The Ku complex is modulated in response to viral infection and other cellular changes

The complex of Ku with DNA is demonstrated to have multiple forms as assayed by gel retardation analysis. In CV1 cells this variation of complex can be modulated in response to viral infection with SV40. By Western blot analysis, a correlation can be made between modification of the complex formed on DNA in response to viral infection with variation of the 85 kDa subunit of Ku. Modification of the 85 kDa subunit can also be seen when cells are exposed to various extracellular stimuli including variation in serum levels, PMA and CaPO4.

Pseudomonas cepacia suppression of sunflower wilt fungus and role of antifungal compounds in controlling the disease

In a field experiment, Pseudomonas cepacia J82rif and J51rif increased sunflower emergence in the presence of the fungus Sclerotinia sclerotiorum. Pyrrolnitrin, aminopyrrolnitrin, and monochloroaminopyrrolnitrin were isolated from J82 and identified by using thin-layer chromatography, high-performance liquid chromatography, and electron impact-mass, UV, and infrared spectroscopy. In growth chamber experiments, two antibiosis-negative mutants were not different from the parent strain in protecting the seeds from the fungus.

Detection of a novel carbon-phosphorus bond cleavage activity in cell-free extracts of an environmental Pseudomonas fluorescens isolate

Cell-free extracts of Pseudomonas fluorescens strain 23F catalyzed the hydrolysis of phosphonoacetate to acetate and inorganic phosphate; the products were detected in almost equimolar quantities. The stable in vitro activity responsible was distinct from phosphonoacetaldehyde hydrolase and appears to represent a novel mode of carbon-phosphorus bond cleavage.

Metabolism of Phosphonoacetate as the Sole Carbon and Phosphorus Source by an Environmental Bacterial Isolate

A gram-negative bacterium isolated from activated sludge was able to utilize up to 25 mM phosphonoacetate as the sole carbon and phosphorus source, with simultaneous excretion of virtually equimolar levels of phosphate. 2-Aminoethylphosphonate was similarly utilized with equivalent growth rates and cellular yields, while 3-aminopropyl-, 4-aminobutyl-, methyl-, ethyl-, and phenylphosphonates served only as phosphorus sources.

High-level quinolone resistance in clinical isolates of Campylobacter jejuni

During a recent clinical trial of ciprofloxacin in the therapy of acute diarrhea, two subjects infected with Campylobacter jejuni who received ciprofloxacin failed microbiologically and one also failed clinically. Although both pretreatment isolates were susceptible to ciprofloxacin, the posttreatment isolates were resistant to ciprofloxacin (MIC = 32 micrograms/ml) and to other quinolones. The posttreatment isolates remained susceptible to nonquinolone antimicrobials. DNA gyrase holoenzyme was isolated from one of the resistant posttreatment isolates and was 8- to 16-fold less sensitive to inhibition by ciprofloxacin than was the gyrase from the paired pretreatment susceptible isolate. Ciprofloxacin accumulation was diminished in the two resistant posttreatment isolates. These results show that mutation in C. jejuni can occur in vivo and is associated with clinically significant resistance to the newer quinolones.

High-resolution tandem mass spectrometry of large biomolecules

Unit-resolution mass spectra have been obtained for peptides as large as 17 kDa, providing information on impurities and adduct ions, as well as accurate molecular weight values. Electrospray ionization produces many multiply-charged species of the same mass; isotopic peak resolution provides direct charge state assignment from the unit mass spacing of the isotopes. This is of special value when the spectrum also has many masses, such as from precursor ion dissociation or impurities. Mass measuring errors not only are concomitantly lower (less than 0.1 Da) than when the isotopic peaks are unresolved but also are independent of variations in 13C/12C natural isotopic abundances. Also, larger errors are avoided that occur when the measured peak envelope includes impurity or adduct ions. This also benefits tandem mass spectrometry; dissociation of peptide ions as large as 8.5 kDa yields fragment masses consistent (less than 0.1 Da) with their amino acid sequences.

