Vihta KD, et al. - In this observational study, researchers examined possible drivers of changes in the incidence of Escherichia coli bloodstream infection and antibiotic susceptibilities (Oxfordshire, United Kingdom) over the past two decades, while stratifying for time since hospital exposure. Results revealed that increases in E. coli bloodstream infections were primarily community associated, with substantial co-amoxiclav resistance. However, little or no change in mortality was reported. The study findings suggested that focusing interventions on primary care facilities, especially those with high co-amoxiclav use, could be effective in decreasing the incidence of co-amoxiclav-resistant E. coli bloodstream infections, in this region and more generally.

Methods

• For this investigation, researchers used all available data on E. coli bloodstream infections and E. coli urinary tract infections (UTIs) from one UK region (Oxfordshire) using anonymized linked microbiological data and hospital electronic health records from the Infections in Oxfordshire Research Database (IORD).
• The incidence of infections across a two-decade period and the annual incidence rate ratio (aIRR) in 2016 was estimated.
• On the basis of microbiological, clinical, and health-care-exposure risk factors, they modelled the data using negative binomial regression.
• To estimate changes in bacterial virulence and the impact of antimicrobial resistance on incidence, they examined infection severity, 30-day all-cause mortality, and community and hospital amoxicillin plus clavulanic acid (co-amoxiclav) use.

Results

• A total of 5,706 E. coli bloodstream infections occurred in 5,215 patients, and 228,376 E. coli UTIs occurred in 137,075 patients from Jan 1, 1998, to Dec 31, 2016.
• Researchers found that 1,365 (24%) E. coli bloodstream infections were nosocomial (onset > 48 hours after hospital admission), 1,132 (20%) were quasi-nosocomial (≤ 30 days after discharge), 1,346 (24%) were quasi-community (31–365 days after discharge), and 1,863 (33%) were community (> 365 days after hospital discharge).
• Findings revealed that the overall incidence increased year on year (aIRR 1.06, 95% CI 1.05–1.06).
• A total of 212 of 515 (41%) E coli bloodstream infections and 3,921 of 13,792 (28%) E. coli UTIs were co-amoxiclav resistant in 2016.
• Increases in E. coli bloodstream infections were driven by increases in community (aIRR 1.10, 95% CI 1.07–1.3; p < 0.0001) and quasi-community (aIRR 1.08, 1.07–1.10; p < 0.0001) cases.
• Data reported that 30-day mortality related to E. coli bloodstream infection diminished after some time in the nosocomial (adjusted rate ratio [RR] 0.98, 95% CI 0.96–1.00; P=0.03) group, and remained stable in the quasi-nosocomial (adjusted RR 0.98, 0.95–1.00; P=0.06), quasi-community (adjusted RR 0.99, 0.96–1.01; P=0.32), and community (adjusted RR 0.99, 0.96–1.01; P=0.21) groups.
• However, mortality was substantial at 14% to 25% across all hospital-exposure groups.
• Researchers found that co-amoxiclav-resistant E. coli bloodstream infections increased in all groups across the study period (by 11% to 18% per year, significantly faster than co-amoxiclav-susceptible E. coli bloodstream infections; P_{heterogeneity} < 0.0001), as did co-amoxiclav-resistant E. coli UTIs (by 14% to 29% per year; P_{heterogeneity} < 0.0001).
• They discovered that previous year co-amoxiclav use in primary-care facilities was related to increased subsequent year community co-amoxiclav-resistant E. coli UTIs (P=0.003).