Figure 2. Differentiation of Rickettsia rickettsii type strain Sheila Smith from Montana from R. rickettsii strains from Central and South America. A tandem repeat region corresponding to 563048–563028 nt of the strain Sheila Smith genome and flanking sequences were amplified with AF (5′-GTGATTGCTATATTTCGCTTT-3′) and AR (5′- CTAAGATTTGTTCCGTATAGG-3′) primers as described elsewhere (7). Repeat sequence (GCCTTAT, indicated with brackets) present in 3 copies in strain Sheila Smith, whereas only 2 copies were present in R. rickettsii isolates from Brazil, Colombia, Costa Rica, and Panama. Homologous sequences of these strains are deposited to GenBank under the following accession nos.: DQ666020, R. rickettsii strain Panama 2004; DQ666021, R. rickettsii strain Brazil; DQ666022, R. rickettsii strain Colombia; DQ666023, and R. rickettsii strain Costa Rica.