Invasive pneumococcal infections in pediatric cardiac transplant patients.

BACKGROUND: Bacterial infections cause significant morbidity and mortality in cardiac transplant patients. Because Streptococcus pneumoniae is the most prominent bacterial pathogen of childhood, the objective of this study was to define the role of S. pneumoniae as a pathogen in the cardiac transplant population. METHODS: Medical records of cardiac transplant patients from March, 1990, through November, 2000, were reviewed to identify invasive pneumococcal infections after transplantation. Demographic, clinical and microbiologic data were reviewed. RESULTS: Nine (11%) of 80 patients had 12 episodes of pneumococcal bacteremia for an incidence rate of 39 cases/1,000 patient years. Patients who were African-American, transplanted before 2 years of age and transplanted because of idiopathic dilated cardiomyopathy were at increased risk of invasive pneumococcal disease (P < 0.05). Six patients were eligible for the 23-valent pneumococcal polysaccharide vaccine before their first invasive infection, but only 1 had received it at the recommended age. Most isolates (82%) were penicillin-susceptible, and no single serotype predominated. There were 2 deaths in the study group, but each was unrelated to infection. Three patients (33%) had recurrent invasive disease with a second serotype an average of 12 months after the first infection. CONCLUSIONS: The incidence of pneumococcal bacteremia in cardiac transplant patients is higher than in the general pediatric population. Risks for infection were being African-American, being younger than 2 years at the time of transplant and being transplanted because of idiopathic cardiomyopathy. It is plausible that pneumococcal vaccine would decrease this risk.

Free radical-induced fragmentation of proteins by quercetin.

The flavonoid, quercetin, is known to bind to DNA and, in the presence of Cu(II) and other ions, causes fragmentation of the molecule. We examined whether quercetin might bind to protein and cause similar fragmentation. By using UV spectroscopic and fluorescence quenching experiments we show that quercetin binds to bovine serum albumin and that the complex does, in the presence of Cu(II), lead to fragmentation of the protein. The binding involves binding to tryptophan residues in the albumin. The reaction is not detected in certain other tryptophan-containing proteins. We discuss the possible implications for protein damage by this and other radical-generating reagents.

Cloning and sequence analysis of an Escherichia coli gene conferring bicyclomycin resistance.

We have cloned and sequenced DNA from Escherichia coli that, when present in a high-copy-number plasmid, confers resistance to the diketopiperazine antibiotic, bicyclomycin (Bc). The DNA includes a 378-amino-acid open reading frame (ORF), disruption of which results in the loss of Bc resistance. This ORF contains the BcR gene. Studies using the minicell expression system reveal that a polypeptide of 31 kDa is produced from this cloned region. The ORF maps at 47.1 min on the E. coli genome map. Sequence comparison between the translated ORF and a protein database reveal between 26.5 and 23.4% aa sequence homology to bacterial transmembrane (TM) proteins including those mediating chloramphenicol (Cm) and tetracycline (Tc) resistance and an arabinose-proton symport protein. Sequence analysis using the Diagon program showed the BcR gene product (BcR) had homology with the N-terminal regions of the CmR and TcR-encoded proteins and weak N-terminal homology with the arabinose-proton symport protein. Hydropathy profiles of the BcR protein and CmR products show a striking similarity, both having twelve predicted TM domains.

Strand scission in DNA induced by dietary flavonoids: role of Cu(I) and oxygen free radicals and biological consequences of scission.

The naturally occurring flavonoid, quercetin, in the presence of Cu(II) and molecular oxygen caused breakage of calf thymus DNA, supercoiled pBR322 plasmid DNA and single stranded M13 phage DNA. In the case of the plasmid, the product(s) were relaxed circles or a mixture of these and linear molecules depending upon the conditions. For the breakage reaction, Cu(II) could be replaced by Fe(III) but not by other ions tested [Fe(II), Co(II), Ni(II), Mn(II) and Ca(II)]. Structurally related flavonoids, rutin, galangin, apigenin and fisetin were effective or less effective than quercetin in causing DNA breakage. In the case of the quercetin-Cu(II) reaction, Cu(I) was shown to be essential intermediate by using the Cu(I)-sequestering reagent, bathocuproine. By using Job plots we established that, in the absence of DNA, five Cu(II) ions were reduced by one quercetin molecule; in contrast two ions were reduced per quercetin molecule in the DNA breakage reaction. Equally neocuproine inhibited the DNA breakage reaction. The involvement of active oxygen in the reaction was established by the inhibition of DNA breakage by superoxide dismutase, iodide, mannitol, formate and catalase (the inhibition was complete in the last case). The strand scission reaction was shown to account for the biological activity of quercetin as assayed by bacteriophage inactivation. From these data we propose a mechanism for the DNA strand scission reaction of quercetin and related flavonoids.

Strand scission in DNA by quercetin and Cu(II): identification of free radical intermediates and biological consequences of scission.

