Volume 12, Number 11—November 2006
Letter
Real-time PCR for Francisella tularensis Types A and B
Table
Comparison of standard diagnostic methods with the multitarget Francisella tularensis TaqMan assay and type A and type B assays using primary specimens
| Specimen | Source | F. tularensis identified* | Subspecies identification† | Multitarget F. tularensis TaqMan assay‡ | Type A assay‡ (Ct value)§ | Type B assay‡ (Ct value) | ||
|---|---|---|---|---|---|---|---|---|
| ISFtu2 | IglC | tul4 | ||||||
| Lymph node aspirate | Human | + | + | + | + | 31 | – | |
| Bronchial wash | Human | + | A | + | + | + | 34 | – |
| Upper lung | Human | + | A | + | + | + | 20 | – |
| Lower lung | Human | + | A | + | + | + | 26 | – |
| Liver | Human | + | A | + | + | + | 29 | – |
| Spleen | Human | + | A | + | + | + | 31 | – |
| Pleural fluid | Human | + | B | + | + | + | – | 36 |
| Blood | Human | + | + | + | + | – | 38 | |
| Spleen | Human | – | – | – | – | – | – | |
| Liver | Human | – | – | – | – | – | – | |
| Cerebrospinal fluid | Human | – | – | – | – | – | – | |
| Blood | Human | – | – | – | – | – | – | |
| Liver/spleen | Tamarin | + | + | + | + | 28 | – | |
| Tissue | Tick¶ | + | A | + | + | + | 26 | – |
| Tissue | Tick¶ | + | A | + | + | + | 33 | – |
| Blood | Prairie dog | + | B | + | + | + | – | 30 |
| Blood | Prairie dog | + | B | + | + | + | – | 27 |
| Spleen | Prairie dog | + | B | + | + | + | – | 21 |
| Spleen | Prairie dog | + | B | + | + | + | – | 31 |
| Spleen | Prairie dog | – | – | – | – | – | – | |
| Liver | Cat | – | – | – | – | – | – | |
| Liver | Rat | – | – | – | – | – | – | |
| Spleen | Rat | – | – | – | – | – | – | |
| Spleen | Squirrel | – | – | – | – | – | –
*F. tularensis infection identified by culture, direct fluorescent antibody testing, or serologic testing. | |
*F. tularensis infection identified by culture, direct fluorescent antibody testing, or serologic testing.
†Subspecies was determined by glycerol fermentation when an isolate was recovered.
‡+ = positive result, 17<Ct <38; – = negative result, no fluorescence detected after 45 cycles of amplification.
§Ct, cycle threshold.
¶Tick species tested were Haemaphysalis leporispalustris and Dermacentor andersoni.