Since no Tylosin A was present in the swine waste during the initial 3
months, the presence of MLSB-resistant bacteria in the swine waste was likely the reason
for the increase in resistance. Subsequently, the levels of MLSB-resistant bacteria in ASBR
biomass stabilized with an average of 44.9% for the 9 months of operation with swine waste
containing Tylosin A.