Frequency and antibiotic susceptibility patterns of urinary pathogens in male outpatients in Argentina.

INTRODUCTION: Knowledge of the etiology and antimicrobial susceptibility patterns of uropathogens is important for determining the best treatment option. This study aimed to determine the distribution and antibiotic susceptibility patterns of bacterial strains isolated from adult male outpatients. METHODOLOGY: Between November 2012 and April 2013, 3,105 community urine samples were analyzed from adult male patients who attended the Laboratorio Hidalgo, Buenos Aires, Argentina. Antimicrobial susceptibility testing was performed by the Kirby-Bauer disc diffusion method. Isolates resistant to third generation cephalosporin were tested for extended-spectrum beta-lactamase (ESBL) production using the double-disk synergy test. RESULTS: Of the 3,105 urine samples analyzed, 791 (25.5%) had significant bacteriuria. The frequency of positive urine cultures increased significantly with patient age. Escherichia coli was isolated most frequently (47.3%), followed by Enterococcus faecalis (13.6%), and Klebsiella pneumoniae (11.9%). Gram-negative organisms represented 78.8% of urinary pathogens. The highest activities against Gram-negative bacteria were found with imipenem (99.0%), amikacin (98.1%), ertapenem (94.2%), fosfomycin (90.7%), and piperacillin-tazobactam (90.1%). The frequencies of ESBLs among E. coli, K. pneumoniae, and P. mirabilis were 15.2 %, 22.3%, and 8%, respectively. Fosfomycin, piperacillin-tazobactam, and nitrofurantoin were most effective against Gram-positive organisms. CONCLUSIONS: Fosfomycin may be an excellent option for cystitis treatment in patients without risk factors, whereas piperacillin-tazobactam is preferred for the treatment of parenchymatous UTIs, complicated UTIs, and UTIs associated with risk factors. To ensure the optimal selection of antibiotics, physicians should have access to up-to-date information about the local prevalence of antimicrobial resistance.

Rápida adquisición de resistencia in vitro al ertapenem en Escherichia coli productora de betalactamasa de espectro extendido / In vitro emergence of ertapenem resistance in Escherichia coli producing extended-spectrum beta-lactamase

Introducción. Las infecciones por Escherichia coli productoras de BLEE son cada vez mas frecuentes en la comunidad. Ertapenem (ERT) presenta muy buena actividad frente a estas cepas y es una excelente indicación en infecciones severas en etapa de manejo ambulatorio. El objetivo de este trabajo fue determinar la frecuencia de selección de mutantes resistentes a carbapenemas en una colección de aislamientos clínicos de E. coli productoras de BLEE. Material y métodos. Se buscaron mutantes resistentes en uno y dos pasos a ERT, imipenem (IMI) y meropenem (MER) por inoculación de 109 ufc/ml en placas de agar Mueller Hinton conteniendo las carbapenemas a diferentes concentraciones. La concentración inhibitoria mínima (CMI) en las cepas originales y mutantes se determinó con el método epsilometrico Etest. Resultados. No se pudieron seleccionar mutantes resistentes con IMI y MER. Al utilizar ERT se obtuvieron mutantes resistentes en 13 de 57 aislamientos clínicos (22,8 %). Todos los mutantes resistentes fueron resistentes a ERT con CMI ≥ 1 mg/L pero mantuvieron sensibilidad a IMI y MER. Se obtuvieron 6 MR segundo paso con ERT las cuales presentaron resistencia de alto nivel a ERT (CMI ≥ 8 mg/L). Se observó resistencia cruzada a MER en 3 de ellas y en 1 a IMI. Los cuatro mutantes resistentes de segundo paso obtenidos con MER fueron resistentes a ERT y MER y en 2 de ellas se observó resistencia cruzada a IMI. Conclusiones. La selección de mutantes resistentes a ERT es frecuente en cepas de E. coli productoras de BLEE. Para obtener mutantes resistentes a MER e IMI es necesario un segundo paso de selección. El uso de ERT en infecciones con inóculo alto, focos no drenados y con cepas productoras de BLEE debería ser vigilado para reducir el riesgo de selección de resistencia (AU)

