Microscopic view of Pseudomonas fluorescens bacteria in sacroiliac joint with military insignia.

Uncommon Infection, Unexpected Recovery: A Soldier's Story of Septic Sacroiliitis

Author's portrait.
Jordan Keane in Health & Wellness August 2025 • 5 min read.

"Discover how a rare bacterial infection was swiftly identified and treated in a young, active soldier, highlighting crucial diagnostic lessons for military healthcare."


In the realm of infectious diseases, septic sacroiliitis stands out as an infrequent and often overlooked condition, particularly among individuals with robust immune systems. This infection, which targets the sacroiliac joint, is typically attributed to gram-positive bacteria, making instances involving gram-negative organisms notably rare. Adding another layer of complexity, Pseudomonas species account for a mere fraction—approximately 5%—of these already scarce cases.

This article presents a unique case: a healthy soldier diagnosed with septic sacroiliitis caused by Pseudomonas fluorescens. This marks the first documented occurrence of this specific bacterial culprit in the context of sacroiliitis. The soldier's journey underscores the diagnostic and management challenges inherent in such atypical infections, emphasizing the importance of heightened awareness and advanced diagnostic techniques.

Septic sacroiliitis often goes unrecognized due to its low incidence and nonspecific presentation. A greater understanding of septic sacroiliitis as a potential cause in troops presenting with fever, low back pain, and weight-bearing difficulties is essential. Given the military population's susceptibility to this commonly unrecognized infection, delayed diagnosis can negatively impact a soldier's military preparedness.

What are the Initial Symptoms and Diagnostic Journey?

Microscopic view of Pseudomonas fluorescens bacteria in sacroiliac joint with military insignia.

A 26-year-old white male soldier sought medical attention for severe left lower-back pain and significantly impaired mobility. His medical history included chronic, moderate, bilateral low-back pain following a fall during combat training a year prior, with evidence of degenerative lumbar disk disease on MRI ten months earlier. Initially, the symptoms were attributed to musculoskeletal issues, common among active individuals. However, as the pain intensified and became debilitating, it became clear that something more serious was at play.

Two months before his eventual hospitalization, the soldier visited an emergency department due to an exacerbation of his low-back pain, which proved unresponsive to increasing doses of oral narcotics. He described the pain as constant, sharp, stabbing, and radiating to his left lateral thigh, requiring the use of a walker for ambulation. Accompanying symptoms included lower abdominal pain and intermittent non-bloody diarrhea. Initial laboratory studies were unremarkable, and concurrent abdominal CT and lumbar MRI scans revealed no acute pathology or sacroiliac (SI) joint involvement. A colonoscopy with random rectal mucosal biopsy yielded normal results.

  • Persistent Pain: Unresolved pain despite conventional treatments.
  • Mobility Issues: Reliance on assistive devices like walkers.
  • Associated Symptoms: Presence of abdominal pain and gastrointestinal disturbances.
Two months later, following a minor fall, the soldier experienced an acute episode of excruciating, focal left sacroiliac pain. This prompted hospital admission. The physical examination revealed prominent tenderness and guarding upon light palpation of the left SI joint. The patient's pain severely limited further orthopedic testing. Despite restricted leg mobility, there were no focal neurologic deficits. Admission laboratory values indicated normal hematologic and metabolic parameters, but the erythrocyte sedimentation rate (ESR) was elevated at 35 mm/h, and C-reactive protein (CRP) was 3.5 mg/dL, suggesting an inflammatory process. HLA-B27 and HIV antibodies were negative. MRI revealed left SI joint effusion with erosive changes and associated bone marrow edema, along with edema in adjacent muscles.

A Swift Response and a Word of Vigilance

This unique case underscores the potential for rapid recovery with targeted oral antimicrobial therapy. It also highlights the importance of enhanced microbiological diagnostic techniques to account for less common pathogens. Raising awareness about septic sacroiliitis as a potential diagnosis for troops presenting with specific symptoms can minimize delays in treatment. This approach is especially important given the young age and trauma exposure typical of military populations, where a delayed diagnosis can significantly impact a soldier's readiness and overall health.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

Everything You Need To Know

1

What is Septic Sacroiliitis?

Septic sacroiliitis is a rare infection affecting the sacroiliac joint. It is infrequently encountered, particularly in individuals with strong immune systems. It is typically caused by bacteria, with gram-positive bacteria being the most common culprits. This infection can lead to significant pain and mobility issues, as seen in the soldier's case, who initially experienced debilitating low-back pain, eventually prompting hospitalization.

2

What is the role of Pseudomonas fluorescens in this context?

Pseudomonas fluorescens is a gram-negative bacterium. In the context described, the young soldier's septic sacroiliitis was uniquely caused by Pseudomonas fluorescens. This is a rare occurrence, as Pseudomonas species account for only about 5% of septic sacroiliitis cases. This instance highlights the importance of considering atypical pathogens in diagnosing and treating such infections.

3

What were the initial symptoms and diagnostic challenges faced by the soldier?

The soldier initially presented with severe left lower-back pain and mobility issues, which was initially attributed to musculoskeletal problems. He experienced constant, sharp, stabbing pain radiating to his left lateral thigh, requiring a walker for ambulation. Accompanying symptoms included lower abdominal pain and intermittent non-bloody diarrhea. Early diagnostic challenges included unremarkable initial laboratory studies and imaging that did not reveal the sacroiliac joint involvement. It was later revealed that he suffered from elevated ESR and CRP levels, suggesting an inflammatory process, before a specific diagnosis was confirmed through MRI.

4

Why is prompt diagnosis and treatment crucial for soldiers with septic sacroiliitis?

Prompt diagnosis and treatment are critical because delayed treatment can negatively impact a soldier's military preparedness and overall health. The military population is susceptible to septic sacroiliitis, and the young age and potential trauma exposure typical of soldiers can complicate the diagnosis. Timely intervention with appropriate antimicrobial therapy can lead to a remarkable recovery, as seen in the soldier's case, underscoring the importance of vigilance and advanced diagnostic techniques.

5

How does this case highlight the importance of advanced diagnostic techniques?

The case underscores the importance of enhanced microbiological diagnostic techniques because the soldier's infection was caused by the rare Pseudomonas fluorescens. Conventional diagnostic approaches might overlook less common pathogens, leading to delayed or incorrect treatment. The use of advanced diagnostic techniques is crucial for identifying the specific causative agent and ensuring the most effective treatment, which in turn can minimize delays in treatment and optimize the chances of a full recovery.

Newsletter Subscribe

Subscribe to get the latest articles and insights directly in your inbox.