RESUMO
BACKGROUND: This study was performed to investigate the prevalence of qnr genes in clinical isolates of Escherichia coli from Korea that produce extended-spectrum beta-lactamases (ESBLs). METHODS: During the period of May to June 2005, we collected clinical isolates of E. coli that were intermediate or resistant to ceftazidime and/or cefotaxime from 11 Korean hospitals. Antimicrobial susceptibility was determined by the disk diffusion and agar dilution methods. ESBL production was confirmed phenotypically by the double-disk synergy test. ESBL and qnr genes were searched for by PCR amplification, and the PCR products were then subjected to direct sequencing. RESULTS: Double-disk synergy tests were positive in 84.3% (118/140) of ceftazidime- and/or cefotaxime-nonsusceptible E. coli isolates. The most prevalent types of ESBL in E. coli isolates were CTX-M-14 (N=41) and CTX-M-15 (N=58). Other ESBLs were also identified, including CTX-M-3 (N=7), CTX-M-9 (N=8), CTX-M-12 (N=1), CTX-M-57 (N=1), SHV-2a (N=2), SHV-12 (N=17) and TEM-52 (N=4). The qnrA1 and qnrB4 genes were identified in 4 and 7 ESBL-producing isolates, respectively. CONCLUSIONS: CTX-M-type enzymes were the most common type of ESBL in E. coli isolates from Korea, and the qnr genes were not uncommon in ESBL-producing E. coli isolates. Dissemination of E. coli containing both ESBL and qnr genes could compromise the future usefulness of the expanded-spectrum antibiotics for the treatment of infections.
Assuntos
Humanos , Testes de Sensibilidade a Antimicrobianos por Disco-Difusão , Escherichia coli/enzimologia , Proteínas de Escherichia coli/classificação , Concentração Inibidora 50 , Reação em Cadeia da Polimerase , beta-Lactamases/biossínteseRESUMO
Las BLEEs son β-lactamasas producidas por una variedad de bacterias gramnegativas, que confieren resistencia a cefalosporinas de tercera y cuarta generación y aztreonam. Son principalmente producidas por K. pneumoniae y E. coli, aunque la naturaleza plasmídica de los genes que las codifican ha permitido una amplia diseminación a otros géneros bacterianos. Se realizó la detección fenotípica y molecular de BLEE a 224 aislados de Enterobacterias provenientes de ocho Centros de Salud de Caracas. El 91,1% de las cepas analizadas mediante el método de doble disco y el NCCLS 2004, fueron productoras de BLEE. El análisis de CIM para ceftazidime, cefotaxime, cefepime y aztreonam mostró una mayor proporción de cepas BLEE con actividad ceftazidimasa, compatibles con las familias SHV y/o TEM, y en menor proporción pertenecientes a la familia CTX-M. Los resultados del PCR basados en la amplificación de los genes blaSHV, blaTEM y blaCTXM, confirmaron el predominio de SHV-BLEE (72%) y CTX-M-BLEE (21,1%). Los carbapenemos con un 100% de sensibilidad. constituyen la mejor opción terapéutica. Esta investigación permitió detectar el tipo de BLEE circulante en ocho centros hospitalarios y es el primer reporte de la determinación de BLEE del tipo CTX-M, en nuestro país.
The extended-spectrum ß-lactamases (ESBLs) are ß-lactamases produced by a variety of gram-negative bacteria that confers resistance to cephalosporins of third and quarter generation and aztreonam. They are most commonly produced by isolates of K. pneumoniae and E. coli, although the plasmidic nature of the genes that encode them has allowed a wide dissemination to other bacterial genera. A phenotypical and molecular detection of ESBLs were carried out to 224 Enterobacteria isolates from eight Health Centers of Caracas . A 91.1% of stumps analyzed by double disk method and the NCCLS 2004, were ESBLs' producers. The MIC analysis for ceftazidime, cefotaxime, cefepime and aztreonam showed a bigger proportion of stumps ESBL with ceftazidimase activity compatible to the SHV families and/or TEM, and in a smaller proportion to the CTX-M family. The PCR results based on genes blaSHV, blaTEM and blaCTX-M, amplification confirmed a predominance of SHV-ESBL (72%) and CTX-M-ESBL (21.1%). Therefore, carbapenems with 100% of sensibility constitute the best therapeutic option. This investigation has allowed the detection of circulating ESBLs type in eight hospitals, and is also the first report that determines the CTX-M type ESBLs in our country.