Abstract: Objective To study the relationship between different serotypes of Ureaplasma urealyticum and their pathogenesis. Methods 172 strains of Ureaplasma urealyticum were isolated from specimens of STD clinic patients, and pure cultures were serotyped by metabolic inhibition test. Results The results showed that all of the strains could be typed, in which, 150 strains (87 2%) attributed to a single type and 22 strains (12.8%) mixed serotypes. Serotypes frequently found were as follows: serotype 4 and 1 (both 31 strains,15.4%), serotype 3 (24 strains,11.9%), serotype 8 (20 strains,10%), serotype 14 (18 strains,9%), serotype 6 (16 strains,8%). Other serotypes were uncommen (3%～6.5%), serotype 7 was not found. No association was found between serotype and sex (P>0.05), except serotype 3 from NGU patients, which was more commonly found in women than in men (P<0.05). Of 172 strains, 102 were isolated from NGU patients. Ninety strains (88.2%) were attributed to a single serotype, and 12 strains (11.8%) mixed serotypes. Serotypes 4,1,and 8 were found frequently (>10%, respectively). Conclusion Serotype 4 was the one most frequently found and strongly related with NGU. It is suggested that the transformation from colonization to pathogenetic status be possible for serotype 3 under the influence of host and a certain environmental condition.

Key words: Ureaplasma urealyticum, Serotyping