RESUMEN
OBJECTIVES: To study the evolution between 1999 and 2002 and mechanisms of antibiotic resistance in a multidrug-resistant Acinetobacter baumannii clone predominant in isolates from elderly patients with respiratory tract infections. METHODS: Susceptibility to antimicrobials was determined using an agar dilution method. Bacterial clones were identified by PCR-fingerprinting and PFGE with ApaI. Carbapenemases were detected by phenotypic tests; by PCR with primers specific for bla (OXA-40), bla(IMP), bla(VIM-1) and bla(VIM-2); and by hybridization with DNA probes. Class 1 integrons were detected using PCR. RESULTS: In 1999 isolates were grouped into two main genotypes: clone I (33%) and clone II (55%). These were also detected in 2002 with a different distribution: clone I (69%), clone II (22%). Resistance to amikacin, meropenem and imipenem increased significantly in clone I over this time, whereas clone II was not affected. In 2002, the incidence of bla(OXA-40) rose to 91% in clone I isolates with some also harbouring bla(VIM-2) and bla(IMP) genes. Different class 1 integrons were detected ranging in size from 550 to 1200 bp. No relationship was found between carbapenemases and class 1 integrons. CONCLUSIONS: In elderly patients, a single clone became predominant among A. baumannii isolates, coinciding with an increase in antibiotic resistance rates. The majority of isolates harboured the bla(OXA-40) carbapenemase gene and some of them also harboured bla(VIM-2) and bla(IMP) genes. The presence of class 1 integrons also increased over time.
Asunto(s)
Infecciones por Acinetobacter/microbiología , Acinetobacter baumannii/efectos de los fármacos , Farmacorresistencia Bacteriana Múltiple/genética , Evolución Molecular , Infecciones del Sistema Respiratorio/microbiología , Acinetobacter baumannii/aislamiento & purificación , Anciano , Anciano de 80 o más Años , Antibacterianos/farmacología , Dermatoglifia del ADN , ADN Bacteriano/análisis , ADN Bacteriano/genética , ADN Bacteriano/metabolismo , Desoxirribonucleasas de Localización Especificada Tipo II/metabolismo , Electroforesis en Gel de Campo Pulsado , Femenino , Humanos , Integrones/genética , Masculino , Pruebas de Sensibilidad Microbiana , Hibridación de Ácido Nucleico , Reacción en Cadena de la Polimerasa , Polimorfismo de Longitud del Fragmento de Restricción , beta-Lactamasas/análisis , beta-Lactamasas/genéticaRESUMEN
INTRODUCTION: The aim of this study was to detect carbapenemases in imipenem-resistant Acinetobacter baumannii isolates obtained in the microbiology department of a Basque Country Public Health Service hospital over a period of 19 months, and to genetically characterize the resistant clones. METHODS: Susceptibility tests to imipenem, meropenem, ticarcillin, ceftazidime, cefotaxime, cefepime and aztreonam were done by determining the minimum inhibitory concentration on agar plates. A tRNA technique was used for species identification and PCR with primers ERIC2, AP3 and M13 for genetic typing of resistant isolates. Carbapenemase production was detected by the Hodge test and metallo-beta-lactamase by the EDTA test and Etest MBL. RESULTS: A total of 76 isolates were resistant to imipenem and 49 of these were resistant to all the betalactam antibiotics tested. Genetic typing showed three predominant clones, denominated I (9 isolates), II (48 isolates) and III (8 isolates). Hodge and EDTA tests were positive in 45 and 8 isolates belonging to clone II, 8 and 4 belonging to clone I and 7 and 3 belonging to clone III, respectively. The Etest confirmed 7 results (45% of the 17 positive EDTA test isolates). CONCLUSION: Our results show that one factor contributing to the high level of imipenem resistance in the isolates analyzed is dissemination of a predominant, multiresistant clone able to produce OXA-type carbapenemases and metallo-beta-lactamases.
Asunto(s)
Infecciones por Acinetobacter/microbiología , Acinetobacter baumannii/efectos de los fármacos , Antibacterianos/farmacología , Proteínas Bacterianas/aislamiento & purificación , Carbapenémicos/farmacología , Imipenem/farmacología , beta-Lactamasas/aislamiento & purificación , Infecciones por Acinetobacter/tratamiento farmacológico , Infecciones por Acinetobacter/epidemiología , Acinetobacter baumannii/enzimología , Acinetobacter baumannii/genética , Acinetobacter baumannii/aislamiento & purificación , Proteínas Bacterianas/genética , Proteínas Bacterianas/fisiología , Carbapenémicos/metabolismo , Infección Hospitalaria/epidemiología , Infección Hospitalaria/microbiología , Brotes de Enfermedades , Farmacorresistencia Bacteriana Múltiple/genética , Farmacorresistencia Bacteriana Múltiple/fisiología , Genotipo , Humanos , Meropenem , Pruebas de Sensibilidad Microbiana , Estudios Multicéntricos como Asunto , España/epidemiología , Tienamicinas/farmacología , Resistencia betalactámica/genética , Resistencia betalactámica/fisiología , beta-Lactamasas/genética , beta-Lactamasas/fisiología , beta-Lactamas/farmacologíaRESUMEN
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