Is empiric antibiotic therapy and blood cultures required for a patient with a sacral ulcer concerning for osteomyelitis, in the absence of fever or leukocytosis (elevated white blood cell count)?

From the Guidelines

For a sacral ulcer concerning for osteomyelitis, even without fever or elevated white blood cell count, blood cultures and empiric antibiotics are generally recommended. Obtain two sets of blood cultures before starting antibiotics, then initiate empiric therapy with vancomycin (15-20 mg/kg IV every 8-12 hours) plus either cefepime (2g IV every 8 hours) or piperacillin-tazobactam (4.5g IV every 6-8 hours) 1. This regimen covers MRSA and gram-negative organisms commonly involved in pressure ulcer infections. Osteomyelitis can present without systemic signs of infection, particularly in elderly or immunocompromised patients. MRI is the preferred imaging modality to confirm bone involvement, and bone biopsy remains the gold standard for diagnosis and targeted antibiotic therapy. While awaiting culture results, continue empiric antibiotics and implement appropriate wound care including debridement of necrotic tissue, pressure offloading, and nutritional support. Once culture results return, narrow antibiotic therapy accordingly. The typical treatment duration for osteomyelitis is 6 weeks, though this may vary based on clinical response and the specific pathogen identified 1.

Some key considerations in the management of osteomyelitis include:

• The anatomic site of infection
• The local vascular supply
• The extent of both soft tissue and bone destruction
• The presence of any systemic signs of infection
• The patient’s preferences for treatment
• The choice of an antimicrobial agent should optimally be based on the results of a bone culture, especially because of the need for long-duration therapy 1

It's also important to note that some patients with apparently incurable infection may require long-term suppressive therapy, or intermittent short courses of treatment for recrudescent symptoms 1. When there are clinical signs of persistent or recurrent infection, the clinician should strongly consider a percutaneous bone biopsy for culture to determine if there is persistent infection or any changes in the pathogens or their antibiotic susceptibilities.

In terms of the duration of antibiotic therapy, a recent randomized controlled trial compared 6 versus 12 weeks of antibiotic therapy for non-surgically treated diabetic foot osteomyelitis and found no significant difference in the remission rate, but significantly fewer adverse effects with the shorter treatment 1. Therefore, 6 weeks of antibiotic therapy is generally recommended for patients who do not undergo resection of infected bone.

From the Research

Empiric Antibiotic Therapy and Blood Cultures for Sacral Ulcer Concerning Osteomyelitis

• In the absence of fever or leukocytosis, the decision to start empiric antibiotic therapy and obtain blood cultures for a patient with a sacral ulcer concerning for osteomyelitis should be based on clinical judgment and individual patient factors 2, 3.
• The standard treatment for chronic osteomyelitis typically involves 6 weeks of parenteral antibiotic therapy, but oral antibiotics may be a reasonable alternative for patients with susceptible organisms 4.
• Blood cultures may be useful in identifying the causative organism and guiding antibiotic therapy, but the reliability of white blood cell scans in detecting disease activity is not significantly affected by antibiotic treatment 5.
• Surgical debridement may be necessary in some cases, and knowledge of sacral anatomy is important to avoid complications such as inadvertent entry into the dural space 6.
• The use of empiric antibiotic therapy and blood cultures should be tailored to the individual patient's needs and clinical presentation, taking into account factors such as the presence of systemic symptoms, the severity of the ulcer, and the patient's overall health status 2, 3, 4, 6, 5.