Nature of bonding in the cyclization reactions of (2-Ethynylphenyl)triazene and 2-Ethynylstyrene.

The topological analysis of the electron localization function (ELF) has been applied to explore the nature of bonding in thermal cyclizations of (2-ethynylphenyl)triazene and 2-ethynylstyrene. These processes have been proposed to occur through both five- (i.e., coarctate) and six-membered (i.e., pericyclic) transition states. The analysis of electron delocalization, as measured from an irreducible ELF f-localization domain reduction diagram, allows us to characterize these cyclizations of 2-ethynylstyrene in terms of a more pronounced pericyclic or coarctate character than those associated with (2-ethynylphenyl)triazene. The latter evolve through pseudopericyclic and pseudocoarctate pathways. It is found that ELF results are also in good agreement with recent magnetic evidence data obtained from the anisotropy of induced current density (ACID) calculations.

[Distribution of capsular types and antimicrobial susceptibility of Streptococcus agalactiae causing infections in Argentina]. / Distribución de tipo capsular y sensibilidad antimicrobiana de Streptococcus agalactiae productores de infecciones en Argentina.

Streptococcus agalactiae is an endogenous bacterium that has emerged in the last 20 years as an etiological agent in both neonatal and perinatal infections, and in immunocompromised patients. The differentiation of the capsular polysaccharide, the presence of surface proteins c, X, R, and molecular methods allow classification in serotypes and genotypes. This identification is a useful tool for epidemiological purposes and virulence studies in this bacterium. The objective of this work was to study the serotypes and the antimicrobial susceptibility of isolates recovered from invasive diseases in different areas of Argentina. In the analyzed sample a fair predominance of Ia and III serotypes was recovered, followed by II and IV serotypes. All the isolates were found to be sensitive to penicillin. A 6% of resistance to erythromycin and a 4.5% to clindamycin were detected. In three of the isolates, constitutive MLS phenotype (resistance to macrolides, lincosamins and streptogramins) was founded, while in the remaining one, inducible MLS phenotype was detected. These results stress the importance of conducting a surveillance of the prevalent serotypes in our country with the goal of future prevention of this disease with an effective vaccine. The knowledge of the antimicrobial susceptibility profile will be also important to obtain therapeutic success in the treatment.

Distribución de tipo capsular y sensibilidad antimicrobiana de Streptococcusagalactiae productores de infecciones en Argentina / Distribution of capsular types and antimicrobial susceptibility of Streptococcus agalactiae causing infections in Argentina

Streptococcus agalactiae es una bacteria colonizante que ha emergido en los últimos años como causante de infecciones neonatales, perinatales y en pacientes con compromiso inmunológico. La caracterización del polisacárido capsular, de las proteínas de superficie (c, X, R), así como el análisis de marcadores moleculares, permiten su clasificación en serotipos y genotipos. Esto resulta de utilidad para fines epidemiológicos y para estudios de virulencia de la bacteria. El objetivo de este trabajo fue conocer los serotipos prevalentes y la sensibilidad antimicrobiana de aislamientos provenientes de procesos infecciosos en pacientes de distintas zonas de Argentina. En la muestra analizada se obtuvo predominio de los serotipos Ia y III, seguido de II y IV. Todas las cepas resultaron sensibles a penicilina. Se observó 6% de resistencia a eritromicina y 4,5% a clindamicina. En 3 de las cepas se detectó fenotipo MLS (resistencia a macrólidos, lincosaminas y estreptograminas) constitutiva y en una cepa, resistencia MLS inducible. Los resultados logrados en este estudio destacan la importancia de efectuar un relevamiento de los serotipos más frecuentes en nuestro país en vistas a la prevención de esta infección con una vacuna que realmente sea eficaz, como así también el conocimiento de la sensibilidad antimicrobiana para lograr éxito terapéutico en los tratamientos.

Streptococcus agalactiae is an endogenous bacterium that has emerged in the last 20 years as an etiological agent in both neonatal and perinatal infections, and in immunocompromised patients. The differentiation of the capsular polysaccharide, the presence of surface proteins c, X, R, and molecular methods allow classification in serotypes and genotypes. This identification is a useful tool for epidemiological purposes and virulence studies in this bacterium. The objective of this work was to study the serotypes and the antimicrobial susceptibility of isolates recovered from invasive diseases in different areas of Argentina. In the analyzed sample a fair predominance of Ia and III serotypes was recovered, followed by II and IV serotypes. All the isolates were found to be sensitive to penicillin. A 6% of resistance to erythromycin and a 4.5% to clindamycin were detected. In three of the isolates, constitutive MLS phenotype (resistance to macrolides, lincosamins and streptogramins) was founded, while in the remaining one, inducible MLS phenotype was detected. These results stress the importance of conducting a surveillance of the prevalent serotypes in our country with the goal of future prevention of this disease with an effective vaccine. The knowledge of the antimicrobial susceptibility profile will be also important to obtain therapeutic success in the treatment.

