Objective:
Quantify incidence and determine predictors of Gram-negative bacilli (GNB) in people who inject drugs (PWID) with injection-drug use (IDU)-related infections.
Design:
Retrospective cohort of hospitalized PWID from 1/2017-12/2019.
Methods:
Inclusion criteria: age ≥18 years, active IDU, treated IDU-attributable infection, organism growth from microbiology cultures. Infection types: infective endocarditis (IE), acute bacterial skin/skin structure infection (ABSSSI), osteoarticular infection (OAI), other bloodstream infections (BSI). Primary outcome was GNB identification from microbiologic culture; descriptive statistics were used to describe the cohort. Multivariable regression was used to identify variables associated with GNB infection.
Results:
230 PWID included; 65 (28%) GNB infections, 165 (72%) Gram-positive infections. The median (IQR) population age was 38 (31-45) years. Most patients were women (56%); 37% had no insurance. Infection types were: IE (41%), ABSSSI (37%), OAI (20%), other BSI (2%). 278 organisms were isolated from 230 patients; most common organisms were methicillin-resistant
Staphylococcus aureus
(43%),
Streptococcus
spp. (19%), methicillin-susceptible
S. aureus
(17%),
Serratia marcescens
(8%); 10% were mixed GNB and Gram-positive infections. 80% of patients received empiric
Pseudomonas aeruginosa
coverage; only 7% had
P. aeruginosa
infections. In multivariable regression, age >50 years (adjOR, 2.9; 95%CI; 1.2-7.2), prior hospitalization within 90-days (adjOR, 2.2; 95%CI; 1.2-4.3), and OAI (adjOR, 3.2; 95%CI; 1.5-6.6) were associated with GNB infection.
Conclusions:
GNB in PWID with IDU-attributed infections were more frequently observed in recently hospitalized, older patients with OAI. The majority of patients received empiric anti-pseudomonal antibiotic coverage, but
P. aeruginosa
was infrequent. PWID are a potential population to target improved empiric antibiotic use.
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