Chiral multiferroicity in two-dimensional hybrid organic-inorganic perovskites.

Chiral multiferroics offer remarkable capabilities for controlling quantum devices at multiple levels. However, these materials are rare due to the competing requirements of long-range orders and strict symmetry constraints. In this study, we present experimental evidence that the coexistence of ferroelectric, magnetic orders, and crystallographic chirality is achievable in hybrid organic-inorganic perovskites [(R/S)-ß-methylphenethylamine]2CuCl4. By employing Landau symmetry mode analysis, we investigate the interplay between chirality and ferroic orders and propose a novel mechanism for chirality transfer in hybrid systems. This mechanism involves the coupling of non-chiral distortions, characterized by defining a pseudo-scalar quantity, ξ = p ⋅ r ( p represents the ferroelectric displacement vector and r denotes the ferro-rotational vector), which distinguishes between (R)- and (S)-chirality based on its sign. Moreover, the reversal of this descriptor's sign can be associated with coordinated transitions in ferroelectric distortions, Jahn-Teller antiferro-distortions, and Dzyaloshinskii-Moriya vectors, indicating the mediating role of crystallographic chirality in magnetoelectric correlations.

Effect of psoas muscle index on early postoperative outcomes in surgically treated spinal tumours in an Asian population.

BACKGROUND: Sarcopenia has been purported to be a pre-operative risk factor that affects patient outcomes in oncological surgery, but no study as of yet has investigated the effect of sarcopenia in patients with spinal tumours. Psoas muscle measurements, including the psoas muscle index (PMI), are an objective way to determine sarcopenia. OBJECTIVES: We investigated if PMI could predict post-operative outcomes (length of hospital stay and post-operative complications) in surgically treated spinal tumour patients in a multi-ethnic Asian population. METHODS: We conducted a retrospective cohort study of patients with spinal tumours who underwent surgery at our tertiary institution from January 2016 to January 2020. PMI was measured on T2-weighted MRI sequences, at the middle of the L3 vertebral body and measurements were collected by 2 independent raters. The primary outcome was length of hospital stay (LOS), and the secondary outcome was post-operative complications. ROC curve was used to attain the cut-off value for PMI and the population was then stratified into 2 groups; sarcopenic if PMI was less than 1.22 and non-sarcopenic if the PMI value was more than or equal to 1.22. Multivariable linear regression was used for LOS, while multivariate logistic regression was used for complications. RESULTS: 57 patients were included with a mean length of stay of 17.8 days (SD 25.1) and the total number of patients with complications were 20 (35.1 %). Mean LOS was significantly higher in the sarcopenic group compared to the non-sarcopenic group. Univariate analysis confirmed the association of lower psoas muscle index corresponding with longer lengths of stay and this was corroborated in a multivariable linear regression model. There were no significant associations between PMI and postoperative complications. CONCLUSIONS: Lower PMI values were significantly associated with a longer LOS. PMI may be warranted for risk stratifying Asian spinal tumour patients undergoing surgery.

Outcomes of Autologous and Synthetic Bone Grafts in Locking Plate Fixation of Comminuted Distal Radius Fractures.

Background The introduction of locking plate technology has improved the feasibility of distal radius fracture fixation without the need for bone grafting, yet challenges persist in cases of severely comminuted fractures and small, unstable intra-articular fragments. This study aimed to assess the outcomes of bone grafting in severely comminuted distal radius fractures treated with locking plates. Methods We performed a retrospective analysis involving 450 patients who underwent distal radius fracture fixations. We evaluated wrist motion, grip strength, and radiographic parameters, including radial inclination, radial tilt, ulnar variance, articular step, and fracture union at standardized intervals. In addition, at the 12- and 24-month marks, we assessed the disabilities of the arm, shoulder, and hand (DASH) questionnaire score. Results Out of the 450 patients who underwent distal radius fracture fixation using volar locking plate systems, 59 individuals (13%) required either autologous bone graft (n = 24) or synthetic bone substitutes (n = 35). In the final follow-up, all fractures had successfully united, displaying an average volar tilt of 4°, radial inclination of 18.8°, and an articular step or gap of 0.1 mm. Conclusion There was no significant difference between the use of autologous or synthetic bone grafts on clinical or radiological outcomes in the long term. Bone grafts are useful in severe metaphyseal comminution and aid in the reduction of articular fragments and bi-cortical comminution.

