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 Original Articles |
| Comparison of Nucleotide Sequence of Thymidylate Synthase from Human-derived Pneumocystis carinii with That from Rat-derived Pneumocystis carinii |
| Hyun-Joo Pai |
| Department of Internal Medicine, Dankook University Medical College, Cheonan, Korea |
Vol.27 Num.4 (p349~354)
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Background : Pneumocystis carinii is an opportunistic pulmonary pathogen that causes P. carinii pneumonia(PCP) in immunocompromised individuals. The organism thrives in a wide variety of mammals and recent reports indicate that genetic differences exist between organisms isolated from humans, ferrets and rats. In order to further examine this diversity within and between host species, a portion of the thymidylate synthase(TS) genes of P. carinii from human was sequenced and compared with known sequences of P. carinii from rat.
Methods : The clinical samples for human-derived P. carinii were bronchoalveolar lavage(BAL) fluid of PCP patients confirmed by methenamine silver stain. Using primers from known TS sequences of rat-derived P. carinii, polymerasse chain reaction was carried out and amplified products were sequenced. Results :
1) 403 bp size DNAs were amplified from 5 samples out of 6.
2) TS genes of human and rat derived P. carinii have 77.2% identity(83.7% if the intron sequences are excluded).
3) Intervening sequences of TS genes from rat and human-derived P. carinii have the same locations and their nucleotide homologies are 60%.
4) TS gene fragment(347bps) of human derived P. carinii had and Adenine + Thymidine content of 66.3%.
5) Amino acid identities were 89.2%.
6) The nucleotide sequences of PCR products amplified from 5 BAL samples were identical including intervening sequences.
Conclusion : These data showed that humans and rats harbor distinct forms of P. carinii and that organisms isolated from different hosts are probably different species of P. carinii.
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Keywords : Pneumocystis carinii, Thymidylate synthase, DNA sequences |
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