Resistencia emergente a la mupirocina en aislados de Staphylococcus aureus resistente a meticilina en un hospital pediátrico terciario en la Argentina / Emerging mupirocin resistance in methicillin-resistant Staphylococcus aureus isolates at a tertiary care children's hospital in Argentina

En América Latina, existen escasos estudios sobre la resistencia a mupirocina y producción de biofilm en Staphylococcus aureus resistente a la meticilina (SARM). En este trabajo, se investigó la resistencia a mupirocina en SARM aislados de pacientes pediátricos con bacteremia y su capacidad para producir biofilm. Se estudió la resistencia a antibióticos por Kirby-Bauer y microdilución en caldo. Se cuantificó el biofilm bacteriano por ensayo de cristal violeta. El 2,3 % (5/217) de los aislados de SARM presentaron un alto nivel de resistencia a mupirocina con una concentración inhibitoria mínima de >512 μ/ml, además de resistencia cruzada con clindamicina, eritromicina, gentamicina y ciprofloxacina. Notablemente, dichos aislados formaron biofilm en un nivel moderado-alto. Este primer reporte en Argentina de aislados clínicos de SARM resistentes a la mupirocina es clave para seguir su evolución en el tiempo a nivel local y en la región de América Latina.

In Latin America, few studies have been done in mupirocin resistance and biofilm formation in methicillin-resistant Staphylococcus aureus (MRSA). This study investigated mupirocin-resistance in MRSA isolates from pediatric patients with bacteremia and their ability to form biofilm. Antibiotic resistance was analyzed with the Kirby-Bauer test and the broth microdilution method. Bacterial biofilm formation was measured using the crystal violet assay. Among MRSA isolates, 2.3 % (5/217) exhibited a high level of mupirocin-resistance with a minimum inhibitory concentration of > 512 μg/mL, in addition to cross-resistance with clindamycin, erythromycin, gentamicin, and ciprofloxacin. Remarkably, biofilm formation in such isolates was moderate to high. This is the first report published in Argentina on clinical isolates of mupirocin-resistant MRSA and it is critical for following its evolution over time at a local level and in the Latin American region.

Emerging mupirocin resistance in methiciüin-resistant Staphylococcus aureus isolates at a tertiary care children's hospital in Argentina. / Resistencia emergente a la mupirocina en aislados de Staphylococcus aureus resistente a meticilina en un hospital pediátrico terciario en la Argentina.

In Latin America, few studies have been done in mupirocin resistance and biofilm formation in methicillin-resistant Staphylococcus aureus (MRSA). This study investigated mupirocin-resistance in MRSA isolates from pediatric patients with bacteremia and their ability to form biofilm. Antibiotic resistance was analyzed with the Kirby-Bauer test and the broth microdilution method. Bacterial biofilm formation was measured using the crystal violet assay. Among MRSA isolates, 2.3 % (5/217) exhibited a high level of mupirocin-resistance with a minimum inhibitory concentration of >512 µg/mL, in addition to cross-resistance with clindamycin, erythromycin, gentamicin, and ciprofloxacin. Remarkably, biofilm formation in such isolates was moderate to high. This is the first report published in Argentina on clinical isolates of mupirocin-resistant MRSA and it is critical for following its evolution over time at a local level and in the Latin American region.

En América Latina, existen escasos estudios sobre la resistencia a mupirocina y producción de biofilm en Staphylococcus aureus resistente a la meticilina (SARM). En este trabajo, se investigó la resistencia a mupirocina en SARM aislados de pacientes pediátricos con bacteremia y su capacidad para producir biofilm. Se estudió la resistencia a antibióticos por Kirby-Bauer y microdilución en caldo. Se cuantificó el biofilm bacteriano por ensayo de cristal violeta. El 2,3 % (5/217) de los aislados de SARM presentaron un alto nivel de resistencia a mupirocina con una concentración inhibitoria mínima de > 512 µ/ml, además de resistencia cruzada con clindamicina, eritromicina, gentamicina y ciprofloxacina. Notablemente, dichos aislados formaron biofilm en un nivel moderado-alto. Este primer reporte en Argentina de aislados clínicos de SARM resistentes a la mupirocina es clave para seguir su evolución en el tiempo a nivel local y en la región de América Latina.

