Quantitative determination of gelatinase activity among enterococci

Gelatinase, hemolysin and aggregation substance have all been reported to b e virulence factors of enterococci. In this study, gelatinase production wa s investigated in isolates of Enterococcus faecalis (n = 93), E. faecium (n = 49) and E, avium (n = 36) recovered from hospitalized patients. Gelatina se was detected in 45% of E. faecalis isolates, but could not be detected i n E. faecium and E. avium. Gelatinase activity was then measured by radial diffusion for the 42 gelatinase-positive E. faecalis isolates. To convert g elatinase activity into proteinase K activity, a standard curve was produce d by placing different concentrations of proteinase K into wells in the gel atine plate. Gelatinase activity per E. faecalis colony ranged from 2.6 X 1 0(-7) to 2.2 X 10(-5) mug/ml, proportionate to the activity of proteinase K . An approximately 84-fold difference in gelatinase concentration was obser ved between the colony producing the highest amount and that producing the lowest amount. This method may be useful for determining the virulence of g iven isolates in relation to gelatinase production as it is quick, easy and inexpensive to perform. (C) 2001 Elsevier Science BN. All rights reserved.