sentence: R. conorii maintained the plasmid over 9 days of culture in the absence of antibiotics , although a loss of copy numbers was recognized ( 3.09 ± 0.52 on day 3 and 0.55 ± 0.14 on day 9 ) ( 16 ) , while the plasmid was maintained in R. monacensis for more than 9 passages in vitro without antibiotic treatment ( 22 ) .