Objective: To determine whether the presence of Ureaplasma urealyticum in the respiratory tracts of very low birth weight infants is associated with increased risk of pneumonia, radiographic evidence of severe bronchopulmonary dysplasia during the second or third week of life (precocious) and oxygen dependency at 36 weeks of corrected postnatal gestational age.
Methods: From October, 1993, to January, 1996, all infants who met the following entry criteria were enrolled in the study: birth weights < or = 1500 g; admission to the NICU within 24 h after birth; evidence on admission of respiratory distress; and no prior antibiotic treatment. Infants were cultured for mycoplasmas, viruses, chlamydiae and aerobic and anaeroic bacteria.
Results: Ninety-four critically ill newborns constituted our study cohort. Within 7 days of birth more infants with U. urealyticum infection showed radiographic features of pneumonia (53.1%, 25 of 47) than infants without U. urealyticum infection (21.2%, 10 of 47). Infants with U. urealyticum were more likely to have radiographic evidence of precocious bronchopulmonary dysplasia than those without this isolate (22.5%, 9 of 40 vs. 2.3%, 1 of 42). The relative risk of oxygen dependency at 36 weeks of corrected age in U. urealyticum-positive infants was 11.0 times that in U. urealyticum-negative infants (95% confidence interval, 1.6 to 75.5). Association of U. urealyticum and chronic lung disease at this age was not weakened after adjustments were made in a multivariate analysis for other significant risk factors including gestational age and presence of a patent ductus arteriosus.
Conclusions: Isolation of U. urealyticum from respiratory tracts is associated with radiographic changes compatible with pneumonia within 7 days of birth, precocious bronchopulmonary dysplasia and severe pulmonary outcome.