Dark ground microscopy
| Obtaining the specimen |
| • Cleanse lesion with saline using gauze swab |
| • Dry and abrade with dry gauze swab; or abrade with scalpel for intact papule or healing ulcer if necessary |
| • Squeeze clear serum—do not dilute with saline |
| • Collect oozing serum with edge of coverslip |
| • Put coverslip onto slide |
| • Press between filter paper evenly |
| Dark field microscope |
| • Use a dark field condenser |
| • Place 1 drop of oil on bottom of slide where the specimen is |
| • Put slide on the stage ensuring oil contact between condenser and slide |
| Objective ×10 |
| • Focus |
| • Close field diaphragm and centre the circular light beam with centring screws |
| • Open field diaphragm |
| Objective ×40 |
| • Search |
| Objective ×100 |
| • Place oil on top of the coverslip before using objective. |
| • Adjust the iris diaphragm in the objective for “darkness” of field |
| • Detail identification of spirochaetes looking for characteristic morphology and motility |