Background The current Danish National Guideline for treatment of pyogenic vertebral osteomyelitis (PVO) recommends 6 weeks antibiotic (AB) treatment, with a 2-week intravenous (IV) AB lead-in followed by 4 weeks oral AB for uncomplicated PVO, and 12 weeks AB treatment with a 2-4-week IV AB lead-in followed by 8 weeks oral AB for complicated PVO.

The primary objective of the current study is to investigate whether shortening the duration of IV AB to one week for both complicated and uncomplicated PVO is non-inferior to the current Danish National Guideline.

Inclusion Criteria:

1. Age ≥18 years
2. Diagnosed with PVO by a physician based on clinical symptoms and findings consistent with PVO in combination with diagnostic imaging (MRI, PET/CT or PET/MRI)
3. The physician responsible for the patient decides to treat the patient for PVO
4. At time of randomization CRP has decreased to < 75% of peak value or to < 20 mg/l
5. At the time of randomization patient has received maximum 7 days of appropriate IV AB for PVO -

Exclusion Criteria:

1. Previous episodes of PVO within the past 24 months
2. Spinal implants inserted prior to current episode of PVO
3. Hypersensitivity to an AB intended for use in the patient and no alternative drugs available.
4. Oral ABs not possible due to suspicion of reduced absorption
5. Oral Abs not possible due to verified or expected bacterial susceptibility or due to expected toxicity of available regimen
6. Identification of fungus, mold, TB, Brucella, Actinomyces, Nocardia and P. aeruginosa as etiology
7. Severe immunocompromise defined as primary immunodeficiencies, uncontrolled HIV/AIDS, organ transplant recipients, hematological malignancies, patients undergoing biological therapy or chemotherapy and patients treated with prednisolone >=20 mg daily >14 days
8. Verified or expected reduced compliance (for example iv drug use)
9. Pregnancy
10. Breastfeeding
11. Women of childbearing potential, who at the time of inclusion are not using and/or who will not use an effective anticonception method during the treatment period.
12. Patients not capable of providing informed consent at time of screening for inclusion
13. Diagnosed or suspected concomitant or unrelated infections necessitating IV AB therapy beyond 7 days of duration at the time of randomization -

The study will be a nationwide, multicenter, investigator initiated, randomized, controlled, parallel group, open label, non-inferiority trial.

The study will be conducted at departments of infectious diseases in Denmark and in collaboration with spinal surgery units carrying out infection-related spinal surgery.

All patients diagnosed with PVO will be assessed for eligibility. Patients will be eligible for inclusion if they fulfill all the inclusion and none of the exclusion criteria.