Faster Bone Gap Union in Medial Opening Wedge High Tibial Osteotomy With 3D-Printed Synthetic Bioresorbable Polycaprolactone and Tricalcium Phosphate Osteotomy Gap Fillers Compared to Allogeneic Osteotomy Gap Fillers: A Retrospective Matched-Pair Cohort Study.

OBJECTIVE: The use of synthetic bone substitute material (BSM) as osteotomy gap fillers have been reported to improve outcomes in medial opening wedge high tibial osteotomy (MOWHTO). This study aims to evaluate the early radiological outcomes (bone union) and complication rates of the novel patient-specific 3D-printed honeycomb-structured polycaprolactone and tricalcium phosphate (PCL-TCP) synthetic graft compared to allogeneic bone grafts as an osteotomy gap filler in MOWHTO. METHODS: A retrospective matched-pair analysis of patients who underwent MOWHTO with either PCL-TCP synthetic graft or allogenic femoral head allograft as osteotomy gap filler was performed. The osteotomy gap was split into equal zones (Zone 1-5), and bone union was evaluated on anteroposterior radiographs based on the van Hemert classification at 1, 3, 6, and 12 months postoperatively. Postoperative complications including infection, lateral hinge fractures, and persistent pain was measured. The study and control group were matched for age, smoking status, diabetes mellitus, and osteotomy gap size. RESULTS: Significantly greater bone union progression was observed in the PCL-TCP group than in the allograft group at 1 month (Zones 1-3), 3 months (Zones 1-4), 6 months (Zones 1-2, 4), and 12 months (Zones 2-3, 5) postoperatively (P < 0.05). No significant difference in complications rates was noted between the two groups at 1 year. CONCLUSIONS: Bone union rates observed in patients who underwent MOWHTO with the PCL-TCP synthetic graft osteotomy gap filler were superior to those in the allograft group at 1 year postoperatively, with no significant difference in complication rates (postoperative infection, lateral hinge fractures, and persistent pain).

Reducing wait times and medical costs for patients: the physiotherapy-led Spine Triage and Rehabilitation (STAR) Clinic.

The Sengkang General Hospital Orthopaedic Spine Outpatient Service is facing a growing challenge of increasing number of referrals and waiting times, placing a significant burden on the system. Primary care referrals have an average wait time of 61.1 days, with 34.5%f patients waiting longer than 60 days from referral to appointment, to see a spine physician.Back pain is a very common presentation, with the vast majority resolving after conservative management which commonly includes analgesia, physiotherapy and reassurance. Unfortunately, many referrals from primary care involve patients who have yet to explore the avenues of conservative management with 90% of our referrals being managed without surgery. Globally, triage services in Western countries conducted by allied health professionals have shown to be an effective method at addressing the escalating wait times with high satisfaction rates. We have endeavoured to emulate this within our department through the implementation of the Spine Triage and Rehabilitation (STAR) Clinic. The STAR clinic aims to empower physiotherapists with the ability to triage patients into surgical and non-surgical categories with their primary physiotherapy expertise to reduce waiting times and increase outpatient capacity.More than 300 patients were recruited, and their progress was tracked over 13 months under the four Ss of: waiting timeS, cost Savings, Safety and patient Satisfaction. This pilot study has been overwhelmingly positive, with significantly reduced waiting times and high cost savings, without any compromise on patient safety and satisfaction.

Molecularly thin, two-dimensional all-organic perovskites.

Recently, the emergence of all-organic perovskites with three-dimensional (3D) structures has expanded the potential applications of perovskite materials. However, the synthesis and utilization of all-organic perovskites in 2D form remain largely unexplored because the design principle has not been developed. We present the successful synthesis of a metal-free 2D layered perovskite, denoted as the Choi-Loh van der Waals phase (CL-v phase), with the chemical formula A2B2X4, where A represents a larger-sized cation compared to B and X denotes an anion. The CL-v phase exhibits a van der Waals gap enabled by interlayer hydrogen bonding and can be exfoliated or grown as molecularly thin 2D organic crystals. The dielectric constants of the CL-v phase range from 4.8 to 5.5 and we demonstrate their potential as gate dielectrics for thin-film transistors.

