Factors that affect the duration of antimicrobial therapy for cellulitis

The recommended duration of antibiotic therapy for patients hospitalized with cellulitis is 5–14 days. However, factors that affect the duration of treatment have rarely been examined. We conducted an observation study in a regional hospital in Japan to examine factors that affect the duration of antibiotic therapy for cellulitis. Our study included 102 patients with cellulitis of the lower extremities who were treated with intravenous cefazolin alone. Intravenous cefazolin was terminated when redness, swelling, and tenderness of the lower extremities disappeared, and subsequently the patients were discharged. The relationship between the duration (days) of treatment with intravenous cefazolin (DIVC) and clinical factors were analyzed. The median DIVC was 8 days (interquartile range, 7–10 days). On univariate analysis, DIVC correlated significantly with patient age (P = 0.0071) and with C-reactive protein levels before treatment (P = 0.0053). DIVC in patients with diabetes mellitus was significantly longer than that in patients without diabetes mellitus (P = 0.0033). DIVC in patients with blood stream infection was significantly longer than that in patients without blood stream infection (P = 0.029). On multivariate analysis, variables independently associated with longer DIVC included patient age (P = 0.044), C-reactive protein levels before treatment (P = 0.017), presence of diabetes mellitus (P = 0.0021), and presence of blood stream infection (P = 0.028). Duration of treatment with intravenous antibiotics for cellulitis is associated with patient age, C-reactive protein levels, coexisting diabetes mellitus, and coexisting blood stream infection. These findings should be considered when treatment plans for cellulitis are devised.