The nuclear autoimmune antigen Ku is also present on the cell surface

Polyclonal antibodies were raised against the individual 85 and 70 kDa subunits of the Ku complex purified from nuclear extract prepared from the T cell line MLA144. They specifically recognise the appropriate subunits of the Ku complex from whole cell extract of HeLa cells using Western blot analysis. They are also able to identify the Ku proteins present in the cell membrane using FACS analysis.

Enterobacter bacteremia: clinical features and emergence of antibiotic resistance during therapy

OBJECTIVES

To study the effect of previously administered antibiotics on the antibiotic susceptibility profile of Enterobacter, the factors affecting mortality, and the emergence of antibiotic resistance during therapy for Enterobacter bacteremia.

DESIGN

Prospective, observational study of consecutive patients with Enterobacter bacteremia.

SETTING

Three university tertiary care centers, one major university-affiliated hospital, and two university-affiliated Veterans Affairs medical centers.

PATIENTS

A total of 129 adult patients were studied.

MEASUREMENTS

The two main end points were emergence of resistance during antibiotic therapy and death.

MAIN RESULTS

Previous administration of third-generation cephalosporins was more likely to be associated with multiresistant Enterobacter isolates in an initial, positive blood culture (22 of 32, 69%) than was administration of antibiotics that did not include a third-generation cephalosporin (14 of 71, 20%; P less than 0.001). Isolation of multiresistant Enterobacter sp. in the initial blood culture was associated with a higher mortality rate (12 of 37, 32%) than was isolation of a more sensitive Enterobacter sp. (14 of 92, 15%; P = 0.03). Emergence of resistance to third-generation cephalosporin therapy (6 of 31, 19%) occurred more often than did emergence of resistance to aminoglycoside (1 of 89, 0.01%; P = 0.001) or other beta-lactam (0 of 50; P = 0.002) therapy.

CONCLUSIONS

More judicious use of third-generation cephalosporins may decrease the incidence of nosocomial multiresistant Enterobacter spp., which in turn may result in a lower mortality for Enterobacter bacteremia. When Enterobacter organisms are isolated from blood, it may be prudent to avoid third-generation cephalosporin therapy regardless of in-vitro susceptibility.

Carbon-phosphorus bond cleavage activity in cell-free extracts of Enterobacter aerogenes ATCC 15038 and Pseudomonas sp. 4ASW

Carbon-phosphorus bond cleavage activity was investigated in cell-free extracts of Enterobacter aerogenes ATCC 15038 (IFO 12010) and Pseudomonas sp. 4ASW, strains known to utilize a range of phosphonates as sole phosphorus source. In vitro phosphonatase activity was detected in extracts of both organisms; however extensive analysis failed to detect any organic product from phosphonates other than phosphonoacetal dehyde. Non-specific liberation of phosphate was observed in Pseudomonas sp. 4ASW, associated with a single fraction of FPLC-purified extract, and is believed to result from the activity of cellular phosphatases.

Autoimmune antigen Ku is enriched on oligonucleotide columns distinct from those containing the octamer binding protein DNA consensus sequence

During purification of the AP1 complex from the T cell line MLA144 we enriched for a complex which bound to an oligonucleotide column containing the AP1 DNA consensus sequence and co-eluted with a fraction required for AP1 binding activity. This complex although co-eluting with AP1 binding activity had previously been determined to be non-specific in its DNA binding properties. Further investigation determined that the complex was a heterodimer of 85 and 70 kDa which was antigenically related to the autoimmune antigen Ku. It is important to be aware of the abundance and avidity of the Ku complex to bind oligonucleotide columns when purifying sequence specific binding proteins.

Imipenem resistance in pseudomonas aeruginosa PAO: mapping of the OprD2 gene

Carbapenem antibiotics have been shown to penetrate the outer membrane of Pseudomonas aeruginosa through a unique porin protein, OprD2. We mapped the OprD2 gene by conjugation using plasmid FP2 and by transduction using phage F116L. This gene maps between 71 and 75 min on the PAO1 chromosome.

