Actividad in-vitro de fosfomicina, sola o en combinaciones, frente a aislamientos clínicos de Pseudomonas aeruginosa resistentes a carbapenémicos / In vitro activity of fosfomycin, alone or in combination, against clinical isolates of carbapenem resistant Pseudomonas aeruginosa

INTRODUCCIÓN: En la actualidad asistimos a un progresivo aumento de aislamientos de microorganismos con patrones de multirresistencia y aun de panresistencia. Fosfomicina (FO) es un antimicrobiano activo frente a una gran variedad de microorganismos, incluyendo cepas de Pseudomonas aeruginosa (P. aeruginosa), que es susceptible de actuar sinérgicamente con otras moléculas. MÉTODOS: El objetivo de este estudio consiste en evaluar la actividad in-vitro de FO frente a 120 cepas de P. aeruginosa resistentes a carbapenémicos, utilizando un método de dilución en agar y otro de difusión en gradiente y, además, explorar, mediante el método de E-test y curvas de muerte, la posible sinergia de FO/amikacina y FO/ciprofloxacino, asociaciones potencialmente eficaces frente a P. aeruginosa resistentes a carbapenémicos. RESULTADOS: Para FO, partiendo de los valores de corte epidemiológicos (ECOFF) que publica European Committee on Antimicrobial Susceptibility Testing (EUCAST), más de las 3 cuartas partes de las cepas serían susceptibles de poder ser tratadas con este antimicrobiano, especialmente en combinación con otro agente. La asociación FO/ciprofloxacino presentó un efecto sinérgico en casi la mitad de los aislamientos (40%), mientras que la asociación FO/amikacina solo alcanzó este efecto sinérgico en el 12% de los casos. CONCLUSIÓN: La aparición de cepas de P. aeruginosa resistentes a carbapenémicos hace necesaria la valoración de tratamientos combinados. Este trabajo sugiere que la combinación FO/ciprofloxacino puede ser útil, presentando un efecto sinérgico en el 40% de los aislamientos estudiados

INTRODUCTION: The increase in microorganisms showing patterns of multi-drug resistance or even pan-drug resistance is of growing concern. Fosfomycin (FO) is well known to be active against a wide variety of microorganisms, including highly resistant strains of Pseudomonas aeruginosa (P. aeruginosa), and can also synergistically act with other molecules. METHODS: This study examines the in vitro activity shown by FO against 120 strains of carbapenem-resistant P. aeruginosa using an agar dilution and a gradient diffusion test. Possible synergistic effects of the combinations of FO/amikacin and FO/ciprofloxacin were also examined using E-test and time-kill techniques. RESULTS: According to the epidemiological cut-off value (ECOFF) issued by the European Committee on Antimicrobial Susceptibility Testing (EUCAST), our results indicate that over three-quarters of the strains tested would be susceptible to FO treatment, especially if combined with another antimicrobial. The FO/ciprofloxacin combination had a synergistic effect on 40% of the clinical isolates, while for FO/amikacin this effect was only observed in 12% of the isolates. CONCLUSION: The appearance of carbapenem-resistant P. aeruginosa strains requires the evaluation by combination therapy. This report suggests that the FO/ciprofloxacin combination can be useful, showing a synergistic effect in 40% of the isolates

[In vitro activity of fosfomycin, alone or in combination, against clinical isolates of carbapenem resistant Pseudomonas aeruginosa]. / Actividad in-vitro de fosfomicina, sola o en combinaciones, frente a aislamientos clínicos de Pseudomonas aeruginosa resistentes a carbapenémicos.

INTRODUCTION: The increase in microorganisms showing patterns of multi-drug resistance or even pan-drug resistance is of growing concern. Fosfomycin (FO) is well known to be active against a wide variety of microorganisms, including highly resistant strains of Pseudomonas aeruginosa (P. aeruginosa), and can also synergistically act with other molecules. METHODS: This study examines the in vitro activity shown by FO against 120 strains of carbapenem-resistant P. aeruginosa using an agar dilution and a gradient diffusion test. Possible synergistic effects of the combinations of FO/amikacin and FO/ciprofloxacin were also examined using E-test and time-kill techniques. RESULTS: According to the epidemiological cut-off value (ECOFF) issued by the European Committee on Antimicrobial Susceptibility Testing (EUCAST), our results indicate that over three-quarters of the strains tested would be susceptible to FO treatment, especially if combined with another antimicrobial. The FO/ciprofloxacin combination had a synergistic effect on 40% of the clinical isolates, while for FO/amikacin this effect was only observed in 12% of the isolates. CONCLUSION: The appearance of carbapenem-resistant P. aeruginosa strains requires the evaluation by combination therapy. This report suggests that the FO/ciprofloxacin combination can be useful, showing a synergistic effect in 40% of the isolates.

Primer aislamiento de Corynebacterium mucifaciens en una úlcera corneal / First case of a corneal ulcer associated with Corynebacterium mucifaciens

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Identification of clinical yeasts by Vitek MS system compared with API ID 32 C.