Carnosic acid acts synergistically with gentamicin in killing methicillin-resistant Staphylococcus aureus clinical isolates.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is resistant to different commonly used antibiotics, stressing the need for further strategies to treat this human pathogen with worldwide prevalence. The use of phytochemicals within the current pharmacology is a promising approach to enhance the antimicrobial activity of common antibiotics in the battle against these bacteria. PURPOSE: The purpose of this study was to determine the antimicrobial effectiveness of carnosic acid, the major constituent of Rosmarinus officinalis L. leaves, in combination with gentamicin against multi-drug resistant MRSA clinical isolates obtained from pediatric patients with bacteremia. MATERIALS AND METHODS: Anti-MRSA activity was studied using the broth microdilution assay and time-kill method. Combinations of subinhibitory concentrations of carnosic acid and gentamicin were examined using the checkerboard method. RESULTS: Carnosic acid exhibited a good antibacterial activity against all multidrug-resistant MRSA clinical isolates tested, which are resistant to four up to nine antibiotics. In addition, the combination of carnosic acid with gentamicin not only decreased the minimal inhibitory concentration (MIC) of both by 4- to 5-fold, but also improved the bactericidal potency of the common antibiotic by 32- to 40-fold against both gentamicin-susceptible and gentamicin-resistant MRSA clinical isolates. A clear bactericidal synergistic activity between carnosic acid and gentamicin in killing multidrug-resistant MRSA clinical isolates with a fractional bactericidal concentration index (FBCI) of 0.28-0.35 was demonstrated. CONCLUSIONS: Our findings show the potential use of carnosic acid in combination with gentamicin as a promising alternative for the control of healthcare-associated infections caused by multidrug-resistant MRSA.

Trends in the resistance profiles of Acinetobacter baumannii endemic clones in a university hospital of Argentina.

A total of 925 Acinetobacter spp. isolates were collected from routine clinical samples of patients admitted to the university hospital of Buenos Aires city during the period 2004-2012. From this collection, 129 isolates identified as Acinetobacter baumannii were selected for molecular studies. Minimal inhibitory concentrations (MICs) of antimicrobials were determined by agar dilution method. Colistin (COL) heteroresistance was investigated by means of population analysis studies. PCR-based methods were used for epidemiological analysis and for the screening of carbapenemases and the bla(tetB) gene. We have observed a steady rise in the MIC50 of imipenem (IMI)-resistant isolates and an increment in the presence of bla(OXA-23)-like gene (74-100%) as well. A rapid increasing rate of minocycline (MIN) resistance and a rise of the MIC50 of the resistant isolates have been detected since the year 2008. All isolates harboured the tet (B) gene. An increase in the value of the tigecycline (TIG) MIC was seen from the year 2007 onwards. This loss of activity was observed among different clones. A rise of COL heteroresistance from 46.4% in 2004 to 95% in 2012 was detected. During this period, COL consumption also increased (11.1-fold). However, COL resistance remained sporadic.

[Microbiological features and risk factors for acquiring multidrug-resistant Acinetobacter baumannii bacteremia in pediatric patients. Case-control study]. / Factores de riesgo para la adquisición y características microbiológicas de las bacteriemias por Acinetobacter baumannii multi-resistente en pediatría: Estudio de casos y controles.

