The persistence of symptoms in Lyme patients treated with antibiotics may be due to the bacteria becoming tolerant to drugs. In lab culture, persistent Lyme bacteria grown into biofilm form were exposed to various antibiotic combinations. The authors found that double antibiotic combinations such as doxycycline and cefoperazone were not enough for biofilm eradication. The addition of either daptomycin or daunomycin was required for bacterial elimination.