[Efficiency of the allergological study in the diagnosis of allergic reactions to beta-lactams]. / Eficiencia del estudio alergológico en el diagnóstico de reacciones a ß-lactámicos.

AIMS: Assessing the rate of ß-lactams-allergic patients who are still labelled as such in their medical records after being performed an allergic test; as well as the rate of no allergic patients who were prescribed one of these antibiotics; and pondering whether the allergic test is hence cost-effective. METHODS: This is a retrospective study developed from 2019 to 2021 focusing on patients suspected of ß-lactams allergy (n=688). By means of an allergy test, it was cleared out if they were actually allergic. Later, we checked if the patient was still labelled as allergic in their medical record. Tracking through the digital health services card, we followed up if the antibiotic was ever prescribed again, and if the drug was then dispensed to the patient. RESULTS: 11.3% of the patients showed hypersensitivity to ß-lactams. Nonetheless, 33.1% of the patients were still considered allergic to these antibiotics in their medical record even though not being such. 32% of the patients - who had their allergy confirmed - had been labelled without the general practitioner's acknowledgment, and 32.8% had even been prescribed a ß-lactam again. CONCLUSIONS: Discarding any allergy to ß-lactams is as important as registering the allergy on medical records after testing the patient. A remarkable quantity of non-allergic patients is still addressed as actual allergic, in spite not being such. Labelling patients as ß-lactams allergic may have consequences, short-term and long-term, for the patient but also for the health service budget.

Beta-lactam antibiotics and viridans group streptococci.

The aim of this review is to present an update on the susceptibility of viridans group streptococci (VGS) to ß-lactam antimicrobials, with emphasis on the Argentinean scenario. VGS are a heterogeneous group including five groups of species, each one exhibiting peculiar susceptibility patterns to penicillin (PEN). Species of the Streptococcus mitis group are frequently nonsusceptible to PEN. PEN resistance is associated with changes in PEN-binding proteins. In Argentina, one to two thirds of VGS are nonsusceptible to PEN. Third generation cephalosporins and carbapenems are currently more effective in vitro than PEN against VGS. Mortality was associated to nonsusceptibility to PEN in at least two studies involving patients with bacteremia caused by VGS. Treatment of endocarditis due to VGS should be adjusted/to the PEN susceptibility of the isolates. Vancomycin may be an alternative choice for treating endocarditis caused by PEN-resistant isolates (MIC≥4µg/ml).

Resistance to ß-lactams in Streptococcus pneumoniae.

Streptococcus pneumoniae is an important causal agent of pneumonia, meningitis, sepsis, bacteremia, and otitis media. Penicillin resistance rates in S. pneumoniae have remained stable in Argentina in the last years. In the late '90s more isolates with MIC of penicillin ≥2µg/ml were observed; however, their frequency has decreased in recent years. The phenotypic expression of penicillin resistance is due to a modification in penicillin-binding proteins associated with a mosaic structure in the coding genes. The expansion of successful resistant clones varies among the different regions and is influenced by the use of antibiotics, vaccines, particularly conjugated ones, as well as population density. Parenteral treatment with high doses of penicillin G continues to be effective for the treatment of pneumonia and bacteremia, oral aminopenicillins for otitis media and sinusitis and third generation cephalosporins for meningitis.

Caracterización de bacilos gramnegativos multi-resistentes, aislados en pacientes hospitalizados en instituciones de salud de Barranquilla (Colombia) / Characterization of multiresistant gram-negative bacilli, isolated in patients hospitalized in health institutions in Barranquilla (Colombia)