Targeted four-dimensional computerized tomography scans for elbow disorders: a literature review and refinement of existing technique with two exemplar cases.

Background: Four-dimensional computerized tomographies (4D-CTs) or motion CTs in elbow disorders have several potential advantages over conventional static imaging such as a reduction of misdiagnoses, a more targeted surgical approach, better patient understanding of their condition and potentially faster operative times. However, the radiation dose is higher than conventional static CT scans so this should be used judiciously. Our study reviews the current literature for 4D-CTs in dynamic elbow disorders and provides a technical note describing radiation-reduced targeted elbow 4D-CTs (te4D-CT) with two exemplar cases alongside our recommendations for when te4D-CTs are indicated. Methods: te4D-CTs are performed in a lateral decubitus elbow above head position. Preliminary static source axial cut CT obtained with subsequent sagittal and axial planes reconstruction and 3D reconstruction obtained, followed by scan performed in motion and reconstructed to 4D Component. te4D-CTs are taken for either flexion and extension (FE) or pronation and supination (PS) motions depending on the clinical pathology suspected following thorough clinical examination. Results: te4D-CT for PS and FE protocol scans had an effective radiation exposure dose of 0.53 and 0.95mSv, respectively, compared to 1.13-1.83 mSv in conventional elbow 4D-CTs. In addition, te4D-CTs have good diagnostic accuracy provided that the FE or PS pathology is identified carefully by the ordering physician. Conclusion: te4D-CT using isolated pronation and supination, or flexion and extension protocols does come with a significantly reduced radiation dose and can be of equal clinical yield compared with 4D-CTs.

In-Plane Ferrielectric Order in van der Waals ß'-In2Se3.

van der Waals ferroic materials exhibit rich potential for implementing future generation functional devices. Among these, layered ß'-In2Se3 has fascinated researchers with its complex superlattice and domain structures. As opposed to ferroelectric α-In2Se3, the understanding of ß'-In2Se3 ferroic properties remains unclear because ferroelectric, antiferroelectric, and ferroelastic characteristics have been separately reported in this material. To develop useful applications, it is necessary to understand the microscopic structural properties and their correlation with macroscopic device characteristics. Herein, using scanning transmission electron microscopy (STEM), we observed that the arrangement of dipoles deviates from the ideal double antiparallel antiferroelectric character due to competition between antiferroelectric and ferroelectric structural ordering. By virtue of second-harmonic generation, four-dimensional STEM, and in-plane piezoresponse force microscopy, the long-range inversion-breaking symmetry, uncompensated local polarization, and net polarization domains are unambiguously verified, revealing ß'-In2Se3 as an in-plane ferrielectric layered material. Additionally, our device study reveals analogous resistive switching behaviors of different types owing to polarization switching, defect migration, and defect-induced charge trapping/detrapping processes.

Ion-Conductive Metallo-Covalent Organic Frameworks Constructed with Tridentate Ligand and Zn Nodes.

Metallo-covalent organic frameworks (metallo-COFs) are organometallic scaffolds in which covalently bonded organic frameworks are interwoven with metal-coordinated pendant groups. Unlike the rigid ligands traditionally used for metal coordination, the utilization of "soft" ligands allows for configurable topology and pore structure in metallo-COFs, particularly when the ligands are generated in situ during dynamic synthesis. In this study, we present the rational synthesis of metallo-COFs based on pyridine-2,6-diimine (pdi), wherein the incorporation of Zn2+ ions and in situ-generated tridentate ligands (pdi) yields metallo-COFs with a square-like lattice. In the absence of Zn2+ ions, a topological isomer COF with a Kagome lattice is instead produced. Thus, the presence or absence of Zn2+ ions allows us to switch between two distinct morphologies corresponding to metallo-COF or COF. In comparison to Brønsted acid-catalyzed COF, which necessitates postmetallization for loading metal ions, the metal-templated COF synthesis method yields COFs with improved crystallinity and approximately 1:1 [Zn2+]/ligand composition. Building upon the metal-templated COF synthesis approach, we successfully synthesized pdiCOF-Zn-2 and pdiCOF-Zn-3, which possess square-like and honeycomb lattices, respectively. The enhanced crystallinity and near 1:1 [Zn2+]/ligand composition of pdiCOF-Zn-3 (honeycomb) facilitate its application as ion transport channels.

