In vitro antimicrobial activity of linezolid tested against vancomycin-resistant enterococci isolated in brazilian hospitals

The emergence of vancomycin-resistant enterococci (VRE) has been described recently in Brazil. This is in contrast to the USA and Europe, where the VRE appeared in the late 1980s. The progressive increase in VRE isolation poses important problems in the antimicrobial therapy of nosocomial infections. Treatment options and effective antimicrobial agents for VRE are often limited and the possibility of transfer of vancomycin genes to other Gram-psitive microorganisms continues. In the search for antimicrobial agents for multiresistant Gram-positive cocci, compounds such as linezolid and quinupristin/dalfopristin have been evaluated. The present study was conducted to evaluate the in vitro activity of the oxazolidinone linezolid and 10 other antimicrobial agents, including quinupristin-dalfopristin, against enterococci isolated in Brazilian hospitals. Thirty-three vancomycin resistant isolates (17 Enterococcus faecium and 16E.faecalis), were analyzed. Strains were isolated from patients at Säo Paulo Hospital, Oswaldo Cruz Hospital, Hospital do Servidor Público Estadual, Santa Marcelina Hospital, Santa Casa de Misericórdia de Säo Paulo, and hospital das Clínicas do Paraná. The samples were tested by a broth microdilution method following the National Committee for Clinical Laboratory Standards (NCCLS) recommendations. All isolates were molecular typed using pulsed-field gel electrophoresis (PFGE). Linezolid was the most active compound against there multiresistant enterocci, showing 100 porcent inhibition at the susceptible breakpoints. Quinupristin and teicoplanin showed poor activy against both species. The molecular ryping results suggest that there has been interhospital spread of vacomycin resistant E. faecium and E. faecalis among Brazilian hospitals. The results of this study indicate that linezolid is an appropriate therapetic option for the treatment of vacomycin-resistant enterococci infections Brazil.

In vitro antimicrobial activity of the aminoglycoside arbekacin tested against oxacillin-resistant Staphylococcus aureus isolated in brasilian hospitals

Arbekacin is an aminoglycoside used in Japan for treating infections caused by gentamicin and oxacillin-resistant S.aureus (ORSA). The objective of this study was to determine the in vitro antimicrobial activity of arbekacin against 454 clinical isolates of ORSA. The isolates were consecutively collected between January and July, 2000, from patients hospitalized in8 Brazilian medical centers. The antimicrobial susceptibillity testing was performed by disk diffusion method according to NCCLS recommendations. The vast majority of the isolates, 453 strains (99.8 percent), were considered susceptible to arbekacin based on the criteria proposed by the Requirements for Antibiotic Products of Japan. Only 1 isolate (0.2 percent) was classified as resistant. On the other hand, high rates of resistance were demonstrated for other aminoglycosides, such as gentamicin (97.6 resistance) and amikacin (97.0 resistance). Resistance rate was also high for ciprofloxacin (98.0 percent). All isolates were considered susceptible to vancomycin. The excellent in vitro antimicrobial activity of arbekacin demonstrated in the study indicates that this antimicrobial agent may play an important role in the treatment of severe ORSA infections, especially those that show poor clinical response with vancomycin monotherapy. Since the aminoglycosides should not be used as monotherapy to treat Gram positive infections, further studies evaluating in vitro and in vivo synergistic activity of arbekacin combinations are necessary to clarify the clinical role of this aminoglycoside.