Distribución de tipo capsular y sensibilidad antimicrobiana de Streptococcus agalactiae productores de infecciones en Argentina. / [Distribution of capsular types and antimicrobial susceptibility of Streptococcus agalactiae causing infections in Argentina]

Streptococcus agalactiae is an endogenous bacterium that has emerged in the last 20 years as an etiological agent in both neonatal and perinatal infections, and in immunocompromised patients. The differentiation of the capsular polysaccharide, the presence of surface proteins c, X, R, and molecular methods allow classification in serotypes and genotypes. This identification is a useful tool for epidemiological purposes and virulence studies in this bacterium. The objective of this work was to study the serotypes and the antimicrobial susceptibility of isolates recovered from invasive diseases in different areas of Argentina. In the analyzed sample a fair predominance of Ia and III serotypes was recovered, followed by II and IV serotypes. All the isolates were found to be sensitive to penicillin. A 6

of resistance to erythromycin and a 4.5

to clindamycin were detected. In three of the isolates, constitutive MLS phenotype (resistance to macrolides, lincosamins and streptogramins) was founded, while in the remaining one, inducible MLS phenotype was detected. These results stress the importance of conducting a surveillance of the prevalent serotypes in our country with the goal of future prevention of this disease with an effective vaccine. The knowledge of the antimicrobial susceptibility profile will be also important to obtain therapeutic success in the treatment.

[Bacteremia in 2 hospitals in Rosario, Argentina]. / Bacteriemias en dos hospitales de Rosario, Argentina.

Bacteremia is associated with high morbidity and mortality. Nosocomial bacteremia is associated with an attributable mortality of 35%. In order to characterize the etiological agent of bacteremia cases during two time periods, 6605 patients were studied as follows: 1) from 1980 to 1982 (n = 2401) and 2) from 1988 to 2000 (n = 4204). A total of 596 cases of bacteremia were detected. The most frequent agents were Staphylococcus aureus, negative coagulase (CNS) Staphylococcus, Klebsiella pneumoniae and Escherichia coli. In the second period, an increase in the frequency of bacteremia caused by gram positive bacteria, particularly gram-positive cocci, was noted. Conversely, gram negative bacteria diminished significantly in the second period, specially enterobacterial species. Methicillin-resistant S. aureus and CNS were significantly more frequently isolated in the second period. Infrequent agents of endocarditis, such as Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, and Corynebacterium urealyticum, were isolated.

[Hepatic abscess and bacteremia due to Lactobacillus rhamnosus]. / Absceso hepático y bacteriemia debida a Lactobacillus rhamnosus.

The incidence of severe infections caused by Lactobacillus spp. is very low. This paper reports a case of a liver abscess and bacteremia due to Lactobacillus rhamnosus. The patient is a 73 year-old woman with antecedent of diabetes mellitus. She has undergone surgery and received antimicrobial therapy (ampicillin plus gentamicin). The clinical outcome was favorable.

Absceso hepático y bacteriemia debida a Lactobacillus rhamnosus / Liver abscess and bacteremia due to Lactobacillus rhamnosus

Las infecciones severas por Lactobacillus spp. son infrecuentes. En una paciente de 73 años, de sexo femenino, diabética descompensada, se presenta un caso de absceso hepático y bacteriemia causado por Lactobacillus rhamnosus. La misma fue sometida a laparotomía con drenaje de absceso del lóbulo derecho y tratada con ampicilina y gentamicina con una evolución favorable. (AU)

Absceso hepático y bacteriemia debida a Lactobacillus rhamnosus / Liver abscess and bacteremia due to Lactobacillus rhamnosus

Las infecciones severas por Lactobacillus spp. son infrecuentes. En una paciente de 73 años, de sexo femenino, diabética descompensada, se presenta un caso de absceso hepático y bacteriemia causado por Lactobacillus rhamnosus. La misma fue sometida a laparotomía con drenaje de absceso del lóbulo derecho y tratada con ampicilina y gentamicina con una evolución favorable.

