The presence of inflammatory mediators in the respiratory tract of young children has been associated with significant pulmonary pathology due to various bacterial and viral pathogens. Development of chronic lung disease in preterm infants has been associated with the recovery of Ureaplasma urealyticum (Uu) from the respiratory tract of these infants, suggesting that similar mechanisms may be involved in the pathogenesis of chronic lung disease due to Uu. It has been proposed that Uu can induce an inflammatory response, which ultimately results in lung injury in susceptible preterm infants. However, the pathogenic mechanisms involved in this process remain to be elucidated.

We obtained endotracheal aspirates (ETA) from 44 intubated preterm infants and performed cultures of the ETA for both Uu and Mycoplasma hominis (Mh). Ten infants had a positive ETA culture; 7 were positive only for Uu, 2 were positive for Uu and Mh, and 1 was positive for only Mh. The infants' mean birth weight was 864 gm (range: 498-1164 gm), and mean gestational age was 26 weeks (range: 24-29 wks). The ETA samples were obtained at a mean age of 9.6 days (range 1-51 days). Eight of 10 infants developed chronic lung disease as defined by oxygen requirement at 28 days of age. The one infant who had only Mh isolated from the ETA culture did not develop chronic lung disease. We measured IL-6 and RANTES from these culture-positive ETA specimens. We were able to detect IL-6 in all the ETA samples from these infants with the mean concentration of 4891 pg/mL (range: 92 - 19080 pg/mL). RANTES was detected in 7 out of 10 ETA samples with a mean concentration of 90 pg/mL (range: 4 - 435 pg/mL). In the infant positive for Mh alone, the ETA concentration of IL-6 was 8068 pg/mL and that of RANTES was 354 pg/mL.

We conclude that the presence of Uu in the lower respiratory tract of preterm infants can elicit inflammatory mediators that may contribute to the development of chronic lung disease. This suggests a potential role for immunomodulatory therapy in infants with chronic lung disease who are colonized with Uu.