Intracellular chelation of iron by bipyridyl inhibits DNA virus replication: ribonucleotide reductase maturation as a probe of intracellular iron pools.

The efficient replication of large DNA viruses requires dNTPs supplied by a viral ribonucleotide reductase. Viral ribonucleotide reductase is an early gene product of both vaccinia and herpes simplex virus. For productive infection, the apoprotein must scavenge iron from the endogenous, labile iron pool(s). The membrane-permeant, intracellular Fe(2+) chelator, 2,2'-bipyridine (bipyridyl, BIP), is known to sequester iron from this pool. We show here that BIP strongly inhibits the replication of both vaccinia and herpes simplex virus, type 1. In a standard plaque assay, 50 microm BIP caused a 50% reduction in plaque-forming units with either virus. Strong inhibition was observed only when BIP was added within 3 h post-infection. This time dependence was observed also in regards to inhibition of viral late protein and DNA synthesis by BIP. BIP did not inhibit the activity of vaccinia ribonucleotide reductase (RR), its synthesis, nor its stability indicating that BIP blocked the activation of the apoprotein. In parallel with its inhibition of vaccinia RR activation, BIP treatment increased the RNA binding activity of the endogenous iron-response protein, IRP1, by 1.9-fold. The data indicate that the diiron prosthetic group in vaccinia RR is assembled from iron taken from the BIP-accessible, labile iron pool that is sampled also by ferritin and the iron-regulated protein found in the cytosol of mammalian cells.

Regulation of high affinity iron uptake in the yeast Saccharomyces cerevisiae. Role of dioxygen and Fe.

High affinity iron uptake in Saccharomyces cerevisiae requires a metal reductase, a multicopper ferroxidase, and an iron permease. Fet3, the apparent ferroxidase, is proposed to facilitate iron uptake by catalyzing the oxidation of reductase-generated Fe(II) to Fe(III) by O2; in this model, Fe(III) is the substrate for the iron permease, encoded by FTR1 (Kaplan, J., and O'Halloran, T. V. (1996) Science 271, 1510-1512). We show here that dioxygen also plays an essential role in the expression of these iron uptake activities. Cells grown anaerobically exhibited no Fe(III) reductase or high affinity iron uptake activity, even if assayed for these activities under air. Northern blot analysis showed that the amount of those mRNAs encoding proteins associated with this uptake was repressed in anaerobic cultures but was rapidly induced by exposure of the culture to dioxygen. The anaerobic repression was reduced in cells expressing an iron-independent form of the trans-activator, Aft1, a protein that regulates the expression of these proteins. Thus, the effect of oxygenation on this expression appeared due at least in part to the state or distribution of iron in the cells. In support of this hypothesis, the membrane-permeant Fe(II) chelator, 2, 2'-bipyridyl, in contrast to the impermeant chelator bathophenanthroline disulfonate, caused a strong and rapid induction of these transcripts under anaerobic conditions. An increase in the steady-state levels of iron-regulated transcripts upon oxygenation or 2,2'-bipyridyl addition occurred within 5 min, indicating that a relatively small, labile intracellular pool of Fe(II) regulates the expression of these activities. The strength of the anaerobic repression was dependent on the low affinity, Fe(II)-specific iron transporter, encoded by FET4, suggesting that this Fe(II) pool was linked in part to iron brought into the cell via Fet4 protein. The data suggest a model in which dioxygen directly or indirectly modulates the Fe(III)/Fe(II) ratio in an iron pool linked to Aft1 protein while bipyridyl increases this ratio by chelating Fe(II). These results indicate that dioxygen both modulates the sensitivity to iron-dependent transcriptional regulation and acts as substrate for Fet3 in the ferroxidase reaction catalyzed by this ceruloplasmin homologue.

The SIR1 gene of Saccharomyces cerevisiae and its role as an extragenic suppressor of several mating-defective mutants.

The SIR1 gene product of Saccharomyces cerevisiae is one of several proteins involved in repressing transcription of the silent mating-type genes. Strains with mutations in the genes coding for these proteins are defective in mating due to derepression of the silent loci. We have found that overexpression of the SIR1 gene suppresses the mating defects of several of these mutants, including nat1 and ard1 mutants (the products of these two genes are responsible for N-terminal acetylation of a subset of yeast proteins), certain sir3 mutants, and a histone H4 mutant. The SIR1 gene has been sequenced and found to contain an open reading frame coding for a 678-amino-acid protein.

Comparison between parental report and results of microbiologic agar assay for presence of antibiotic in urine of Argentinian children with acute lower respiratory tract infection.

This study compares two sources of information on prior use of antibiotics in children with acute lower respiratory tract infection. The presence of antibiotics in respiratory specimens complicates recovery of bacterial pathogens and the selection of appropriate antibiotic treatment. The first source of information is the parents, who are asked about recent use of antibiotics by their child. The second source is an agar diffusion assay that detects antibiotics in urine specimens. In Argentina, where antibiotics are readily available without prescription, parental information about a child's recent antibiotic therapy was found to be relatively reliable only when their answer was affirmative.

