Clinical correlation of variations in the internal transcribed spacer regions of rRNA genes in Pneumocystis carinii f.sp. hominis

AIDS. 2001 Mar 9;15(4):451-9. doi: 10.1097/00002030-200103090-00003.


Objectives: To analyse the importance of sequence variations in the internal transcribed spacer (ITS) regions 1 and 2 of the nuclear rRNA operon in AIDS patients with Pneumocystis carinii pneumonia (PCP).

Design and methods: ITS 1 and 2 genotypes were determined in 162 bronchoalveolar lavage samples from 130 patients participating in a prospective cohort study of PCP.

Results: A total of 49 different ITS genotypes were detected. ITS genotype was not associated with the clinical severity or outcome of PCP. In 37 of 162 (23%) samples infection with two or more genotypes was observed. A genotype switch was detected in six of 10 patients (60%) with recurrent episodes of PCP. However, genotype changes were also seen in 10 of 19 patients (53%) who had repeated bronchoscopies within the same episode of PCP. The same ITS type was observed twice in 13 (46%) of the 28 patients with repeat bronchoscopies during single or recurrent episodes of pneumonia, but in only 14 of 81 (17%) randomly selected pairs (P < 0.01).

Conclusion: Although the detection of ITS genotypes is not a random event, changes in genotype can be detected in a single episode of disease, with 23% of PCP patients being infected with more than one P. carinii genotype, thus complicating the use of this locus as a genetic marker to separate new infection from the reactivation of latent infection. ITS genotypes are not associated with the clinical severity of PCP.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • AIDS-Related Opportunistic Infections / microbiology*
  • Adult
  • Aged
  • Cohort Studies
  • DNA, Intergenic
  • Female
  • Genetic Markers
  • Genetic Variation
  • Genotype
  • HIV Seropositivity / complications*
  • HIV-1
  • Humans
  • Male
  • Middle Aged
  • Pneumocystis / genetics*
  • Pneumocystis / pathogenicity
  • Pneumonia, Pneumocystis / complications
  • Pneumonia, Pneumocystis / diagnosis
  • Pneumonia, Pneumocystis / microbiology*
  • Prospective Studies
  • rRNA Operon / genetics*


  • DNA, Intergenic
  • Genetic Markers