Electron Spin Decoherence Dynamics in Magnetic Manganese Hybrid Organic-Inorganic Crystals: The Effect of Lattice Dimensionality.

Organic-inorganic metal hybrids with their tailorable lattice dimensionality and intrinsic spin-splitting properties are interesting material platforms for spintronic applications. While the spin decoherence process is extensively studied in lead- and tin-based hybrids, these systems generally show short spin decoherence lifetimes, and their correlation with the lattice framework is still not well-understood. Herein, we synthesized magnetic manganese hybrid single crystals of (4-fluorobenzylamine)2MnCl4, ((R)-3-fluoropyrrolidinium)MnCl3, and (pyrrolidinium)2MnCl4, which represent a change in lattice dimensionality from 2D and 1D to 0D, and studied their spin decoherence processes using continuous-wave electron spin resonance spectroscopy. All manganese hybrids exhibit nanosecond-scale spin decoherence time τ2 dominated by the symmetry-directed spin exchange interaction strengths of Mn2+-Mn2+ pairs, which is much longer than lead- and tin-based metal hybrids. In contrast to the similar temperature variation laws of τ2 in 2D and 0D structures, which first increase and gradually drop afterward, the 1D structure presents a monotonous rise of τ2 with the temperatures, indicating the strong correlation of spin decoherence with the lattice rigidity of the inorganic framework. This is also rationalized on the basis that the spin decoherence is governed by the competitive contributions from motional narrowing (prolonging the τ2) and electron-phonon coupling interaction (shortening the τ2), both of which are thermally activated, with the difference that the former is more pronounced in rigid crystalline lattices.

Near-90° Switch in the Polar Axis of Dion-Jacobson Perovskites by Halide Substitution.

Ferroelectricity in two-dimensional hybrid (2D) organic-inorganic perovskites (HOIPs) can be engineered by tuning the chemical composition of the organic or inorganic components to lower the structural symmetry and order-disorder phase change. Less efforts are made toward understanding how the direction of the polar axis is affected by the chemical structure, which directly impacts the anisotropic charge order and nonlinear optical response. To date, the reported ferroelectric 2D Dion-Jacobson (DJ) [PbI4]2- perovskites exhibit exclusively out-of-plane polarization. Here, we discover that the polar axis in ferroelectric 2D Dion-Jacobson (DJ) perovskites can be tuned from the out-of-plane (OOP) to the in-plane (IP) direction by substituting the iodide with bromide in the lead halide layer. The spatial symmetry of the nonlinear optical response in bromide and iodide DJ perovskites was probed by polarized second harmonic generation (SHG). Density functional theory calculations revealed that the switching of the polar axis, synonymous with the change in the orientation of the sum of the dipole moments (DMs) of organic cations, is caused by the conformation change of organic cations induced by halide substitution.

Strain-Driven Solid-Solid Crystal Conversion in Chiral Hybrid Pseudo-Perovskites with Paramagnetic-to-Ferromagnetic Transition.

Hybrid organic-inorganic perovskites (HOIPs) are promising stimuli-responsive materials (SPMs) owing to their molecular softness and tailorable structural dimensionality. The design of mechanically responsive HOIPs requires an in-depth understanding of how lattice strain induces intermolecular rearrangement that impacts physical properties. While chirality transfer from an organic cation to an inorganic lattice is known to influence chiral-optical properties, its effect on strain-induced phase conversion has not been explored. As opposed to achiral or racemic organic cations, chiral organic cations can potentially afford a new dimension in strain-responsive structural change. Herein, we demonstrate that mechanical strain induces a solid phase crystal conversion in chiral halide pseudo-perovskite single crystals (R/S)-(FE)2CuCl4 (FE = (4-Fluorophenyl)ethylamine) from a 0D isolated CuCl4 tetrahedral to 1D corner-sharing CuFCl5 octahedral framework via the incorporation of Cu···F interaction and N-H···F hydrogen bonding. This strain-induced crystal-to-crystal conversion involves the connection of neighboring 0D CuCl4 tetrahedra via Cu2+-Cl--Cu2+ linkages as well as the incorporation of a F-terminated organic cation as one of the X atoms in BX6 octahedra, leading to a reduced band gap and paramagnetic-to-ferromagnetic conversion. Control experiments using nonchiral or racemic perovskite analogs show the absence of such solid phase conversion. To demonstrate pressure-sensitive properties, the 0D phase is dispersed in water-soluble poly(vinyl alcohol) (PVA) polymer, which can be applied to a large-scale pressure-induced array display on fibrous Spandex substrates via a screen-printing method.

