Surgical site infection (SSI) is an infection of the incision, or of the deeper tissues handled during the operation, that appears within the postoperative surveillance window. In low- and middle-income countries it may affect up to a quarter of surgical patients in some settings, and it brings longer admissions, higher costs and a growing problem of multidrug-resistant organisms (1). In tertiary hospitals of Karachi, patients who developed SSI stayed longer and generated considerably higher treatment costs than uninfected patients (2).

Pakistan has only recently gained national data on this problem. The PakSurg 1 multicenter cohort followed 1,711 elective surgical patients across 28 hospitals and recorded SSI in 9.5%, with trauma surgery, contaminated wounds and prolonged admission carrying the greatest risk (3). Single-center reports vary widely, from an infection rate below 1% after open hernioplasty at a tehsil hospital in Lahore (4) to 26.8% after emergency gastrointestinal surgery in Karachi (5). Such variation reflects differences in case mix, follow-up and infection-control practice, which is why each unit needs its own data.

Local studies have also pointed to the patients most at risk. In a general surgical series from Abbottabad, comorbidity, prolonged operations and inadequate preoperative preparation were the main contributors to SSI (6). Among diabetic patients undergoing elective surgery in Lahore, one in four developed SSI, and poor glycemic control, operations lasting two hours or more, contaminated wounds and smoking were independent predictors (7). The role of antibiotics in clean surgery remains debated. In Multan, a single preoperative dose was as effective as an extended course after mesh repair of inguinal hernia (8), and in low-risk laparoscopic cholecystectomy prophylaxis did not lower SSI at all (9). A review from Abbottabad accordingly argues for selective rather than routine prophylaxis in low-risk elective cases (10). Training of operating room staff in Islamabad improved knowledge and self-reported prevention practice (11), in keeping with international evidence that most SSIs are preventable when proven measures are applied consistently (12).

Clean procedures such as hernioplasty, thyroidectomy and excision of breast lumps or lipomas make up a large share of elective general surgery in our hospitals, yet local information on which patients become infected after them is scarce. This study was therefore undertaken to determine the frequency of postoperative wound infection in potentially clean cases in the General Surgery Ward of Bacha Khan Medical Complex, Mardan, and to identify the demographic, clinical and perioperative factors associated with it.

This cross-sectional analytical study was conducted in the General Surgery Ward of Bacha Khan Medical Complex, Swabi, from May 2025 to November 2025 after approval from the institutional ethical review board. Written informed consent was obtained from every participant. A total of 150 patients were included by non-probability consecutive sampling. Patients of either gender aged [≥18] years who underwent elective hernioplasty, incisional hernia repair, thyroidectomy, breast lump excision, lipoma excision or hydrocelectomy were eligible. Patients undergoing emergency, contaminated or dirty procedures, and those with an existing skin infection at the operative site, were excluded. For every patient, age, gender, body mass index (BMI), diabetes mellitus, hypertension, anemia, smoking status and American Society of Anesthesiologists (ASA) grade were recorded on a structured proforma. Operative details included the procedure, duration of surgery in minutes, use and timing of prophylactic antibiotics (preoperative or intraoperative), wound class (clean or clean-contaminated), placement of a surgical drain and the grade of the operating surgeon (consultant or resident). The outcome, postoperative wound infection, was diagnosed on clinical grounds according to CDC criteria, during the hospital stay and follow-up visits up to 30 days, and was graded as superficial or deep. Pus or wound discharge from infected wounds was sent for culture, and the isolated organism was recorded. Length of hospital stay was noted in days. Data were analyzed using SPSS version 26. Continuous variables were expressed as mean ± standard deviation and median with interquartile range (IQR), and were compared between infected and non-infected patients with the Mann–Whitney U test. Categorical variables were expressed as frequencies and percentages and compared using Pearson's chi-square test; Fisher's exact test was applied to 2×2 tables. Cramér's V was calculated as a measure of effect size. The frequency of infection was reported with a 95% Wilson confidence interval, and crude odds ratios (OR) with 95% CI were calculated for binary exposures. Multivariable logistic regression was attempted, but complete separation in several strata (categories in which all or none of the patients were infected) made the adjusted estimates unstable, so only unadjusted associations are presented. A two-sided p-value <0.05 was considered statistically significant.