Absceso hepático y bacteriemia debida a Lactobacillus rhamnosus. / [Hepatic abscess and bacteremia due to Lactobacillus rhamnosus]

The incidence of severe infections caused by Lactobacillus spp. is very low. This paper reports a case of a liver abscess and bacteremia due to Lactobacillus rhamnosus. The patient is a 73 year-old woman with antecedent of diabetes mellitus. She has undergone surgery and received antimicrobial therapy (ampicillin plus gentamicin). The clinical outcome was favorable.

Bacteriemias en dos hospitales de Rosario, Argentina. / [Bacteremia in 2 hospitals in Rosario, Argentina]

Bacteremia is associated with high morbidity and mortality. Nosocomial bacteremia is associated with an attributable mortality of 35

. In order to characterize the etiological agent of bacteremia cases during two time periods, 6605 patients were studied as follows: 1) from 1980 to 1982 (n = 2401) and 2) from 1988 to 2000 (n = 4204). A total of 596 cases of bacteremia were detected. The most frequent agents were Staphylococcus aureus, negative coagulase (CNS) Staphylococcus, Klebsiella pneumoniae and Escherichia coli. In the second period, an increase in the frequency of bacteremia caused by gram positive bacteria, particularly gram-positive cocci, was noted. Conversely, gram negative bacteria diminished significantly in the second period, specially enterobacterial species. Methicillin-resistant S. aureus and CNS were significantly more frequently isolated in the second period. Infrequent agents of endocarditis, such as Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, and Corynebacterium urealyticum, were isolated.

Bacteriemias en dos hospitales de Rosario, Argentina / [Bacteremia in 2 hospitals in Rosario, Argentina]

Bacteremia is associated with high morbidity and mortality. Nosocomial bacteremia is associated with an attributable mortality of 35

. In order to characterize the etiological agent of bacteremia cases during two time periods, 6605 patients were studied as follows: 1) from 1980 to 1982 (n = 2401) and 2) from 1988 to 2000 (n = 4204). A total of 596 cases of bacteremia were detected. The most frequent agents were Staphylococcus aureus, negative coagulase (CNS) Staphylococcus, Klebsiella pneumoniae and Escherichia coli. In the second period, an increase in the frequency of bacteremia caused by gram positive bacteria, particularly gram-positive cocci, was noted. Conversely, gram negative bacteria diminished significantly in the second period, specially enterobacterial species. Methicillin-resistant S. aureus and CNS were significantly more frequently isolated in the second period. Infrequent agents of endocarditis, such as Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, and Corynebacterium urealyticum, were isolated.

Calorimetric and computational study of 1,3,5-trithiane.

To understand the differences in conformational behavior and reactivity of oxygen- and sulfur-containing 1,3,5-heterocyclohexanes, the enthalpies of formation and sublimation of 1,3,5-trithiane, 1, have been measured. The numerical value of the enthalpy of formation for this compound in the solid state is -8.6 +/- 2.6 kJ mol(-1), while the corresponding value in the gaseous state is 84.6 +/- 2.6 kJ mol(-1). The value for the enthalpy of sublimation is 93.2 +/- 0.2 kJ mol(-1). Standard ab initio molecular orbital calculations at the G2(MP2), G2, and G3 levels were performed, and the calculated enthalpies of formation are compared with the experimental data. These experimental and theoretical studies support the relevance of through-space lone pair-lone pair electronic repulsion in the sulfur heterocycle.

Importance of hand germ contamination in health-care workers as possible carriers of nosocomial infections.

The importance of hands in the transmission of nosocomial infection has been world wide admitted. However, it is difficult to induce this behavior in health-care workers. The aim of the present work was to point out the importance of hand bacteria colonization, the influence of hand washing and of patient physical examination. One hundred health-care workers were randomly divided in two groups: Group A without hand washing previous to patient physical examination or handling (PPE); group B with hand washing previous to PPE. Direct fingerprint samples in Columbia agar before and after PPE were obtained. The colonies were counted and identified by conventional techniques, and antibiograms according to NCCLS were performed. Before PPE group A participants showed a high number of bacteria regarding group B participants (73.9 Vs 20.7; p < 0.001); 44 out of 50 participants were carriers of potentially pathogen bacteria. No group B participants were carriers of potential pathogen bacteria before PPE. The latter group showed an increase in number of bacteria after PPE (20.7 CFU (before) Vs 115.9 CFU (after); p < 0.001). Sixteen group B participants were contaminated after PPE with potential pathogens such as S. aureus (50% of them methicillin resistant); Escherichia coli, Pseudomonas aeruginosa and Enterococcus faecalis, half of them multiresistant. We can conclude on the importance of these results to implement educational programs and to provide the health-care workers with the proper commodities to fulfill this practice.

