Maternal Colonization, Perinatal Exposure, and Neonatal Acquisition of Resistant Enterobacterales

BackgroundMulti-drug resistant Enterobacterales, in particular with ceftriaxone resistance (CefR-E), are globally prevalent. Pregnant people colonized with resistant Enterobacterales are at risk of perinatally transmitting to neonates; infections with CefR-E strains are associated with higher mortality, morbidity and health care costs. This study aimed to estimate the rate of gut colonization of AmpR-E (ampicillin resistant Enterobacterales) and CefR-E in a population of healthy mother-infant dyads in the Chicago area and investigate the genetic characteristics of CefR-E. MethodsPregnant persons anticipating vaginal birth at two Chicago area hospitals were enrolled. Patients with preterm delivery (<35 weeks), fever during labor, cesarean delivery, exposure to antibiotics in 3rd trimester, and neonatal intensive care were excluded. Pregnancy and birth history were obtained from parent and medical record. Maternal vaginal and rectal swabs, and infant stool samples were collected and screened for resistance by plating on MacConkey with ceftriaxone. Whole genome sequencing (WGS) and analysis was conducted on the CefR-E isolates. ResultsBetween July 2020 and April 2022, 261 mother-infant dyads were enrolled with 184 maternal samples and 157 infant stool samples analyzed. Rate of maternal AmpR-E gut colonization was 97% (179/184). Rate of maternal and infant CefR-E gut colonization was 14% (26/184) and 7% (11/157) respectively. Perinatal transmission of CefR-E was 50% (11 of 22) positive mothers with available infant sample). No clinical variables were significantly associated with maternal CefR-E colonization or perinatal transmission. Type of infant nutrition (breastmilk) was significantly associated with decreased perinatal transmission of AmpR-E to infant (p=0.015). WGS of the CefR-E showed that 19/42 isolates were E. coli, and transmission primarily occurred from mothers colonized with E. coli. ConclusionsThis study demonstrates that a sizable minority of pregnant persons are colonized with CefR-E in the U.S., a higher burden than previously reported for developed countries. Enterobacterales appear adept in perinatal transmission, with half of infants born to colonized pregnant persons harboring CefR-E in first week of life.