We performed a clinical evaluation of the Vitek MS matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) system with the commercial database version 2.0 for rapid identification of medically important yeasts as compared with the conventional phenotypic method API ID 32 C. We tested 161 clinical isolates, nine isolates from culture collections and five reference strains. In case of discrepant results or no identification with one or both methods, molecular identification techniques were employed. Concordance between both methods was observed with 160/175 isolates (91.42%) and misidentifications by both systems occurred only when taxa were not included in the respective databases, i.e., one isolate of Candida etchellsii was identified as C. globosa by Vitek MS and two isolates of C. orthopsilosis were identified as C. parapsilosis by API ID 32 C. Vitek MS could not identify nine strains (5.14%) and API ID 32 C did not identify 13 (7.42%). Vitek MS was more reliable than API ID 32 C and reduced the time required for the identification of clinical isolates to only a few minutes.

Staphylococcus coagulasa negativos resistentes al linezolid: características fenotípicas, genotípicas y sensibilidad a combinaciones de antibióticos / Linezolid resistant coagulase-negative Staphylococcus: Phenotypical and genotypical characteristics and sensitivity to antibiotic combinations

Objetivo Recuperamos 22 aislados de estafilococos coagulasa negativos resistentes al linezolid de nuestro hospital para su identificación, sensibilidad, perfil epidemiológico, mecanismos de la resistencia al linezolid y posibles combinaciones antibióticas sinérgicas. Métodos La identificación de los aislados fue realizada mediante espectrometría de masas (Vitek-MS, BioMérieux). La sensibilidad se realizó con el sistema Vitek-2 (bioMérieux) y el método de microdilución en caldo según las recomendaciones del CLSI. Se realizó electroforesis en gel de campo pulsado (PFGE) para estudiar la relación genética de los aislados. Los mecanismos de la resistencia al linezolid fueron evaluados por PCR/secuenciación: presencia del gen cfr, mutaciones puntuales en el dominio V del ARN ribosomal 23S y mutaciones ribosomales adicionales (en los genes rplC, rplD y rplV). La actividad in vitro del linezolid fue estudiada por separado y en combinación con otros 3 antibióticos utilizando tiras de E-test. Resultados Veinte aislados fueron identificados como Staphylococcus epidermidis y 2 como Staphylococcus hominis. La PFGE demostró que los aislados pertenecían a diferentes clones: 21 de los aislados presentaron mutaciones en la región del dominio V del ARNr 23S y en el 54,5% fue encontrado el gen cfr. La administración previa de linezolid fue documentada en la mayor parte de casos. El linezolid en combinación con gentamicina mostró una actividad sinérgica en el 45,5% de los aislados. Conclusiones Staphylococcus epidermidis fue la especie de estafilococos coagulasa negativos resistentes al linezolid más frecuentes. Los valores de CMI fueron además elevados para otros antiestafilocócicos. Todas las cepas presentaron varios mecanismos de resistencia al linezolid. Nuestros datos sugieren que linezolid más gentamicina podría ser una combinación sinérgica frente a los estafilococos coagulasa negativos resistentes al linezolid(AU)

Objective We recovered 22 coagulase-negative staphylococci isolates in our hospital to study their identity, susceptibility, epidemiological profile, linezolid resistance mechanisms, and the possibilities of different antibiotic combinations. Methods Isolate identification was performed using mass spectrometry (Vitek-MS, bioMérieux). Susceptibility testing was carried out with the Vitek-2 system and the broth microdilution method according to CLSI guidelines. Pulsed-field gel electrophoresis (PFGE) was performed to analyze the genetic relationship between isolates. Linezolid resistance mechanisms were evaluated by PCR/sequencing: presence of cfr gene, point mutations in domain V of 23S ribosomal RNA and additional ribosomal mutations (in the rplC, rplD and rplV genes). The in vitro activity of linezolid was investigated alone and in combination with another three antibiotics acting on different cellular targets, using E-test strips. Results Twenty isolates were identified as Staphylococcus epidermidis, and 2 as Staphylococcus hominis. PFGE showed that isolates belonged to diverse clones, 21 of them presented mutations in the domain V region of 23S rRNA and the cfr gene was found in 54.5%. Prior administration of linezolid was documented in most of cases. Linezolid in combination with gentamicin showed a synergistic activity in 45.5% of isolates. Conclusions Staphylococcus epidermidis was the most prevalent linezolid-resistant coagulase-negative staphylococci. All isolates showed increased MIC values compared to other anti-staphylococcal drugs and several linezolid resistance mechanisms. Our data suggest that linezolid plus gentamicin could be a synergistic combination against linezolid-resistant coagulase-negative staphylococci(AU)

[Accuracy of Etest method to study Campylobacter spp. susceptibility to erythromycin, ciprofloxacin and tetracycline]. / Precisión del método E-test para el estudio de la sensibilidad de Campylobacter spp. a eritromicina, ciprofloxacino y tetraciclina.