Quercetin was shown to reduce oxygen to superoxide. In the presence of Cu(II), the hydroxyl radical was formed. The strand scission of DNA was shown to occur under conditions in which Cu(II), quercetin and either hydrogen peroxide or oxygen were present and superoxide was not a necessary intermediate. Strand scission involved the hydroxyl radical and a radical DNA intermediate. The strand scission reaction was shown to account for the biological activity of quercetin as assayed by bacteriophage inactivation.

Strand scission in DNA induced by quercetin and Cu(II): role of Cu(I) and oxygen free radicals.

The naturally occurring flavonoid, quercetin, in the presence of Cu(II) and molecular oxygen caused breakage of calf thymus DNA, supercoiled pBR322 plasmid DNA and single-stranded M13 phage DNA. In the case of the plasmid, the product(s) were relaxed circles or a mixture of these and linear molecules depending upon the conditions. For the breakage reaction, Cu(II) could be replaced by Fe(III) but not by other ions tested [Fe(II), Co(II), Ni(II) and Ca(II)]. Structurally related flavonoids, rutin, galangin, apigenin and fisetin, were ineffective or less effective than quercetin in causing DNA breakage. In the case of the quercetin--Cu(II) reaction, Cu(I) was shown to be an essential intermediate by using the Cu(I)-sequestering reagents, neocuproine and bathocuproine. By using Job plots we established that, in the absence of DNA, five Cu(II) ions can be reduced by one quercetin molecule; in contrast, two ions were reduced per quercetin molecule in the DNA breakage reaction. Equally neocuproine inhibited the DNA breakage reaction. The involvement of active oxygen in the reaction was established by the inhibition of DNA breakage by superoxide dismutase, iodide, mannitol, formate and catalase (the inhibition was complete in the last case). From these data we propose a mechanism for the DNA strand scission reaction of quercetin and related flavonoids.

Inactivation of bacteriophage lambda and lambda DNA by nitrogen mustard.

Bacteriophage lambda and lambda DNA were treated with alkylating agents. The survival of phage was assayed by infectivity and that of DNA by infectivity of phage particles assembled from the DNA in vitro. Phage lambda were more sensitive to nitrogen mustard (C1(CH2)2NMe(CH2)2C1; HN2) than was lambda DNA. The inactivation of lambda DNA was biphasic; the second component of the inactivation was sensitive to mutations allelic for recA, polA and uvrB. This behaviour was not shown by pBR322 plasmid DNA treated with HN2 nor by lambda DNA treated with monofunctional alkylating agents (or HN2 if the second alkylation reaction was stopped by addition of a mercaptan). From Arrhenius plots, the activation energy for the reactions with DNA and interact phage were found to be different. The activation energy for the inactivation of intact phage was the same as that (measured independently) for the predominant reaction (or class of reactions) in which HN2 cross-links DNA to protein in lambda particles. From these data we conclude that the inactivation of lambda by HN2 is due, primarily, to DNA-protein cross-linking. The implications for the mode of action of DNA-reactive bifunctional anti-viral and cytotoxic compounds are discussed.

Bacteriophage K7, a double stranded DNA phage that infects strains of Escherichia coli harbouring drug resistance factors of incompatability group W.

Bacteriophage K7 is specific for Escherichia coli strains harbouring R factors of incompatability group W, including hybrid coliphage P1-Myxococcus virescens plasmids. The phage has an unusual morphology with an isometric head and long tail of variable length. The tail lengths appear to fall into classes corresoonsing to simple multimers of a unit length. Partially purified lysates of the phage include material that may represent phage particles in the process of biogenesis and other material demonstrating attachment of phage to cell envelope. Newly released phage DNA contains single standed ends. In the course of work. E. coli strains that harbour R factor Sa were found to be apparently restrictive.

Transduction of Myxococcus virescens by coliphage P1CM: generation of plasmids containing both phage and Myxococcus genes.

Chloramphenicol-resistant Myxococcus virescens were obtained by infecting myxococci with Escherichia coli specialized transducing phage P1CM. The drug-resistant myxococci were phenotypically unstable. They contained more than one type of plasmid; these plasmids were not found in the parent strain. Chloramphenicol-resistant E. coli were obtained by transformation with either a fraction of myxococcal DNA containing the plasmids or with P1CM prophage DNA. These transformants contained plasmids. Escherichia coli transformed by DNA from the myxococci contained both P1CM and myxococcal genes. Individual transformant clones differed in the genetic make-up of their plasmids. Among the myxococcal genes expressed in these plasmid-harbouring E. coli strains were a capacity for self-transmissibility and a pattern of phage sensitivity characteristic of R factor incompatibility group W. Escherichia coli transformed with P1CM prophage contained incomplete P1CM genomes; none of the chloramphenicol-resistant transformants produced P1CM phage particles. The significance of these findings for an understanding of mechanisms for the generation of R factors is discussed.