RESUMEN
Six clinical CTX-M-producing isolates of the family Enterobacteriaceae were detected between 1999 and 2000 in different French hospitals. Two strains produced CTX-M-1 and CTX-M-3 and four strains produced CTX-M-14, a mutant Ala-231-->Val of CTX-M-9. A putative transposable element, ISEcp-1, was located 43 bp upstream of all the bla(CTX-M) genes. Two CTX-M-14-encoding plasmids exhibited similar restriction patterns. The CTX-M-1- and CTX-M-3-encoding plasmids were related to the CTX-M-1- and CTX-M-3-encoding plasmids previously reported in 1990 in France and in 1998 in Poland, respectively.
Asunto(s)
Enterobacteriaceae/enzimología , Proteínas de Escherichia coli , beta-Lactamasas/metabolismo , Elementos Transponibles de ADN/genética , Enterobacteriaceae/genética , Francia , Humanos , beta-Lactamasas/genéticaRESUMEN
Three clinical strains (Escherichia coli Rio-6, E. coli Rio-7, and Enterobacter cloacae Rio-9) collected in 1996 and 1999 from hospitals in Rio de Janeiro (Brazil) were resistant to broad-spectrum cephalosporins and gave a positive double-disk synergy test. Two bla(CTX-M) genes encoding beta-lactamases of pl 7.9 and 8.2 were implicated in this resistance: the bla(CTX-M-9) gene observed in E. coli Rio-7 and E. cloacae Rio-9 and a novel CTX-M-encoding gene, designated bla(CTX-M-16), observed in E. coli strain Rio-6. The deduced amino acid sequence of CTX-M-16 differed from CTX-M-9 only by the substitution Asp-240-->Gly. The CTX-M-16-producing E. coli transformant exhibited the same level of resistance to cefotaxime (MIC, 16 microg/ml) but had a higher MIC of ceftazidime (MIC, 8 versus 1 microg/ml) than the CTX-M-9-producing transformant. Enzymatic studies revealed that CTX-M-16 had a 13-fold higher affinity for aztreonam and a 7.5-fold higher k(cat) for ceftazidime than CTX-M-9, thereby showing that the residue in position 240 can modulate the enzymatic properties of CTX-M enzymes. The two bla(CTX-M-9) genes and the bla(CTX-M-16) gene were located on different plasmids, suggesting the presence of mobile elements associated with CTX-M-encoding genes. CTX-M-2 and CTX-M-8 enzymes were found in Brazil in 1996, and two other CTX-M beta-lactamases, CTX-M-9 and CTX-M-16, were subsequently observed. These reports are evidence of the diversity of CTX-M-type extended-spectrum beta-lactamases in Brazil.
Asunto(s)
Sustitución de Aminoácidos/genética , Cefotaxima/farmacología , Resistencia a las Cefalosporinas/genética , Cefalosporinas/farmacología , Enterobacteriaceae/enzimología , Mutación , beta-Lactamasas/genética , Secuencia de Aminoácidos , Ácido Aspártico/genética , Brasil , ADN Bacteriano/análisis , Farmacorresistencia Microbiana , Enterobacteriaceae/efectos de los fármacos , Enterobacteriaceae/genética , Escherichia coli/efectos de los fármacos , Escherichia coli/enzimología , Escherichia coli/genética , Técnicas de Transferencia de Gen , Glicina/genética , Humanos , Datos de Secuencia Molecular , Homología de Secuencia de Aminoácido , beta-Lactamasas/metabolismoRESUMEN
A multicenter EORTC study was conducted in children with acute lymphocytic leukemia to determine whether 5 g/m2 of methotrexate (MTX) (24 h i.v. infusion, four cycles) is an appropriate dosage for obtaining CSF drug concentrations approaching the critical cytotoxic level of 10(-6) M. A total of 193 cycles were analyzed for 58 patients. At the end of the 24 h infusion, the mean MTX serum level was 65.27 +/- 33.11 microM; the mean CSF MTX level was 1.47 +/- 1.1 microM; no significant difference in CSF MTX levels was observed between patients with (n = 20) and those without i.v. Ara-C (n = 38). The mean CSF MTX/serum MTX ratio was 0.029 +/- 0.027. CSF drug concentrations greater than or equal to 10(-6) M were achieved in 81% of the courses. The highest level was 8.4 X 10(-6) M. Only 5% of patients failed to achieve this drug concentration in at least one cycle. No significant correlation was observed between blood and CSF MTX levels. Mean CSF MTX levels were comparable from one cycle to another.