# Nationwide Observational Case–Control Study of Risk Factors for Aerococcus Bloodstream Infections, Sweden

## TL;DR

This study identifies risk factors for Aerococcus bloodstream infections in Sweden, showing they are more common in elderly men with neurological or urinary conditions.

## Contribution

The study provides the first nationwide analysis of risk factors for Aerococcus bloodstream infections in Sweden.

## Key findings

- Aerococcal BSI incidence was 1.48 per 100,000 person-years.
- Neurologic and urologic conditions increased BSI risk significantly.
- Elderly men were most affected, highlighting a need for increased awareness.

## Abstract

Risk factors for developing bloodstream infections (BSIs) caused by Aerococcus bacteria remain insufficiently examined. In this nationwide case–control study in Sweden, 19 of 23 clinical microbiological laboratories identified patients who had aerococcal BSIs during 2012–2016. We compared each of those index patients with 4 controls matched for age, sex, and county of residence. Overall, 588 episodes of aerococcal BSI occurred over 39.6 million person-years, corresponding to an average incidence of 1.48/100,000 person-years (95% CI 1.37–1.60/100,000 person-years). Most infections developed in men >65 years of age. Aerococcal BSI was associated with neurologic (adjusted odds ratio 2.89 [95% CI 2.26–3.70]) and urologic (adjusted odds ratio 2.15 [95% CI 1.72—2.68]) conditions and previous hospitalization or infection treatment. Our findings support the previously observed predilection for aerococcal BSIs developing in elderly men with urinary tract disorders. Awareness of Aerococcus spp. in patients, especially elderly men, will be needed to manage invasive infections.