Table 1. Airborne transmission of P. carinii stage populations to nude rats.
|
Detection of P. carinii organisms (at the end of contact) |
PcP development (7 weeks postcontact) | |||
|---|---|---|---|---|
|
Seeder rats
|
Receiver rats | Receiver rats | ||
| P. carinii-stage population inoculated to seeder rats | Mean P. carinii burden (1) | Molecular detection (2) | Molecular detection (3) | Microscopic and molecular detection (4) |
| Pure P. carinii total population | 6.2 × 103 ± 2.48 × 103 (n = 19) | All positive (n = 19) | 3 positive (n = 4) | All negative (n = 4) |
| Pure P. carinii trophic forms | 8.9 × 103 ± 4.9 × 103 (n = 19) | All positive (n = 19) | All negative (n = 4) | All negative (n = 4) |
| Pure P. carinii cystic forms | 3.9 × 103 ± 2.0 × 103 (n = 16) | All positive (n = 16) | 3 positive (n = 4) | All negative (n = 4) |
(1) P. carinii burden is microscopically quantified as the number of trophic forms and/or cystic forms on calibrated RAL-555 stained-smears (2). A single-round touchdown PCR (TD-PCR) targeting the multicopy gene coding for the ribosomal RNA of the large mitochondrial subunit (mtLSUrRNA) was used to detect P. carinii gDNA in lung tissue extracts of seeder rats [32]. (3) Since TD-PCR at the mtLSUrRNA locus revealed to be negative for receiver rats, nested-PCR (nPCR) at the same locus was subsequently performed on whole lung tissue extract to increase sensitivity [5]. (4) Following 7 weeks of immunosuppression, PcP development was microscopically monitored on smears of lung tissue extracts stained with RAL-555 [26-29]; as careful microscopical screening revealed to be negative, nPCR at the mtLSUrRNA was performed on all lung tissue extracts. Whole lung tissue extracts of all sentinel rats (n = 6) were also screened for the presence of P. carinii gDNA by nPCR at the mtLSUrRNA locus and all samples were negative. The number (n) of individual rats analyzed is indicated for each animal group.