Infant ESBL Acquisition Associated With Unit Colonization Pressure

A study in JAMA Network Open found that higher unit-level colonization pressure with extended-spectrum β-lactamase (ESBL)-harboring bacteria was associated with greater odds of infant acquisition of ESBL gut colonization. The association remained after adjustment for prematurity, length of stay, prior antibiotic exposure, and neonatal unit.

The repeated cross-sectional study included 24 tertiary neonatal units in 8 European countries between January 2022 and June 2024. Investigators conducted 4 unit-wide surveys separated by 4-, 7-, and 14-day intervals, collected stool samples, and used real-time quantitative polymerase chain reaction to detect resistance genes.

Overall, 943 infants contributed 1847 infant-survey observations, and stool results were available for 1448 observations. ESBL-encoding genes were the most commonly detected resistance genes, appearing in 205 samples (14.2%). The acquisition analysis included 533 infants who contributed 829 complete surveys; 90 infants (16.9%) became ESBL-colonized during follow-up.

For each 10-percentage-point increase in colonization pressure at the previous survey, the adjusted mean odds ratio for ESBL acquisition was 1.89 (95% credible interval [CrI], 1.22-2.94) over 4 days, 1.76 (95% CrI, 1.26-2.63) over 7 days, and 1.73 (95% CrI, 1.15-2.52) over 14 days. In a sensitivity analysis limited to units with some ESBL colonization, estimates remained directionally consistent, but wider credible intervals included the null.

The authors noted that the study was observational and cross-sectional and that missing stool samples could have underestimated colonization pressure or acquisition. They also cited possible selection bias, residual confounding, and the inability of the surveillance approach to identify bacterial species or reconstruct transmission pathways. Investigators said unit-wide infection prevention and control approaches may be important, while future trials could assess which interventions reduce colonization pressure and whether they also reduce acquisition.

Source: Cook A, Berkell M, van Werkhoven CH, et al. Neonatal unit colonization pressure and acquisition of extended-spectrum β-lactamase gut colonization. JAMA Netw Open. 2026;9(9):e2632644. doi:10.1001/jamanetworkopen.2026.32644