RESUMEN
Pseudomonas aeruginosa GW-1 was isolated in 2000 in South Africa from blood cultures of a 38-year-old female who developed nosocomial pneumonia. This isolate harbored a self-transferable ca. 100-kb plasmid that conferred an expanded-spectrum cephalosporin resistance profile associated with an intermediate susceptibility to imipenem. A beta-lactamase gene, bla(GES-2), was cloned from whole-cell DNA of P. aeruginosa GW-1 and expressed in Escherichia coli. GES-2, with a pI value of 5.8, hydrolyzed expanded-spectrum cephalosporins, and its substrate profile was extended to include imipenem compared to that of GES-1, identified previously in Klebsiella pneumoniae. GES-2 activity was less inhibited by clavulanic acid, tazobactam and imipenem than GES-1. The GES-2 amino acid sequence differs from that of GES-1 by a glycine-to-asparagine substitution in position 170 located in the omega loop of Ambler class A enzymes. This amino acid change may explain the extension of the substrate profile of the plasmid-encoded beta-lactamase GES-2.
Asunto(s)
Imipenem/metabolismo , Pseudomonas aeruginosa/enzimología , Tienamicinas/metabolismo , beta-Lactamasas/metabolismo , Secuencia de Aminoácidos , Clonación Molecular , Hidrólisis , Insulina/análogos & derivados , Insulina Lispro , Cinética , Pruebas de Sensibilidad Microbiana , Datos de Secuencia Molecular , Homología de Secuencia de Aminoácido , Resistencia betalactámica/fisiología , beta-Lactamasas/genética , beta-Lactamas/farmacologíaRESUMEN
Haemophilus parainfluenzae isolates recovered from patients with respiratory diseases were studied for their ability to undergo genetic transformation by isogenic DNA. Two chromosomal markers, streptomycin resistance and nalidixic acid resistance, were tested for transformation efficiencies in H. parainfluenzae recipients from three biotypes. Most efficient in transformation was biotype II, followed by biotype I, while biotype III was nontransformable. Lack of transformation was not owing to poor donor activity of DNA, but to inability of the cells to develop competence. Strains that formed clumps in liquid media were nontransformable. Since the transformable biotype II is one of the prevalent biotypes world wide, one can speculate that DNA transformation probably plays a major role in the spread of drug resistance in H. parainfluenzae.