Targeted screening and treatment of Ureaplasma colonisation in preterm infants: a single tertiary centre experience

INTRODUCTION Bronchopulmonary dysplasia (BPD) is a major cause of mortality and morbidity in preterm infants.1Ureaplasma spp. is a common commensal of the vagina microbiota, and vertical transmission to infants can occur in utero or during vaginal delivery.2 Neonatal pulmonary Ureaplasma colonisation has been implicated in the pathogenesis of dysregulated pulmonary inflammation and BPD.3 Systematic reviews have reported a significant association between Ureaplasma colonisation and BPD in preterm infants.4,5 With its antibacterial and immunomodulatory effects,6,7 azithromycin provides a therapeutic option to eradicate Ureaplasma and reduce inflammation-mediated BPD. A pilot trial showed that a 3-day regimen (intravenous 20 mg/kg once daily) effectively eradicated Ureaplasma in colonised infants but was not effective in reducing BPD.8 The impact of azithromycin treatment on BPD remains unclear.9 This study reports a single-centre experience with targeted screening and azithromycin treatment of Ureaplasma colonisation in preterm infants in a tertiary neonatal intensive care unit (NICU), with evaluation of the Ureaplasma eradication rate, treatment tolerability and its impact on death or BPD at 36 weeks postmenstrual age (PMA). METHODS This is a retrospective review of the medical records of infants with gestational age (GA) ≤32 weeks or birth weight ≤1500 g screened for Ureaplasma colonisation from 1 June 2020 to 30 June 2022 at the NICU of KK Women’s and Children’s Hospital, Singapore’s largest tertiary perinatal referral centre. Infants with congenital malformation(s) were excluded. The study was a service evaluation and was thus exempted from ethics approval (SingHealth Centralised Institutional Review Board 2022/2293). In June 2020, the NICU implemented a targeted screening guideline for Ureaplasma colonisation in the first week of life in infants with GA ≤32 weeks or birth weight ≤1500 g and at least one of the following risk factors or clinical presentations of Ureaplasma colonisation: (a) preterm premature rupture of membranes (PPROM) >72 h; (b) any history of PPROM with clinical chorioamnionitis;10 (c) leucocytosis in the first week;11,12 (d) chest X-ray changes consistent with interstitial pneumonitis13 or pulmonary interstitial emphysema;14 and (e) persistent high ventilatory requirements in the first week (mean airway pressure >10 cmH20) or high fraction of inspired oxygen (>25%) on non-invasive ventilation. Clinical chorioamnionitis was defined as the presence of maternal fever >38°C with two of the following: maternal tachycardia (>100/min), fetal tachycardia (>160/min), uterine tenderness, foul/purulent amniotic fluid or maternal leucocytosis (white blood cells >15,000/mm3).15 Endotracheal or nasopharyngeal aspirate was obtained for Ureaplasma culture. Ureaplasma polymerase chain reaction (PCR) assay was not available in our institution. Intravenous or oral azithromycin (20 mg/kg once daily for 3 days),8 ideally started within the first week of life, was recommended for infants with positive Ureaplasma culture and who required invasive ventilation. A repeat culture was suggested between 5 and 7 days after treatment. The screening and treatment guideline was available on the hospital intranet. Screening and treatment decisions were left to the discretion of the treating physician. Neonatal and maternal data were collected from electronic medical records. Treatment details and Ureaplasma eradication rates were collated for infants treated with azithromycin. Patients were evaluated for treatment adverse effects, including hypersensitivity, gastrointestinal, dermatological, cardiovascular and hepatic adverse effects. Outcomes of death or BPD at 36 weeks PMA were collated until hospital discharge. BPD definitions and severity classifications were based on the oxygen requirement at 36 weeks PMA as developed by the National Institute of Child Health and Human Development (2001).16,17 Statistical analysis was performed using IBM SPSS Statistics version 27.0 (IBM Corp, Armonk, NY, USA). Categorical variables were analysed using chi-square or Fisher’s exact test. Continuous variables were analysed using Mann–Whitney U-test. A P value <0.05 was considered statistically significant. RESULTS During the study period, 382 very low birth weight (<1500 g) infants were admitted to the NICU. Sixty (15.7%) infants with birth weight ≤1500 g or GA ≤32 weeks were screened for Ureaplasma colonisation and included in our study. Baseline characteristics are presented in Table 1. The median GA and birth weight of the infants were 25.8 (interquartile range IQR 24.3–27.2) weeks and 745 (IQR 650–946) g, respectively. A higher proportion of Ureaplasma-negative infants required invasive respiratory support at screening compared to Ureaplasma-positive infants (89.4% vs. 61.5%, P = 0.031). There was no difference in other characteristics between the Ureaplasma-positive and -negative groups. Forty-two (70.0%) endotracheal and 18 (30.0%) nasopharyngeal aspirates were sent for Ureaplasma culture at a median age of 5 (IQR 2–10) days. Nineteen (31.7%) infants were screened after the first week of life. The median culture turnaround time was 7 days.Table 1: Baseline demographic and clinical characteristics of the study participants in the cohort and stratified by Ureaplasma respiratory colonisation status.Ureaplasma culture was positive in 13 (21.7%) infants. Ten of them who were on invasive ventilator