# Mycotic Aneurysm of the Infrarenal Abdominal Aorta Caused by Campylobacter fetus Identified After 10-Day Antibiotic Therapy

## TL;DR

A rare case of a mycotic aneurysm caused by Campylobacter fetus was identified using 16S rRNA gene sequencing after standard tests failed.

## Contribution

Demonstrates the utility of 16S rRNA gene sequencing in diagnosing infections when traditional methods fail.

## Key findings

- Campylobacter fetus was identified as the causative agent of a mycotic aneurysm.
- 16S rRNA gene sequencing successfully detected the pathogen after Gram staining and culture failed.
- The patient had an abdominal mycotic aneurysm with comorbid hypertension.

## Abstract

We report a rare case of a mycotic aneurysm caused by Campylobacter fetus, undetectable by Gram staining or surgical specimen culture obtained after 10 days of antimicrobial therapy. However, the pathogen was successfully detected by 16S rRNA gene sequencing. An 83-year-old woman with comorbid hypertension presented with lumbar and lateral abdominal pain and was diagnosed with an abdominal mycotic aneurysm. Despite its low sensitivity for a negative Gram staining test and culture-negative specimens, 16S rRNA gene sequencing can identify the causative organism and facilitate appropriate antibiotic therapy.