Resumen Introducción: La resistencia a carbapenémicos en bacilos gramnegativos es un problema de salud pública mundial, debido a que se asocia con altas tasas de mortalidad, aumento en los niveles de resistencia a otros antimicrobianos, elevación en el potencial de diseminación e incremento en los costos de atención en salud. Objetivo: Caracterizar bacilos gramnegativos multirresistentes, aislados en pacientes hospitalizados en instituciones de salud de Barranquilla (Colombia). Material y Métodos: Estudio descriptivo acerca de la caracterización fenotípica y genotípica de la resistencia bacteriana en las infecciones asociadas a la atención en salud, mediada por carbapenemasas en aislados bacterianos enviados por los laboratorios pertenecientes a la red de laboratorios del Departamento del Atlántico. Resultados: La KPC fue la carbapenemasa más frecuente en las Enterobacterales (27,6%), predominando en Klebsiella pneumoniae (13,1%) sola y asociada a otras carbapenemasas. En Pseudomonas aeruginosa predominó la carbapenemasa VIM (32,8%) y la OXA en Acinetobacter baumannii (17,1%). Conclusión: Se encontró una amplia distribución de cepas multi-resistentes productoras de carbapenemasas en instituciones de salud de Barranquilla, las cuales expresaron los siguientes mecanismos de resistencia: KPC, VIM, NDM, OXA.

Abstract Background: The emergence of carbapenem resistant gramnegative bacilli has become a problem of public health worldwide, because it is associated with high mortality rates, increased levels of resistance to other antimicrobials, increased potential for dissemination transition and increase in health care costs. Aim: To characterize multiresistant gram-negative bacilli, isolated in patients hospitalized in health institutions of Barranquilla (Colombia). Methods: A descriptive study was conducted on the phenotypic and genotypic characterization of bacterial resistance in infections associated with health care, mediated by carbapenemases in bacterial isolates sent by laboratories belonging to the laboratory network of the Department of Atlántico. Results: KPC was the most frequent carbapenemase in Enterobacterales (27.6%), predominantly in Klebsiella pneumoniae (13.1%) alone and associated with other carbapenemases. In Pseudomonas aeruginosa, VIM carbapenemase (32.8%) predominated and OXA in Acinetobacter baumannii (17.1%). Conclusion: A wide distribution of multi-resistant strains producing carbapenemases in Atlantic health institutions was found, which expressed the following resistance mechanisms: KPC, VIM, NDM, OXA.

Resistencia enzimática en Pseudomonas aeruginosa, aspectos clínicos y de laboratorio / Enzymatic resistance in Pseudomonas aeruginosa, clinical and laboratory aspects

Resumen Pseudomonas aeruginosa es uno de los principales patógenos que causa infecciones asociadas a la atención en salud (IAAS). Su capacidad de adaptación, diseminación, resistencia intrínseca a los antimicrobianos y de adquirir nuevos mecanismos a través de elementos genéticos móviles, hacen que el tratamiento de las infecciones por este microorganismo sea un desafío para el médico clínico. Intrínsecamente, P. aeruginosa, presenta una reducida permeabilidad en la membrana externa, debido a la expresión de bombas de expulsión, y una cefalosporinasa tipo AmpC inducible. Además, P. aeruginosa es capaz de adquirir nuevos determinantes de resistencia por transferencia horizontal en forma de casetes situados en integrones, y a su vez, localizados en transposones o plásmidos. Dentro de la resistencia enzimática que presenta P. aeruginosa destacan las β-lactamasas, incluyendo aquellas de espectro extendido (BLEE) y las carbapenemasas. Pero también enzimas modificadoras de los aminoglucósidos, haciendo que este microorganismo pueda presentar fenotipos de multi-resistencia (MDR), resistencia extrema (XDR) y panresistencia (PDR) a los antimicrobianos denominados antipseudomonas, incluyendo a las nuevas cefalosporinas con inhibidores de beta-lactamasas.

