Fungal Spine Infections

Fungal spine infection, fungal spondylodiscitis or vertebral osteomyelitis, is rare but serious, accounting for only 1-2% of all spinal infections. Its incidence is rising with the number of immunocompromised patients: HIV, solid organ transplantation, chemotherapy and chronic immunosuppressive medication.

Why it matters. It mimics bacterial infection clinically but does not respond to antibacterial therapy, so it is easily missed. Delayed diagnosis leads to progressive neurological deficit, spinal instability and disseminated disease with high mortality. A high index of suspicion is required in any immunocompromised patient with a spine infection, and tissue biopsy is the gold standard for diagnosis.

Who. Immunocompromised hosts predominate:

• HIV/AIDS with a CD4 count less than 100 cells/mcL
• Solid organ transplant recipients on immunosuppression
• Haematological malignancies (leukaemia, lymphoma) undergoing chemotherapy
• Chronic corticosteroid use, more than 20mg of prednisone daily for more than 3 weeks
• Diabetes mellitus with poor glycaemic control (HbA1c greater than 9%), which increases the risk of Candida and mucormycosis
• Cirrhosis and chronic alcohol use, which predispose to disseminated candidiasis
• IV drug use (Candida from contaminated needles)
• Recent spine surgery or invasive procedures

Where. Candida and Aspergillus occur worldwide and are nosocomial. The endemic mycoses have a specific geography, and the travel history is part of the diagnosis:

• Coccidioides: Southwest USA (California, Arizona, New Mexico)
• Histoplasma: Mississippi and Ohio River valleys
• Blastomyces: Great Lakes region, Mississippi valley
• Cryptococcus: worldwide but higher in AIDS patients; meningitis

Routes of infection. Fungi reach the spine by haematogenous spread, direct inoculation or contiguous spread, and each route has its own organisms and pattern of involvement.

CandidaAspergillusEndemic Mycoses

The dominant pathogen in healthcare-associated fungal spondylodiscitis. Published aggregations disagree on which organism is commonest overall (Das found Candida albicans 62.7%, Ganesh found Aspergillus 38.2%) because both pool published cases from different eras rather than measuring incidence. What is consistent is the setting: Candida follows candidaemia from central lines, parenteral nutrition, prolonged ICU stay, abdominal surgery and injecting drug use. Recent broad-spectrum antibiotics add to the risk.

Species. C. albicans is the most common, but C. glabrata, C. tropicalis and C. parapsilosis are increasingly recognised.

Behaviour. Candida presents indolently with back pain and a low-grade fever, and is often diagnosed late, when a neurological deficit develops. It involves the disc well, with disc space narrowing on imaging.

Treatment. Fluconazole for susceptible species (C. albicans, C. tropicalis) and an echinocandin for resistant species or critically ill patients, for a minimum of 6 months and up to 12 months if disease is extensive. Doses are in the Management table.

Who gets it. Aspergillus dominates in the profoundly immunocompromised:

• Haematological malignancies
• Haematopoietic stem cell transplantation
• Prolonged neutropenia
• Chronic granulomatous disease
• High-dose corticosteroids

Species. A. fumigatus is the most common; A. flavus and A. niger also occur.

Behaviour. Aspergillus is more aggressive than Candida. It preferentially destroys bone, so bony destruction is prominent, resulting in vertebral collapse and kyphotic deformity, while the disc is relatively spared at first. A paravertebral mass is common.

Treatment. Voriconazole is first line and liposomal amphotericin B the alternative, for a minimum of 12 weeks and often 6-12 months. Surgical debridement is often required because of the extensive bony destruction.

Aspergillus Has High Mortality

Disseminated aspergillosis carries 30-50% mortality despite treatment. Early diagnosis and aggressive combination therapy (surgical debridement PLUS voriconazole) improves outcomes. Delay in diagnosis often results in progressive neurological deterioration and death from disseminated disease.

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Exposure. The endemic mycoses need travel to, or residence in, an endemic region. Dissemination occurs months to years after the primary pulmonary infection, so a remote travel history may be the relevant one. They cause chronic granulomatous inflammation with caseous necrosis that mimics tuberculosis clinically and radiographically.

