(401) Increasing Antimicrobial Resistance Among Post-Cesarean Surgical Site Infections at a Large Public Hospital from 2009-2019

Objective: To evaluate trends of bacterial composition and antimicrobial resistance among post cesarean surgical site infections (SSIs) in a cohort exposed to contemporary antibiotic prophylaxis.

Study Design: This is a single-institution retrospective cohort study of post-cesarean SSIs for whom culture data was available between 2009-2019 at a large county hospital. Medical records were reviewed to examine microbes isolated, and antimicrobial susceptibility data over time and by wound class. Wounds were clinically classified as superficial, deep, or organ space SSIs according to National Healthcare Safety Network guidelines. Logistic regression was completed to look at trends over time for antimicrobial resistance and bacterial composition.

Results: Of 41,338 cesarean sections, 484 cultured wounds were identified. 104 individuals (21.5%) had chorioamnionitis preceding delivery. SSI incidence remained below 2% consistently; however, positive cultures increased during the study (p=0.005). For all organisms isolated, resistance to any antibiotic increased at a rate of 0.65 per year (p=0.13 for trend). Escherichia coli (E.coli) was the most prevalent microbe identified in 67(13.8%), including 55(11.4%) superficial and 12(2.5%) deep or organ space infections. Significant increases in both the frequency of E. coli isolates among superficial SSIs (0.75 per year, p=0.005) and antibiotic resistance of E.coli (0.49 per year, p=0.014) were seen. Of E. coli isolates with susceptibility testing, 9/23 (37.5%) were resistant to ampicillin, 25/58 (49.1%) to ampicillin-sulbactam, 13/63 (23%) to gentamicin, and 23/66 (34.8%) to Bactrim.

Conclusion: While post-operative cesarean SSI rates have remained relatively constant at a single center over the past decade, antibiotic resistance is increasing, particularly among E. coli isolates. The impact of increasing antimicrobial resistance on maternal and neonatal morbidity and infection-associated healthcare costs warrants further study, and safety data for newer antimicrobial agents in pregnancy and lactation are urgently needed.