Of the 150 patients, 61 developed postoperative wound infection, giving a frequency of 40.7% (95% CI 33.1–48.7%). Deep infection was seen in 35 (57.4%) and superficial infection in 26 (42.6%) of the infected patients. Culture grew Staphylococcus aureus in 24 (39.3%), Escherichia coli in 15 (24.6%), Klebsiella species in 12 (19.7%) and Pseudomonas species in 10 (16.4%) cases.

The baseline profile of the study population is shown in Table 1. The mean age was 48.6 ± 13.3 years, and men made up 60.7% of the sample. Nearly half the patients were diabetic and more than half were hypertensive. Hernioplasty was the most frequent operation, most wounds were clean, and 89.3% of patients received antibiotic prophylaxis.

Table 1. Baseline characteristics of the study population (n = 150)

SD, standard deviation; IQR, interquartile range; BMI, body mass index; ASA, American Society of Anesthesiologists.

Table 2 compares the frequency of infection across categorical variables. Strong associations were observed with anemia (95.7% vs 16.3%; Cramér's V 0.74), diabetes (74.0% vs 9.1%), hypertension (68.6% vs 3.1%) and male gender (56.0% vs 16.9%). Every patient with ASA grade III, every clean-contaminated wound and every incisional hernia repair became infected, and so did all 15 patients whose antibiotic was given intraoperatively. Drain placement and consultant-performed surgery were also associated with infection, whereas smoking was not (44.8% vs 37.3%; p=0.405).

Table 2. Frequency of postoperative wound infection by patient and perioperative characteristics

χ², Pearson chi-square statistic. p-values are from Fisher's exact test for 2×2 tables and Pearson's chi-square test for larger tables; several cells contain small expected counts.

As shown in Table 3, patients who developed infection were about 22 years older in median age and had a median BMI of 30.5 kg/m², compared with 25.1 kg/m² in those without infection. Their operations lasted twice as long (median 115 vs 55 minutes), and their hospital stay was three times longer (median 9 vs 3 days). All four differences were statistically significant (p<0.001).

Table 3. Comparison of continuous variables between infected and non-infected patients

IQR, interquartile range; BMI, body mass index. p-values from the Mann–Whitney U test.

Crude odds ratios are summarized in Table 4. Anemia carried the highest odds of infection (OR 112.59), followed by hypertension, diabetes, consultant-performed surgery and drain placement. Receipt of prophylactic antibiotics was associated with higher, not lower, odds of infection (OR 12.16; p=0.002), a finding that most likely reflects which patients received prophylaxis rather than any harmful effect. The confidence intervals for anemia and hypertension were very wide because of the small number of non-infected patients in the exposed groups. Smoking did not reach significance (OR 1.36; 95% CI 0.71–2.62).

Table 4. Crude odds ratios for postoperative wound infection

OR, odds ratio; CI, confidence interval (Woolf method). Estimates are unadjusted; ASA grade III, clean-contaminated wound class, incisional hernia repair and intraoperative antibiotic timing are not shown because zero cells make the odds ratio undefined.

