Association of skin infections with sharing of injection drug preparation equipment among people who inject drugs

Background: Sharing needles and injection drug preparation equipment (IDPE) among people who inject drugs (PWID) are well-established risk factors for viral transmission. Shared needles and IDPE may serve as bacterial niduses for skin and soft tissue infections (SSTI). Given the rising rates of SSTI in PWID, we investigated the association of needle and IDPE sharing on incidence of SSTI in a cohort of PWID. Methods: Inpatient PWID ( N = 252) were recruited to a randomized controlled trial of an intervention aimed at reducing infections. The primary outcome was self-reported incidence of SSTI one-year post-hospitalization. In this secondary analysis, we assessed two variables: 1) sharing of IDPE alone, 2) sharing needles with or without IDPE, and compared these groups separately to persons who reported no sharing of needles or IDPE via a mixed effects negative binomial regression model to estimate the effect of baseline sharing behavior on SSTI during follow-up via incidence rate ratios (IRR). Results: Participant characteristics: 38 years [mean], 58% male, 60% White, 90% primarily injected opioids, 1.58 (+/- 2.35) mean SSTI in the year prior to baseline. In terms of sharing behavior, 29% didn't share needles or IDPE, 13% shared IDPE only, and 58% shared needles with or without IDPE three months prior to baseline. After adjusting for co-variables, PWID who shared IDPE alone had a 2.2 fold higher IRR of SSTI (95%CI 1.27; 3.85, p = 0.005) and PWID who shared needles with or without IDPE had a 3.31 fold higher IRR of SSTI (95%CI 2.04; 5.37, p < 0.001), compared to those who did not share any equipment. The number of SSTI at baseline was associated with an IRR of 1.20 of SSTI during follow-up (95%CI 1.09; 1.32, p < 0.001). Conclusions: In this cohort of hospitalized PWID, we found a significant association between baseline sharing of IDPE alone and of sharing of needles with or without IDPE with one-year incidence of SSTI.