Surgical site infection (SSI) is among the most frequent healthcare-associated infections in surgical patients and is classified, according to the tissue involved, as superficial incisional, deep incisional or organ/space infection.[1] It is a major cause of avoidable morbidity, prolonged hospital stay and increased cost, and its prevention is a global patient-safety priority.[2] In orthopaedic surgery, the presence of an implant changes the course of infection: bacteria adhere to the device and form biofilm, which protects them from host defences and antimicrobial agents and makes eradication difficult without surgical intervention.[3] Infection after internal fixation of a fracture is now recognised as a distinct clinical entity, fracture-related infection (FRI). An international consensus has defined confirmatory criteria—a fistula, sinus or wound breakdown communicating with the bone or implant, purulent drainage, or phenotypically indistinguishable organisms recovered from at least two separate deep tissue or implant specimens—and suggestive criteria based on clinical, radiological and laboratory features.[4] Not every postoperative wound infection involves bone or implant, and this distinction affects both treatment and interpretation of culture results. For surveillance, the United States National Healthcare Safety Network (NHSN) monitors superficial incisional SSI for 30 days and deep or organ/space SSI after open reduction of fracture for 90 days.[5] Infections presenting later are nevertheless encountered in routine orthopaedic practice. In a multicentre cohort of 433 FRIs, S. aureus was the commonest pathogen across early, delayed and late presentations, and the distribution of pathogens did not differ significantly with time from surgery.[6] Host factors such as diabetes mellitus, smoking and excessive alcohol consumption have been associated with impaired wound healing and higher rates of postoperative infection in systematic reviews.[7–9] Successful management requires a combination of surgical debridement, decisions on implant retention or removal, and pathogen-directed antimicrobial therapy.[10,11] These decisions depend on reliable local information about the organisms involved and their susceptibility, which may differ from published data from high-income settings. The present study was therefore undertaken to identify the organisms isolated from postoperative wound infections following elective orthopaedic fracture fixation surgeries in a tertiary care teaching hospital and to describe the profile of risk factors, management and short-term outcomes among the affected patients.

Study design and setting This hospital-based retrospective observational study was conducted in the Department of Orthopaedics, Karwar Institute of Medical Sciences (KRIMS), Karwar, Uttara Kannada, Karnataka, India, a tertiary care teaching hospital. Medical, operative and laboratory records of patients who underwent elective orthopaedic fracture fixation and subsequently developed a postoperative wound infection during January 2024 to March 2025 were reviewed. Study participants Patients were included if they were aged 18–70 years, had undergone elective internal fixation of a closed fracture of the upper or lower limb, and developed a postoperative wound infection between 30 days and one year after surgery. Patients with open fractures, polytrauma, infections presenting within 30 days of surgery, and infections associated with joint arthroplasty were excluded. The 30-day to one-year window was a study-specific inclusion criterion chosen to describe infections presenting after the early postoperative period. Infections were classified as superficial or deep (involving deep soft tissue, bone or implant) on the basis of clinical and operative findings, with reference to the CDC/NHSN SSI definitions and the FRI consensus criteria. [1,4,5] Data collection Data were extracted using a structured proforma and included age, sex, fracture site, type of fixation device, interval from surgery to the onset of infection, and comorbid conditions and exposures. Diabetes mellitus was recorded from the clinical history and glycated haemoglobin (HbA1c). Smoking was defined as a history of more than 10 pack-years. Chronic alcohol use was recorded as documented in the case record. Clinical features recorded were pain, swelling, wound discharge and fever. Laboratory and imaging investigations included complete blood count, erythrocyte sedimentation rate, C-reactive protein, procalcitonin, HbA1c and plain radiographs. Microbiological methods Wound swabs were collected from all patients. In patients who underwent surgery, three to five deep tissue specimens were obtained intraoperatively from separate sites. Specimens were transported promptly to the Department of Microbiology and processed by Gram staining and culture on blood agar, MacConkey agar and chocolate agar under aerobic conditions; anaerobic culture was also performed. Isolates were identified using the VITEK 2 automated system (bioMérieux, France). Antimicrobial susceptibility testing was performed by the Kirby–Bauer disc diffusion method and/or VITEK 2, and results were interpreted according to Clinical and Laboratory Standards Institute (CLSI) M100 guidelines, 34th edition.[12] An organism was considered causative when it was recovered from deep tissue specimens (or, in the patient managed without surgery, from the wound swab) in a clinically compatible setting. Results were categorised at the patient level as monomicrobial S. aureus, monomicrobial Gram-negative, or mixed infection. Management All patients were admitted. Surgical management comprised excision of necrotic tissue, thorough saline irrigation and management of dead space. Stable implants in fractures that had not yet united were retained; implants were removed when the fracture had united or the implant was loose. Antibiotics were selected on the basis of culture and susceptibility results, and were given initially by the intravenous route followed by oral therapy, for a total of 4–6 weeks. Outcome measures The primary outcome was the profile of organisms isolated. Secondary outcomes were the frequency of risk factors among affected patients, the type of management, and clinical recovery and recurrence at three months. Clinical recovery was defined as resolution of local signs of infection with a healed wound. Recurrence was defined as the reappearance of local signs of infection at the same site during follow-up. Patients were followed up for three months after completion of antibiotic therapy, and all 13 patients completed follow-up. Statistical analysis Data were entered and analysed descriptively in Microsoft Excel (Microsoft Corp., Redmond, WA, USA). Categorical variables are presented as frequencies and percentages, with 13 patients as the denominator, and continuous variables as mean and range. Because all included patients had infection and no uninfected comparison group was available, inferential tests of association were not performed. The study is reported in accordance with the STROBE statement for observational studies.[13] Ethical considerations The study was reviewed and approved by the Institutional Ethics Committee, Karwar Institute of Medical Sciences, Karwar, in its Full Committee Meeting held on 17 July 2026 (Ref. No. IEC/KRIMS/O/85/2026). Patient data were anonymised before analysis.