received azithromycin; three patients were treated presumptively on median postnatal Day 3 (IQR 2–8) while awaiting culture results, while seven received targeted therapy initiated on median postnatal Day 9 (IQR 8–21). Treatment was not started in three infants who were clinically stable and did not require invasive ventilation. Culture was repeated in seven infants, with Ureaplasma eradicated in six (85.7%) infants. Of the 47 (21.3%) Ureaplasma-negative infants, ten also received presumptive treatment at the physician’s discretion based on clinical suspicion and/or risk factor(s) for Ureaplasma colonisation. Of a total of 20 infants treated, 19 (95.0%) received intravenous azithromycin. All infants completed the 3-day regimen without any treatment-related adverse events. Of the 13 Ureaplasma-positive infants, nine out of ten (90%) of the infants treated with azithromycin developed severe BPD at 36 weeks PMA, while the remaining one (10%) infant did not have BPD. None of the three untreated Ureaplasma-positive infants had BPD. There was no mortality among Ureaplasma-positive infants. Among Ureaplasma-negative infants, the BPD rates were 70.0% and 86.5% and the mortality rates were 20.0% and 5.4% in the ten azithromycin-treated infants and 37 untreated infants, respectively. The incidence of the composite outcome of death or BPD was high in our study population regardless of Ureaplasma colonisation status Table 2.Table 2: Study outcomes at 36 weeks postmenstrual age of the total cohort and stratified by Ureaplasma respiratory colonisation status.DISCUSSION In this retrospective study, a Ureaplasma colonisation rate of 21.7% was observed in our cohort. Other studies have reported colonisation rates ranging from 20% to 50% in very low birth weight infants.18,19,20 Post-treatment Ureaplasma cultures in seven infants revealed an eradication rate of 85.7%. Despite the high eradication rate, 90% of treated Ureaplasma-positive infants developed severe BPD. It is unclear if the lack of BPD benefit is related to late azithromycin initiation (median postnatal age 8 IQR 4.5–15 days), possibly contributed by the culture median turnaround time of 7 days. In a European NICU survey, most neonatologists recommended starting treatment immediately after birth to minimise pulmonary inflammation,21 a predictor of BPD.22 Most studies on azithromycin for BPD prophylaxis23,24,25 and Ureaplasma eradication8 initiated treatment within 72 h of life. Rapid PCR detection could have facilitated early treatment. Viscardi et al.8 reported a 100% Ureaplasma eradication rate with intravenous azithromycin (20 mg/kg daily for 3 days) in 19 colonised infants. Similar to our study, no BPD difference was observed between treatment and placebo groups, both in the overall cohort and in the Ureaplasma-positive subgroup. Based on low-quality evidence, a recent meta-analysis of azithromycin for BPD prevention revealed no difference in BPD with a trend towards lower BPD in Ureaplasma-positive neonates.26 After the completion of our study, a large randomised placebo controlled trial conducted in 796 preterm infants concluded that intravenous azithromycin (20 mg/kg daily for 3 days followed by 10 mg/kg daily for 7 days) did not improve survival without moderate or severe BPD, regardless of Ureaplasma colonisation.27Ureaplasma colonisation rate was 22% in that study. To date, there are no studies involving a large number of Ureaplasma-colonised infants. In our cohort, none of the three untreated Ureaplasma-positive infants developed BPD. Although the number was small, this suggests that it may be safe to withhold treatment in stable infants not requiring invasive ventilation. In Ureaplasma-negative infants, azithromycin treatment did not affect BPD incidence or mortality. This, along with the lack of BPD reduction in Ureaplasma-positive infants, does not support routine or presumptive treatment in preterm infants. All infants tolerated the 3-day therapy without drug-related adverse effects. This is consistent with the favourable tolerability reported in earlier studies conducted in preterm infants.8,23,24,25 The incidence of BPD was high (80.0%) in our cohort compared to the annual BPD incidence of 25.0%–35.7% for all our very low birth weight admissions from 2020 to 2022, suggesting that our screening criteria for Ureaplasma colonisation are highly predictive of BPD outcomes. Ureaplasma colonisation did not impact BPD or mortality in our high-risk population. Our study has limitations. It is a retrospective single-centre study, thus limiting the generalisability of our findings. The actual number of patients meeting our screening criteria was not audited, and our study population was small with 13 Ureaplasma-positive patients. Lastly, azithromycin was started at a median postnatal age of 8 days in the ten treated Ureaplasma-positive patients, possibly masking early treatment benefits on BPD outcomes. Based on our single-centre experience, we conclude that azithromycin therapy is associated with high Ureaplasma eradication rates and good tolerability in preterm infants. However, treatment did not impact BPD outcome or mortality in both the Ureaplasma-positive and -negative subgroups. Larger prospective studies are needed to evaluate the clinical benefits of early azithromycin treatment in Ureaplasma-positive preterm infants. Acknowledgement We thank Mr Alan Chui and Ms Rowena B Dela Puerta from KK Women’s and Children’s Hospital, Singapore, for their assistance in this study. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.