Growth of infectious and non-infectious B. burgdorferi at different salt concentrations.

Borrelia burgdorferi, the causative agent of Lyme disease, grows in vitro in modified Barbour-Stoenner-Kelly (BSK-H) medium. We have studied the effect of increased osmotic strength of culture media on growth of infectious and non-infectious B. burgdorferi strains B31 and N40. Relatively small increases in the NaCl concentration of the medium significantly inhibited growth in infectious as well as non-infectious strains. Growth of low passage, infectious clone B31-4a was more sensitive to increased NaCl concentrations than high passage, non-infectious clone B31-a. Growth of two infectious N40 strains, one low passage (N40-Lp) and one high passage (N40-P31) was more resistant to increased NaCl concentration than growth of infectious B31-4a. Osmotic strength is an important physical parameter for growth of B. burgdorferi in vitro and could influence its ability to adapt and to establish an infection within ticks and mammals.