Neonatal Unit Colonization Pressure and Acquisition of Extended-Spectrum β-Lactamase Gut Colonization

Understanding how neonatal unit colonization pressure, the proportion of infants carrying resistant bacteria on a unit, is associated with antibiotic-resistant bacterial acquisition risk can inform the design and implementation of effective infection prevention and control (IPC) interventions.

To describe resistant bacterial gene prevalence in European neonatal units and to assess the association between unit-level extended-spectrum β-lactamase (ESBL) colonization pressure and infant-level ESBL acquisition.

Multicenter study in 24 tertiary neonatal units in 8 European countries (Estonia, Greece, Germany, Italy, Poland, Spain, Switzerland, and the United Kingdom) using repeated cross-sectional surveys collecting stool samples from infants over 4 surveys with 4-, 7-, and 14-day intervals, analyzed using real-time quantitative polymerase chain reaction (PCR) between January 2022 and June 2024 as part of the NeoIPC project. All infants present on the neonatal unit at 8:00 am on the day of the survey were eligible; infants could contribute to multiple surveys.

ESBL colonization pressure at previous survey.

Incident infant gut colonization with ESBL-harboring bacteria (ESBL-colonized). Bayesian hierarchical logistic regression modeling was used to assess the association between colonization pressure and infant-level acquisition risk on the neonatal unit.

Overall, 943 infants (547 of 943 male [58.0%]; median [IQR] gestational age, 34 [30-38] weeks, and median [IQR] birth weight, 2130 [1254-3084] g) contributed to 1847 infant-survey observations. Stool samples were collected and PCR results obtained in 1448 of 1847 infant surveys (78.4%). The most common genes detected were those encoding ESBLs (205 of 1448 samples [14.2%]), with high unit-level variation. In the colonization acquisition analysis, we included 829 samples from 533 infants hospitalized since birth who were either newly admitted since or not colonized at the previous survey time point; 90 of 533 infants (16.9%) became ESBL-colonized. Their median (IQR) gestational age was 34 (30-37) weeks, and median (IQR) length of stay at survey was 14 (5-32) days. Colonization pressure was associated with increased odds of becoming ESBL-colonized for all survey intervals (4-day interval: mean odds ratio [OR], 1.89; 95% credible interval [CrI], 1.22-2.94; 7-day interval: OR, 1.76; 95% CrI, 1.26-2.63; 14-day interval: OR, 1.73; 95% CrI, 1.15-2.52 per 10% increase of colonization pressure).

In this cross-sectional study, ESBL colonization pressure was associated with individual risk of acquiring ESBL on the neonatal unit. Unit-level interventions targeting colonization rather than infection may have important direct and indirect benefits in units with high colonization pressure.