In this study, four in ten patients undergoing potentially clean general surgical procedures developed a wound infection. This is far higher than the 9.5% reported for elective surgery in the national PakSurg 1 cohort (3) and the 26.8% seen after emergency gastrointestinal surgery in Karachi (5), and it dwarfs the 0.91% reported after open hernioplasty in Lahore (4). Part of the gap is likely real, reflecting an older and heavily comorbid population, but part may be methodological, because case definitions and the intensity of follow-up differ considerably between studies. Deep infections outnumbered superficial ones in our patients, whereas superficial infection predominated in PakSurg 1 (3) and in a Karachi series of general surgical SSIs (13). The figure should therefore be read as the burden in this ward rather than a benchmark for clean surgery. Infected patients were markedly older and heavier. Age has been confirmed as an independent risk factor in more than 700,000 joint replacements in German national surveillance (14), and obesity impairs tissue perfusion and makes wound closure technically harder. Our infected patients also had operations twice as long as those without infection. Prolonged surgery was a key contributor in Abbottabad (6) and an independent predictor among diabetic patients in Lahore (7), and a meta-analysis has linked longer operative time with both SSI and periprosthetic joint infection (15). Longer procedures mean more tissue trauma, longer exposure of the wound and falling tissue levels of the prophylactic antibiotic. Anemia showed the strongest association in our data. In an analysis by Pakistani investigators of more than 180,000 thyroidectomies, anemia was a major risk factor for transfusion, and transfusion was in turn independently associated with SSI (16). A propensity-matched study of ventral hernia repair also found that preoperative anemia independently raised the odds of serious SSI (17). Anemia reduces oxygen delivery to healing tissue and often accompanies malnutrition and chronic disease. Diabetes was also strongly linked to infection, in agreement with the Lahore series in which poor glycemic control tripled the odds of SSI (7). Hypertension is rarely reported as an independent factor, and its association here probably reflects its overlap with age, obesity and diabetes in the same patients. Male patients were infected more than three times as often as female patients, which matches a Lahore cancer center where male gender was the only independent predictor of perineal wound infection (18). ASA grade III carried an infection rate of 100% in our study, and higher ASA class almost quadrupled the odds of SSI in a French vascular cohort (19). ASA grade summarizes overall physiological reserve, so it captures several of the comorbidities discussed above. The universal infection after incisional hernia repair is also plausible, because these operations involve wider dissection, larger mesh and longer operating time. Drain placement was associated with a twentyfold increase in the crude odds of infection. In a randomized trial in general surgery, nine of the ten patients who developed SSI had a drain, and the authors advised against routine drainage (20). In our patients, drains were probably placed in larger and longer operations, which may explain much of this association. Two findings run against expectation. First, patients who received prophylactic antibiotics were more often infected. Prophylaxis was almost certainly given for the higher-risk procedures, while short, low-risk excisions went without it; this is confounding by indication, not harm. Pakistani trials in hernia repair and laparoscopic cholecystectomy found no benefit from extended or routine prophylaxis in low-risk cases (8,9). Notably, all 15 patients whose antibiotic was given intraoperatively became infected, supporting trial evidence that the dose should be in the tissues before incision (20). Second, consultants' cases carried more infections than residents' cases. This is the reverse of reports in which junior surgeons were linked with SSI (19) and most likely reflects the allocation of complex, high-risk cases to consultants. Smoking was not associated with infection, although a meta-analysis shows a clear effect on deep SSI (21); our sample was probably too small to detect a modest difference. Staphylococcus aureus was the most frequent isolate, followed by Escherichia coli, Klebsiella and Pseudomonas. A similar spectrum was found in a multicenter Ethiopian study, where S. aureus made up 31% of isolates (22). At the Aga Khan University Hospital, many infected orthopedic wounds yielded no growth despite clinical infection (23), and an extensively drug-resistant Acinetobacter SSI reported from Peshawar shows how quickly resistance is becoming a local problem (24). The predominance of S. aureus points to the patient's own skin flora, and screening and decolonization before high-risk surgery are now recommended in European guidelines (25). This study has some limitations. It was conducted in a single center with a modest sample, and the associations are unadjusted because complete separation in several strata prevented stable multivariable modelling. The very large odds ratios and their wide confidence intervals should therefore be interpreted with caution, and some factors probably act through one another. Nineteen clean-contaminated cases were retained in the analysis, which may have raised the overall infection rate. Antimicrobial susceptibility of the isolates was not assessed. Finally, length of stay is partly a consequence of infection rather than a cause.

Postoperative wound infection affected 40.7% of patients undergoing potentially clean general surgical procedures in our ward. Infection was concentrated among older patients with anemia, diabetes, hypertension, higher BMI and ASA grade III, and after longer operations, incisional hernia repairs and procedures with drains. Correcting anemia and hyperglycemia before elective surgery, giving prophylaxis before incision and limiting routine drains are practical steps for this unit. A larger prospective study with multivariable analysis is recommended.

