AUGMENTED PRODUCTION OF EXTRACELLULAR-SUPEROXIDE BY BLOOD ISOLATES OFENTEROCOCCUS-FAECALIS

To assess the frequency of extracellular superoxide (O-2(-)) productio n by enterococci, multiple species were surveyed in a whole organism a ssay for their ability to reduce ferricytochrome c in a superoxide dis mutase-inhibitable fashion. For stool and clinical enterococcal isolat es and 12 type strains, only Enterococcus faecalis (87/91 isolates and ATCC 19443), Enterococcus faecium (5/13 isolates), Enterococcus casse liflavus (ATCC 25788), and Enterococcus gallinarum (ATCC 35038) produc ed extracellular O-2(-). Among 106 strains comprising 13 species of en teric gram-negative bacilli and gram-positive cocci, only Lactococcus lactis subspecies lactis produced extracellular O-2(-). Mean (+/-SE) r ates of extracellular O-2(-) production in vitro by E. faecalis for is olates associated with bacteremia and endocarditis and for isolates fr om stool were 2.4+/-0.2, 1.9+/-0.2, and 1.5+/-0.3 nmol of O-2(-) min(- 1) 10(9) cfu(-1), respectively (P = .025, analysis of variance), sugge sting an association between invasiveness and extracellular O-2(-) pro duction.