Neonatal sepsis-causing bacterial pathogens and outcome of trends of their antimicrobial susceptibility a 20-year period at a neonatal intensive care unit

Background: Due to increases in the number of infants born with younger gestational age (GA) and lower birth weight, the incidence of neonatal sepsis is increasing. Purpose: We investigated the changes in the prevalence of bacterial pathogens, their antimicrobial susceptibility, and sepsis-related mortality during 20 years at a neonatal intensive care unit. Methods: The study period was divided into two 10-year phases (1998-2007 vs. 2008-2017). Medical records were reviewed to gather data on demographics, causative microbial pathogens, incidence of multidrug-resistant organisms, antimicrobial susceptibility, and rates of sepsis-related mortality. Results: In both study phases, the most common pathogens for neonatal sepsis were coagulase-negative Staphylococcus (CoNS) (28.6%) and Enterobacter cloacae (16.1%) for early-onset sepsis (EOS, <= 72 hours after birth) and CoNS (54.7%) and Staphylococcus aureus (12.9%) for late-onset sepsis (LOS, >72 hours after birth). CoNS and S. aureus showed 100% sensitivity to vancomycin in both phases. The susceptibility of S. aureus to oxacillin increased from 19.2% to 57.9% in phase II than phase I. K. pneumonia and E. cloacae showed increases in its susceptibility to gentamicin, cefotaxime and ceftriaxone in phase II than phase I. In both phases, the most common pathogens that caused sepsis-related death were K. pneumoniae (18.2%) and Pseudomonas aeruginosa (13.6%). Sepsis-related mortality rate was higher in infants with GA <37 weeks than those with GA over 37 weeks (P=0.016). In addition, the mortality rate of neonatal sepsis caused by gram-negative bacteria was significantly higher than that caused by gram-positive bacteria (P<0.001). Conclusions: CoNS was the most common pathogen for EOS and LOS. While we found significant changes in antimicrobial sensitivities over time. GA below 37 weeks and gram-negative organisms are associated with mortality rate.