Pneumocystis colonization is highly prevalent in the autopsied lungs of the general population.

BACKGROUND: Increasing reports of Pneumocystis DNA in noninvasive respiratory specimens from immunocompetent asymptomatic adults and the characteristic lung tropism of Pneumocystis suggest that asymptomatic pulmonary infections with Pneumocystis occur after primary infection. However, studies searching for Pneumocystis in the autopsied lungs of healthy immunocompetent adults have not met with success. METHODS: Lungs of people who died of violent causes (accidents, homicide, and suicide) and of nonviolent causes (diseases causing a rapid demise in the street) in Santiago, Chile-for whom an autopsy was legally required-were examined for Pneumocystis by nested polymerase chain reaction (PCR) DNA amplification of the mitochondrial large subunit ribosomal RNA-specific P. jirovecii gene and immunofluorescent microscopic analysis. Lung tissue concentration methods and analysis of approximately 3% of the weight of the right upper lobe (RUL) were needed to reach the sensitivity threshold of the assays. Individuals determined to be P. jirovecii negative after analysis of 3% of the RUL weight in the violent death group were confirmed to be negative by analyzing additional tissue, totaling 6%-7% of the RUL weight. RESULTS: P. jirovecii was identified by nested PCR in 50 (64.9%) of 77 individuals (34 [61.8%] of 55 in the violent death group and 15 [78.9%] of 19 in the nonviolent death group; P > .05) and additionally by microscopic analysis in all individuals who tested positive for P. jirovecii DNA in the violent death group. Analysis of tissue beyond 3.0% of the RUL weight for the individuals who tested negative yielded consistently negative results. CONCLUSIONS: A mild P. jirovecii pulmonary infection is prevalent in more than half of the general adult population. Our results strengthen the concept that immunocompetent adults develop frequent self-limited reinfections throughout life and participate in the circulation of P. jirovecii as an infective reservoir for susceptible individuals.

Diagnosis of the primary infection by pneumocystis in autopsy specimens from two infants using lung impression smears (touch preps).

The primary infection by Pneumocystis of normal, healthy infants is asymptomatic and goes undiagnosed. Microscopy diagnosis of Pneumocystis was sought in lung impression smears (LIS) from two ~3-month-old infants dying unexpectedly in the community. Pneumocystis nuclei and cysts were identified using Hema-Gurr with subsequent Gomori-Grocott staining in the same spot documenting that these stains may be complementary. LIS provide for an observer-dependent, inexpensive, and ready-available method for detection of Pneumocystis in infant lungs.

Fungal colonization with Pneumocystis correlates to increasing chloride channel accessory 1 (hCLCA1) suggesting a pathway for up-regulation of airway mucus responses, in infant lungs.

Fungal colonization with Pneumocystis is associated with increased airway mucus in infants during their primary Pneumocystis infection, and to severity of COPD in adults. The pathogenic mechanisms are under investigation. Interestingly, increased levels of hCLCA1 - a member of the calcium-sensitive chloride conductance family of proteins that drives mucus hypersecretion - have been associated with increased mucus production in patients diagnosed with COPD and in immunocompetent rodents with Pneumocystis infection. Pneumocystis is highly prevalent in infants; therefore, the contribution of Pneumocystis to hCLCA1 expression was examined in autopsied infant lungs. Respiratory viruses that may potentially increase mucus, were also examined. hCLCA1 expression was measured using actin-normalized Western-blot, and the burden of Pneumocystis organisms was quantified by qPCR in 55 autopsied lungs from apparently healthy infants who died in the community. Respiratory viruses were diagnosed using RT-PCR for RSV, metapneumovirus, influenza, and parainfluenza viruses; and by PCR for adenovirus. hCLCA1 levels in virus positive samples were comparable to those in virus-negative samples. An association between Pneumocystis and increased hCLCA1 expression was documented (P=0.028). Additionally, increasing Pneumocystis burden correlated with increasing hCLCA1 protein expression levels (P=0.017). Results strengthen the evidence of Pneumocystis-associated up-regulation of mucus-related airway responses in infant lungs. Further characterization of this immunocompetent host-Pneumocystis-interaction, including assessment of potential clinical significance, is warranted.

Detection of Pneumocystis carinii f. sp. hominis and viruses in presumably immunocompetent infants who died in the hospital or in the community.

Fresh-frozen lung and tracheal-aspirate specimens obtained from 112 infants who died in Santiago, Chile, during 1998-2000 were analyzed for the presence of Pneumocystis DNA, by use of nested DNA amplification of the large subunit mitochondrial rRNA, and for the presence of viruses, by use of culture and immunofluorescence. Pneumocystis DNA was detected in specimens from 45 (51.7%) of 87 infants who died in the community and from 5 (20%) of 25 infants who died in the hospital (P=.006). Primary infection with Pneumocystis was highly frequent among infants who die unexpectedly in the community. Infection with viruses was more common in infants who died in the hospital.