A novel chromosomal TEM derivative and alterations in outer membrane proteins together mediate selective ceftazidime resistance in Escherichia coli

A clinical Escherichia coli isolate (MG32) resistant to ceftazidime but susceptible to other third-generation cephalosporins was previously examined and found to harbor TEM-1 and exhibit alterations in outer membrane proteins. Reexamination of this isolate revealed the additional presence of a novel TEM-1 derivative, now designated TEM-12. Evaluation of ceftazidime and cefotaxime minimum inhibitory concentrations for isogenic derivatives demonstrated a major role for TEM-12 in the decreased susceptibility observed. This was selectively enhanced for ceftazidime resistance by the altered porins of E. coli MG32. TEM-12 appeared identical to TEM-101, an in vitro TEM derivative, in both isoelectric point (pI 5.25) and substrate profile. Hybridization and cloning of the TEM-12 determinant revealed that, unlike other TEM derivatives, TEM-12 is chromosomally encoded, not plasmid-encoded.

Evolving strategies for the genetic engineering of herbicide resistance in plants

Developments in plant genetic engineering technology will shortly permit the commercial introduction of transgenic crop varieties resistant to a number of non-selective herbicides. High levels of tolerance have been achieved both by overexpression of a target protein and by modification of that target to an insensitive form. However the results of preliminary trials suggest that in some instances the yield penalty for such genetic alterations will be prohibitive. An alternative strategy, based on the transfer and expression of a gene encoding a herbicide-detoxifying enzyme, appears to offer high resistance levels at low metabolic cost and is expected to assume increasing importance, although it may not prove suitable for all herbicides.

Multiple components are required for sequence recognition of the AP1 site in the gibbon ape leukemia virus enhancer

At least two subunits contributed to the formation in vitro of a specific complex binding to the AP1 consensus sequence (TGAGTCA) in the gibbon ape leukemia virus (GALV) enhancer in MLA144 cells. This complex can be dissociated on a monomeric GALV oligonucleotide affinity column. One protein, termed the core protein, was retained on the oligonucleotide affinity column. The second protein flowed through the oligonucleotide affinity column and, when alone, did not bind to DNA; however, when present with the core protein, it bound strongly and very specifically to the GALV sequence. MLA144 cells contained only trace amounts of c-fos and c-jun by immunoblot analysis, suggesting that the proteins specifically binding to the GALV AP1 site were distinct from c-fos and c-jun. In addition to the major complex that recognized the GALV element, MLA144 cells contained a minor complex that is chromatographically different from and antigenically related to c-fos. The factor in the flowthrough complemented a human T-cell nuclear extract (Jurkat cell line), which, when alone, had no assayable complex that specifically bound to the GALV enhancer; this complementation gave rise to a specific complex similar to that seen in MLA144 cells. Together, these results suggest that the GALV enhancer can interact with multicomponent protein complexes in a cell-line-specific manner.

Novel plasmid-mediated beta-lactamase (TEM-10) conferring selective resistance to ceftazidime and aztreonam in clinical isolates of Klebsiella pneumoniae

Two clinical isolates of Klebsiella pneumoniae from seriously ill patients in Chicago, Ill., have been identified as resistant to ceftazidime and aztreonam but susceptible to other cephalosporins. This unusual antibiogram was shown to be due to a novel plasmid-mediated beta-lactamase which readily hydrolyzed ceftazidime and aztreonam in addition to penicillins such as piperacillin and carbenicillin. This enzyme and its attendant resistance were transferred to Escherichia coli by conjugation on a 50-kilobase plasmid. Isoelectric focusing revealed a single beta-lactamase band with a molecular weight of 29,000 and an isoelectric point of 5.57 in the resistant isolates and transconjugants. The beta-lactamase inhibitors clavulanic acid and sulbactam restored beta-lactam susceptibility in the resistant isolates. Fifty percent inhibitory concentrations of clavulanic acid and sulbactam were 4.4 and 940 nM, respectively. DNA hybridization studies indicated that this enzyme, designated TEM-10, is related to well-established TEM-type beta-lactamases. However, the TEM-10 enzyme was inhibited by p-chloromercuribenzoate, in contrast to TEM-2 beta-lactamase. On the basis of substrate and inhibition profiles, the TEM-10 enzyme could be easily discriminated from TEM-5 and RHH-I beta-lactamases.