Demographic and clinical characteristics A total of 13 patients met the inclusion criteria. The mean age was 51 years (range 36–63 years), and 9 (69.2%) were male (Table 1). Diabetes mellitus was the commonest comorbidity, present in 6 (46.2%) patients, of whom 4 had HbA1c above 7.5%. A smoking history was recorded in 5 (38.5%) and chronic alcohol use in 5 (38.5%) patients. One patient (7.7%) had childhood-onset asthma treated with inhaled and intermittent oral corticosteroids. Some patients had more than one risk factor. Fractures involved the lower limb in 9 (69.2%) patients and the upper limb in 4 (30.8%). Infections presented between 30 and 250 days after surgery. Table 1: Demographic and clinical characteristics of patients (N = 13) Characteristic n (%) Age (years), mean (range) 51 (36–63) Male 9 (69.2) Female 4 (30.8) Lower-limb fracture 9 (69.2) Upper-limb fracture 4 (30.8) Diabetes mellitus 6 (46.2) HbA1c > 7.5% 4 of 6 Smoking (> 10 pack-years) 5 (38.5) Chronic alcohol use 5 (38.5) Asthma on corticosteroids 1 (7.7) Interval from surgery to infection (days) 30–250 Values are n (%) unless otherwise stated. Risk factors may coexist in the same patient; percentages use N = 13. Microbiological profile All 13 patients had a positive culture. S. aureus was the commonest single organism, isolated alone in 6 (46.2%) patients (Table 2). Monomicrobial Gram-negative infections occurred in 5 (38.5%) patients: P. aeruginosa in 2 (15.4%), K. pneumoniae in 2 (15.4%) and E. coli in 1 (7.7%). Mixed infection was found in 2 (15.4%) patients, consisting of S. aureus with K. pneumoniae or with P. aeruginosa. Overall, S. aureus was involved in 8 (61.5%) infections and Gram-negative bacilli in 7 (53.8%). Table 2: Organisms isolated from postoperative wound infections (N = 13) Organism (patient-level category) n (%) Staphylococcus aureus alone 6 (46.2) Pseudomonas aeruginosa alone 2 (15.4) Klebsiella pneumoniae alone 2 (15.4) Escherichia coli alone 1 (7.7) Mixed (S. aureus + K. pneumoniae or P. aeruginosa) 2 (15.4) Total 13 (100.0) Any S. aureus 8 (61.5) Any Gram-negative bacillus 7 (53.8) Categories in the first six rows are mutually exclusive; the last two rows overlap because of mixed infections. Percentages may not sum to 100 because of rounding. Management and outcome Ten (76.9%) patients underwent debridement with implant retention, two (15.4%) underwent debridement with implant removal, and the one (7.7%) patient with superficial infection was treated with local wound care and antibiotics alone (Table 3). Antibiotic therapy lasted 4–6 weeks. All 13 patients recovered clinically, and no recurrence was observed during the three-month follow-up after completion of antibiotic therapy. Table 3: Management and short-term outcome (N = 13) Management / outcome n (%) Debridement with implant retention 10 (76.9) Debridement with implant removal 2 (15.4) Local wound care and antibiotics (no surgery) 1 (7.7) Antibiotic duration (weeks) 4–6 Clinical recovery at 3 months 13 (100.0) Recurrence at 3 months 0 (0.0) Management categories are mutually exclusive.