Perfiles de resistencia de las distintas especies del género Staphylococcus frente a quince antimicrobianos de uso clínico / Resistance profiles of the various species of the genus Staphylococcus to 15 clinically-used antimicrobials

Se estudiaron 78 cepas de distinas especies del género Staphylococcus (29 S. aureus, 48 Staphylococcus coagulasa-negativos y 1 cepa de S. intermedius) para conocer los perfiles de resistencia frente a quince antimicrobianos de uso clínico. De las 48 cepas de Staphylococcus coagulasa-negativos estudiadas, 8 (4 S. epidermidis, 1 S. haemolyticus, 1 S. hominis, 2 S. xylosus) presentaron un perfil de resistencia semejante a S. aureus frente a antibióticos beta-lactámicos, aminoglicósidos, cloranfenicol y fosfomicina. Diez de las restantes cepas de Staphylococcus coagulasa negativos estudiadas presentaron actividad de beta-lactamasa. A pesar que las 7 cepas de S. saprophyticus estudiadas fueron beta-lactamasa-negativas aún luego de la inducción, la concentración inhibitoria mínima a penicilina G fue ligeramene mayor en comparación al valor obtenido en las cepas beta-lactamasas-negativas del resto de las especies. La resistencia a eritromicina fue coincidente con la resistencia a clindamicina en la mayoría de las especies coagulasa-negativas estudiadas, y la resistencia a aminoglicósidos parece ser mediada por las mismas enzimas modificantes en todo el género. Todo el género fue sensible a vancomicina. La rifampicina fue muy activa contra todas las cepas de Staphylococcus coagulasa-negativas. Las cepas de S. aureus rifampicina-resistentes fueron todas resistentes a oxacilina, aunque con respecto al resto de antimicrobianos probados, el patrón de resistencia fue diferente para cada cepa ...

Perfiles de resistencia de las distintas especies del género Staphylococcus frente a quince antimicrobianos de uso clínico / Resistance profiles of the various species of the genus Staphylococcus to 15 clinically-used antimicrobials

Se estudiaron 78 cepas de distinas especies del género Staphylococcus (29 S. aureus, 48 Staphylococcus coagulasa-negativos y 1 cepa de S. intermedius) para conocer los perfiles de resistencia frente a quince antimicrobianos de uso clínico. De las 48 cepas de Staphylococcus coagulasa-negativos estudiadas, 8 (4 S. epidermidis, 1 S. haemolyticus, 1 S. hominis, 2 S. xylosus) presentaron un perfil de resistencia semejante a S. aureus frente a antibióticos beta-lactámicos, aminoglicósidos, cloranfenicol y fosfomicina. Diez de las restantes cepas de Staphylococcus coagulasa negativos estudiadas presentaron actividad de beta-lactamasa. A pesar que las 7 cepas de S. saprophyticus estudiadas fueron beta-lactamasa-negativas aún luego de la inducción, la concentración inhibitoria mínima a penicilina G fue ligeramene mayor en comparación al valor obtenido en las cepas beta-lactamasas-negativas del resto de las especies. La resistencia a eritromicina fue coincidente con la resistencia a clindamicina en la mayoría de las especies coagulasa-negativas estudiadas, y la resistencia a aminoglicósidos parece ser mediada por las mismas enzimas modificantes en todo el género. Todo el género fue sensible a vancomicina. La rifampicina fue muy activa contra todas las cepas de Staphylococcus coagulasa-negativas. Las cepas de S. aureus rifampicina-resistentes fueron todas resistentes a oxacilina, aunque con respecto al resto de antimicrobianos probados, el patrón de resistencia fue diferente para cada cepa ... (AU)

[Resistance profiles of the various species of the genus Staphylococcus to 15 clinically-used antimicrobials]. / Perfiles de resistencia de las distintas especies del género Staphylococcus frente a quince antimicrobianos de uso clínico.

A total of 78 strains of 11 species of Staphylococcus genus (29 S. aureus, 48 Staphylococcus coagulase-negative and 1 S. intermedius strain,) were studied in order to determine the resistance patterns to fifteen commonly used antimicrobial agents. Out of 48 Staphylococcus coagulase-negative strains studied, 8 (4/15 S. epidermidis, 1/10 S. hominis, 1/6 S. haemolyticus, 2/3 S. xylosus) showed resistance patterns similar to that of S. aureus strains against beta-lactam antibiotics, aminoglycosides, chloramphenicol and fosfomycin, and 10 exhibit beta-lactamase-activity. Although the 7 S. saprophyticus strains assayed were beta-lactamase-negative by the chromogenic cephalosporin method after induction, the penicillin G minimal inhibitory concentration values were slightly higher than those obtained with other beta-lactamase-negative species. The susceptibilities to erythromycin and clindamycin suggested that macrolides-lincosamides-streptogramin type B (MLS) resistance was present in a large number of Staphylococcus coagulase-negative strains. In all the Staphylococcus genus, the aminoglycosides resistance seems to be mediated by the same aminoglycosides modifying-enzymes. Vancomycin was very active against the 11 species assayed. Rifampicin was effective with all Staphylococcus coagulase-negative strains. The S. aureus rifampicin-resistant were also resistant to oxacillin, and variable against aminoglycosides, chloramphenicol, fosfomycin, erythromycin and clindamycin. Only 5 strains were resistant to trimethoprim-sulfamethoxazole (TMS), 1 S. aureus oxacillin-susceptible, 1 S. aureus oxacillin-resistant, 2 S. xylosus and 1 S. warneri strains.

