Recovery from a single blood culture of two Enterococcus gallinarum isolates carrying both vanC-1 and vanA cluster genes and differing in glycopeptide susceptibility

Two Enterococcus gallinarum isolates distinguished by different colony size s were recovered from the same blood culture from a woman with acute myeloi d leukemia. They were designated E31 (the one with larger colonies) and E32 (the one with smaller colonies). Both isolates were glycopeptide resistant , but the MICs of vancomycin and teicoplanin for E31 (32 and 2 mug/ml, resp ectively, consistent with the VanC phenotype) and E32 (128 and 16 mug/ml, r espectively, consistent with the VanA phenotype) were different. E31 and E3 2 had the same plasmid profile and showed identical pulsed-field gel electr ophoresis patterns after digestion of total DNA with NotI and a two-band va riation after digestion with SmaI. Polymerase chain reaction experiments sh owed that both isolates had both the vanC-1 and vanA genes and carried a Tn 1546-related transposon lacking orf1, vanY, and vanZ. The absence of these three genes was confirmed by Southern analysis with appropriate probes. Sou thern hybridization experiments using a vanA probe showed that this atypica l Tn1546-related element appeared to be located on the chromosome. In both E31 and E32, the vanA probe hybridized to EcoRV and HindIII fragments large r in size than the hybridizing fragments observed in the VanA prototype str ain Enterococcus faecium BM4147, suggesting the lack of the relevant EcoRV and HindIII restriction sites.