Intercalation-driven ferroelectric-to-ferroelastic conversion in a layered hybrid perovskite crystal.

Two-dimensional (2D) organic-inorganic hybrid perovskites have attracted intense interests due to their quantum well structure and tunable excitonic properties. As an alternative to the well-studied divalent metal hybrid perovskite based on Pb2+, Sn2+ and Cu2+, the trivalent metal-based (eg. Sb3+ with ns2 outer-shell electronic configuration) hybrid perovskite with the A3M2X9 formula (A = monovalent cations, M = trivalent metal, X = halide) offer intriguing possibilities for engineering ferroic properties. Here, we synthesized 2D ferroelectric hybrid perovskite (TMA)3Sb2Cl9 with measurable in-plane and out-of-plane polarization. Interestingly, (TMA)3Sb2Cl9 can be intercalated with FeCl4 ions to form a ferroelastic and piezoelectric single crystal, (TMA)4-Fe(iii)Cl4-Sb2Cl9. Density functional theory calculations were carried out to investigate the unusual mechanism of ferroelectric-ferroelastic crossover in these crystals.

The classification of 1D `perovskites'.

There has been a huge amount of interest in perovskites recently and new structures of hybrid perovskites are frequently reported. The classification of perovskites has been unambiguous in the discussion of 3D and layered 2D perovskites due to the dimensional constraints. However, in 1D perovskites, the additional degrees of freedom have resulted in a large number of possible structural configurations. The new proposed notation aims to classify these structures based on the connectivity of the octahedra of the perovskite, which has a periodic repeating pattern. However, the notation should be restricted to simple 1D perovskites and haloplumbate structures as the notation would become too cumbersome when applied to an exotic framework which has 3D characteristics, such as perovskite polytypes.

The Photophysics of Polythiophene Nanoparticles for Biological Applications.

In this work the photophysics of poly(3-hexylthiophene) nanoparticles (NPs) is investigated in the context of their biological applications. The NPs, made as colloidal suspensions in aqueous buffers, present a distinct absorption band in the low-energy region. On the basis of systematic analysis of absorption and transient absorption (TA) spectra taken under different pH conditions, this band is associated with charge-transfer states generated by the polarization of loosely bound polymer chains and originating from complexes formed with electron-withdrawing species. Importantly, the ground-state depletion of these states upon photoexcitation is active even on microsecond timescales, thus suggesting that they act as precursor states for long-living polarons; this could be beneficial for cellular stimulation. Preliminary transient absorption microscopy results for NPs internalized within the cells reveal the presence of long-living species, further substantiating their relevance in biointerfaces.

Vigilancia de la resistencia de Enterococcus sp. a la vancomicina y evaluación in vitro de nuevas alternativas terapéuticas / Resistance vigilance of enterococcus sp. to the vancomycim and in vitro evaluation of therapeutics alternatives news

Introducción: La emergencia de cepas de Enterococcus resistentes a la vancomicina (VRE) es un problema mundial que ya ha sido descrito en nuestro país. El presente estudio se realizó con el propósito de determinar la prevalencia de VRE en nuestro hospital y evaluar la actividad in vitro de los antibióticos de primera y segunda línea y de dos nuevas alternativas de reciente aparición en el mercado local: linezolida y moxifloxacina. Material y Métodos: Se incluyótodas las cepas de enterococcus spp provenientes de las muestras clínicas del Hospital Nacional Arzobispo Loayza (HNAL) de Lima. Se realizó un antibiograma estándar según la técnica de Kirby-Bauer. Se determinó la actividad in vitro del linezolida y la moxifloxacina en las cepas resistentes a la vancomicina. Resultados: Se aisló 681 cepas de Enterococcus spp, 24 (3.5 por ciento) de las cuales fueron resistentes a la vancomicina. El estudio de la sensibilidad de las 24 cepas VRE mostró que el 20.8 por ciento (5 cepas) eran sensibles a la gentamicina, el 50 por ciento (12 cepas) a la estreptomicina y ninguna a la ampicilina, cloramfenicol, rifampicina, eritromicina, nitrofurantoína, tetraciclina ni a teicoplanina. En cuanto a la sensibilidad a la moxifloxacina solo una cepa, con una concentración inhibitria mínima igual a 0,38 mg/ml pudo ser considerada sensible a este antibiótico. En lo referente al linezolida, 22 de las 24 cepas VRE fueron sensibles a esta molécula. Conclusiones: El explosivo aumento de enterococos resistentes a la ampicilina ha motivado el uso indiscriminado de los glicopéptidos. Antimicrobianos como el linezolida podrían ser alternativas terapéuticas que permitan disminuir las tasas resistencia a estos fármacos de primera línea.