Abstract Pseudomonas aeruginosa is one of the major pathogens causing healthcare-associated infections (HAI). Its capacity of adaptation, dissemination, intrinsic resistance to antimicrobials and of acquiring new mechanisms through mobile genetic elements, make the treatment of infections by this microorganism a challenge for the clinician. Intrinsically, P. aeruginosa, presents a reduced permeability in the external membrane, due to the expression of efflux pumps, and an inducible AmpC-type cephalosporinase. In addition, P. aeruginosa is able to acquire new resistance determinants by horizontal transfer in the form of cassettes located in integrons, and in turn located in transposons or plasmids. Within the enzymatic resistance that P. aeruginosa presents, betalactamases, including extended spectrum (ESBL) and carbapenemases. But also aminoglycoside modifying enzymes, stand out, causing this microorganism to present multi-resistance phenotypes (MDR), extreme resistance (XDR) and pan-resistance (PDR) to the called antipseudomonal antibiotics, including the new cephalosporins with betalactamase inhibitors.

Desarrollo y validación de un modelo diagnóstico de resistencia antimicrobiana por beta-lactamasas de espectro extendido en infecciones urinarias adquiridas en la comunidad. ¿Cómo ajustar la predicción en prevalencias variables del desenlace? La utilidad de la contracción de predictores con regresión LASSO / Development and validation of a diagnostic model of antimicrobial resistance by extended-spectrum beta-lactamases in community-acquired urinary tract infections. How to adjust the prediction in variable outcome prevalences? The usefulness of contracting predictors with LASSO regression

INTRODUCCIÓN: Para el caso de infección urinaria adquirida en la comunidad la identificación de enterobacterias con beta-lactamasas de espectro extendido (BLEE) puede optimizar las estrategias de tratamiento, control y seguimiento; sin embargo, el efecto de prevalencias variables de este patrón de resistencia ha afectado la validez externa de este tipo de modelos. OBJETIVO: Desarrollar un modelo predictor diagnóstico que ajuste el error de predicción en prevalencias variables utilizando la regresión LASSO. MÉTODOS: Se diseñó un modelo predictor diagnóstico de infección urinaria adquirida en la comunidad por enterobacterias productoras de BLEE. Se empleó un estudio de corte transversal, tanto para la construcción como para la validación. Para evaluar el efecto de la prevalencia variable del desenlace, la validación se realizó con población en la que la proporción de aislados con este mecanismo de resistencia fue menor, los participantes fueron pacientes adultos que consultaron a servicios de urgencias de dos instituciones hospitalarias de mediano nivel de complejidad de la ciudad de Medellín. Para ajustar el efecto de un medio ambiente con menor proporción de resistencia antimicrobiana, utilizamos la contracción de predictores por regresión LASSO. RESULTADOS: Se incluyeron 303 pacientes para la construcción del modelo, se evaluaron seis predictores y la validación se realizó en 220 pacientes. CONCLUSIÓN: El modelo ajustado con regresión LASSO favoreció la validez externa del modelo en poblaciones con proporción de aislados productores de BLEE en urocultivo de pacientes ambulatorio entre 11 y 16%. Este estudio brinda criterios para un aislamiento temprano cuando los predictores están presentes en poblaciones con proporciones de resistencia en urocultivos ambulatorios cercanas a 15% y propone una metodología para ajuste de error en el diseño de modelos de predicción en resistencia antimicrobiana

BACKGROUND: In the case of community-acquired urinary tract infection, the identification of Enterobacteriaceae with extended spectrum beta-lactamases (ESBL) can optimize treatment, control and follow-up strategies, however the effect of variable prevalences of this resistance pattern has affected the external validity of this type of models. AIM: To develop a diagnostic predictive model that adjusts the prediction error in variable prevalences using the LASSO regression. METHODS: A diagnostic predictive model of community-acquired urinary tract infection by infection by ESBL producing Enterobacteriaceae was designed. A cross-sectional study was used for both construction and validation. To assess the effect of the variable prevalence of the outcome, the validation was performed with a population in which the proportion of isolates with this resistance mechanism was lower, the participants were adult patients who consulted the emergency services of two medium-level hospital institutions. complexity of the city of Medellin. To adjust for the effect of an environment with a lower proportion of antimicrobial resistance, we used the contraction of predictors by LASSO regression. RESULTS: 303 patients were included for the construction of the model, six predictors were evaluated and validation was carried out in 220 patients. CONCLUSION: The adjusted model with LASSO regression favored the external validity of the model in populations with a proportion of ESBL producing isolates in urine culture of outpatients between 11 and 16%. This study provides criteria for early isolation when predictors are present in populations with proportions of resistance in ambulatory urine cultures close to 15% and proposes a methodology for the adjustment of errors in the design of prediction models for antimicrobial resistance.

