Vertical transmission of Pneumocystis jirovecii in humans
https://wwwnc.cdc.gov/eid/article/15/1/08-0242_article
This study aimed to assess whether Pneumocystis jirovecii can be transmitted transplacentally from immunocompetent mothers to fetuses using molecular assays. It demonstrated the presence of P. jirovecii DNA at two gene loci in lung tissues of 35% of fetuses and placentas of 5%, providing molecular evidence of vertical transmission. These findings suggest that P. jirovecii may cross the placental barrier in humans, warranting further investigation into its potential role in miscarriage or fetal compromise
Pneumocystis jirovecii is a stenoxenic fungal pathogen whose primary route of transmission is considered airborne, yet the early acquisition observed in infants has led to the hypothesis of additional pathways, including vertical transmission. To investigate this possibility, we analyzed paraffin-embedded placental and fetal lung tissues from 20 miscarriages at a mean gestational age of 28 ± 8 weeks. DNA extraction was performed under stringent conditions, and nested PCR targeting two independent genetic loci of P. jirovecii—the mitochondrial large subunit rRNA gene and the dihydropteroate synthase gene—was applied, with sequencing used to confirm positive results and determine genotypes. Molecular evidence of P. jirovecii was obtained in 11 fetal lung and 8 placental samples, with dual-locus confirmation in 7 (35%) of 20 fetuses and in 1 (5%) of 20 placentas. Sequence analysis identified three polymorphisms in the mtLSU-rRNA gene, while all DHPS sequences corresponded to wild-type genotypes. The detection of fungal DNA in a substantial proportion of fetal tissues indicates that transplacental passage of P. jirovecii from immunocompetent mothers to the fetus is possible, potentially facilitated by the physiological immunodepression associated with pregnancy. Although the presence of the microorganism in aborted fetuses does not establish a causal role in miscarriage, the high frequency observed raises the possibility that vertical transmission contributes both to adverse pregnancy outcomes and to the early-life colonization widely reported in infants. These findings represent the first molecular demonstration of in utero transmission of P. jirovecii in humans and highlight the need for further studies to define its epidemiological significance, its clinical consequences for neonatal health, and its implications for maternal–fetal medicine.
