RESUMEN
Rates of metallo-beta-lactamase and 16S rRNA methylase production were investigated in 51 imipenem-resistant Pseudomonas aeruginosa clinical isolates collected from hospitals in São Paulo, Brazil. Of them, 57% and 75% produced SPM-1 and RmtD, respectively. Of note, 51% produced both enzymes, suggesting that their coproduction is already common in this geographic area.
Asunto(s)
Antibacterianos/farmacología , Farmacorresistencia Bacteriana/genética , Imipenem/farmacología , Metiltransferasas/genética , Infecciones por Pseudomonas/microbiología , Pseudomonas aeruginosa/genética , beta-Lactamasas/genética , Brasil/epidemiología , Infección Hospitalaria/microbiología , Electroforesis en Gel de Poliacrilamida , Humanos , Metiltransferasas/biosíntesis , Pruebas de Sensibilidad Microbiana , Infecciones por Pseudomonas/epidemiología , Pseudomonas aeruginosa/efectos de los fármacos , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , beta-Lactamasas/biosíntesisRESUMEN
Serious infections with Pseudomonas aeruginosa are frequently treated with the combination of a beta-lactam antimicrobial and an aminoglycoside. P. aeruginosa strain PA0905 was isolated in 2005 from an inpatient in Brazil. It showed a panresistant phenotype that included resistance to beta-lactams, aminoglycosides, and fluoroquinolones. The beta-lactam resistance was conferred by the production of the metallo-beta-lactamase SPM-1. No inhibitory zone was observed when a disk diffusion test was performed with the semisynthetic aminoglycoside arbekacin, raising suspicion of 16S rRNA methylase production. A cloning experiment subsequently revealed the presence of a novel 16S rRNA methylase, RmtD, which accounted for the high-level resistance to all 4,6-disubstituted deoxystreptamine aminoglycosides, such as amikacin, tobramycin, and gentamicin. RmtD shared a moderate degree of identity with RmtA, another 16S rRNA methylase that was initially reported to occur in P. aeruginosa in Japan in 2003. This is the first identification of aminoglycoside resistance mediated by a 16S rRNA methylase in South America. This is also the first report to document coproduction of a metallo-beta-lactamase and a 16S rRNA methylase, a combination that would severely compromise therapeutic options for the infected patients.