon was restricted to a small 350-bp region, was stably maintained in Shigella, Salmonella, Serratia, and Citrobacter species and its replication was polA independent. pKL1 encoded only a single protein, RepA (Mr 17960), which specifically bound to pKL1 DNA. No apparent homologies with other RepA protein sequences could be detected. Thus the SCP, pKL1, is a novel minimal plasmid replicon encoding only enough information to ensure perpetuation. A hypothesis is presented describing SCPs as a class of selfish DNA that persists simply due to its ability to replicate and to its stability based on high copy number.

Conjugation, Genetic↗
PubMed1993

The bacteriophage Mu middle operon: essential and nonessential functions.

Transcription during the bacteriophage Mu lytic cycle occurs in three phases: early, middle, and late. Previous DNA sequence analysis of the middle operon revealed five potential open reading frames (ORFs) with lengths of 39, 42, 72, 120, and 140 amino acids. The distal 140-amino-acid ORF encodes C, the activator of late transcription. Expression of the middle operon under the control of a T7 promoter and T7 RNA polymerase resulted in production of two polypeptides of 15 (ORF 120) and 16.5 kDa (C). Introduction of a linker containing a translation terminator into ORF120 resulted in the production of a truncated form of the ORF120 polypeptide. When the ORF120 linker mutation and several middle operon deletion mutations were assayed for their effect on Mu growth in Escherichia coli K12, the deletions caused 6- to 22-min delays in lysis, and two resulted in a smaller plaque morphology, but all gave normal plating efficiencies and burst sizes. The plating efficiencies for all the mutants were also similar to that of wild-type Mu on alternate hosts E. coli C, Citrobacter freundii, Shigella sonnei, and Shigella flexneri. These results indicate that, with the exception of C, the middle operon ORFs are not essential for phage development.

Amino Acid Sequence↗
PubMed1982

Genetic and molecular studies of the regulation of atypical citrate utilization and variable Vi antigen expression in enteric bacteria.

1. The atypical citrate-utilizing ability to two strains of E. coli has been shown to be plasmid-encoded. Strain V414 carries a 130 Mdal conjugative Cit+ plasmid that also specifies Tcr and Cmr. Strain V517 carries 9 different plasmid species but only the 36 Mdal species is correlated with Cit+ ability. These plasmids are different from previously reported Cit+ plasmids of E. coli and Salmonella, which express thermosensitive conjugal transfer systems. 2. A 9 kb Pstl fragment, carrying the Cit+ genes of pWR60, has been cloned into the pBR325 plasmid. 3. Metabolic studies indicate that intact citrate is not incorporated directly into whole cells. Rather, atypical citrate utilization by these E. coli strains appears to involve partial metabolism of citrate at the cell surface before or during uptake. 4. The expression of atypical Cit+ ability by the parental pWR60 plasmid or by the recombinant pWR61 plasmid appears reversible and may involve an expression switch mechanism (i.e., insertion sequence element). 5. Two widely separated genetic loci, viaA and viaB, are necessary for Vi antigen synthesis in Salmonella and Citrobacter. In some strains of C. freundii, Vi antigen expression is reversible, a phenomenon which can be visualized by a colonial morphology transition between Vi-expressing and -nonexpressing forms. 6. The C. freundii viaB locus appears to encode the Vi antigen as well as the genetic "switch" mechanism controlling reversible Vi antigen expression. The viaA locus, which is found in several different bacterial species, may encode some common property (e.g., cell surface structure or enzymatic activity) that is needed for Vi antigen expression. 7. S. typhi and E. coli K12 hybrid strains which carry the C. freundii viaB locus have been constructed. These hybrid strains express reversible Vi antigen expression, even in the absence of general recombination (i.e., functional recA gene product). 8. The C. freundii viaB locus was transposed via Mu-mediated events to an F'lac plasmid in the E. coli K12 hybrid strain WR2376. F' plasmids carrying the viaB locus should serve as a highly enriched source of viaB DNA for physical examination of the switch mechanism. 9. Genetic manipulations such as those described herein can be used to study virtually any plasmid, viral, or chromosomally-encoded property. The resultant better understanding of biochemical pathways and of genetic regulatory control systems, and the isolation of desired gene sequences should provide ample information and materials for improving chemical processes and constructing vaccines against various organisms.

Antigens, Bacterial↗
PubMed2000

E. coli invasion of brain microvascular endothelial cells as a pathogenetic basis of meningitis.

A major limitation to advances in prevention and therapy of bacterial meningitis is our incomplete understanding of the pathogenesis of this disease. Successful isolation and cultivation of BMEC, which constitute the blood brain barrier, and the development of experimental hematogenous meningitis animal model, which mimics closely the pathogenesis of human meningitis, enabled us to dissect the pathogenetic mechanisms of bacterial meningitis. We have shown for the first time using E. coli as a paradigm the mechanisms of bacterial crossing of the blood-brain barrier into the central nervous system. We have shown that invasion of BMEC is a requirement for E. coli K1 crossing of the blood-brain barrier in vivo (Prasadarao et al., 1996b; Huang et al., 1995). We have identified several novel E. coli proteins (i.e., Ibe10, Ibe7, and Ibe23) contributing to invasion of BMEC. We have also established a novel phenotype, i.e., invasion of BMEC, of a well known major E. coli protein, OmpA. In addition, we have shown that some of these E. coli proteins (i.e., OmpA, Ibe10) interact with novel endothelial receptors present on BMEC, not on systemic vascular endothelial cells. Further understanding and characterization of these E. coli-BMEC interactions should allow us to develop novel strategies to prevent this serious infection. In addition, the in vitro and in vivo models of the blood-brain barrier and the information derived from our study should be beneficial to investigating the pathogenesis of meningitis due to other organisms such as group B streptococci, Listeria monocytogenes, Streptococcus pneumoniae and Citrobacter.

Animals↗
PubMed1990

Circulation in Italy of beta-lactamase-producing strains within the major groups of bacterial pathogens.

A multicenter study was undertaken in Italy to assess the circulation of beta-lactamase-producing organisms and their current incidence within the major groups of bacterial pathogens. Almost four thousand strains, all freshly isolated from clinical material, were examined at four centers serving different areas of Italy. Despite some significant center-to-center differences, this survey documented the occurrence of a large overall circulation of beta-lactamase-producing organisms among clinical bacterial isolates. In particular, ampicillin resistance was recorded in one third to one half of the isolates of some Enterobacteriaceae, including Escherichia coli, Proteus, and Citrobacter species, and 80-90% of these resistant strains proved to be beta-lactamase producers. Both ampicillin resistance and beta-lactamase production were almost the rule in other Enterobacteriaceae, including Klebsiella, Enterobacter, and Serratia species. beta-lactamase was also produced by about 80% of glucose-non-fermenting gram-negative bacteria and Aeromonas hydrophila strains, by all of the isolates of Branhamella catarrhalis manifesting ampicillin resistance (i.e. more than half the total number of isolates), and by about two thirds of the ampicillin-resistant Haemophilus strains (which accounted for 20-25% of all Haemophilus isolates examined). In contrast, no beta-lactamase producers were observed among Neisseria gonorrhoeae isolates.

Ampicillin Resistance↗