The perioperative antibiotic prophylaxis is evidence-based in orthopedic surgery. While its duration ranges from a single dose to three doses throughout the world, the choice of the prophylactic agents is undisputed. Worldwide, the surgeons use 1st or 2nd-generation cephalosporins (or vancomycin in some cases).

However, there are particular clinical situation with a high risk of antibiotic-resistant surgical site infections (SSI); independently of the duration of adminis-tered prophylaxis. These resistant SSI's occur in contaminated wounds, or during surgery under current therapeutic antibiotics, and base on "selection" by antibiotics used for therapy or for prophylaxis.

The perioperative antibiotic prophylaxis is evidence-based for the majority of orthopedic surgeries. While the debate of its duration and timing (single-dose versus triple-dose; before or after the intraoperative microbiological sampling) may continue, no clinicians doubt on the efficiency of the recommended prophylactic agents; that are mostly 1st or 2nd-generation cephalosporins, co-amoxiclav or other exceptional agents in cases of (pseudo)-allergy. However. and traditionally, up to the half of all detected pathogens of orthopedic SSI's are not covered by the prior prophylactic regimens: e.g. SSIs due to methicillin-resistant cocci or non-fermenting Gram-negative rods in orthopedic surgery.

Additionally, orthopedic surgeons operating selected patient populations (neoplasms, open fractures, postoperative wound dehiscence9, diabetic foot infections or already infected body sites) experience a high risk of prophylactic-resistant pathogens, or pathogens resistant to current therapeutic antibiotics regimens. At least 10% of all new intraoperative tissue samples, during iterative surgical debridement, yield (new) pathogens unknown to the clinicians.

This is due to selection by prophylactic or therapeutic antibiotics, which only kill the previously detected pathogens, but left over newly introduced contaminants, remnant parts of partially-diagnosed polymicrobial infections; ultimately leading to a new SSIs occurring during therapy for the first infection at the orthopedic site. This selection is unpredictable involving both Gram-positive skin pathogens as well as (multi) resistant Gram-negative rods.From a microbiological point of view, only a maximal Gram-negative coverage, alongside with a large Gram-negative coverage, would cover these selections.

The literature is in-existing how to prevent these selections. Most clinicians just continue with the standard prophylactic recommendation, or the current thera-peutic antibiotic regimen. Theoretically, clinicians cannot exclude that these selected patient populations eventually might profit from a broad-spectrum prophylaxis.

The BAPTIST trials only concern the perioperative antibiotic prophylaxis in selected situations of orthopedic surgery: tumor surgery, debridement for postoperative dehiscent wounds, debridement under antibiotics, open fractures, skin colonization with multidrug-resistant bacteria, plus, as a control; spine surgery in selected multimorbid patients. The investigators alternately randomize the standard prophylaxis (or by continuing the current antibiotic treatment) to the additional broad-spectrum single-shot of vancomycin 1g IV & single-shot of gentamicin 5 mg/kg intravenously; before an eventual intraoperative sampling. End-of-Treatment (EOT) and/or Test-of-Cure (TOC) occur latest at the 6-week's surgical control visit. The rest of the hospital stay, treatment, the use of negative-pressure vacuum therapy, other interventions, local antibiotic therapies; therapies or procedure are at the discretion of the treating clinicians.

The investogators will randomize surgical interventions defined by the inclusion criteria in a prospective-alternating scheme (1:1) according to the scheduled position in the operating theatres. The anesthetists (or the nurses at the hospitalization units) the will administer the standard prophylaxis (or the therapeutic antibiotics) alone, or with the addition of the single-shot broad-spectrum prophylaxis regimen composed of vancomycin and gentamicin. In case of clinical suspicion of infection or massive contamination, the surgeons will perform at least three microbiological intraoperative tissue samples. Each surgery counts as an independent event. If a patient is debrided several times, he/she can have different prophylaxis regimens during each of the interventions. After the prophylactic regimen, the clinicians are free to continue with a targeted or empirical therapeutic antibiotic regimen. The antibiotic therapy per se is not an objective of this current trials.

The treatment period includes the following daily study visits:

• Visit 1 - Enrollment (Day 1)
• EOT (end of microbiological cultures) - Day 14 (+/- 3 days)
• TOC (clinical surgical control) - Day 42 (+/- 14 days)
• Follow-up (telephone) for implant-related surgery - 1 year (+/- 2 months)

Inclusion Criteria

• Age ≥ 18 years
• Surgery under current or recent therapeutic antibiotics (antibiotic-free window <14 days and past antibiotic prescription >4 days)
• Surgery for open fractures and wounds; including 2nd and 3rd looks
• Potentially contaminated wound revision in the operating theatre
• Tumor (oncologic) surgery (if prior radiotherapy and/or bone involvement)
• Spine surgery with ASA-Score >= 3 points, sacral involvement, or re-vision surgery
• Known skin colonization with multidrug-resistant Gram-negative bacteria

Exclusion Criteria:

• Inability to understand the study procedure for linguistic or cognitive rea-sons
• Surgery without intraoperative microbiological samples
• Allergy or major intolerance to vancomycin and/or gentamicin
• Anticipated clinical follow-up of less than 6 weeks after inclusion
• Pregnant or breastfeeding women
• Known carriage of multiresistant Gram-negative bacteria in the urine or anal region

The investigators might share anonomyzed key elements (data) upon scientific request to the corresponding person

2025

The ivestigators might bilaterally share anonomyzed key elements (data) upon scientific request to the corresponding person

The microbiologists culturing the pathogens of eventual surgical site infections are blinded to the prior prophylaxis during the index surgery