Prevalencia y caracterización genotípica de cepas de Staphylococcus aureus resistente a meticilina aisladas en un hospital regional mexicano / Prevalence and genotypic characterization of methicillin-resistant strains of Staphylococcus aureus isolated in a Mexican regional hospital

Resumen Introducción: Staphylococcus aureus es uno de los patógenos con mayor prevalencia en el mundo, asociado a una alta tasa de mortalidad y un rápido desarrollo de resistencia a los antimicrobianos. A pesar de su patogenicidad, su seguimiento epidemiológico en México es escaso. Objetivo: Analizar la epidemiología molecular local y determinar el origen clonal de cepas resistentes a meticilina (RM) aisladas de pacientes internados en el Hospital Central "Dr. Ignacio Morones Prieto". Métodos: Se llevó a cabo un estudio prospectivo de corte transversal, de julio a diciembre de 2016. La caracterización de las cepas se realizó mediante genotipificación Spa, la determinación por RPC punto final de la frecuencia de genes de virulencia específicos y su antibiograma. Resultados: A partir de estos datos, se obtuvo que la prevalencia de S. aureus RM fue de 25,7%, destacando la presencia del tipo Spa t895 en 76% de las cepas resistentes y un patrón similar de susceptibilidad a antimicrobianos. Conclusión: Los resultados de este estudio indican que la prevalencia regional de SARM no se ha modificado en los últimos 10 años y proporcionan información valiosa del origen clonal y los factores de virulencia de las cepas de S. aureus aisladas en la región.

Abstract Background: Staphylococcus aureus is one of most prevalent pathogens in the world associated with a high mortality rate and a rapid development of resistance to antibiotics. Despite its pathogenicity, epidemiological monitoring in Mexico is scarce. Aim: To analyze the local molecular epidemiology and determine the clonal origin of methicillin-resistant (MR) strains isolated from patients admitted to Hospital "Dr. Ignacio Morones Prieto". Methods: A cross-sectional prospective study was carried out from July to December 2016. The characterization of the strains was carried out by Spa genotyping, frequency of specific virulence genes by PCR and antibiogram. Results: The prevalence of MRSA was 25.7%, highlighting the presence of the Spa type t895 in 76% of the resistant strains and a similar pattern of susceptibility to antibiotics. Conclusion: The results of this study indicate that the regional prevalence of MRSA has not changed in the last 10 years and provide valuable information on the clonal origin and the virulence factors of the strains of S. aureus isolated in the region.

Farmacocinética poblacional de carbamacepina en pacientes epilépticos adultos / Population pharmacokinetics of carbamazepine in adults with epilepsy

The aim of the present study was to determinate the factors affecting carbamazepine (CBZ) clearance (CL) in adults with epilepsy using a mixed-effect model and sparse data collected during routine clinical care. The patient population comprised 104 adults receiving CBZ. A total of 161 CBZ steady state serum concentration samples were analyzed. Population CL was calculated by using NONMEM with a one compartment model with first-order absorption and elimination. The following covariates were tested for their influence on clearance (CL): total body weight, age, dose/day, sex, surface area (SA) and comedication with primidone (PRIM), valproic acid or phenytoin (DFH). The final regression model for carbamazepine clearance found best to describe the data was: CL = (0.614 SA + 0.0016 dose/day)(1 + 0.278 DFH)(1 + 0.326 PRIM).

El objetivo de este trabajo es determinar los factores que influyen en el aclaramiento (CL) de carbamacepina (CBZ) en pacientes epilépticos adultos usando un modelo de efectos mixtos y datos de concentraciones séricas de CBZ generados del cuidado rutinario de los pacientes. El número de pacientes incluidos en el estudio fue de 104. Se analizaron un total de 161 concentraciones séricas de CBZ en el estado estacionario. El aclaramiento poblacional se determinó con el programa NONMEM aplicando un modelo monocompartimental con absorción y eliminación de primer orden. Se analizó la influencia de las siguientes covariables sobre el CL: peso corporal total, edad, dosis/día, sexo, superficie corporal (SC) y la comedicación con primidona (PRIM), ácido valproico o difenilhidantoína (DFH). El modelo final de regresión obtenido es el siguiente: CL = (0.614 SC + 0.0016 dosis/día)( 1+ 0.278 DFH)(1 + 0.326 PRIM).

Bioavailability of etoposide after oral administration of the solution marketed for intravenous use: Therapeutic and pharmacoeconomic perspectives

Background. Oral etoposide administration is a suitable alternative to the intravenous route; therefore, commercial capsules have been developed. Before these capsules were available in Mexico, we studied drug bioavailability after oral administration of the intravenous etoposide solution (IVES). Methods. Eight adult cancer patients received a 50-mg oral etoposide dose as IVES and blood samples were collected over a period of 24 h. plasma etoposide concentration was determined by high-performance liquid chromatography, plasma concentration against time curves were constructed, and biovailability parameters were calculated. Results. Oral IVES yielded an adequate bioavailability profile because Cmax was 2.38 ñ 0.30 µg/mL, AUC was 12.87 ñ 2.02 µg/mL and half-life was 6.72 ñ 0.97 h. Conclusions. Considering that the pharmacokinetic aim is to maintain plasm concentrations between 0.5 and 1.0 µg/mL for several hours while avioding high concentrations, i.e., of 10 µg/mL or higher, oral administration of 50-mg etoposide as IVES appears to be a suitable dosing option. In addition, oral IVES is considerably less expensive than intravenous administration in terms of both drug presentation and administration

Pharmacokinetics of oral ranitidine in Mexicans

The pharmacokinetics of oral ranitidine were studied in 24 Mexican male healthy volunteers. Subjects received a tablet containing 150 mg of ranitidine (Azantac TM, Glaxo de Mexico, Mexico, City) after an overnight fast and blood samples were drawn at several times for a period of 24 h. Ranitidine concentration in plasma was measured by high performance liquid chromatography and pharmacokinetic parameters were determined by non-compartmental analysis. Ranitide plasma concentration increased with time, reaching a maximum of (mean ñ SEM) 484 ñ 34 ng/ml in 2.7 ñ 0.2 h. Plasma levels then decayed with a terminal half-life of 4.8 ñ 0.3 h. The area under the plasma concentration against time curve was 2440 ñ 126 ngh/ml. Oral ranitidine pharmacokinetic parameters in mexicans appeared to be similar to those previously reported for caucasians

Comparison between sprague-dawley and wistar rats as an experimental model of pharmacokinetic alterations induced by spinal cord injury

Two strains of rats, Sprague-Dawley and Wistar, were assayed in order to determine which strain is the more suitable experimental model for the study of pharmacokinetic alterations inuced by spinal cord injury. Animals were submitted to spinal cord contusion at the T8-T9 level by the weight drop method. A single acetaminophen oral dose (100 mg/kg) was administered 24 h after injury and blood samples were drawn for a period of 4 h. Acetaminophen concentration in whole blood was determined by high performance liquid chromatography and pharmacokinetic parameters were estimated. For both strains, Cmax and AUC were significantly lower, whereas tmax remained uchanged, in injured animals compared to sham-injured controls. Circulating acetaminophen concentrations were higher; therefore, pharmacokinetic alterations were more easily discerned, in Sprague-Dawley than in Wistar rats. It is concluded that the Sprague-Dawley strain is a more suitable model for the study of pharmacokinetic alternations induced by spinal cord injury