Resistance to ß-lactams in enterococci.

Enterococci are intrinsically resistant to several antimicrobial classes and show a great ability to acquire new mechanisms of resistance. Resistance to ß-lactam antibiotics is a major concern because these drugs either alone or in combination are commonly used for the treatment of enterococcal infections. Ampicillin resistance, which is rare in Enterococcus faecalis, occurs in most of the hospital-associated Enterococcus faecium isolates. High-level resistance to ampicillin in E. faecium is mainly due to the enhanced production of PBP5 and/or by polymorphisms in the beta subunit of this protein. The dissemination of high-level ampicillin resistance can be the result of both clonal spread of strains with mutated pbp5 genes and horizontal gene transfer.

Sensibilización a los alérgenos de las penicilinas en pacientes que padecen enfermedades alérgicas / Sensitization to penicillin allergens in patients suffering from allergic diseases

Los antibióticos ß-lactámicos son los más utilizados, dada su eficacia para patógenos bacterianos comunes y su precio relativamente bajo. Para evaluar la sensibilización a los alérgenos mayores y menores de la penicilina en pacientes que padecen enfermedades alérgicas, se realizó un estudio observacional analítico de casos y controles, en el universo de 458 individuos derivados al Servicio de Alergia Previsora (Camagüey, Cuba), desde enero del 2010 hasta noviembre del 2016. Se seleccionó una muestra de 178 niños y adultos con el diagnóstico de asma, rinitis y urticaria de las edades 6 a 60 años. Los que tenían antecedentes, no confirmados, de alergia a penicilinas se consideraron casos (n=60) y los que no tenían el antecedente controles (n=118). Toda la muestra tenía pruebas de Prick positivas a uno o más de los ácaros domésticos Dermatophagoides pteronysinus, Dermatophagoides siboney y Blomia tropicalis, así como a algún alimento. Un grupo de ellos también resultaron positivos a PPL y MD. Se distribuyeron los pacientes en sensibilizados o no con los alérgenos PPL y MD. La prevalencia general de alergia a las penicilinas fue de 24,15 por ciento (15,7 por ciento en los casos y 8,9 por ciento en los controles). La prueba DAP® - Penicilinas mostró mayor número de positivos en los casos que en los controles (p=0,037, OR=5,21). Del total de alérgicos a las penicilinas, el mayor número de pacientes correspondieron al sexo femenino (p=0,031). El test cutáneo con alérgenos PPL y MD puede confirmar el diagnóstico de alergia a penicilinas en pacientes atópicos(AU)

ß-lactam antibiotics are the most widely used, given their efficacy for common bacterial pathogens and their relatively low price. To evaluate sensitization to major and minor allergens of penicillin in patients suffering from allergic diseases, an observational, analytical study of cases and controls was carried out in the universe of 458 individuals referred to the Previsora Allergy Service (Camagüey, Cuba) from January 2010 to November 2016. A sample of 178 children and adults aged 6 to 60 years diagnosed with asthma, rhinitis and urticarial was selected. Those who had a medical history, not confirmed, of allergy to penicillins were considered cases (n=60) and those who did not have the antecedent were the controls (n=118). All the sample had positive Prick tests to one or more of the house mites Dermatophagoides pteronysinus, Dermatophagoides siboney and Blomia tropicalis, as well as against some foods. Some individuals were also positive for PPL and MD. Patients were distributed in sensitized or not with the allergens PPL and MD. The general prevalence of allergy to penicillins was 24.15 percent (15.7 percent in cases and 8.9 percent in controls). The DAP® - Penicillins test showed a greater number of positives in cases than in controls (p=0.037; OR=5.21). The largest number of patients allergic to penicillins corresponded to the female sex (p=0.031). The skin test with allergens PPL and MD can confirm the diagnosis of allergy to penicillins in atopic patients(AU)

Susceptibility to ß-lactams in ß-hemolytic streptococci.

