Maternal azithromycin therapy for Ureaplasma intraamniotic infection delays preterm delivery and reduces fetal lung injury in a primate model

Abstract

Objective: We assessed the efficacy of a maternal multidose azithromycin (AZI) regimen, with and without antiinflammatory agents to delay preterm birth and to mitigate fetal lung injury associated with Ureaplasma parvum intraamniotic infection.

Study design: Long-term catheterized rhesus monkeys (n = 16) received intraamniotic inoculation of U parvum (10(7) colony-forming U/mL, serovar 1). After contraction onset, rhesus monkeys received no treatment (n = 6); AZI (12.5 mg/kg, every 12 h, intravenous for 10 days; n = 5); or AZI plus dexamethasone and indomethacin (n = 5). Outcomes included amniotic fluid proinflammatory mediators, U parvum cultures and polymerase chain reaction, AZI pharmacokinetics, and the extent of fetal lung inflammation.

Results: Maternal AZI therapy eradicated U parvum intraamniotic infection from the amniotic fluid within 4 days. Placenta and fetal tissues were 90% culture negative at delivery. AZI therapy significantly delayed preterm delivery and prevented advanced fetal lung injury, although residual acute chorioamnionitis persisted.

Conclusion: Specific maternal antibiotic therapy can eradicate U parvum from the amniotic fluid and key fetal organs, with subsequent prolongation of pregnancy, which provides a therapeutic window of opportunity to effectively reduce the severity of fetal lung injury.

Conflict of interest statement

DISCLOSURE: None of the authors have a conflict of interest

Copyright © 2012 Mosby, Inc. All rights reserved.

Figures

Figure 1. Kaplan–Meier Plot Illustrating the Percentage of Animals Remaining Undelivered in Days Following Intra–Amniotic Inoculation of U. parvum

The survival analysis compared data for U. parvum untreated animals (red line, n=6) with the combined data for AZI and AZI plus DEX/INDO treated animals (black line, n=10). There is a clear and uniform prolongation of in utero fetal survival and an increase in the mean inoculation–to–delivery interval in the AZI treated animals compared to untreated U. parvum IAI (20.9 ± 1.4 days vs. 13.7 ± 2.5 days, respectively; P<0.05).

Figure 2. Temporal Relationship of Maternal Plasma and Amniotic Fluid Azithromycin (AZI) Concentrations

A representative animal illustrating maternal plasma (blue circles) and amniotic fluid (black triangles) AZI concentrations (ng/ml) during maternal multi–dosing (12.5mg/kg, q12h, IV for 10 days) and subsequent washout period. Ureaplasma colony counts (CFU/ml) are also depicted (red circles). Frequent sampling was performed at the beginning and end of AZI administration; daily samples were obtained during the intervening days of AZI infusion (gray shaded bar) and in the A.M. after cessation of treatment (AZI washout period). Steady–state levels of AZI (75–300ng/ml) in the amniotic fluid equaled or surpassed maternal plasma concentrations at the end of the 10–day treatment interval, thus indicating accumulation of AZI in the amniotic fluid which provides an extended therapeutic window. At stead–state, AZI inhibitory concentrations in the amniotic fluid exceeded the EC50, the concentration needed to eradicate 50% of U. parvum, by 5–fold (red dashed line).

Figure 3. Amniotic fluid U. parvum (CFU/ml) Growth Curves (log scale)

A representative group of animals from each AZI treatment group is shown (AZI alone, colored circles, n=3 and AZI plus DEX/INDO, colored squares; n=3) from inoculation–to–treatment and from the start of treatment–to–clearance (gray shaded area). In all animals, amniotic fluid CFU/ml peaked before the start of treatment and declined rapidly in the first 24h of AZI treatment. U. parvum microorganisms were eradicated from the amniotic fluid within 4 days (range 2–7 days).

Figure 4. Histopathology of the Fetal Lung

Comparative evaluation of fetal lung histology among U. parvum IAI and antimicrobial treatment animals is illustrated. (A) Control non–infected lung at 131dGA showing partial atelectasis and absence of alveolar inflammatory cells; (B)U. parvum IAI for 15days (153dGA) demonstrating hyperplasia and hypertrophy of type II pneumocytes (arrow head); (C)U. parvum IAI for 21days (146dGA) illustrates large peribronchiolar lymphocytic aggregates and hyperplasia of bronchiolar epithelium (L); (D)U. parvum IAI for 7days (155dGA) treated with AZI plus DEX/INDO showing resolution of pneumonitis with residual leukocytes in respiratory bronchioles and alveoli (arrows) and an absence of lymphocytic aggregates; (H&E slides; mag. 400×, scale bar = 50µm).

Figure 5. Histopathology of the Placenta and Fetal Membranes

Microscopic appearance of the chorionic plate (A) and fetal membranes (insert) from a saline control animal near term demonstrating intact amnion epithelium and collagen layer with absence of leukocytic infiltration; (B) Following 21 days of IAI, accumulation of neutrophils was observed marginating into the chorion (arrows), which represented the minimal criteria for histologic evidence of IAI. There was also a fetal vascular inflammatory response (arrow head); (C–D) Marked histologic evidence of infection was represented by both chorionic and amnionic layer involvement by neutrophils (arrows), defined as chorioamnionitis. The predominant effect of maternal antimicrobial therapy was to reduce the frequency and degree of the leukocytic inflammatory response in the amnionic layer (Bvs.C). (H&E slides; mag. 400×, scale bar = 200µm; Amnion = a; Chorion = c, Decidua = d).