Antimicrobial susceptibility of aerobic Gram-positive cocci and anaerobic bacteria clinically isolated in 2010 and 2012

Abstract

The activities of antibacterial agents against aerobic Gram-positive cocci (31 genus or species, 1,020 strains in 2010, 992 strains in 2012) and anaerobic bacteria (23 genus or species, 178 strains in 2010, 211 strains in 2012) isolated from clinical specimens in 2010 and 2012 at clinical facilities in Japan were studied using either broth microdilution or agar dilution method. The ratios of methicillin-resistant Staphylococcus aureus (MRSA) isolates to all S. aureus were 54.2% in 2010 and 51.4% in 2012. Those of methicillin-resistant Staphylococcus epidermidis (MRSE) isolates to all S. epidermidis were 82.5% in 2010 and 84.9% in 2012. The prevalence rates of these resistant strains maintained similar levels after the surveillance study started in 1992. Against these methicillin-resistant strains, vancomycin (VCM) showed good antibacterial activity with the MIC₉₀s of ≤2 μg/mL in 2010 and 2012. The ratios of genotypic penicillinsusceptible Streptococcus pneumoniae isolates increased to 20.4% in 2012 after the decline from 2002 to 2010. Against all the strains of Enterococcus faecalis and Enterococcus faecium, VCM and teicoplanin showed good activities with the MIC₉₀s of ≤2 μg/mL and no VCM-resistant strains was found in 2010 and 2012. The MIC₉₀s of linezolid were 2 and 4 μg/mL in 2010 and 2012, respectively, and the rates of non-susceptible strains reached more than 10%. Against Clostridium difficile, the MIC₉₀s of VCM were 1 μg/mL in 2010 and 2012, but there was a strain with the VCM MIC of 4 μg/mL in 2012. Carbapenems showed good activity against Bacteroides spp. and Prevotella spp. with MIC₉₀s of ≤2 μg/mL.

As the results of this study, there was no significant increase of highly resistant or multi-drug resistant strains among aerobic gram-positive cocci and anaerobic bacteria.