Effect of drug combinations on stationary phase B. burgdorferi culturea.

a. Ten day old stationary phase B. burgdorferi culture enriched with micro-colonies was treated with 10 µg/ml drugs alone or in different combinations (each drug is 10 µg/ml) for 7 days. The percentage of residual viable B. burgdorferi was calculated according to the regression equation and ratio of Green/Red fluorescence using the SYBR Green I/PI assay as described [16]. Direct microscopy counting was employed to verify the results of SYBR Green I/PI assay. The most effective drug combinations as reflected by residual viable cell percentages of less than 30% are shown in bold type. The best drug combinations without daptomycin are underlined. Abbreviations: Dox, doxycycline; Amo, amoxicillin; CefP, cefoperazone; Cfz, clofazimine; Mcz, miconazole; Pmb, polymyxin B; Dap, daptomycin; Smx, sulfamethoxazole; Cab, carbencillin; Car, carbomycin; Van, vancomycin; Ofl, ofloxacin; Clar, clarithromycin; Tig, tigecycline; Hcq, hydroxychloroquine; Rif, rifampin. “-” indicates not determined. C = drug-free controlb. To eliminate the influence of red color of antibiotics, fluorescence data was corrected using antibiotic control.c. P-values of the standard t-test for the all treated group versus the drug-free control were less than 0.01 except the data marked with “c”.Effect of drug combinations on stationary phase B. burgdorferi culturea.