DIAGNOSTIC METHODS: Concentrations

Tips and Pitfalls!

1. Centrifugation speed (formalin/ethyl acetate concentration) is critical for the adequate recovery of organisms. Recommended time/speed is 10 min at 500 Xg; this will allow recovery of all protozoa, including coccidian oocysts and microsporidian spores.
2. Remember: operculated eggs (trematode, Diphyllobothrium latum) and heavy eggs (unfertilized Ascaris lumbricoides eggs) will not float using the zinc sulfate flotation concentration method.
3. If using ethyl acetate and plastic tubes, remember to clean out the excess ethyl acetate from the inside of the tube with a cotton-tipped swab before making a wet mount. This will prevent excess ethyl acetate from giving a "bubbly" appearance under the coverslip. Wiping the inside of the tube is not as critical when using glass tubes.