BACKGROUND: Multidrug-resistant Acinetobacter baumannii (MAB) is an important nosocomial pathogen. OBJECTIVES: To analyze the risk factors for acquiring MAB, and the clinical and microbiological characteristics of MAB bacteremia (MABB) in children. MATERIALS AND METHODS: Control-case study 2005-2008. Demographic and clinical data from all MABB and from non-multiresistant gram-negative bacteremias were recorded. Identification at species level, antimicrobial susceptibility tests, time-kill studies and clonally relationships were performed. Stata 8.0 was used for data analysis. RESULTS: A total of 50 MABB and 100 controls were included. Ninety four percent of patients acquired MAB in ICU and the 88% had underlying diseases. All patients had invasive procedures previous to MABB. The median of hospitalization stay previous to MABB was different in cases than in controls (16 vs 7 days, p < 0.001). Five clones were detected among the MABB. Time-killing curves showed bactericidal activity of ampicillin/sulbactam plus gentamicin and polymixin B. Three patients with MAB died. In a multivariate analysis final predictors of MABB were: previous use of broad-spectrum antibiotics [OR: 7,0; IC 95% 1,93-25,0; p: 0,003] and mechanical ventilation [OR: 4,19; IC 95% 1,66-10,0; p: 0,002]. CONCLUSIONS: MABB were detected in patients with underlying conditions, invasive procedures and prolonged hospitalization. Predictors of MABB were mechanical previous use of broad-spectrum antibiotics and mechanical ventilation.

Factores de riesgo para la adquisición y características microbiológicas de las bacteriemias por Acinetobacter baumannii multi-resistente en pediatría: Estudio de casos y controles / Microbiological features and risk factors for acquiring multidrug-resistant Acinetobacter baumannii bacteremia in pediatric patients: Case-control study

Background: Multidrug-resistant Acinetobacter baumannii (MAB) is an important nosocomial pathogen. Objectives: To analyze the risk factors for acquiring MAB, and the clinical and microbiological characteristics of MAB bacteremia (MABB) in children. Materials and Methods: Control-case study 2005-2008. Demographic and clinical data from all MABB and from non-multiresistant gram-negative bacteremias were recorded. Identification at species level, antimicrobial susceptibility tests, time-kill studies and clonally relationships were performed. Stata 8.0 was used for data analysis. Results: A total of 50 MABB and 100 controls were included. Ninety four percent of patients acquired MAB in ICU and the 88% had underlying diseases. All patients had invasive procedures previous to MABB. The median of hospitalization stay previous to MABB was different in cases than in controls (16 vs 7 days, p < 0.001). Five clones were detected among the MABB. Time-killing curves showed bactericidal activity of ampicillin/sulbactam plus gentamicin and polymixin B. Three patients with MAB died. In a multivariate analysis final predictors of MABB were: previous use of broad-spectrum antibiotics [OR: 7,0; IC 95% 1,93-25,0; p: 0,003] and mechanical ventilation [OR: 4,19; IC 95% 1,66-10,0; p: 0,002]. Conclusions: MABB were detected in patients with underlying conditions, invasive procedures and prolonged hospitalization. Predictors of MABB were mechanical previous use of broad-spectrum antibiotics and mechanical ventilation.

Introducción: Acinetobacter baumannii multi-resistente (ABM) es un patógeno intrahospitalario de importancia. Objetivos: Analizar factores de riesgo de adquisición y características clínicas y microbiológicas de las bacteriemias por ABM (BABM) en pediatría. Métodos: Estudio de casos y controles período 2005-2008. Se incluyeron variables demográficas y clínicas de pacientes con BABM y por otros bacilos gramnegativos no ABM. Se realizaron pruebas para identificación de especie, susceptibilidad antimicrobiana y detección feno-genotípica de mecanismos de resistencia, sinergia y clonalidad. Análisis estadístico: Stata 8.0. Resultados: Se incluyeron 50 BABM y 100 controles. El 94% de los pacientes adquirieron la BABM en UCI y 88% tenía patologías subyacentes. La mediana de días de internación previa a la bacteriemia fue mayor en los casos (16 vs 7 días, p < 0,001). Se detectaron cinco clones de ABM. Se encontró efecto bactericida in vitro con polimixina B y con ampicilina/sulbactam+gentamicina. Tres casos fallecieron. Análisis multivariado: predictores finales de BABM fueron: antimicrobiano previo de amplio espectro [OR: 7,0; IC 95% 1,93-25,0; p: 0,003] y asistencia respiratoria mecánica (ARM) [OR: 4,19; IC 95% 1,66-10,0; p: 0,002]. Conclusiones: Las BABM fueron detectadas en pacientes con enfermedad subyacente, con procedimientos invasores previos e internación prolongada. Fueron predictores de BABM el tratamiento antimicrobiano de amplio espectro y ARM previa.