Enterococcus faecium Clade Competition in the Presence of β-Lactam Antibiotics in a Mouse GI Tract Colonization Model

Previously, we showed that Enterococcus faecium Glade B strains outcompeted health care-associated Glade A1 strains in murine gastrointestinal colonization. Here, parenterally administered piperacillin-tazobactam and ceftriaxone significantly promoted colonization by Glade A1 over Glade B strains except that ceftriaxone, at the dose used, did not favor the least beta-lactam-resistant A1 strain. The advantage that beta-lactam administration gives to more highly ampicillin-resistant E. faecium over ampicillin-susceptible strains mirrors what occurs in hospitalized patients administered these antibiotics.

Automated summary

In previous research, it was found that health care-associated Glade A1 strains of Enterococcus faecium were outcompeted by Glade B strains in murine gastrointestinal colonization. However, parenterally administered piperacillin-tazobactam and ceftriaxone significantly promoted the colonization of Glade A1 strains, except for the least beta-lactam-resistant A1 strain. This study reflects the advantage of beta-lactam administration in promoting the colonization of highly ampicillin-resistant E. faecium strains over susceptible strains, similar to what happens in hospitalized patients.