Biochemical Tests for Differential Identification of Enterococci with VanC phenotype / 대한임상미생물학회지

BACKGROUND: Pigment production and acidification of ribose are most frequently used biochemical tests for the differentiation of three enterococcal species carrying vanC genes such as Enterococcus gallinarum, Enterococcus casseliflavus, and Enterococcus flavescens. However, pigment production may occasionally be negative in E. casseliflavus, and some of E. casseliflavus may be negative or delayed reaction with ribose fermentation test. So, we performed this study to find out biochemical tests capable of distinguishing the strains possessing vanC genotypes. METHOD: A total of 17 enterococci composed of 14 clinical isolates with motility or pigment positive strains and three ATCC strains(E. gallinarum ATCC 49573, E. casseliflavus ATCC 25788, and E. flavescens ATCC 49997) Were tested by multiplex PCR of the vanC genes(vanC-1, vanC-2 and vanC-3)and various biochemical tests. RESULTS: Among the 17 isolates including three ATCC control strains, four were genotyped as VanC-1, 11 were VanC-2, one were vanC-2/3, and any of vanC genes were not detected in one clinical isolate, respectively, Among the enterococci with vanC genotype, acid production from alphaD-cyclodextrin and hippurate hydrolysis were positive only in VanC-1 gneotype(E. gallinarum), acid production from glycerol and methyl-alpha-D-mannopyranoside were positive only in vanC-2 genotype(E. casseliflavus), and acid production from rhamnose and pigment production were negative only in VanC-1 genotype. Acid production from alphaD-cyclodextrin was negative only in vanC-2 genotype. The positive rate of ribose fermentation of VanC-1, VanC-2, and VanC-2/3(E. flavescens) genotype were 100%, 82%, and 0%, respectively. CONCLUSION: Acid production from rhamnose, alphaD-cyclodextrin, betaD-cyclodextrin, glycerol and methly-alphaD-mannopyranoside, pigment production, and hippurate hydrolysis test were useful biochemical tests for differentitating E. gallinarum form E. casseliflavus. The production of acid from alphaD-cyclodextrin, glycerol, methyl-alpha-D-mannopyranoside and were suitable biochemical tests for differentiating E. casseliflavus from E. flavescens.

Vancomycin-resistant Enterococci: Incidence, Antimicrobial Susceptibility, and Resistance Genotypes / 대한임상병리학회지

BACKGROUND: Infections caused by vancomycin-resistant enterococci (VRE) are becoming increasingly prevalent throughout the world. VRE can spread by direct patient-to-patient contact as well as on the hands of personnel and contaminated environmental surfaces. The purpose of this study was to examine the incidence of VRE among total enterococci from clinical specimen and investigate the antimicrobial characteristics and resistance genotypes of isolated VRE. METHODS: A total of 790 enterococcal isolates from patients over a period of 12 months were screened for vancomycin resistance using brain heart infusion agar plates supplemented with 6 g/mL of vancomycin. The incidence of VRE among enterococcal isolates was calculated from microbiology statistics program. Twenty three isolates of VRE were tested for minimal inhibitory concentrations (MIC) of vancomycin, penicillin, and gentamicin and resistance genotypes. RESULTS: In the first half period, the incidence of VRE was 1.9%, and in the second half, the incidence increased to 7.7%. Thirteen strains were found to be highly resistant to vancomycin, penicillin and gentamicin (MIC, >128 g/mL). According to the direct PCR analyses, the frequency of vanB, vanC1, and vanC2 types was 13, 7, and 3 strains, respectively. CONCLUSIONS: Continued vigilance, strict enforcement of infection control, and curtailment of vancomycin use seem to be our best approaches to controlling this increasingly important problem. For this purposes, accurate and timely detection of vancomycin-resistance and periodic investigation for incidence are essential.