fos/jun and octamer-binding protein interact with a common site in a negative element of the human c-myc gene

A negative element has previously been localized to a 57-base pair segment approximately 300 base pairs upstream of the human c-myc promoter P1. Within this element, a 26-base pair region was protected in vitro from DNase I digestion with a HeLa cell nuclear factor(s). Two specific DNA-protein complexes were identified in gel retardation assays using HeLa cell nuclear extracts and an oligonucleotide probe spanning the footprinted region. Exonuclease and chemical footprint analyses suggested that the binding sites for both complexes are almost entirely overlapping. One of the complexes was eliminated by oligonucleotide competitors possessing known AP-1 binding sites. This same complex reacted strongly with anti-fos immunoglobulin suggesting a role for c-fos in governing c-myc expression. Precipitation of fos protein bound to c-myc DNA that was immobilized on beads confirmed the involvement of c-fos in a specific complex with the c-myc upstream sequence. In contrast, the other complex seen by the c-myc probe could not be competitively inhibited by AP-1 binding sites and was not affected by anti-fos antibody. Instead, this complex was efficiently eliminated by unlabeled oligonucleotides containing the octamer DNA motif found in immunoglobulin gene promoters. Purified octamer-binding proteins formed stable complexes with the 26-base pair c-myc sequences. These results demonstrate that degeneracy in the consensus recognition sequences of these distinct factors allows each of them to bind the c-myc negative element. The interaction of known transcriptional activators with a negative element suggests that the same factors can mediate both transcriptional activation and repression.

Salmonellal empyema in a heart transplant recipient

We report Salmonellal empyema in a heart transplant recipient. The patient required decortication and prolonged antibiotic therapy for cure.

Distinct factors bind the AP-1 consensus sites in gibbon ape leukemia virus and simian virus 40 enhancers

We have demonstrated that the gibbon ape leukemia virus (GALV) enhancer AP-1 element and the simian virus 40 AP-1 enhancer element bind different factors in HeLa nuclear extracts. A 39-kilodalton HeLa nuclear protein and the c-fos protein bind to the GALV element. Antibodies to c-fos abolish binding to the GALV AP-1 site. In contrast, anti-c-fos immunoglobulin fails to inhibit formation of the simian virus 40-specific complex from extracts of HeLa cells. Thus, AP-1-binding complexes are subject to compositional variation at different binding sites.

Selective imipenem resistance in Pseudomonas aeruginosa associated with diminished outer membrane permeability

The permeability of the outer membranes of imipenem-susceptible and imipenem-resistant clinical isolates of Pseudomonas aeruginosa was investigated by the liposome swelling assay. Sugars and cephaloridine penetrated rapidly, whereas imipenem penetrated poorly into liposomes constructed from porin-rich outer membrane fractions of the resistant isolates.

Resistance to imipenem in Pseudomonas aeruginosa: clinical experience and biochemical mechanisms

Emergence of resistance to imipenem during therapy for Pseudomonas aeruginosa infections is common and may result in treatment failure. Resistance emerges most often during therapy for lower respiratory tract infections. There are several unique features of this resistance to imipenem. First, cross-resistance to other beta-lactam agents is not observed. Second, the mechanism of resistance in most of the isolates studied to date appears to be related to a selective permeability barrier across the bacterial outer membrane, usually associated with discrete alterations in the electrophoretic profiles of outer membrane proteins. These data suggest that imipenem may traverse the outer membrane of P. aeruginosa via a specific porin protein that is not critical for penetration of other beta-lactam antibiotics.

