Emphysematous Vertebral Osteomyelitis and Epidural Abscess Caused by Disseminated Klebsiella Infection

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1. Cause and Etiology

Causative Organism:

·         Klebsiella pneumoniae is a Gram-negative, encapsulated, facultatively anaerobic bacillus in the family Enterobacteriaceae.

·         Hypervirulent strains, especially Klebsiella pneumoniae serotypes K1 and K2, are increasingly associated with disseminated infections, including liver abscess, endophthalmitis, meningitis, and spinal infections.

Routes of Infection:

·         Hematogenous spread from a primary focus, typically from:

o    Pyogenic liver abscess (especially in diabetics)

o    Urinary tract infections

o    Pneumonia

·         Rarely, direct inoculation or contiguous spread from adjacent structures.

Risk Factors:

·         Diabetes mellitus (strongest risk factor)

·         Immunosuppression (e.g., malignancy, steroid use)

·         Chronic kidney disease

·         Advanced age

·         Alcohol use disorder

·         Asian ethnicity (hypervirulent strains are more prevalent in East Asia)

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2. Pathophysiology

·         Dissemination: Hypervirulent Klebsiella strains have enhanced ability to invade tissues and evade host immune response, often leading to metastatic infections.

·         Gas Production: Emphysematous changes occur due to:

o    Bacterial fermentation of glucose and tissue substrates under anaerobic or hypoxic conditions.

o    Production of hydrogen and carbon dioxide gases.

·         Spinal Involvement:

o    Infection localizes to the vertebral body via Batson’s plexus or arterial seeding.

o    Inflammatory destruction of bone and intervertebral disc (discitis-osteomyelitis).

o    Extension to the epidural space forming an abscess.

o    Gas accumulation may occur in the vertebrae, paraspinal soft tissues, or epidural space.

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3. Epidemiology

·         Incidence: Emphysematous vertebral osteomyelitis is rare, with only sporadic case reports.

·         Demographics:

o    Most patients are middle-aged to elderly.

o    Males are slightly more affected.

o    High prevalence of diabetes in affected individuals (>70% in case series).

·         Geography: More frequently reported in East Asia, particularly Taiwan, South Korea, and Japan.

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4. Clinical Presentation

Onset:

·         Subacute to acute, often over days to weeks.

Symptoms:

·         Severe localized back pain (most common symptom)

·         Fever and chills

·         Neurological deficits (radiculopathy, paraparesis, or paraplegia due to cord compression)

·         Constitutional symptoms (weight loss, malaise)

Signs:

·         Tenderness over affected spinal levels

·         Limited spinal motion

·         Neurological signs (depending on the extent of the epidural abscess)

·         Possible signs of systemic infection (sepsis, altered mental status)

Associated findings:

·         Hepatic abscess (especially in hypervirulent Klebsiella infection)

·         Metastatic septic emboli (lungs, brain, eye)

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5. Imaging Features

A. CT Scan

·         Gas: Hypodense areas within vertebral bodies or discs representing intraosseous gas.

·         Bone destruction: Endplate erosion, lytic lesions.

·         Soft tissue involvement: Paravertebral or psoas muscle abscesses.

·         Epidural abscess: May show as a hypoattenuating collection with mass effect.

B. MRI (Gold standard for spinal infection)

·         T1-weighted: Hypointense vertebral body and disc signal.

·         T2-weighted/STIR: Hyperintense vertebral bodies, disc, and paraspinal soft tissues.

·         Contrast-enhanced:

o    Rim-enhancing epidural abscess.

o    Enhancement of vertebral bodies and disc.

·         Epidural space: Compression of thecal sac or spinal cord.

C. X-ray (less sensitive, late findings):

·         Vertebral collapse

·         Disc space narrowing

·         Gas (rarely seen)

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6. Treatment

A. Medical Management

·         Antibiotics:

o    Empiric: Broad-spectrum IV antibiotics targeting Gram-negative and anaerobic bacteria (e.g., cefepime + metronidazole or meropenem).

o    Tailored therapy: Based on culture and sensitivity (ESBL-producing strains may require carbapenems).

o    Duration: Typically 6–12 weeks of IV antibiotics.

B. Surgical Management

·         Indicated for:

o    Neurological compromise (e.g., epidural abscess with cord compression)

o    Spinal instability

o    Poor response to medical treatment

o    Large abscesses

·         Procedures:

o    Decompressive laminectomy and drainage

o    Corpectomy and spinal stabilization (if needed)

C. Adjunctive Management

·         Glycemic control in diabetics

·         Management of primary infection source (e.g., liver abscess drainage)

·         Supportive care: Pain control, bracing, rehabilitation

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7. Prognosis

Determinants of Outcome:

·         Early diagnosis and treatment

·         Presence of neurological deficits at presentation

·         Control of primary infection source

·         Underlying comorbidities (especially diabetes)

Outcomes:

·         With timely intervention, many patients recover without permanent neurologic deficit.

·         Mortality can be high in cases with delayed treatment or widespread sepsis.

·         Risk of recurrence or chronic osteomyelitis if not adequately treated.

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Summary Table

Category	Details
Organism	Klebsiella pneumoniae (often hypervirulent strains)
Risk Factors	Diabetes, immunosuppression, liver abscess
Route	Hematogenous spread
Symptoms	Back pain, fever, neurologic deficits
Imaging	Gas in vertebrae/disc/epidural space (CT/MRI), bone destruction
Treatment	IV antibiotics (6–12 weeks), surgical drainage if needed
Prognosis	Good with early treatment; worsens with delayed care or sepsis

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References

1.    Lee CH, et al. Klebsiella pneumoniae Spinal Epidural Abscess Associated with Liver Abscess. Infection. 2012.

2.    Fang CT, et al. Klebsiella pneumoniae genotype K1: An emerging pathogen in invasive infections. Clin Infect Dis. 2004.

3.    Kim YJ, et al. Emphysematous vertebral osteomyelitis: Report of two cases. Spine J. 2010.

4.     Sonneville R, et al. Bacterial spinal epidural abscess. Lancet Infect Dis. 2017.

5.    Wu MH, et al. Klebsiella pneumoniae liver abscess associated with metastatic endophthalmitis. Arch Intern Med. 2007.