Coccidioides immitis/posadasii. A primary pulmonary infection for which the spine is a recognised site of dissemination, though no cited source on this page quantifies how often. Multifocal spinal involvement is common. Treatment is fluconazole, or liposomal amphotericin B for severe cases, with surgery for neurological deficit or instability.

Histoplasma capsulatum. Involves the spine less often than Coccidioides, in AIDS patients or those with chronic granulomatous disease. Treatment is itraconazole.

Blastomyces dermatitidis. Spinal involvement is rare and presents with chronic back pain and draining sinuses. Treatment is itraconazole 200mg TID for 3 days, then 200mg daily for 6-12 months.

Mucormycosis behaves and is treated very differently from Candida and Aspergillus, and it is a surgical emergency.

Agents and hosts. It is caused by the Mucorales (Rhizopus, Mucor, Rhizomucor, Lichtheimia, Cunninghamella). The classic host has uncontrolled diabetes, especially diabetic ketoacidosis, in which acidosis impairs neutrophils and frees iron. Iron overload and deferoxamine therapy are the other classic setting, because the drug acts as a siderophore that delivers iron to the fungus. Haematological malignancy, neutropenia and transplantation complete the list, with IV drug use and direct or traumatic inoculation the routes to the spine specifically.

Angioinvasion. Mucorales invade blood vessels, causing thrombosis, infarction and rapid, extensive tissue necrosis. Disease spreads fast, and antifungals penetrate the dead, thrombosed tissue poorly, which is why surgery is central rather than adjunctive.

Histology. Broad, non-septate (pauci-septate), ribbon-like hyphae with wide-angle (approximately 90-degree), irregular branching, against the narrow, septate hyphae of Aspergillus with acute-angle (approximately 45-degree) branching. Cultures are frequently negative, so the diagnosis is often made on histology; do not wait for a culture to act.

Treatment. Urgent, aggressive and often repeated surgical debridement of all necrotic tissue, with liposomal amphotericin B first line and isavuconazole or posaconazole for step-down or salvage. Reverse the driver: correct the DKA or hyperglycaemia, stop deferoxamine and reduce immunosuppression. Mortality is very high.

Actinomyces and Nocardia are filamentous, branching Gram-positive bacteria that can be mistaken for fungi. They are treated with antibiotics, not antifungals, so recognising them changes management completely.

Actinomyces (e.g. A. israelii) is an anaerobic or microaerophilic filament and part of the endogenous flora of the oropharynx, GI tract and female genital tract. It reaches the spine by contiguous spread: classically cervicofacial ("lumpy jaw") disease extending to the cervical spine, or thoracic (aspiration) and abdominopelvic (IUD-associated) disease invading the adjacent vertebrae. It crosses tissue planes and the disc and forms chronic indurated masses with sinus tracts discharging "sulphur granules". It is not acid-fast. Treatment is prolonged high-dose penicillin, IV then oral, often for 6-12 months.

Nocardia (e.g. the N. asteroides complex) is aerobic and weakly or partially acid-fast on modified Ziehl-Neelsen (Kinyoun) staining, the key feature separating it from Actinomyces. It lives in soil and affects the immunocompromised (steroids, transplant, malignancy), typically as primary pulmonary disease with haematogenous dissemination to brain and bone or spine. Treatment is prolonged high-dose co-trimoxazole (TMP-SMX), often with a carbapenem or amikacin for severe disease.

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Symptoms. Onset is indolent, over weeks to months, and constitutional symptoms are less prominent than in bacterial infection:

• Back pain (90%), insidious and progressively worsening
• Low-grade fever (40-60%), which may be absent
• Night sweats and weight loss (40%)
• Radicular pain from nerve root compression (30%)
• Neurological deficit (50-70%), often a late presentation

When to think fungal. A spine infection that fails to improve on appropriate antibiotics, particularly in an immunocompromised patient. Empiric antibacterial therapy is often started before a fungal diagnosis is considered.

