The enzymatic modification of aminoglycosides by aminoglycoside-acetyltransferases (AAC), aminoglycoside-adenyltransferases (AAD), and aminoglycoside-phosphotransferases (APH), is the most common resistance mechanism in P. aeruginosa and these enzymes can be coded on mobile genetic elements that contribute to their dispersion. One hundred and thirty seven P. aeruginosa isolates from the University Hospital, Cumana, Venezuela (HUAPA) were evaluated. Antimicrobial susceptibility was determined by the disk diffusion method and theaac, aadB and aph genes were detected by PCR. Most of the P. aeruginosa isolates (33/137) were identified from the Intensive Care Unit (ICU), mainly from discharges (96/137). The frequency of resistant P. aeruginosaisolates was found to be higher for the aminoglycosides tobramycin and amikacin (30.7 and 29.9%, respectively). Phenotype VI, resistant to these antibiotics, was the most frequent (14/49), followed by phenotype I, resistant to all the aminoglycosides tested (12/49). The aac(6´)-Ib,aphA1 and aadB genes were the most frequently detected, and the simultaneous presence of several resistance genes in the same isolate was demonstrated. Aminoglycoside resistance in isolates ofP. aeruginosa at the HUAPA is partly due to the presence of the aac(6´)-Ib, aphA1 andaadB genes, but the high rates of antimicrobial resistance suggest the existence of several mechanisms acting together. This is the first report of aminoglycoside resistance genes in Venezuela and one of the few in Latin America.

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Introduction: The treatment of urinary tract infections has become more challenging due to the increasing frequency of multidrug-resistant Escherichia coli in human populations.Objective: To characterize multidrug-resistant E. coli isolates causing community-acquired urinary tract infections in Cumaná, Venezuela, and associate possible risk factors for infection by extended-spectrum beta-lactamases (ESBL)-producing isolates.Materials and methods: We included all the patients with urinary tract infections attending the urology outpatient consultation and emergency unit in the Hospital de Cumaná, Estado Sucre, Venezuela, from January through June, 2014. blaTEM, blaSHV and blaCTX-M genes detection was carried out by PCR.Results: We found a high prevalence of multidrug-resistant E. coli (25.2%) with 20.4% of the isolates producing ESBL. The ESBL-producing isolates showed a high frequency (66.7%) of simultaneous resistance to trimethoprim-sulphamethoxazole, fluoroquinolones and aminoglycosides compared to non-producing isolates (2.4%). Of the resistant isolates, 65.4% carried the blaTEM gene, 34.6% the blaCTX-M and 23.1% the blaSHV. The blaCTX-M genes detected belonged to the CTX-M-1 and CTX-M-2 groups. Plasmid transfer was demonstrated by in vitro conjugation in 17 of the 26 ESBL-producing isolates. All three genes detected were transferred to the transconjugants. Age over 60 years, complicated urinary tract infections and previous use of a catheter predisposed patients to infection by ESBL-producing E. coli.Conclusions: The high frequency of multidrug-resistant ESBL-producing isolates should alert the regional health authorities to take measures to reduce the risk of outbreaks caused by these types of bacteria in the community.

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El presente estudio tuvo como objetivo evaluar la frecuencia de enterobacterias nosocomiales productoras de b-lactamasas de espectro extendido en pacientes recluidos en el Servicio Autónomo Hospital Universitario “Antonio Patricio de Alcalá, Cumaná-Venezuela, durante el período septiembre-noviembre del 2005. La producción de b-lactamasas de espectro extendido y la susceptibilidad antimicrobiana <em>in vitro, </em>fue determinada por el método de sinergismo de doble disco y difusión en disco. Se obtuvieron 35 aislados bacterianos y el mayor número de Infecciones Intrahospitalarias se presentó en la unidad de cuidados intensivos y retén con 13/35 (37,15%) y 9/35 (25,72%) casos, respectivamente.<p>El 51,42% de cultivos positivos se presentó en muestras de secreciones. <em>Klebsiella pneumoniae </em>mostró una frecuencia de 20/35 (57,14%). Sólo 27/35 aislados (77,14%) produjeron b-lactamasas de espectro extendido y <em>Klebsiella pneumoniae </em>fue la especie más frecuente en la producción de éstas, con 14/35 (40,0%). Las enterobacterias expresaron mayor porcentaje de resistencia a ceftazidima (77,77%), cefotaxima (70,37%) y cefepima (40,74%). <em>K. pneumoniae </em>y <em>E. coli</em>, mostraron 59,25% de resistencia a amoxicilina/ácido clavulánico.</p><p>Todas presentaron 100% de sensibilidad a carbapenemas. Los largos períodos de hospitalización constituyen uno de los principales factores de riesgo para adquirir infecciones intrahospitalarias y la aparición de cepas productoras de b-lactamasas de espectro extendido resultan del mal uso de cefalosporinas de amplio espectro, lo cual plantea retos importantes por la necesidad de usar carbapenemas con el riesgo de ejercer una presión selectiva que cause, a futuro, su resistencia.</p>