Molecular characterization of one stable strain of Trypanosoma cruzi, the 21
SF, representative of the pattern of strains isolated from the endemic area of São
Felipe, State of Bahia, Brazil, maintained for 15 years in laboratory by serial passages in mice
and classified as biodeme Type II and zymodeme 2 has been investigated. The kinetoplast
DNA (kDNA) of parental strain, 5 clones and 14 subclones were analyzed. Schizodeme was
established by comparative study of the fragments obtained from digestion of the 330-bp
fragments amplified by polymerase chain reaction (PCR) from the variable regions of the
minicicles, and digested by restriction endonucleases Rsa I and Hinf I. Our results show a high
percentual of similarity between the restriction fragment lenght polymorphism (RFLP) for the
parental strain and its clones and among these individual clones and their subclones at a level
of 80 to 100%.This homology indicates a predominance of the same "principal clone" in the
21SF strain and confirms the homogeneity previously observed at biological and isozymic
analysis. These results suggest the possibility that the T. cruzi strains with similar
biological and isoenzymic patterns, circulating in this endemic area, are representative of one
dominant clone.
The presence of "principal clones" could be responsible for a predominant tropism of the
parasites for specific organs and tissues and this could contribute to the pattern of
clinico-pathological manifestations of Chagas's disease in one geographical area.
