Purpose Infectious microorganisms are hypothesized to contribute to the pathogenesis of chronic lung disease of prematurity (CLD) in very low birthweight (VLBW) infants. This hypothesis remains controversial. We hypothesized that colonization of the respiratory tree with Ureaplasma urealyticum (Uu), Adenovirus, or Chlamydia sp. increases the risk of CLD. Both Ureaplasma urealyticum and Adenovirus have been associated with CLD in previous studies. We analyzed endotracheal aspirate samples using PCR, a highly specific and sensitive method.
Methods Intubated, VLBW (≤1500 g) infants admitted at ≤72hrs of age between 1/01/99 and 12/31/02 were studied. Uu, Adenovirus, and Chlamydia sp. were detected by PCR from endotracheal aspirate samples. Outcome measures included CLD defined as O2 supplementation at 36 weeks corrected gestational age (CGA), and a combined outcome of death from lung disease or CLD at 36 weeks CGA. The frequency of detection of Uu, Adenovirus, and Chlamydia sp. was compared between patients with and without CLD using chi-squared and Fisher's exact tests. Logistic regression analysis was used to control for covariates.
Results 139 patients were enrolled, all were screened for Uu, 33 (25%) were positive; 136 patients were screened for Adenovirus, 22 (16%) were positive; 133 patients were screened for Chlamydia, 8 (6%), were positive. At 36 weeks CGA, 18 patients had died or been transferred, 68 (57%) were O2 dependent. Detection of Uu was associated with CLD at 36 wks CGA (p ≤0.001), Adenovirus (p 0.52) and Chlamydia (p 0.33) were not. Controlling for covariates, days of mechanical ventilation, OR for Uu and CLD at 36 weeks CGA was 3.08, with 95% CI (0.78, 11.6). 59% of subjects met the criteria for the combined outcome of death or CLD. Uu was significantly associated with this outcome (p ≤.0001), Adenovirus (p 0.39) and Chlamydia (p 0.36) were not. Controlling for covariates, OR for Uu and CLD at 36 weeks or death due to lung disease was 4.7, with 95% CI (1.026, 21.2).
Conclusions In our population, detection of Ureaplasma urealyticum in the respiratory tree of VLBW infants is associated with the combined outcome of need for supplemental O2 at 36 weeks CGA or death due to lung disease. Adenovirus was commonly detected in our population, but was not associated with CLD. Chlamydia sp. were rarely detected, and were not associated with CLD.