injection drug use-associated bloodstream infections are propagated by community outbreaks of diverse lineages.

BACKGROUND

The ongoing injection drug use (IDU) crisis in the United States has been complicated by an emerging epidemic of IDU-associated bloodstream infections (IDU-BSI).

METHODS

We performed a case-control study comparing IDU-BSI and non-IDU BSI cases identified in a large US Midwestern academic medical center between Jan 1, 2016 and Dec 21, 2019. We obtained the whole-genome sequences of 154  IDU-BSI and 91  non-IDU BSI cases, which were matched with clinical data. We performed phylogenetic and comparative genomic analyses to investigate clonal expansion of lineages and molecular features characteristic of IDU-BSI isolates.

RESULTS

Here we show that patients with IDU-BSI experience longer durations of bacteremia and have lower medical therapy completion rates. In phylogenetic analyses, 45/154 and 1/91 contemporaneous IDU-BSI and non-IDU BSI staphylococcal isolates, respectively, group into multiple, unique clonal clusters, revealing that pathogen community transmission distinctively spurs IDU-BSI. Lastly, multiple lineages deficient in canonical virulence genes are overrepresented among IDU-BSI, which may contribute to the distinguishable clinical presentation of IDU-BSI cases.

CONCLUSIONS

We identify clonal expansion of multiple lineages among IDU-BSI isolates, but not non-IDU BSI isolates, in a community with limited access to needle exchange facilities. In the setting of expanding numbers of staphylococcal IDU-BSI cases consideration should be given to treating IDU-associated invasive staphylococcal infections as a communicable disease.