Abstract
Recombined porcine continuous-flow culture (RPCF) maintained in a continuous-flow fermentation system is effective in protecting neonatal and weaned pigs against infection by enteropathogens. In the current
study, we demonstrate the effect of RPCF on vancomycin-resistant enterococci (VRE) in the presence and absence of subtherapeutic levels of vancomycin. Also examined was the ability of VRE to transfer vancomycin
resistance to endogenous
Enterococcus faecalis
137.1. When RPCF was challenged with VRE, the rate of VRE clearance was dependent on the method of challenge. In the control experiment, RPCF was challenged
with 7.0 log
10
/CFU/ml VRE. Clearance of VRE from the culture was observed within 7 days at a rate of 1.44 log
10
/day. RPCF containing 0.001
μ
g/ml vancomycin cleared VRE at
a slightly lower rate of 0.94 log
10
/day. RPCF containing 0.01
μ
g/ml or 0.1
μ
g/ml vancomycin reduced the level of VRE from 7.0 log
10
/CFU/ml to 2.0 log
10
/CFU/ml
within 9 days, but failed to clear the VRE after 24 days. During the period of decline, the VRE clearance rate for the 0.01
μ
g/ml and 0.1
μ
g/ml vancomycin-treated cultures was 0.52 log
10
/day,
and 0.53 log
10
/day, respectively.
E. faecalis
137.1 endogenous to RPCF did not acquire the vancomycin resistance genes throughout the experiment as evidenced by direct selection, ribotyping,
and pulsed-field gel electrophoresis.