Near-universal prevalence of Pneumocystis and associated increase in mucus in the lungs of infants with sudden unexpected death.
BACKGROUND
Pneumocystis without obvious accompanying pathology is occasionally reported in autopsied infant lungs. Its prevalence and significance are unknown. Interestingly, this mild infection induces a strong activation of mucus secretion-related genes in young immunocompetent rodents that has not been explored in infants. Excess mucus is induced by multiple airway offenders through nonspecific pathways and would explain a cofactor role of Pneumocystis in respiratory disease. We undertook characterization of the prevalence of Pneumocystis and associated mucus in infant lungs.


METHODS
Samples from 128 infants (mean age, 101 days) who died suddenly and unexpectedly in Santiago during 1999-2004 were examined for Pneumocystis using nested polymerase chain reaction (nPCR) amplification of the P. jirovecii mtLSU ribosomal RNA gene and immunofluorescence microscopy (IF). Pneumocystis-negative infants 28 days and older and their age-closest positives were studied for MUC5AC expression and Pneumocystis burden by Western blot and quantitative PCR, respectively.


RESULTS
Pneumocystis DNA was detected by nPCR in 105 of the 128 infants (82.0%) and Pneumocystis organisms were visualized by IF in 99 (94.3%) of the DNA-positive infants. The infection was commonest at 3-4 months with 40 of 41 (97.6%) infants of that age testing positive. MUC5AC was significantly increased in Pneumocystis-positive tissue specimens (P = .013). Death was unexplained in 113 (88.3%) infants; Pneumocystis was detected in 95 (84.0%) of them vs 10 of 15 (66.7%) with explained death (P = .28).


CONCLUSIONS
A highly focal Pneumocystis infection associated to increased mucus expression is almost universally present in the lungs of infants dying unexpectedly in the community regardless of autopsy diagnosis.
Programa de Microbiología, Instituto de Ciencias Biomédicas, Facultad de Medicina Universidad de Chile, Santiago, Chile. svargas@med.uchile.cl
Sergio L
SL
Vargas
Carolina A
CA
Ponce
Miriam
M
Gallo
Francisco
F
Pérez
J-Felipe
JF
Astorga
Rebeca
R
Bustamante
Magali
M
Chabé
Isabelle
I
Durand-Joly
Pablo
P
Iturra
Robert F
RF
Miller
El Moukthar
el M
Aliouat
Eduardo
E
Dei-Cas
D001344:Autopsy; D015169:Colony Count, Microbial; D004271:DNA, Fungal / Q000235:genetics; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008168:Lung / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D008297:Male; D008853:Microscopy; D055271:Mucin 5AC / Q000378:metabolism; D009093:Mucus / Q000378:metabolism*; D021141:Nucleic Acid Amplification Techniques; D011010:Pneumocystis / Q000235:genetics / Q000302:isolation & purification*; D011020:Pneumonia, Pneumocystis / Q000175:diagnosis / Q000453:epidemiology* / Q000382:microbiology; D015995:Prevalence; D012680:Sensitivity and Specificity; D013398:Sudden Infant Death / Q000175:diagnosis / Q000453:epidemiology*
D004271:DNA, Fungal; C524678:MUC5AC protein, human; D055271:Mucin 5AC