# Rapid acquisition of daptomycin resistance in a Corynebacterium striatum osteoarticular infection: case report and discussion on antimicrobial resistance

## TL;DR

A patient with a bone infection caused by Corynebacterium striatum developed resistance to daptomycin after treatment, highlighting the need for caution in using this antibiotic for long-term infections.

## Contribution

This study reports a rare case of rapid daptomycin resistance in C. striatum and identifies potential genetic mutations linked to resistance.

## Key findings

- A daptomycin-susceptible C. striatum isolate became resistant after 14 days of monotherapy.
- Whole-genome sequencing identified a nonsense mutation in pgsA likely responsible for daptomycin resistance.
- Mutations in mltG and ftsI genes may explain increased β-lactam resistance in the resistant strain.

## Abstract

Corynebacterium striatum, a commensal of the skin microbiota, can cause invasive osteoarticular infections that are challenging to diagnose and treat due to biofilm formation. Daptomycin, owing to its potent activity against gram-positive bacteria and favorable toxicity profile, is frequently used as empirical therapy in the management of postoperative bone and joint infections. However, cases of acquired resistance remain rare and poorly understood.

We describe a case of chronic T11–T12 spondylodiscitis in a paraplegic patient. During the first surgical intervention, a daptomycin-susceptible C. striatum isolate (CORY-1) was recovered. The patient received 14 days of daptomycin monotherapy (10 mg/kg). At the time of the second surgery, a daptomycin-resistant C. striatum strain (CORY-2) was isolated. Whole-genome sequencing revealed only 13 single nucleotide polymorphisms between the two isolates, including a nonsense mutation in pgsA, likely responsible for resistance. Additional mutations in mltG and ftsI genes may contribute to the modest increases observed in β-lactam minimum inhibitory concentrations.

This case highlights the risk of rapid daptomycin resistance emergence in C. striatum under selective pressure. Daptomycin should be used with caution for long-term infections caused by this species. Alternative agents such as vancomycin or oxazolidinones may offer more reliable therapeutic options.