Vigilancia de la resistencia de Staphylococcus aureus a la oxacilina-vancomicina y patrones de corresistencia / Resistance vigilance of Staphylococcus aureus oxacillin-vencomycin and coresistance patrons

La aparición en los últimos años de bacterias grampositivas multirresistentes ha dificultado el tratamiento de ciertas infecciones intrahospitalarias y ha reducido las opciones terapéuticas. Esto es particularmente cierto para los Staphylococcus aureus resistentes a la meticilina (MRSA) y las recientemente aparecidas cepas de S. aureus de sensibilidad disminuida y resistentes a la vancomicina (VISA, VRSA) debido a la importancia de este antibiótico de uso hospitalario. Entre enero del 2000 y diciembre del 2001 se aislaron en nuestro laboratorio 609 cepas de Staphylococcus aureus, 74 por ciento de las cuales fueron resistentes a la meticilina. Altos niveles de resistencia a la eritromicina, clindamicina, cirpofloxacina, gentamicina, rifampicina, cloramfenicol, tetraciclina y cotrimoxasol fueron encontrados en las cepas MRSA responsables de infecciones intrahospitalarias. Las MRSA fueron principalmente responsables de infección de herida operatoria, neumonía e infecciones cutáneas superficiales. La detección de cepas VISA/VRSA es difícil y requiere tests de laboratorio especiales. En nuestro estudio no detectamos la presencia de ninguna cepa no sensible a la vancomicina. Sin una continua vigilancia, adecuadas medidas de bioseguridad y un uso racional de los antibióticos se seguirá encontrando altas tasas de prevalencia de MRSA.

Evaluación in vitro de Ticarcilina, Ceftazidima, Piperacilina y la asociación Piperacilina+Tazobactam sobre Pseudomonas aeruginosa intrahospitalaria / In vitro evaluation of Ticarcilina, Ceftazidima, Piperacilina and the association Piperacilina+Tazobactam on Pseudo monkeys aeruginosa intrahospitalaria

El objetivo del presente estudio ha sido identificar y clasificarlos antibiofenotipos de resistencia a los betalactámicos presentes en las cepas de Pseudomonas aeruginosa, aisladas en el Hospital Arzobispo Loayza y evaluar la actividad in vitro frente a estas cepas intrahospitalarias de tres betalactámicos anti-piociánicos y de la asociación de uno de ellos con inhibidor de betalactamasas. Se estudiaron 70 cepas no repetitivas de Pseudomonas aeruginosa aisladas a partir de muestras clínicas de pacientes hospitalizados por no menos de 72 horas. Se realizaron antibiogramas por difusión en agar (método de Kirby-Bauer modificado) y se determinaron las concentraciones inhibitorias mínimas (MIC) mediante la técnica del E-test. Finalmente se identificaron y clasificaron los antibiofenotipos de Pseudomonas aeruginosa para los betalactámicos. Los resultados muestran que en 41.4% de cepas de Pseudomonas aeruginosa fue sensible a la Ticarcilina, mientras que el 60% de las cepas fueron sensibles a la Piperacilina (sola y en asociación con el Tazobactam). La Ceftazidima tuvo una actividad superior a la Ticarcilina y a la Piperacilina (70.4% de cepas sensibles). En conclusión, los porcentajes de resistencia encontrados para Ceftazidima, Ticarcilina, Piperacilina y Piperacilina + Tazobactam, invalidan el uso de estas moléculas en el tratamiento probabilístico de una infección a Pseudomonas aeruginosa. Sin embargo, una recupración parcial de los niveles de sensibilidad es posible para la Ceftazidima mediante la aplicación de ciertas restricciones.