Examination. Look for tenderness at the affected level and reduced range of motion, and examine motor, sensory and reflex function. Assess for an epidural abscess: saddle anaesthesia, bowel or bladder dysfunction. Then look for other sites of infection: pulmonary crackles, skin lesions and retinal lesions (Candida endophthalmitis).

Blood tests. ESR and CRP are elevated, but less dramatically than in bacterial infection (ESR 40-80mm/hr typical). Leukocytosis may be absent and anaemia of chronic disease is common. Every patient with suspected fungal infection should be tested for HIV.

Blood cultures are frequently negative in fungal spine infection and lower-yield than in bacterial disease. No cited source on this page gives a figure for either, so treat a negative blood culture as uninformative rather than reassuring.

Serology. Beta-D-glucan (Candida, Aspergillus), galactomannan (Aspergillus), and Coccidioides serology if there has been endemic exposure. With PCR, serology aids rapid diagnosis.

MRI with contrast is the gold standard image. It shows the extent of vertebral and disc involvement, paravertebral abscess, epidural extension and neural compression. T2 hyperintense paraspinal masses with rim enhancement are characteristic.

CT defines bony destruction and cortical integrity better and is useful for surgical planning. CT of the chest, abdomen and pelvis looks for pulmonary or disseminated infection (aspergillosis, coccidioidomycosis) and other sites of involvement.

Tissue diagnosis is mandatory. CT-guided needle biopsy is the initial approach, sent for fungal and bacterial culture, fungal stains (GMS, PAS) and AFB stains. Open surgical biopsy follows if the needle biopsy is non-diagnostic, or when a neurological deficit needs decompression; take multiple samples from the vertebral body, disc and abscess. Histopathology looks for granulomas and fungal elements on GMS or PAS, and the characteristic morphology helps identify the organism (Aspergillus: septate hyphae with acute-angle branching).

Molecular and advanced testing.

• PCR: rapid identification of Aspergillus, Candida and endemic fungi from tissue or fluid
• MALDI-TOF mass spectrometry: rapid species identification from culture isolates
• Antifungal susceptibility testing: essential for Candida (fluconazole resistance is common in C. glabrata) and Aspergillus

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Imaging characteristics. Fungal infection extends into the paravertebral and epidural spaces more often than bacterial infection, and subligamentous spread is uncommon. Multiple non-contiguous levels suggest haematogenous dissemination. The percentage ranges in this table are conventional teaching estimates from the spinal-infection literature, not measurements from a cited cohort; the verified microbiological and outcome figures on this page are in the Evidence Base section.

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The principles. Identify the organism from tissue, because targeted therapy depends on it. Give antifungals for a long time, operate for the indications below, and reverse the immunosuppression where possible: reduce steroids, optimise HIV control and defer chemotherapy. Combination therapy, medical PLUS surgical, is often needed for the best outcome.

Algorithm

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Medical ManagementSurgical Management

Duration. Antifungal therapy runs a minimum of 6-12 months and often longer, against 6 weeks for a bacterial infection; Aspergillus is the exception, with a stated minimum of 12 weeks. Treat until clinical resolution, CRP normalisation and radiographic improvement. Lifelong suppressive therapy may be necessary in patients who remain severely immunosuppressed (AIDS with CD4 less than 100, transplant recipients).

Candida albicans

First-Line Treatment

Fluconazole 400-800mg PO daily

Alternative

Micafungin 100mg IV daily

Duration

6-12 months

Candida glabrata (resistant)

First-Line Treatment

Micafungin 100mg IV daily

Alternative

Caspofungin 70mg loading, then 50mg daily

Duration

6-12 months

Aspergillus

First-Line Treatment

Voriconazole 6mg/kg IV q12h day 1, then 4mg/kg IV q12h (or 200mg PO BID)

Alternative

Liposomal amphotericin B 5mg/kg IV daily

Duration

12 weeks to 12 months

Coccidioides

First-Line Treatment

Fluconazole 400-800mg PO daily

Alternative

Liposomal amphotericin B (severe cases)

