Antimicrobial resistance among Gram-positive bacteria isolated in Latin American hospitals

Antimicrobial resistance patterns of the most frequently isolated Gram-positive bacteria in selected Latin American hospitals were evaluated under the auspices of the SENTRY Antimicrobial Surveillance Program. The strains were consecutively collected (one per patient) between January 2003 and December 2008 and tested by reference broth microdilution methods at the monitoring central laboratory (JMI Laboratories, North Liberty, Iowa, USA). A total of 12,324 Gram-positive cocci were analyzed. The organisms were isolated from bloodstream (53.2%) and skin and skin structure infections (16.4%). Resistance to oxacillin (MRSA) was observed in 40.0% of Staphylococcus aureus, varying from 32.7% in Brazil to 49.7% in Chile. Resistance to erythromycin (90.1%), clindamycin (84.4%), and levofloxacin (86.8%) was very high in MRSA. Vancomycin, linezolid and daptomycin were all very active against S. aureus strains tested (>99.9-100.0% susceptible), but daptomycin (MIC(50/90), 0.25/0.5 microg/ml) was four- to eight-fold more potent than three comparators. Vancomycin resistance increased from 5.0% in 2003 to 15.5% in 2008 among enterococci (VRE); the most significant increase occurred among isolates from Brazilian medical centers (from 6.9 to 31.1%). Daptomycin was the most active antimicrobial tested against enterococci in general (MIC(50/90) microg/ml; 100.0% susceptible), followed by linezolid (MIC(50/90), 1/2 microg/ml; 99.9% susceptible), teicoplanin (MIC(50 )and MIC(90 )of <2 microg/ml; 91.3% susceptible), vancomycin (MIC(50/90), 1/8 microg/ml; 89.6% susceptible). In summary, daptomycin and linezolid showed excellent in vitro activity against Gram-positive organisms (12,324) collected in Latin American hospitals, including MRSA, VRE and other multidrug-resistant organisms.