Group A (GAS), B (GBS), C (GCS) and G (GGS) ß-hemolytic streptococci are important human pathogens. They cause infections of different severity and frequency. Nowadays, after 70 years of use, penicillin is still universally active against GAS, GCS and GGS. However, therapeutic failures have been recorded in 2-28% of pharyngitis cases (median: 12%) attributable to different causes. By contrast, some GBS with reduced susceptibility to penicillin have been described, especially in Japan. In this group of bacteria, it is important to highlight that confirmation by reference methods is mandatory when decreased susceptibility to penicillin is suspected as well as checked for the detection of the mechanisms involved.

Sensibilización a los alérgenos de las penicilinas en pacientes que padecen enfermedades alérgicas / Sensitization to penicillin allergens in patients suffering from allergic diseases

Los antibióticos ß-lactámicos son los más utilizados, dada su eficacia para patógenos bacterianos comunes y su precio relativamente bajo. Para evaluar la sensibilización a los alérgenos mayores y menores de la penicilina en pacientes que padecen enfermedades alérgicas, se realizó un estudio observacional analítico de casos y controles, en el universo de 458 individuos derivados al Servicio de Alergia Previsora (Camagüey, Cuba), desde enero del 2010 hasta noviembre del 2016. Se seleccionó una muestra de 178 niños y adultos con el diagnóstico de asma, rinitis y urticaria de las edades 6 a 60 años. Los que tenían antecedentes, no confirmados, de alergia a penicilinas se consideraron casos (n=60) y los que no tenían el antecedente controles (n=118). Toda la muestra tenía pruebas de Prick positivas a uno o más de los ácaros domésticos Dermatophagoides pteronysinus, Dermatophagoides siboney y Blomia tropicalis, así como a algún alimento. Un grupo de ellos también resultaron positivos a PPL y MD. Se distribuyeron los pacientes en sensibilizados o no con los alérgenos PPL y MD. La prevalencia general de alergia a las penicilinas fue de 24,15 por ciento (15,7 por ciento en los casos y 8,9 por ciento en los controles). La prueba DAP® - Penicilinas mostró mayor número de positivos en los casos que en los controles (p=0,037, OR=5,21). Del total de alérgicos a las penicilinas, el mayor número de pacientes correspondieron al sexo femenino (p=0,031). El test cutáneo con alérgenos PPL y MD puede confirmar el diagnóstico de alergia a penicilinas en pacientes atópicos(AU)

ß-lactam antibiotics are the most widely used, given their efficacy for common bacterial pathogens and their relatively low price. To evaluate sensitization to major and minor allergens of penicillin in patients suffering from allergic diseases, an observational, analytical study of cases and controls was carried out in the universe of 458 individuals referred to the Previsora Allergy Service (Camagüey, Cuba) from January 2010 to November 2016. A sample of 178 children and adults aged 6 to 60 years diagnosed with asthma, rhinitis and urticarial was selected. Those who had a medical history, not confirmed, of allergy to penicillins were considered cases (n=60) and those who did not have the antecedent were the controls (n=118). All the sample had positive Prick tests to one or more of the house mites Dermatophagoides pteronysinus, Dermatophagoides siboney and Blomia tropicalis, as well as against some foods. Some individuals were also positive for PPL and MD. Patients were distributed in sensitized or not with the allergens PPL and MD. The general prevalence of allergy to penicillins was 24.15 percent (15.7 percent in cases and 8.9 percent in controls). The DAP® - Penicillins test showed a greater number of positives in cases than in controls (p=0.037; OR=5.21). The largest number of patients allergic to penicillins corresponded to the female sex (p=0.031). The skin test with allergens PPL and MD can confirm the diagnosis of allergy to penicillins in atopic patients(AU)

[Pneumococcal meningitis in children under 15 years of age in Misiones (Argentina). Sixteen year's epidemiological surveillance]. / Meningitis neumocócica en niños menores de 15 años. Dieciséis años de vigilancia epidemiológica en Misiones, Argentina.

