# Both, Limited and Often Fatal Systemic Infections Caused by Leuconostoc spp. in Older, Previously Ill Men Are Usually Acquired in the Outpatient Setting

## TL;DR

Leuconostoc bacteria, often used in food and probiotics, can cause severe infections in older men with health issues, usually acquired outside hospitals.

## Contribution

This study identifies outpatient acquisition and higher mortality in men with Leuconostoc infections and underlying conditions.

## Key findings

- Leuconostoc infections are mostly acquired in outpatient settings, not in hospitals.
- Men over 60 with severe underlying diseases are at high risk of fatal systemic infections.
- Five out of seven men with blood cultures for Leuconostoc died, while all women survived.

## Abstract

Leuconostoc spp. are vancomycin-resistant Gram-positive cocci that are used in food production and as pre- and probiotics. However, Leuconostoc spp. can also cause infections. In the present study, the records of patients with Leuconostoc spp. detection between January 2012 and March 2025 were analyzed, inclusive of the underlying risk factors. Leuconostoc spp. was isolated from 32 patients (21 male, 11 females), including nine patients with blood culture evidence. In the majority of patients, Leuconostoc spp. were obtained on the day of admission to the hospital or in the first few days thereafter, arguing against nosocomial acquisition. The median age of men and women (65.3 and 67.8 years) was similar, but seven of the 14 male patients over the age of 65 had the bacteria in blood culture. The female patients with blood culture evidence had suffered from peripartum thrombophlebitis and from anorexia nervosa (BMI 8.8 kg/m2). In contrast, men with Leuconostoc spp. in the blood culture had severe, limiting underlying diseases. While the two women survived, five of the seven blood-culture-positive men died. Overall, our results show that Leuconostoc spp. is mainly acquired in outpatient settings, but men are at a higher risk of acquisition. Colonized men over the age of 60 with severe underlying diseases have a high risk of systemic infection with a fatal outcome.