Am. J. Respir. Crit. Care Med., Vol 153, No. 5, May 1996, 1567-1570.
Lung hyaluronan decreases during group B streptococcal pneumonia in neonatal piglets
SE Juul, MG Kinsella, WE Truog, RL Gibson and GJ Redding
Department of Pediatrics, University of Washington, Seattle, USA.
Neonatal Group B streptococcus (GBS) sepsis and pneumonia result in lung
injury and remain a major cause of morbidity and mortality in the newborn.
Increased lung hyaluronan (HA) content is an important component of the
lung's early response to damage in diseases such as adult respiratory
distress syndrome (ARDS), infant respiratory distress syndrome (IRDS), and
bleomycin-induced fibrosis. It is known, however, that GBS virulence
factors include specific secretory enzymes such as hyaluronidase, an enzyme
which breaks down HA. We therefore hypothesized that in lobar GBS
pneumonia, lung HA would be decreased compared with normal values, and that
in lobar pneumonia with atelectasis, lung HA would be further decreased
because of increased substrate availability. The right lower lobes (RLL)
and left lower lobes (LLL) of anesthetized piglets 16 +/- 2 d old were each
selectively inoculated with 1 x 10(9) colony-forming units (CFU) GBS via an
endobronchial catheter (n = 7). The LLL was subsequently collapsed by
endobronchial occlusion following 10 min of 100% O2. Control animals (n =
6) was anesthetized, instrumented, and ventilated without exposure to GBS.
At 4 h, lungs were removed and HA extracted and assayed using a competitive
inhibition assay. HA extracted from areas of lobar pneumonia was
significantly decreased (27 +/- 6.6 micrograms/g wet lung, p < 0.005)
when compared with control values of control piglets (51 +/- 19.6
micrograms/g wet lung). Atelectasis plus lobar pneumonia further decreased
lung HA to 10 +/- 13.3 micrograms/g wet lung, p < 0.0001. We conclude
that lobar GBS decreases lung HA and that this process is augmented by
collapsed lung regions, and speculate that this departure from the usual
early lung response to injury contributes to GBS invasion of lung
parenchyma.