Comparison of European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Etest methods with the CLSI broth microdilution method for echinocandin susceptibility testing of Candida species.

The antifungal broth microdilution (BMD) method of the European Committee on Antibiotic Susceptibility Testing (EUCAST) and the Etest agar diffusion method were compared with the Clinical and Laboratory Standards Institute (CLSI) BMD method M27-A3 for anidulafungin, caspofungin, and micafungin susceptibility testing of 133 clinical isolates of Candida species. The isolates were characterized for the presence or absence of fks1 and/or fks2 gene mutations and included 34 isolates of C. glabrata (4 mutant strains), 32 of C. albicans (1 mutant strain), 25 of C. parapsilosis, 19 of C. guilliermondii, 12 of C. tropicalis (2 mutant strains), and 11 of C. krusei. Excellent essential agreement (EA; within 2 dilutions) between the CLSI and EUCAST and CLSI and Etest MIC results was observed. The overall EA between the EUCAST and CLSI results ranged from 89.5% (caspofungin) to 99.2% (micafungin), whereas the EA between the Etest and CLSI results ranged from 90.2% (caspofungin) to 93.2% (anidulafungin). The categorical agreement (CA) between methods for each antifungal agent was assessed using previously determined epidemiological cutoff values (ECVs). Excellent CA (>90%) was observed for all comparisons between the EUCAST and CLSI results with the exceptions of C. glabrata and caspofungin (85.3%) and C. krusei and caspofungin (54.5%). The CA between the Etest and CLSI results was also excellent for all comparisons, with the exception of C. krusei and caspofungin (81.8%). All three methods were able to differentiate wild-type (WT) strains from those with fks mutations. With anidulafungin as the test reagent, the CLSI method identified 5 of 7 mutant strains, whereas the EUCAST method and the Etest identified 6 of 7 mutant strains. With either caspofungin or micafungin as the test reagent, the CLSI method identified all 7 mutant strains and the EUCAST method identified 6 of 7 mutant strains. The Etest identified all 7 mutant strains using caspofungin as the reagent. All three test methods showed a high level of agreement and of ability to distinguish fks mutant strains of Candida species from WT strains using each of the echinocandins.

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.

Commercial broth microdilution panel validation and reproducibility trials for NVP PDF-713 (LBM 415), a novel inhibitor of bacterial peptide deformylase.

NVP PDF-713 (LBM 415) is a peptide deformylase inhibitor being progressed into clinical trials. Dry-form broth microdilution panels of NVP PDF-713 were compared to reference MIC panels of 552 recent clinical isolates. Most (99.2%) dry-form MIC results were within +/- 1 log(2) dilution of the reference panel MICs. Of the bacteria tested, Streptococcus pneumoniae and Haemophilus influenzae showed a bias towards higher and lower MICs, respectively. Same-day and between-day reproducibility tests showed that 98.9% and 96.7% of MIC values, respectively, were within +/- 1 log(2) dilution step, thereby demonstrating a high degree of reliability of the dry-form MIC product for clinical studies.