Duration

12-18 months, often lifelong

Histoplasma

First-Line Treatment

Itraconazole 200mg TID for 3 days, then 200mg PO BID

Alternative

Liposomal amphotericin B (severe cases)

Duration

12+ months

Organism	First-Line Treatment	Alternative	Duration
Candida albicans	Fluconazole 400-800mg PO daily	Micafungin 100mg IV daily	6-12 months
Candida glabrata (resistant)	Micafungin 100mg IV daily	Caspofungin 70mg loading, then 50mg daily	6-12 months
Aspergillus	Voriconazole 6mg/kg IV q12h day 1, then 4mg/kg IV q12h (or 200mg PO BID)	Liposomal amphotericin B 5mg/kg IV daily	12 weeks to 12 months
Coccidioides	Fluconazole 400-800mg PO daily	Liposomal amphotericin B (severe cases)	12-18 months, often lifelong
Histoplasma	Itraconazole 200mg TID for 3 days, then 200mg PO BID	Liposomal amphotericin B (severe cases)	12+ months

Monitoring. Voriconazole and itraconazole levels vary significantly between patients, so both are measured.

• Clinical response: pain, fever and neurological status, weekly at first
• Inflammatory markers: CRP and ESR monthly, which should trend down over 3-6 months
• Drug levels: voriconazole trough 1-5.5mcg/mL, itraconazole trough greater than 1mcg/mL
• Toxicity: LFTs monthly (azole hepatotoxicity), creatinine (amphotericin nephrotoxicity), visual changes (voriconazole)
• Imaging: MRI at 3 and 6 months, expecting slow radiographic improvement

Failure to improve clinically or radiographically at 3 months suggests the need for surgery or a change of antifungal regimen.

Absolute indications. Any one of these:

• Progressive neurological deficit (motor weakness, cauda equina syndrome)
• Spinal instability (vertebral collapse, kyphotic deformity greater than 30°)
• Epidural abscess with cord compression
• Medical treatment failure: progression despite 4-6 weeks of appropriate antifungals

Relative indications.

• Tissue diagnosis needed (CT biopsy non-diagnostic or technically difficult)
• Extensive bony destruction requiring reconstruction
• Large paravertebral abscess amenable to drainage

Choosing the approach. The three approaches are selected by where the disease actually is, not escalated through in sequence. Fungal spondylodiscitis, like tuberculous disease, is predominantly an anterior column problem: the vertebral body and disc are destroyed while the posterior elements are often spared. The guiding question is whether the pathology to be reached and the instability to be corrected lie in front of the cord, behind it, or both. A posterior-only operation on anterior destruction decompresses the cord but leaves the infected bone and the collapsing column untouched.

Posterolateral decompression, for posterior disease. For a posterior or posterolateral epidural abscess needing laminectomy to decompress the cord. Laminectomy at the affected level or levels, evacuate the abscess, decompress the neural elements, take tissue for culture and pathology, debride infected bone and instrument if unstable. It is a single approach familiar to most spine surgeons, but its access to the anterior vertebral body and disc is limited, and that is where fungal disease usually lives, so this approach alone is often insufficient.

Anterior corpectomy, which reaches the primary pathology. For vertebral body destruction with anterior column failure or kyphotic deformity. Through a transthoracic, retroperitoneal or transabdominal approach, the corpectomy and disc removal debride all infected tissue, and the column is reconstructed with an expandable cage or structural allograft, adding an anterior plate if there is no posterior instrumentation. It gives direct access to the vertebral body, excellent debridement and single-stage reconstruction. The cost is higher morbidity than a posterior approach, with vascular injury and, after a transthoracic approach, pulmonary complications in a patient who is often immunocompromised to begin with.

Combined anterior-posterior, for circumferential disease. For severe destruction with instability, or extensive disease requiring circumferential debridement. Posterior instrumentation for stability comes first, then anterior corpectomy and reconstruction, staged or on the same day if the patient is stable. It gives the most complete debridement and maximum stability, at the price of the highest morbidity and longest operative time, and staging may be needed: a real consideration in a patient whose immunosuppression is both the reason for the infection and the reason they tolerate surgery badly.

