TYPING OF PNEUMOCYSTIS-CARINII F SP. HOMINIS BY SINGLE-STRAND CONFORMATION POLYMORPHISM OF 4 GENOMIC REGIONS

To better investigate Pneumocystis carinii f. sp, hominis epidemiology , we have developed a molecular typing method, Because of the limited genetic variability of the P. carinii hominis genome, a multitarget ap proach was used. Four variable regions of the genome were amplified by PCR, polymorphism in each region was assessed by the single-strand co nformation polymorphism (SSCP) technique, and the results for the four regions of each patient were combined, Bronchoalveolar lavage specime ns collected from 11 patients were examined, Four patients were probab ly infected by a single strain, since their specimens yielded simple S SCP patterns (two bands corresponding to one allele), The combinations of these patterns were unique, suggesting that the strains which infe cted these patients were different, For the other seven patients, comp lex patterns were found (three or four bands corresponding to two alle les), The presence of more than one allele of a region in a patient is likely to be due to coinfection, Polymorphism was also assessed by se quencing, which revealed variations at nucleotide positions previously reported to vary. About half of the observed alleles had already been reported by laboratories in different countries, Multitarget typing o f P. carinii hominis by PCR-SSCP should allow investigation of strain diversity and thus be useful for future epidemiological studies.