We report the results of pneumococcal meningitis surveillance conducted at the Provincial Pediatric Hospital of Posadas, Misiones (Argentina), before the conjugate vaccine was introduced into the national vaccination schedule. Between January 1994 and December 2009, 167 cases of Streptococcus pneumoniae meningitis were diagnosed in children aged 1 month to 15 years. The attack rate/100,000 children ranged from 19.2 (1997) to 4.3 (2009), with a mean of 10.6 and a tendency to decrease (y=-0.689x+16.52). The number of cases per 100,000 children decreased from 146.6 to 34.8 and particularly involved the group of children aged 1 to 11 months (94/167, 56%). Thirty point seven percent (30.7%) (46/150) of the isolates were resistant to penicillin whereas 16.7% (25/150) were non-susceptible to cefotaxime. ß-lactam resistance increased as from 1997 and began to decline in 2005. Nineteen serotypes were detected; type 14 was predominant and accounted for 32% (40/125). Eighty four point eight percent (84.8%) of the isolates were circumscribed to nine serotypes: 14, 5, 1, 7F, 18C, 6B, 9N, 9V and 4. Theoretical coverage for patients aged <2 years and >2 years was 84.1% (74/88) and 83.8% (31/37) for the 10-valent vaccine and 89.8 % (79/88) and 83.8% (31/37) for the 13-valent vaccine respectively. Penicillin resistance was restricted to 8 serotypes (14, 6B, 6A, 9V, 4, 23B, 19A1) and nonsusceptibility to cefotaxime was circumscribed to 3 serotypes (14, 9V and 1). This study will allow to evaluate the impact of the implementation of conjugate vaccines on our area.

[Beta-lactamic antibiotics allergy in cataract surgery. Prevalence and preoperative characteristics of allergic patients]. / Alergia a antibióticos ß-lactámicos en cirugía de cataratas. Prevalencia y características preoperatorias de los pacientes alérgicos.

OBJECTIVE: To describe the proportion of patients allergic to ß-lactam antibiotics and the prevalence of preoperative conjunctival bacteria among those undergoing cataract surgery in our area. METHOD: Retrospective cross-sectional study of prevalence of ß-lactam allergic patients consecutively scheduled for cataract surgery from 11 July 2005 to November 2012. For studying the prevalence of conjunctival bacteria and clinical characteristics in the patients' preoperative examination, those under 18 years and those with cataract surgery combined with other eye surgeries were excluded. Data from the first preoperative examination of the remaining patients were selected. Clinical data were extracted from the database generated in the evaluation made for anesthetic purposes, and the microbiological data from the laboratory database. Both bases were linked through a patient history code. A comparison was made between the prevalence of conjunctival bacteria and clinical characteristics in allergic and non-allergic patients. RESULTS: From 12,409 adults selected for the bacteriological study, 862 (6.96%) were allergic to ß-lactams, their mean age (74.45 years) was higher than that of the non-allergic (P=.005). The proportion of women (71.4%) in the allergic patient group was much higher than that of men. The prevalence of pathogenic bacteria (especially Bacillus spp and Pseudomonas aeruginosa), lung disease and heart failure, was higher in allergic patients. CONCLUSIONS: The prevalence of allergy to ß-lactams in this study is within the range described in other populations. The higher prevalence of pathogenic bacteria and the predominance of women in those allergic to ß-lactams are useful data to guide their surgical prophylaxis.