Perfiles de resistencia de las distintas especies del género Staphylococcus frente a quince antimicrobianos de uso clínico. / [Resistance profiles of the various species of the genus Staphylococcus to 15 clinically-used antimicrobials]

A total of 78 strains of 11 species of Staphylococcus genus (29 S. aureus, 48 Staphylococcus coagulase-negative and 1 S. intermedius strain,) were studied in order to determine the resistance patterns to fifteen commonly used antimicrobial agents. Out of 48 Staphylococcus coagulase-negative strains studied, 8 (4/15 S. epidermidis, 1/10 S. hominis, 1/6 S. haemolyticus, 2/3 S. xylosus) showed resistance patterns similar to that of S. aureus strains against beta-lactam antibiotics, aminoglycosides, chloramphenicol and fosfomycin, and 10 exhibit beta-lactamase-activity. Although the 7 S. saprophyticus strains assayed were beta-lactamase-negative by the chromogenic cephalosporin method after induction, the penicillin G minimal inhibitory concentration values were slightly higher than those obtained with other beta-lactamase-negative species. The susceptibilities to erythromycin and clindamycin suggested that macrolides-lincosamides-streptogramin type B (MLS) resistance was present in a large number of Staphylococcus coagulase-negative strains. In all the Staphylococcus genus, the aminoglycosides resistance seems to be mediated by the same aminoglycosides modifying-enzymes. Vancomycin was very active against the 11 species assayed. Rifampicin was effective with all Staphylococcus coagulase-negative strains. The S. aureus rifampicin-resistant were also resistant to oxacillin, and variable against aminoglycosides, chloramphenicol, fosfomycin, erythromycin and clindamycin. Only 5 strains were resistant to trimethoprim-sulfamethoxazole (TMS), 1 S. aureus oxacillin-susceptible, 1 S. aureus oxacillin-resistant, 2 S. xylosus and 1 S. warneri strains.

[Minimal biochemical tests for interspecies identification in the Staphylococcus genus]. / Pruebas bioquímicas mínimas para la identificación interespecie en el género Staphylococcus.

A total of 50 different strains from clinical specimens and/or from experimental surgery were typified. The Staphylococcus genus was subdivided according to minimal test results for Staphylococcus genus differentiation into 3 groups: A. the coagulase-positive/novobiocin-susceptible species; B. the coagulase-negative/novobiocin-resistant species and C. the coagulase-negative/novobiocin-susceptible species. Species belonging to the different groups were differentiated by means of minimal biochemical tests readily available to all clinical bacteriology laboratories. To evaluate the predictive value of the procedure employed, the following strains were used as unknown: S. capitis, S. simulans, S. hominis, S. warneci, S. intermedius, S hyicus subsp. hycus, S hyicus subsp. chromogenes and S. haemolyticus. Results indicated that, for the coagulase-positive/novobiocin-susceptible group, the production of pigment and acetoin plus beta-galactosidase were sufficient for interspecies differentiation. For the coagulase-negative/novobiocin-resistant group, urease and phosphatase activity plus production of acid from xylose proved to be sufficient. The coagulase-negative/novobiocin-susceptible group required the greatest number of tests, due to phenotypical variability of species, including: reduction of nitrates; production of acetoin; use of arginine and the production of acid from maltose and/or trehalose. Preliminary findings justify routine application of these minimal tests for Staphylococcus genus differentiation.

Pruebas bioquímicas mínimas para la identificación interespecie en el género Staphylococcus. / [Minimal biochemical tests for interspecies identification in the Staphylococcus genus]

A total of 50 different strains from clinical specimens and/or from experimental surgery were typified. The Staphylococcus genus was subdivided according to minimal test results for Staphylococcus genus differentiation into 3 groups: A. the coagulase-positive/novobiocin-susceptible species; B. the coagulase-negative/novobiocin-resistant species and C. the coagulase-negative/novobiocin-susceptible species. Species belonging to the different groups were differentiated by means of minimal biochemical tests readily available to all clinical bacteriology laboratories. To evaluate the predictive value of the procedure employed, the following strains were used as unknown: S. capitis, S. simulans, S. hominis, S. warneci, S. intermedius, S hyicus subsp. hycus, S hyicus subsp. chromogenes and S. haemolyticus. Results indicated that, for the coagulase-positive/novobiocin-susceptible group, the production of pigment and acetoin plus beta-galactosidase were sufficient for interspecies differentiation. For the coagulase-negative/novobiocin-resistant group, urease and phosphatase activity plus production of acid from xylose proved to be sufficient. The coagulase-negative/novobiocin-susceptible group required the greatest number of tests, due to phenotypical variability of species, including: reduction of nitrates; production of acetoin; use of arginine and the production of acid from maltose and/or trehalose. Preliminary findings justify routine application of these minimal tests for Staphylococcus genus differentiation.