Abstract
Humans can be infected percutaneously by pathogenic Leptospira found in polluted water. In this study, an infection scenario was considered in which Leptospira swam in still water, came in contact with skin, and then invaded it. Specifically, adhesion potential of Leptospira onto skin was estimated by applying an interfacial free energy concept. In addition, the swimming force of Leptospira in still water and its invasion force to invade soft agar, used as a surrogate for skin, were estimated using a spiral-type magnetic micromachine. These results showed that the change in free energy (ΔGadh) of the experimental strain L. biflexa was approximately equal to -21 dyn/cm (-0.0021 N/m). This value would readily allow its adhesion onto skin, which was demonstrated with experiments of L. biflexa adhesion onto human fingers. Leptospira could rotate when its torque was greater than 2.9 × 10-18 Nm and swim in still water when the flagellar motion was assumed to be 100 rotations/s. Leptospira could also invade soft agar with an invasion force of 9.0 × 10-13 to 2.2 × 10-12 N. These factors could be used for controlling leptospirosis before medical intervention is necessary and may help in developing means for infection prophylaxis.
