5% NaCl and on bile esculin agar (Oxoid Sunnyvale, California, USA) to determine their hydrolysis grade. Disks impregnated with the substrate L-pyrrolidonyl-beta-naphthylamide were used to perform pyrrolidonase tests (Oxoid Biochemical Identification System, Oxoid LTD., Basingstoke, Hampshire, JSH-23 molecular weight England). Reduction of tellurite (Merck, Darmstadt, Germany)

was evaluated via growing the bacteria on 0.04% potassium tellurite. Antibiotic susceptibility The antibiotic susceptibility profiles of the 12 VREF isolates were determined via the minimum inhibitory concentration (MIC) technique by means of the microdilution method using Mueller-Hinton this website broth (MHB), as recommended by the Clinical and Laboratory Standards Institute. MIC tests were performed for vancomycin (MP Biomedicals, Solon, Ohio, USA), teicoplanin (Sigma-Aldrich, St. oLouis, Missouri, USA), chloramphenicol (MP Biomedicals, Solon, Ohio, USA), ciprofloxacin (MP Biomedicals, Solon, Ohio, USA), streptomycin (Alexis Biochemical, San Diego California, USA), linezolid (Sigma-Aldrich, St. Louis, Missouri, USA), rifampicin (MP, Biomedicals, Ohio, USA), nitrofurantoin (MP Biomedicals, Solon, Ohio, USA), tetracycline (MP Biomedicals, Solon, Ohio, USA), doxycycline (Sigma-Aldrich, St. Louis, Missouri, USA), erythromycin (MP Biomedicals, Solon, Ohio, USA), tigecycline (Sigma-Aldrich, St. Louis, Missouri, USA), gentamicin (MP Biomedicals, Solon, Ohio, USA) and amoxicillin-clavulanate

(Glaxo-Smith-Kline, Philadelphia, Pennsylvania, USA). Several concentrations (256–0.625 μg/ml) of the antibiotics were tested in Mueller Hinton broth, selleck screening library with 100 μl of those dilutions being loaded into each well of a microplate. For each dilution, 100 μl of a bacterial suspension (1.5×108 CFU/ml) was inoculated and grown overnight at 37°C under a CO2 atmosphere. After bacterial growth was detected, the MIC for each isolate of E. faecium was reported as the highest concentration (μg/ml) of antibiotics in which no growth was observed. The E. faecalis ATCC® 29212 strain

(American Type Culture Collection Manassas, VA, USA) was used as a control. These isolates were eltoprazine also evaluated for high-level aminoglycoside resistance (HLAR) to streptomycin (1,000 μg/ml) and gentamicin (500 μg/ml). Detection of the glycopeptide resistance genes vanA and vanB PCR was performed to detect the glycopeptide resistance genes vanA and vanB in the 12 E. faecium clinical isolates using specific primers (Table 1) [23]. Briefly, genomic DNA was purified using the Wizard Genomic DNA Purification Kit (Promega Madison, Wisconsin, USA) from a bacterial culture grown in BHI broth incubated at 37°C for 24 h. The amplification reactions were prepared in a final volume of 50 μl, as follows: 25 μl of amplification mix (22 mM Tris/HCl, pH 8.4; 55 mM KCl; 1.65 mM MgCl2; 25 μM each dNTP; 0.6 U recombinant Taq DNA polymerase/ml), 100 ng/μl of bacterial DNA, 10 μl of H2O and 5 μl of primer solution (10 pg/μl).