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Hyperoxia potentiates Ureaplasma urealyticum pneumonia in newborn mice
D T Crouse1, G H Cassell, K B Waites
1Department of Pediatrics, University of Alabama, Birmingham 35294.
Abstract:
The effect of continuous exposure to 80% oxygen on newborn mice with Ureaplasma urealyticum pneumonia was determined. Mice were inoculated intranasally with either U. urealyticum or sterile broth and then housed in either 80% oxygen or room air (21% oxygen). The mice were sacrificed at either 7 or 14 days after inoculation. Significantly more mice in the U. urealyticum group housed in 80% O2 than in the room air-exposed group were culture positive 14 days after inoculation (P = 0.042), but no difference was found at 7 days. The presence of alveolar macrophages, neutrophils, and lymphocytes and alveolar wall thickness were determined. Overall, the group housed in 80% O2 and inoculated with U. urealyticum had severe pulmonary lesions at both time points, while the lesion severity in the room air-exposed group inoculated with U. urealyticum and the group housed in 80% O2 and inoculated with sterile broth was dependent on the time point. Mortality was significantly higher in the group housed in 80% O2 and inoculated with U. urealyticum than it was in all other groups (P less than 0.001). Our results indicate that hyperoxia causes the persistence of U. urealyticum in the lungs of newborn mice, acutely potentiates the inflammatory response, and turns an otherwise self-limited pneumonia into a lethal disease.
Insights
High oxygen exposure worsens Ureaplasma urealyticum pneumonia in newborn mice. This hyperoxia increases bacterial persistence, inflammation, and mortality, turning mild pneumonia into a fatal condition.
Area of Science:
- Neonatal respiratory research
- Microbiology
- Pulmonary pathology
Background:
- Ureaplasma urealyticum is a common cause of pneumonia in premature infants.
- The impact of hyperoxia on U. urealyticum pneumonia in neonates is not fully understood.
Purpose of the Study:
- To investigate the effects of continuous 80% oxygen exposure on newborn mice with Ureaplasma urealyticum pneumonia.
Main Methods:
- Mice were intranasally inoculated with U. urealyticum or sterile broth.
- Mice were housed in 80% oxygen or room air (21% oxygen).
- Cultures, lung histology, and mortality were assessed at 7 and 14 days.
Main Results:
- Hyperoxia (80% O2) significantly increased U. urealyticum persistence at 14 days.
- Mice exposed to hyperoxia and U. urealyticum showed severe lung lesions and significantly higher mortality.
- Hyperoxia potentiated the inflammatory response in the lungs.
Conclusions:
- Continuous hyperoxia exacerbates U. urealyticum pneumonia in newborn mice.
- Hyperoxia promotes bacterial persistence and increases lung inflammation and mortality.
- This suggests hyperoxia transforms a self-limiting pneumonia into a lethal disease in neonates.