Comparison of MKP and BSK-H media for the cultivation and isolation of Borrelia burgdorferi sensu lato

The isolation of B. burgdorferi sensu lato requires the use of complex cultivation media. The aim of the study was to compare the usefulness of BSK-H (a commercial medium produced by HiMedia, India) and MKP medium. MKP and BSK-H media were prepared in accordance with the relevant protocols. Borrelia strains and skin culture biopsies were simultaneously inoculated into both media, incubated and checked for growth. Borrelial growth characteristics, isolation rates and characteristics of the isolated borreliae were analysed and compared. Initially, numbers of spirochaetes were higher in BSK-H than in MKP; however, in comparison with MKP, the strains subcultured in BSK-H medium were more frequently irregular, thin and non-motile, and rapidly died. In addition, the borrelial isolation rate from erythema migrans skin samples was higher in MKP than in BSK-H medium (108/171, 63.2% versus 70/171, 40.9%; p<0.0001). The far most frequently isolated species was Borrelia afzelii (92.9% and 97.2% strains isolated from BSK-H and MKP, respectively). Comparison of strains cultured from individual patients in both media showed differences in plasmid contents in 9/46 (19.6%) strain pairs, and protein profiles differed in 30/43 (69.8%) strain pairs, most often in the expression of OspC (in 27/28 patients OspC was expressed only in strains growing in MKP). BSK-H medium supports the growth of borrelial strains but MKP is superior with regard to the isolation rate, morphology and motility of strains. BSK-H medium supports fast initial growth of borreliae but this is followed by rapid deformation and death of the spirochaetes.