INTRODUCTION: In industrialized countries Campylobacter jejuni is the enteropathogen most frequently isolated from the feces of patients with gastroenteritis. The Etest accuracy to categorize Campylobacter spp. susceptibility to erythromycin, ciprofloxacin and tetracycline was evaluated. METHODS: Ninety strains were studied. The Etest® was performed following the manufacturer's instructions on commercial plates of Mueller-Hinton blood. The breakpoints were those recommended by the Clinical Laboratory Standards Institute (CLSI) for broth microdilution. The gold standard was the broth microdilution method as recommended by CLSI. RESULTS: The Etest agreement with the reference method was 100%, 97% and 98% for erythromycin, ciprofloxacin and tetracycline, respectively. No major or very major errors were found. CONCLUSIONS: The Etest results are equivalent to those obtained using the gold standard. The Etest is a valid method to determine susceptibility to tetracycline. It is also a suitable method to categorize strains classified as non-resistant to erythromycin and ciprofloxacin by the diffusion method.

Precisión del método E-test para el estudio de la sensibilidad de Campylobacter spp. a eritromicina, ciprofloxacino y tetraciclina / Accuracy of Etest method to study Campylobacter spp. susceptibility to erythromycin, ciprofloxacin and tetracycline

Introducción. En los países industrializados el enteropatógeno bacteriano más frecuentemente aislado de las heces de pacientes con gastroenteritis es Campylobacter jejuni. Evaluamos la precisión del Etest para categorizar la susceptibilidad de Campylobacter spp. frente a eritromicina, ciprofloxacino y tetraciclina. Métodos. Estudiamos 90 cepas. El Etest® se realizó en placas comerciales de Mueller Hinton con sangre siguiendo las instrucciones del fabricante. Los puntos de corte fueron los recomendados por el Clinical Laboratory Standards Institute (CLSI) para microdilución en caldo. El método de referencia fue el de microdilución en caldo descrito por el CLSI. Resultados. La concordancia del Etest con el método de referencia fue 100%, 97% y 98% para eritromicina, ciprofloxacino y tetraciclina respectivamente. No hubo errores graves ni muy graves. Conclusiones. Con Etest se obtienen resultados equivalentes a los del método de referencia por lo que es válido para categorizar las cepas clasificadas como no resistentes a eritromicina y ciprofloxacino mediante el método de difusión y determinar la susceptibilidad frente a tetraciclina(AU)

Introduction. In industrialized countries Campylobacter jejuni is the enteropathogen most frequently isolated from the feces of patients with gastroenteritis. The Etest accuracy to categorize Campylobacter spp. susceptibility to erythromycin, ciprofloxacin and tetracycline was evaluated. Methods. Ninety strains were studied. The Etest® was performed following the manufacturer’s instructions on commercial plates of Mueller-Hinton blood. The breakpoints were those recommended by the Clinical Laboratory Standards Institute (CLSI) for broth microdilution. The gold standard was the broth microdilution method as recommended by CLSI. Results. The Etest agreement with the reference method was 100%, 97% and 98% for erythromycin, ciprofloxacin and tetracycline, respectively. No major or very major errors were found. Conclusions. The Etest results are equivalent to those obtained using the gold standard. The Etest is a valid method to determine susceptibility to tetracycline. It is also a suitable method to categorize strains classified as non-resistant to erythromycin and ciprofloxacin by the diffusion method(AU)

[Linezolid resistant coagulase-negative Staphylococcus: phenotypical and genotypical characteristics and sensitivity to antibiotic combinations]. / Staphylococcus coagulasa negativos resistentes al linezolid: características fenotípicas, genotípicas y sensibilidad a combinaciones de antibióticos.

OBJECTIVE: We recovered 22 coagulase-negative staphylococci isolates in our hospital to study their identity, susceptibility, epidemiological profile, linezolid resistance mechanisms, and the possibilities of different antibiotic combinations. METHODS: Isolate identification was performed using mass spectrometry (Vitek-MS, bioMérieux). Susceptibility testing was carried out with the Vitek-2 system and the broth microdilution method according to CLSI guidelines. Pulsed-field gel electrophoresis (PFGE) was performed to analyze the genetic relationship between isolates. Linezolid resistance mechanisms were evaluated by PCR/sequencing: presence of cfr gene, point mutations in domain V of 23S ribosomal RNA and additional ribosomal mutations (in the rplC, rplD and rplV genes). The in vitro activity of linezolid was investigated alone and in combination with another three antibiotics acting on different cellular targets, using E-test strips. RESULTS: Twenty isolates were identified as Staphylococcus epidermidis, and 2 as Staphylococcus hominis. PFGE showed that isolates belonged to diverse clones, 21 of them presented mutations in the domain V region of 23S rRNA and the cfr gene was found in 54.5%. Prior administration of linezolid was documented in most of cases. Linezolid in combination with gentamicin showed a synergistic activity in 45.5% of isolates. CONCLUSIONS: Staphylococcus epidermidis was the most prevalent linezolid-resistant coagulase-negative staphylococci. All isolates showed increased MIC values compared to other anti-staphylococcal drugs and several linezolid resistance mechanisms. Our data suggest that linezolid plus gentamicin could be a synergistic combination against linezolid-resistant coagulase-negative staphylococci.