Drug sensitivity and expression of beta-lactamase in enterococci isolated at Okayama University Hospital

The following results were obtained from a study of Enterococci isolated at the Okayama University Hospital from 1990 to 1994. 1) The isolation frequency of Enterococci was about 6% for each year. 2) The percentage of Enterococcus faecalis (E. faecalis) among Enterococci decreased each year, but the percentage of Enterococcus faecium (E. faecium), and Enterococcus avium (E. avium) increased each year. 3) Results of drug sensitivity tests revealed that the incidence of ofloxacin (OFLX) resistant E. faecalis and E. avium increased each year. Also, the resistance of E. faecalis to ampicillin (ABPC), the primary medication choice for treating E. faecalis, increased each year. 4) A few vancomycin (VCM) non-sensitive Enterococci were isolated. These bacteria showed low-sensitivity toward ABPC, imipenem (IPM), gentamicin (GM), and OFLX, and the extent of multiple drug resistance increased each year. 5) One hundred strains of Enterococci were selected to examine the expression of beta-lactamase using the broth method and the iodine-starch method. However, beta-lactamase producing strains were not detected.