The objetive of this study has been to identify and to classity the antibiophenotypes of resistence to the betalacams in the Pseudomonas aeruginosa strains isolated in the Hospital Arzobispo Loayza of Lima and to evaluate the in vitro activity of these nosocomial strains agaist three antiPsedudomonas betalactams and the association of one of these with an inhibitor of betalactamase. Seventy non-repetitious strains of Pseudomonas aeruginosa isolated from samples of patients hospitalized by not less than 72 hours were studies. The used antibiograms were diffusion in agar (Kirby Bauer's method) and the minimal inhibitory concentration (MIC) were determined throught the technique of the E-test. Finally, the antibiophenotypes of Pseudomonas aeruginosa for the betalactams were and classified. The results show that 41.1% of strains of Pseudomonas aeruginosa was sensitive to Ticarcilin, while 605 of the strains was sensitive to Piperacilin (alone and in association with Tazobactam). Ceftazidime had a higher activity than Ticarcilin and Piperacilin (70.4% of the sensitive strains). In conclusion, the percentages of resistance found for Ceftazidime, Ticarcilin, Piperacilin and Piperacilin + Tazobactam invalidate the use of these antibioics in the probabilistic treatment of an infection due to Pseudomonas aeruginosa. However, a partial recovery of the sensitivity levels is possible for Ceftazidime through the application of certain restrictions.

Microbiología de las neumonías intrahospitalarias y su impacto en el uso empírico de los antibióticos / Microbiology of neumonias intrahospitable and its impact in the empirico use of the antibioticos

A pesar de los grandes avances diagnósticos y terapéuticos en Infectología, la neumonía intrahospitalaria (NIH) continua siendo la principal causa de muerte por infección adquirida en el hospital, especialmente en los pacientes sometidos a ventilación mecánica asistida. Aún cuando la experiencia clínica acumulada es considerable no existe un verdadero consenso sobre los métodos diagnósticos ideales y las estrategias terapéuticas más adecuadas. Este artículo es una revisión actualizada de la información nacional e internacional sobre la epidemiología, fisiopatología y diagnóstico de la NIH con un especial énfasis en la bacteriología y la formulación de propuestas de tratamientos empíricos que permitan un acercamiento inicial seguro y eficaz para este problema.

Sensibilidad bacteriana a las cefalosporinas de tercera y cuarta generación en diferentes áreas hospitalarias: estudio multicéntrico / Study multicéntric: bacterial sensitivity to third and fourth generation cephalosporins in differents areas hospitable

Se presenta un estudio prospectivo de corte transversal, de vigilancia epidemiológica, para determinar la sensibilidad bacteriana, por Servicio Hospitalario, a cefalosporinas de tercera y cuarta generación (ceftriaxona, cefotaxina, ceftazidima, cefoperazona y cefepime) mediante la prueba de disco de Kirby Bauer. Se incluyeron muestras bacteriológicas de 13 centros: 10 de Lima, dos de Arequipa y uno de Chiclayo. La sensibilidad más alta de Staphylococcus aureus se encontró en los servicios ambulatorios (Consulta Externa y Urgencia), situación que disminuyó casi a la mitad en los servicios de hospitalización (Medicina Interna, Cirugía y Cuidados Críticos). La sensibilidad de E.coli no mostró variación entre los servicios, a excepción de ser de menor grado en la Unidad de Cuidados Críticos. Las cepas de klebsiella pneumoniae y Enterobacter aerogenes aisladas en Consulta Externa, mostraron ser más sensibles que las procedentes de áreas de hospitalización, sobre todo Medicina Interna y Cirugía. La sensibilidad de Pseudomonas aeruginosa fue más alta en las muestras obtenidas en los servicios ambulatorios. Klebsiella, Enterobacter y Pseudomonas fueron más sensibles a cefepime que a ceftazidima. Se concluye que, según el Servicio de referencia de la muestra, hay variación en la sensibilidad bacteriana a cefalosporinas de tercera y cuarta generación