USE OF CEPHALEXIN-AZTREONAM-ARABINOSE AGAR FOR SELECTIVE ISOLATION OFENTEROCOCCUS-FAECIUM

Cephalexin-aztreonam-arabinose agar (CAA), a new selective agar, was e xamined in comparison with nalidixic acid-colistin agar for the differ entiation of Enterococcus faecium from other enterococci and the abili ty to isolate the organism from feces. Two hundred sixteen enterococcu s isolates and a variety of gram-positive and gram-negative control st rains were inoculated onto both media. All control strains of E. faeci um were easily differentiated from Enterococcus faecalis and Enterococ cus durans on the basis of arabinose fermentation on CAA. Differentiat ion of E. faecium from other enterococci or Streptococcus bovis was no t possible on nalidixic acid-colistin agar. Increased isolation of E. faecium was demonstrated on CAA when both media were compared for the isolation of the organism from feces. CAA has been shown to possess ex cellent differential and selective features allowing the simple and ef fective isolation of E. faecium from heavily contaminated sites.