FIG 1.

Carbapenem consumption and proportion of carbapenem-nonsusceptible Citrobacter spp. (CNSC), 2000 to 2018. Carbapenem daily defined doses (DDDs) per 1,000 patient days (yellow bars) and the proportion of Citrobacter species isolates that were carbapenem nonsusceptible (solid blue line) were quantified for each year between 2000 and 2018 at UPMC-PUH. Testing of 2,817 total Citrobacter species isolates revealed that 78 unique patients had CNSC (defined as ertapenem nonsusceptible). The dotted blue line shows a linear regression for increased CNSC proportion over time (R² = 0.257; P = 0.03). Carbapenem DDDs per 1,000 patient days also increased over time (R² = 0.831; P < 0.001) and correlated with the increase in CNSC (lag = 0 years; R² = 0.660).