Introduction. The occurrence of community-associated infections due to extended-spectrum β-lactamase (ESBL)-producing Escherichia coli is increasing worldwide. These organisms are frequently resistant to many of the antimicrobial agents but remain susceptible to carbapenems. We investigated the in vitro emergence of carbapenem resistance in a collection of clinical isolates of ESBL -producing E. coli Material and methods. First and second-step resistant mutants were obtained from E. coli with ESBL. Aliquots of 50μl containing > 109 CFU were applied to Mueller-Hinton plates containing meropenem, imipenem or ertapenem. MICs for native strains and mutants were determined using the epsilometric test (E-test). Results. Resistant mutants were not selected with imipenem or meropenem. E. coli growth was observed on ertapenem (0.5 mg/L)-containing plates in 13 of 57 clinical isolates (22.8 %).The ertapenem MIC for these first-step mutants were ≥ 1 mg/L, remaining susceptible to imipenem and meropenem. The first-step mutants were used as native strains. Six second-step resistant mutants were selected with ertapenem. All were fully resistant (CMI ≥ 8 mg/L) to ertapenem, three were resistant to meropenem and one to imipenem. Four second-step resistant mutants were selected with meropenem. All were resistant to ertapenem, meropenem, and two of them were resistant to imipenem. Conclusions. Stable resistant mutants were easy to select with ertapenem among ESBL-producing E. coli. Two steps were necessary to select resistant mutants to meropenem or imipenem. The use of ertapenem in high-inoculum infections or in undrained focus of infection should be monitored to reduce the risk on selection of resistance (AU)

[High prevalence of beta hemolytic streptococci isolated from throat swabs in Buenos Aires]. / Aumento en la prevalencia de estreptococos beta hemoliticos en hisopados faríngeos en Buenos Aires.

Beta hemolytic streptococci, particulary group A, are the most frequently isolated pathogens in cases of pharyngoamigdalitis. Other beta hemolytic streptococci also produce this pathology. An increase of positive cultures for group A streptococci was detected during 2004 in relation to previous years. The aim of this study was to determine the isolation rates of beta hemolytic streptococci groups A, C and G during a period of 5 years. Pharyngeal exudates were obtained from children (aged 6 months to 18 years) and adults. Swabs were cultured on Columbia agar plates containing 5% sheep blood. Lancefield grouping was performed using a latex immunoagglutination test. Group A beta hemolytic streptococci were isolated significantly more frequently from pediatric population than from adults. Groups A, C and G beta hemolytic streptococci were isolated significantly more frequently during 2004 than in previous years. Group G beta hemolytic was more prevalent in adult population than in patients less than 18 years of age. Among the isolated beta hemolytic streptococci, in adults and children, 18.9% and 5.8% were non-group A streptococci, respectively. Therefore special attention should be paid not only to group A beta hemolytic streptococci but also to other groups. Throat culture is the most reliable method for detecting the presence of the beta hemolytic streptococci and should also be indicated in adult patients.

Aumento en la prevalencia de estreptococos beta hemoliticos en hisopados faríngeos en Buenos Aires. / [High prevalence of beta hemolytic streptococci isolated from throat swabs in Buenos Aires]

Beta hemolytic streptococci, particulary group A, are the most frequently isolated pathogens in cases of pharyngoamigdalitis. Other beta hemolytic streptococci also produce this pathology. An increase of positive cultures for group A streptococci was detected during 2004 in relation to previous years. The aim of this study was to determine the isolation rates of beta hemolytic streptococci groups A, C and G during a period of 5 years. Pharyngeal exudates were obtained from children (aged 6 months to 18 years) and adults. Swabs were cultured on Columbia agar plates containing 5

sheep blood. Lancefield grouping was performed using a latex immunoagglutination test. Group A beta hemolytic streptococci were isolated significantly more frequently from pediatric population than from adults. Groups A, C and G beta hemolytic streptococci were isolated significantly more frequently during 2004 than in previous years. Group G beta hemolytic was more prevalent in adult population than in patients less than 18 years of age. Among the isolated beta hemolytic streptococci, in adults and children, 18.9

and 5.8

were non-group A streptococci, respectively. Therefore special attention should be paid not only to group A beta hemolytic streptococci but also to other groups. Throat culture is the most reliable method for detecting the presence of the beta hemolytic streptococci and should also be indicated in adult patients.