DECLARATIONS

Funding: This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.

Conflict of interest: The authors declare no conflict of interest.

Acknowledgements: The authors thank the nursing and paramedical staff of the General Surgery Ward, Bacha Khan Medical Complex, Swabi for their help with patient follow-up and data collection.

1. Tahir MF, Mughal S, Nadeem A, Khan M, Hannat R, Jaber Amin MH. Reducing the burden of surgical site infections in low and middle-income countries: challenges and recommendations. Ann Med Surg (Lond). 2025;87(8):5335-5337. doi:10.1097/MS9.0000000000003473
2. Tariq A, Ali H, Zafar F, Ahmed F, Manzoor A, Perveen S, et al. Evaluation of antibiotic utilization pattern and economic outcomes associated with surgical site infection in surgical department of tertiary care hospitals Karachi, Pakistan. Pak J Pharm Sci. 2024;37(3):695-703.
3. Waqar U, Ahmed S, Fatimi AS, Ahmed W, Martins RS, Waheed H, et al. Epidemiology and risk factors of surgical site infections in elective surgeries in Pakistan (2022-2023): a multicentre, prospective cohort study from PakSurg 1. Lancet Reg Health Southeast Asia. 2026;50:100786. doi:10.1016/j.lansea.2026.100786
4. Muhammad SD, Faisal MS, Shafiq MA, Saeed MR. Incidence of surgical site infection following open hernioplasty and comparison of infection rate among ventral and groin hernia repairs at a THQ hospital Lahore: a single surgeon experience. J Pak Med Assoc. 2023;73(6):1241-1244. doi:10.47391/JPMA.6379
5. Ehtesham U, Khan Y, Siddiqui MTUH, Ashraf F, Murtaza G. Emergency surgery score as a predictor of postoperative surgical site infection in patients undergoing emergency surgery for gastrointestinal diseases: A prospective cohort study. Pak J Med Sci. 2026;42(6):1599-1605. doi:10.12669/pjms.42.6.15726
6. Rehman HU, Iqbal A, Ahmad I, Fayyaz H, Ali L, Iqbal J, et al. Exploring the impact of risk factors, preventive measures, and management strategies on surgical site infections in general surgery: a comprehensive assessment. J Ayub Med Coll Abbottabad. 2024;36(2):364-368. doi:10.55519/JAMC-02-13499
7. Anwar MS, Malik R, Shoaib HM, Ahmed J, Hassan S, Atta Ullah M, et al. Assessment of Risk Factors for Surgical Site Infection in Diabetic Patients Undergoing Elective Surgery. Cureus. 2026;18(5):e108920. doi:10.7759/cureus.108920
8. Masood A, Arshad AR, Ashraf M. Comparison between outcome of single dose of prophylactic antibiotic versus postoperative antibiotic in inguinal hernia surgery. Pak J Med Sci. 2022;38(5):1210-1215. doi:10.12669/pjms.38.5.5332
9. Ullah K, Dogar AW, Jan Z, Bilal H, Tahir MJ, Hamza A, et al. Role of antibiotic prophylaxis on surgical site infection prevention in a low-risk population undergoing laparoscopic cholecystectomy: A randomized controlled study. Ann Med Surg (Lond). 2022;78:103804. doi:10.1016/j.amsu.2022.103804
10. Suleman MU, Mursaleen M, Khalil U, Subhani MA, Tabassum SN. Antibiotic prophylaxis in elective laparoscopic cholecystectomy: a narrative review of efficacy, safety, and antimicrobial stewardship. Ann Med Surg (Lond). 2025;87(12):8486-8489. doi:10.1097/MS9.0000000000004059
11. Khan MNA, Verstegen DML, Shahid A, Dolmans DHJM, van Mook WNA. The impact of interprofessional task-based training on the prevention of surgical site infection in a low-income country. BMC Med Educ. 2021;21(1):607. doi:10.1186/s12909-021-03046-3
12. Seidelman JL, Mantyh CR, Anderson DJ. Surgical Site Infection Prevention: A Review. JAMA. 2023;329(3):244-252. doi:10.1001/jama.2022.24075
