Microbiology Trends among Postcesarean Surgical Site Infections at a Large Public Hospital

Abstract This study aims to characterize a decade-long trajectory of pathogen distribution and antimicrobial resistance among postcesarean surgical site infections (SSIs) at a high-volume safety-net hospital preceding widespread adoption of adjunctive azithromycin prophylaxis and standardized infection–prevention bundles. Retrospective cohort study of cesarean deliveries from October 2009 through October 2019. For patients with multiple deliveries, the initial cesarean during this period was analyzed. Patient and obstetric characteristics and neonatal outcomes were compared between individuals with and without SSI, identified by hospital Infection–Prevention surveillance. Wound culture pathogens and susceptibilities were characterized. Logistic regression with year as a covariate estimated odds of SSI, culture positivity, and infection with predominant pathogens. Of 30,501 initial cesareans, 550(1.8%) were complicated by SSI; 484 (88%) had complete records and were included in the analysis. Odds of SSI increased 5% per year (odds ratio [OR] 1.05, 95% confidence interval [CI] 1.02–1.08, p = 0.001), and culture positivity increased by 13% per year (OR 1.13, 95% CI 1.06–1.21, p < 0.001). Individuals with SSI were younger, had higher body mass indices (BMIs), more pregestational diabetes, labor induction, and chorioamnionitis. Neonates of mothers with SSI experienced more sepsis evaluations and culture-positive sepsis. Most SSIs were superficial (404 [83.5%]), with 63 (13.0%) as deep incisional, and 17 (3.5%) as organ/space. Escherichia coli (13.8%) and methicillin-sensitive Staphylococcus aureus (13.8%) were most common. Odds of E. coli increased by 15% each year (OR 1.15, 95% CI 1.05–1.26, p = 0.004) and Enterococcus faecalis by 16% (OR 1.16, 95% CI 1.03–1.31, p = 0.014). Seven extended-spectrum beta-lactamase (ESBL)-producing E. coli were identified, all in the past 2 years of the study. Across a prebundle/pre-azithromycin decade, cesareans complicated by SSIs gradually increased and were associated with maternal and neonatal morbidity. Odds of E. coli and E. faecalis identification rose significantly, and cases of ESBL E. coli emerged. These findings establish a baseline against which postbundle and azithromycin surveillance can be compared and underscore the need for cesarean-specific antimicrobial resistance reporting in national surveillance systems.