This study describes the organisms and host risk factors in postoperative wound infections presenting 30 days to one year after elective fracture fixation at a tertiary care teaching hospital in coastal Karnataka. S. aureus was the commonest single pathogen, while Gram-negative bacilli were involved in more than half of the infections. Diabetes, smoking and alcohol use were frequent among affected patients, and most infections were managed successfully with debridement and implant retention. The predominance of S. aureus is consistent with the international literature on implant-associated orthopaedic infection. In a large Belgian–Dutch cohort, Depypere et al. identified S. aureus in 31.4% of FRIs, and 25.3% of infections were polymicrobial.[14] Corrigan et al. found S. aureus to be the commonest pathogen regardless of the time of presentation.[6] The ability of S. aureus to adhere to implant surfaces and form biofilm explains its central role in these infections and its persistence despite antimicrobial therapy.[3] The notable finding of the present study is the involvement of Gram-negative bacilli—P. aeruginosa, K. pneumoniae and E. coli—in 53.8% of infections. This proportion is higher than that generally reported from European cohorts,[14] although differences in case definition, sampling practice, prior antibiotic exposure and sample size limit direct comparison. A substantial Gram-negative contribution in this setting is clinically relevant: empirical regimens directed only at Gram-positive cocci may be inadequate while culture results are awaited, and intraoperative deep tissue sampling before antibiotic administration is essential to guide definitive therapy. The present data cannot, however, identify the source of these organisms or establish a regional trend. Infections in this study presented between 30 and 250 days after surgery. Time from surgery alone does not reliably predict the organism involved,[6] and late presentation should not be assumed to indicate low-virulence organisms or haematogenous seeding. Accordingly, a diagnosis based on deep tissue culture, rather than on timing or superficial swabs, should guide treatment.[4] Diabetes mellitus was present in nearly half of the patients, and most of them had suboptimal glycaemic control. A meta-analysis has shown that diabetes is associated with an increased risk of SSI (pooled odds ratio 1.53).[7] Smoking impairs tissue oxygenation and wound healing and increases wound complications and infection,[8] and preoperative alcohol consumption has been associated with postoperative infection and other complications.[9] The high frequency of these factors in the present study is in keeping with this evidence. However, because only infected patients were studied, their frequencies could not be compared with those in uninfected patients, and independent risk factors could not be identified. These factors should be regarded as a risk factor profile, which highlights targets for preoperative optimisation such as glycaemic control and smoking and alcohol cessation. Debridement with implant retention was performed in most patients, in line with consensus principles that support retention of a stable implant in an ununited fracture, combined with thorough debridement and targeted antimicrobial therapy.[10] All patients recovered without recurrence at three months. The antibiotic duration of 4–6 weeks in this study was shorter than the approximately 12 weeks suggested by international consensus for infections managed with implant retention, while 6 weeks is commonly advised after complete implant removal.[11] The OVIVA trial showed that appropriately selected oral antibiotic therapy was non-inferior to intravenous therapy during the first six weeks of treatment of bone and joint infection,[15] which supports early transition to oral agents. Given the small sample and short follow-up, the present results cannot establish that shorter courses are adequate, and longer follow-up is needed to detect late recurrence. Strengths and limitations The study focuses on a defined population—elective fixation of closed fractures—and combines microbiological, clinical and treatment data from a resource-limited setting where such data are scarce. Its limitations include the small sample size, retrospective single-centre design and lack of an uninfected comparison group, which preclude estimation of infection incidence and analytical assessment of risk factors. One superficial infection was included, and not all cases could be classified against consensus FRI criteria. Isolate-level antimicrobial susceptibility data were not available for analysis, and follow-up was limited to three months. These factors may introduce selection and information bias and limit generalisability. Recommendations Prospective surveillance of all elective fracture fixations, with a complete operative denominator, standardised diagnostic criteria, multiple deep tissue cultures, susceptibility testing and follow-up for at least 12 months, is recommended. Inclusion of uninfected patients would allow true risk factor analysis and estimation of local infection rates. A local antibiogram for orthopaedic implant infections would support rational empirical antibiotic selection.

In this study of postoperative wound infections following elective orthopaedic fracture fixation, S. aureus was the commonest single pathogen, and Gram-negative bacilli were involved in more than half of the infections. Diabetes mellitus, smoking and alcohol use were common among affected patients. Debridement with implant retention and culture-guided antibiotics were associated with favourable short-term outcomes. Empirical treatment protocols should take account of the local Gram-negative burden, and larger controlled prospective studies are required to confirm independent risk factors and long-term outcomes.

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