13. Rafaqat W, Fatima HS, Kumar A, Khan S, Khurram M. Machine Learning Model for Assessment of Risk Factors and Postoperative Day for Superficial vs Deep/Organ-Space Surgical Site Infections. Surg Innov. 2023;30(4):455-462. doi:10.1177/15533506231170933
14. Bischoff P, Kramer TS, Schröder C, Behnke M, Schwab F, Geffers C, et al. Age as a risk factor for surgical site infections: German surveillance data on total hip replacement and total knee replacement procedures 2009 to 2018. Euro Surveill. 2023;28(9). doi:10.2807/1560-7917.ES.2023.28.9.2200535
15. Scigliano NM, Carender CN, Glass NA, Deberg J, Bedard NA. Operative Time and Risk of Surgical Site Infection and Periprosthetic Joint Infection: A Systematic Review and Meta-Analysis. Iowa Orthop J. 2022;42(1):155-161.
16. Waqar U, Tariq J, Chaudhry AA, Iftikhar H, Zafar H, Abbas SA. A comprehensive assessment of blood transfusions in elective thyroidectomy based on 180,483 patients. Laryngoscope. 2022;132(10):2078-2084. doi:10.1002/lary.30098
17. Benner C, Spence KT, Childers WK. Preoperative anemia is a risk factor for poor perioperative outcomes in ventral hernia repair. Hernia. 2022;26(6):1599-1604. doi:10.1007/s10029-022-02572-3
18. Zahara FT, Nasr M, Zubair U, Shah MA, Awais M, Anas Bin Akhtar M, et al. Exploring the risk factors for perineal wound infection after laparoscopic abdominoperineal resection. Ann Med Surg (Lond). 2026;88(7):3983-3988. doi:10.1097/MS9.0000000000005102
19. Tresson P, Quiquandon S, Rivoire E, Boibieux A, Vanhems P, Bordet M, et al. American Society of Anesthesiologists-physical status classification as an independent risk factor of surgical site infection after infra-inguinal arterial bypass. Ann Surg. 2023;277(5):e1157-e1163. doi:10.1097/SLA.0000000000005182
20. Lakkanna A, Rajender G, Sakaray YR, Tandup C, Khare S, Savlania A, et al. Impact of the timing of antibiotic prophylaxis on the surgical site infections in patients undergoing elective general surgery. Indian J Pharmacol. 2025;57(5):334-337. doi:10.4103/ijp.ijp_797_24
21. Tran DNA, Nguyen BTT, Nguyen TT, Chen YP, Kuo YJ. Adverse effect of smoking on surgical site infection following ankle and calcaneal fracture fixation: a meta-analysis. EFORT Open Rev. 2024;9(8):817-826. doi:10.1530/EOR-23-0139
22. Worku S, Abebe T, Alemu A, Seyoum B, Swedberg G, Abdissa A, et al. Bacterial profile of surgical site infection and antimicrobial resistance patterns in Ethiopia: a multicentre prospective cross-sectional study. Ann Clin Microbiol Antimicrob. 2023;22(1):96. doi:10.1186/s12941-023-00643-6
23. Hashmi P, Ahmad T, Muhammad ZA. Microbiology of surgical site infection in closed upper limb fractures: Data from a prospective trauma registry. J Pak Med Assoc. 2022;72(6):1184-1187. doi:10.47391/JPMA.2031
24. Waheed F, Khan AS, Babar U, Khan MS. Surgical site infection with extreme drug-resistant Acinetobacter baumanii: a wake-up call! J Ayub Med Coll Abbottabad. 2024;36(2):430-432. doi:10.55519/JAMC-02-12363

Righi E, Mutters NT, Guirao X, Dolores Del Toro M, Eckmann C, Friedrich AW, et al. European Society of Clinical Microbiology and Infectious Diseases/European Committee on infection control clinical guidelines on pre-operative decolonization and targeted prophylaxis in patients colonized by multidrug-resistant Gram-positive bacteria before surgery. Clin Microbiol Infect. 2024;30(12):1537-1550. doi:10.1016/j.cmi.2024.07.01