Serious infections due to penicillin-resistant strains of viridans streptococci with altered penicillin-binding proteins

We investigated the mechanism of resistance to penicillin in two penicillin-resistant clinical isolates of viridans streptococci that caused life-threatening infections in two patients not receiving chronic penicillin therapy. The first was a strain of Streptococcus intermedius that was isolated from the cerebrospinal fluid of a patient with post-neurosurgical meningitis. The second was a strain of Streptococcus mitis recovered from the bloodstream of a leukemic patient with neutropenia. Both patients failed to respond to penicillin. The mechanism of resistance in these strains was associated with diminished affinity for penicillin of their penicillin-binding proteins, as compared with those of penicillin-susceptible control strains. We conclude that penicillin-resistant viridans streptococci may cause serious infections even in patients not receiving chronic penicillin therapy, that this resistance is clinically significant and may result in failure of penicillin therapy, and that the mechanism of resistance in these strains is associated with diminished affinity of the penicillin-binding proteins for penicillin.

Lung volumes in Polynesian children

Polynesian (Maori and Pacific Island) children account for approximately one quarter of the children in New Zealand, but good data for lung function in this group are not available. In this review, we report lung volume measurements in 571 healthy children 5 to 13 yr of age: 270 Polynesians (139 boys and 131 girls) and 301 Europeans (177 boys and 124 girls). All measurements were made in a body plethysmograph. Polynesian boys had significantly larger VC, FVC, FRC, TLC, and expiratory reserve volume than did Polynesian girls. Polynesian and European children generally showed different slope and intercept relationships for the prediction of lung volume from height. Racial differences are not adequately explained by differences in body proportions or social factors including parental smoking. Possible explanations include racial differences in lung growth and maturation.

Pneumocystis carinii pneumonia: a lethal complication of "pulse" methylprednisolone therapy

A previously healthy, HIV-negative, 67-year-old man developed rapidly progressive glomerulonephritis. Following "pulse" methylprednisolone therapy he developed Pneumocystis carinii pneumonia. This complication should be recognized as a potential hazard of "pulse" steroid therapy.

Binding of a cellular protein to the gibbon ape leukemia virus enhancer

The gibbon ape leukemia virus (GALV) contains enhancer activity within its long terminal repeat. In the GALV Seato strain this activity resides in a 48-base-pair (bp) repeated element. We demonstrate the existence of a cellular protein which binds in this region of the Seato strain. A sensitive method for enriching protein-DNA complexes from crude extracts coupled with exonuclease and DNase footprint analysis revealed the specific binding of this protein to a 21-bp region within each repeated element. A 22-bp oligonucleotide fragment defined solely by the 21-bp footprint binds a protein in vitro and displays enhancer activity in vivo, suggesting that this protein is a major determinant of GALV enhancer activity. The protein is present in three cell lines which are positive for enhancer activity and is not detected in Jurkat cells, which are negative for enhancer activity. Only GALV long-terminal-repeat variants which support high levels of enhancer activity in vivo compete with this protein for specific binding in vitro, suggesting a potential role for the protein in determining enhancer activity. This protein binding is not inhibited by competition with heterologous retroviral enhancers, demonstrating that it is not a ubiquitous retroviral enhancer binding protein.

Emergence of resistance to ceftazidime during therapy for Enterobacter cloacae infections

The mechanism of resistance to ceftazidime in two clinical isolates of Enterobacter cloacae that emerged during therapy with broad-spectrum beta-lactam antibiotics was studied. Both isolates acquired broad resistance to advanced-spectrum beta-lactam drugs other than imipenem. Biotyping confirmed strain identity in both cases, and no new plasmids were detected in the resistant isolates. Both resistant isolates produced beta-lactamase constitutively. Slow but definite hydrolysis of ceftazidime was demonstrated by using purified beta-lactamase in a spectrophotometric assay. Further evidence that beta-lactamase is responsible for resistance in these organisms was provided by the demonstration that cefoxitin, a potent inducer of beta-lactamase, antagonized the activity of ceftazidime against these isolates. This antagonism could be prevented by inhibition of derepression of beta-lactamase with clindamycin. Clindamycin also prevented regrowth of ceftazidime-treated cells in time-kill studies and markedly reduced production of beta-lactamase in induced cultures at concentrations as low as 2 micrograms/ml.