TABLE 4.

Quantitation of sucrose-purified seeds of different R. rickettsii isolates by plaque assay and SQ-PCR

IsolateNo. of rickettsiae (PFU/ml [PFU/ml after centrifugation])aCtNo. of calculated DNA copies/ml after 1 to 4 yrs of seed storage
After overnight freezeAfter 1 to 4 yrs of storage
Brazil3.80 × 107 ± 0.92 × 1072.30 × 107 ± 0.45 × 107 (1.30 × 109 ± 0.23 × 109)24.80 ± 0.234.97 × 108 ± 0.91 × 108
84JG1.92 × 107 ± 0.43 × 107 (1.5 × 109)1.45 × 107 ± 0.15 × 107 (7.05 × 109 ± 1.28 × 109)21.92 ± 0.254.74 × 108 ± 0.86 × 109
Hlp#26.0 × 1054.33 × 105 ± 0.58 × 105 (1.10 × 107 ± 0.26 × 107)24.47 ± 0.832.83 × 108 ± 1.72 × 108
Bitterroot9.13 × 107 ± 2.02 × 1072.90 × 106 ± 0.73 × 106 (6.48 × 107 ± 1.56 × 107)23.80 ± 0.241.38 × 109 ± 0.27 × 109
Colombia2.55 × 107 ± 0.05 × 1071.97 × 107 ± 0.15 × 107 (6.30 × 108 ± 0.89 × 108)23.27 ± 0.251.13 × 109 ± 0.20 × 109
Lost Horse Canyon1.03 × 107 ± 0.25 × 1072.15 × 107 ± 0.45 × 107 (4.58 × 108 ± 0.92 × 108)22.99 ± 0.273.11 × 109 ± 0.61 × 109
Morgan2.10 × 106 ± 0.63 × 1061.70 × 107 ± 0.60 × 107 (7.43 × 108 ± 0.57 × 108)25.18 ± 0.454.01 × 108 ± 2.05 × 108
Price T4.0 × 107 ± 1.05 × 1071.77 × 107 ± 0.23 × 107 (4.60 × 108 ± 0.46 × 108)20.13 ± 0.471.21 × 1010 ± 0.38 × 1010
Sheila Smith3.90 × 107 ± 1.06 × 107 (9.0 × 108 ± 5.0 × 108)Not done21.98 ± 0.593.16 × 108 ± 1.06 × 108b
  • a Numbers in parentheses are PFU titers determined after centrifugation of rickettsiae onto Vero cells. Data are means±standard errors of the means.

  • b The DNA copy number for isolate Sheila Smith was determined only for freshly prepared frozen seed.