Antimicrobial Susceptibility to ß-lactams and Metronidazole of Microorganisms Isolated from Chronic and Aggressive Periodontitis / Susceptibilidad Antimicrobiana a ß-lactámicos y Metronidazol de Microorganismos Aislados de Periodontitis Crónica y Agresiva

The objective of this study was to evaluate the microbial susceptibility to ß-lactams and metronidazole, and evaluate the production of ß-lactamases by microorganisms isolated from patients with chronic or aggressive periodontitis. The samples were obtained from 50 patients with periodontitis and microorganisms were isolated onto selective and nonselective culture media, identified by biochemical methods and tested for susceptibility to antimicrobial agents (amoxicillin, amoxicillin/clavulanate, cefoxitin, imipenem, metronidazole, penicillin G). The isolates were resistant to at least 1 mg/ml of any drug tested were evaluated to verify the production of ß-lactamases by the method of double layer (or biological) and chromogenic cephalosporin using nitrocefin. The results evidenced resistance to amoxicillin and penicillin G, while the susceptibility to association amoxicillin/clavulanate, imipenem and cefoxitin was widely disseminated among the organisms. Resistance to these drugs showed a clear correlation with the production of ß-lactamase in the majority of microbial groups.

El objetivo fue evaluar la susceptibilidad a ß-lactámicos y metronidazol, y evaluar la producción de ß-lactamasas por microorganismos aislados de pacientes con periodontitis crónica y agresivo. Las muestras fueron obtenido de 50 pacientes con periodontitis y microorganismos aislados en medios de cultivo selectivos y no selectivos, identificados por métodos bioquímicos y probados a la susceptibilidad a los antimicrobianos (amoxicilina, amoxicilina/clavulanato, cefoxitina, imipenem, metronidazol, penicilina G). Los aislados fueron resistentes a por lo menos 1 mg/ml de cualquier drogas analizadas fueron evaluados para verificar la producción de ß-lactamasas por el método de doble capa (o biológico) y nitrocefina. Los resultados mostraron resistencia a amoxicilina y penicilina G, mientras la susceptibilidad a la asociación amoxicilina/ clavulanate, cefoxitina y imipenem fue ampliamente difundido entre los microrganismos. Resistencia a estas drogas mostraron una clara correlación con la producción de ß-lactamasas en la mayoría de grupos microbianos.

Mecanismo de resistencia a antibióticos ß-lactámicos en Staphylococcus aureus / Mechanisms of resistance to ß-lactam antibiotics in Staphylococcus aureus

S. aureus ha demostrado un gran poder de adaptación a los agentes antimicrobianos, adquiriendo paso a paso resistencia a todos los antibióticos disponibles para el tratamiento de las infecciones que ocasiona. Existen tres mecanismos de resistencia a los antibióticos ß-lactámicos en S. aureus: resistencia mediada por enzimas (penicilinasas o ß-lactamasas) las cuales desactivan al antibiótico; resistencia intrínseca, que no es debida a la inactivación de drogas y es responsable dela resistencia a meticilina; y la modificación de las proteínas de unión a penicilinas (PBPs). Además, S. aureus puede expresar el fenómeno de tolerancia, en el que ocurre una disociación de las acciones inhibitoria y bactericida de los antibióticos ß-lactámicos. De éstos, el mecanismo más importante, es la resistencia intrínseca que es probablemente más compleja, debido a que varios factores pueden afectar también su expresión

S. aureus has shown a great power of adaptation to antimicrobial agents, acquiring, step-bystep, resistance to all available antibiotics for treatment of the infections it causes. S. aureus has three major mechanisms of resistance to ß-lactam antibiotics: enzyme mediated (penicillinase or ß-lactamase) by which the antibiotic is inactivated; intrinsic resistance, which is not due to drug inactivation and accounts for methicillin resistance; and modifications of penicillin-binding proteins (PBPs). Additionally, S. aureus can express the tolerance phenomenon, in which there is a dissociation of the inhibitory and killing actions of ß-lactam antibiotics. Of these, the most important mechanism is intrinsic resistance, which is probably more complex because several factors can affect its expression