Or search: costia, giardia, protozoan, protozoon, flagellate, leishmania, mastigophora, zoomastigote, polymastigote, zooflagellate, dinoflagellate, hypermastigote
3 Syllables: SUU
dominance, dominant, Donovan, fraudulent, Jonathan, Ottoman, prominence, prominent, Protestant, Providence, Solomon, Solomon's, tolerance, tolerant
4 Syllables: USUU
concomitants, diocesan, improvidence, intolerance, intolerant, predominance, predominant, reconnaissance
4 Syllables: UUSU
concomitant
5 Syllables: UUSUU
cosmopolitan, metropolitan, Neapolitan

Found 26 words across 4 groupings. Skipped 1 excess word of a similar stem.