Influence of alkyl substitution on the gas-phase stability of 1-adamantyl cation and on the solvent effects in the solvolysis of 1-bromoadamantane.

1-Adamantyl cations having three methyl groups or one, two, or three isopropyl groups on the 3-, 5-, and 7-positions were found by FT ICR to be more stable than the 1-adamantyl cation and that the stability increases with the number of isopropyl group. The relative stabilities calculated by PM3 were in good agreement with the experimental results. In contrast, the sequence of the rates for the solvolysis in nonaqueous solvents are 3,5,7-(Me)(3)-1-AdBr < 1-bromoadamantane (1-AdBr) < 3,5,7-(n-Pr)(3)-1-AdBr < 3,5,7-(i-Pr)(3)-1-AdBr. The rates of solvolysis of 3,5,7-(i-Pr)(3)-1-AdBr and 3,5,7-(n-Pr)(3)-1-AdBr relative to 1-AdBr at 25 degrees C are 15 and 3.8 in EtOH, respectively, but markedly decreases with the increase in the amount of added water, reaching 0.84 and 0.15, respectively, in 60% EtOH. Reflecting these effects of water, the Grunwald-Winstein (GW) relationship for 3,5,7-(i-Pr)(3)-1-AdBr and 3,5,7-(n-Pr)(3)-1-AdBr against Y(Br) is linear for nonaqueous alcohols (EtOH, MeOH, TFE-EtOH, TFE, 97% HFIP), but marked downward deviations are observed for aqueous organic solvents, in particular, aqueous ethanol and aqueous acetone. The effect of the alkyl substituents to diminish relative solvolytic reactivity in EtOH-H(2)O mixtures may be ascribed to a blend of steric hindrance to Betarphinsted base-type hydration to the beta-hydrogens and hydrophobic interaction of the alkyl groups with ethanol to make the primary solvation shell less ionizing. The introduction of one nonyl group to the 3-position showed much smaller deviations in the GW relationship than the case of 3,5,7-(n-Pr)(3)-1-AdBr. The markedly decelerated solvolysis of alkylated 1-bromoadamantanes in aqueous organic solvents is a kinetic version of anomalously diminished dissociation of alkylbenzoic acids in aqueous ethanol and aqueous tert-butyl alcohol that was demonstrated by Wepster and co-workers a decade ago and ascribed to hydrophobic effects.

An experimental and theoretical study of the basicity of tetra-tert-butyltetrahedrane.

The gas-phase basicity (GB) of tetra-tert-butyltetrahedrane (tBu4THD) was determined by FT-ICR mass spectrometry and comparison with reference compounds of known basicity. Its GB, 1035+/-10 kJ x mol(-1), makes tetra-tert-butyltetrahedrane one of the strongest bases reported so far. Ab initio calculations [B3LYP/6-31G(d) and B3LYP/6-311 + G(d,p)//6-31G(d)] have been carried out in order to compare the high experimental basicity of tBu4THD with that estimated theoretically. Both B3LYP/6-31G(d) and QCISD(T) calculations were used to determine the reaction path which connects the initial tetrahedrane-ammonium complex with the final products, protonated cyclobutadiene (CBDH+) and ammonia.

[Arcanobacterium haemolyticum sinusitis]. / Sinusitis debida a Arcanobacterium haemolyticum.

Arcanobacterium haemolyticum is a bacterial pharyngeal pathogen that predominantly infects adolescents and young adults. It rarely causes severe infection. A case of sinusitis in an 18-year-old female patient with a skin rash is presented. The strain was susceptible to erythromicin, ampicilin, vancomicin, cephalotin, clindamicin, rifampicin and penicillin. Erythromicin has been proposed as first-line therapy.

Sinusitis debida a Arcanobacterium haemolyticum. / [Arcanobacterium haemolyticum sinusitis]

Arcanobacterium haemolyticum is a bacterial pharyngeal pathogen that predominantly infects adolescents and young adults. It rarely causes severe infection. A case of sinusitis in an 18-year-old female patient with a skin rash is presented. The strain was susceptible to erythromicin, ampicilin, vancomicin, cephalotin, clindamicin, rifampicin and penicillin. Erythromicin has been proposed as first-line therapy.