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Debridement. Remove ALL infected tissue, including disc, vertebral body and paraspinal abscess, and send multiple samples for fungal, bacterial and mycobacterial culture and for pathology.

Reconstruction. Restore height and alignment with structural support: an expandable cage, allograft, or PMMA if fusion is not planned. Avoid autograft (risk of infection).

Instrumentation. Pedicle screws 2 levels above and below the infected segment, supplemented by an anterior plate after an anterior-only approach. Unlike in high-grade bacterial infection, instrumentation can generally be retained, because fungal biofilm behaviour and the need for stability differ.

After surgery. Continue antifungals for 6-12 months postoperatively, with a TLSO brace for 3 months and early mobilisation once neurologically and haemodynamically stable. Reported fusion success is higher with combination therapy than with medical therapy alone in severe disease; precise rates vary between the small published series, and no cited source on this page measures them, so the honest statement is the direction, not a percentage.

Surgical Debridement Improves Outcomes

Combination therapy (surgical debridement PLUS prolonged antifungals) has better outcomes than medical therapy alone in fungal spine infections with neurological deficit or extensive bony destruction. In a pooled literature review (Ganesh), surgery plus antifungals carried lower mortality than medical therapy alone for both Aspergillus (26.9% vs 60%) and Candida (0% vs 28.6%), an association heavily confounded by who was fit enough to operate on. Surgery provides tissue diagnosis, decompresses neural elements, and removes bulk of infected/devitalized tissue allowing antifungals to work more effectively. Do NOT delay surgery in patient with progressive neurological deficit.

Global Epidemiology

Fungal spine infection accounts for roughly 1-2% of all spinal infections worldwide, with a reported incidence near 2.2 per 100,000 person-years. Distribution is driven by host immunosuppression (HIV, transplantation, haematological malignancy, chronic steroids, diabetes) and by geography for the endemic mycoses. Candida and Aspergillus occur worldwide and are largely healthcare- or immunosuppression-associated, whereas Coccidioides (Southwest USA, parts of Central/South America), Histoplasma (Americas, parts of Africa/Asia) and Blastomyces (North America) are geographically restricted. In published pooled series the lumbar spine is most often affected, with male predominance and a mean age in the mid-50s.

Side-by-Side Guidance

Registries and Practice Variation

There is no dedicated arthroplasty-style registry for spinal fungal infection; evidence rests on pooled case series and surveillance networks (e.g. ECMM/FungiScope, national antifungal-resistance surveillance such as CDC/EUCAST programmes). High-resource settings emphasise molecular diagnostics (PCR, MALDI-TOF), beta-D-glucan/galactomannan assays, therapeutic drug monitoring of azoles, and ready access to liposomal amphotericin B and newer triazoles. In limited-resource settings, delayed diagnosis, restricted access to voriconazole/isavuconazole and amphotericin formulations, and overlap with tuberculosis (which is far more common and radiographically similar) drive worse outcomes and a lower threshold for empiric anti-tuberculous therapy before fungal disease is considered.

Empiric antifungals before tissue diagnosis. Whether to start empiric antifungals in a deteriorating high-risk patient while awaiting culture (which takes 2-6 weeks), or to hold therapy to preserve culture yield, is unresolved. Most authorities favour empiric cover in the immunocompromised, deteriorating patient, accepting reduced culture sensitivity.

Optimal duration. A minimum of 6-12 months is widely cited, but the evidence is observational. The endpoint (CRP normalisation, radiographic resolution or a fixed duration) and the role of indefinite suppression in persistent immunosuppression remain debated, with no randomised data.

Hardware in active infection. Instrumentation is generally retained, but the threshold for hardware removal versus suppression over retained metal is not standardised.

Combination antifungal therapy. Combining antifungals (e.g. voriconazole plus an echinocandin or amphotericin) for severe or refractory spinal aspergillosis is extrapolated from invasive aspergillosis data; spine-specific evidence is absent and toxicity is additive.