European Journal of Cardiovascular Medicine

Surgical site infections (SSIs) are among the most prevalent healthcare-associated infections worldwide, representing a major cause of postoperative morbidity, prolonged hospitalization, and increased healthcare expenditure (1,2). The World Health Organization (WHO) identifies SSIs as the most surveyed and frequent type of healthcare-associated infection in low- and middle-income countries (LMICs), where the risk is estimated to be two to five times higher than in high-income nations (3). Globally, the pooled incidence of SSIs is approximately 2.5% (95% CI: 1.6–3.7%), but rates may exceed 10% in resource-limited settings due to infrastructural and procedural constraints (4). The aetiology of SSIs is multifactorial, involving patient-related, procedure-related, and environmental factors. Common patient factors include diabetes mellitus, malnutrition, anaemia, and advanced age, whereas procedural factors involve prolonged operative duration, emergency surgeries, contaminated wounds, and improper timing of surgical antimicrobial prophylaxis (SAP) (5). Environmental contributors such as inadequate sterilization in the Central Sterile Supply Department (CSSD), improper dressing material handling, and lack of positive pressure ventilation or HEPA filtration in operating rooms further exacerbate infection risk (6).

In India, the burden of SSIs remains considerably high. The Indian Council of Medical Research (ICMR) multicentric surveillance reported an overall SSI incidence of 5.2%, with orthopaedic and obstetric surgeries being the most affected categories (7). Other tertiary care studies across Gujarat and Andhra Pradesh have shown incidence rates ranging from 8% to 16%, influenced by factors such as emergency procedures, prolonged preoperative hospital stay, and delayed SAP administration (8,9). Staphylococcus aureus (including MRSA) and Gram-negative organisms such as Escherichia coli, Klebsiella, and Pseudomonas aeruginosa remain the predominant isolates in Indian hospitals (5,8).

Despite the implementation of infection control programs, challenges persist in maintaining sterile operative environments, appropriate antibiotic prophylaxis timing, and effective CSSD practices. Hence, continuous SSI surveillance, along with root cause analysis and corrective action, remains crucial to reducing infection rates and improving surgical outcomes. The present study was undertaken to analyse SSI cases over a one-year period in a tertiary care hospital, focusing on incidence, microbial profile, associated risk factors, and preventive measures, with the objective of identifying modifiable determinants to guide future infection control strategies.

Aim

To study the incidence, microbial profile, and risk factors associated with surgical site infections (SSIs) in a tertiary care hospital over a one-year surveillance period.

Objectives

1. To identify and analyse the patient-related, procedural, and environmental factors contributing to the development of surgical site infections.
2. To determine the microbiological profile and antibiotic sensitivity pattern of isolates obtained from surgical site infections and suggest appropriate preventive measures.

Study Design and Setting

This was a prospective observational surveillance study conducted in the Hospital Infection Control Department of a tertiary care teaching hospital in South India. The study was carried out over a one-year period, from June 2024 to June 2025, as part of the hospital’s routine surgical site infection (SSI) surveillance program.

Study Population

All patients who underwent surgical procedures in various departments including Orthopaedics, Obstetrics and Gynaecology, and General Surgery during the study period were included in the surveillance. Patients were followed up during their hospital stay and, where applicable, after discharge for signs or symptoms suggestive of SSI.

Inclusion Criteria

1. Patients of all age groups and genders undergoing elective or emergency surgical procedures.
2. Patients developing signs and symptoms consistent with CDC-defined SSI criteria (superficial incisional, deep incisional, or organ/space infection) within 90 days postoperatively, if prosthetic material was used.

Exclusion Criteria

1. Patients with pre-existing infection at or near the operative site prior to surgery.
2. Cases where incomplete clinical records or follow-up data were unavailable.
3. Minor procedures done under local anaesthesia without incision closure.

Data Collection

Data were collected using a standardized SSI surveillance form designed by the Hospital Infection Control Committee (HICC). The following information was recorded:

• Demographic data: Age, gender, inpatient number, date of admission, and date of surgery.
• Surgical details: Type of surgery, department, indication, elective or emergency status, and wound classification (clean, clean-contaminated, contaminated, dirty).
• Clinical findings: Date of first SSI criteria met, type of infection (superficial, deep, organ/space), presence of discharge, pain, redness, swelling, and fever.
• Comorbidities: Diabetes mellitus, hypertension, anaemia, immunosuppressant use, etc.
• Antimicrobial prophylaxis details: Drug used, timing before incision, and adherence to hospital antibiotic policy.
• Environmental and procedural factors: Availability of HEPA filters and positive pressure in the operating theatre, CSSD sterilization quality, and dressing material storage practices.

Microbiological Analysis

Samples (wound swabs, pus aspirates, or tissue specimens) were collected aseptically from all suspected SSI cases and sent to the Microbiology Department for culture and sensitivity testing.

• Cultures were processed using standard microbiological techniques on blood agar and MacConkey agar, and incubated at 37°C for 24–48 hours.
• Isolated organisms were identified by conventional biochemical tests.
• Antibiotic susceptibility testing was performed using the Kirby–Bauer disk diffusion method following Clinical and Laboratory Standards Institute (CLSI) guidelines (2024 update).

Outcome Measures

The following outcomes were assessed:

1. Incidence and pattern of SSIs across surgical departments.
2. Frequency of specific microorganisms isolated and their resistance patterns.
3. Relationship of SSIs with host factors (e.g., diabetes, age), procedural variables (e.g., SAP timing, duration, type of surgery), and environmental parameters (e.g., CSSD decontamination, OT ventilation).

Data Entry and Statistical Analysis: Data were entered into Microsoft Excel 2019 and analysed using SPSS. Descriptive statistics were used to summarize demographic and clinical variables (mean, standard deviation, and percentages). Chi-square test or Fisher’s exact test was applied to assess associations between categorical variables such as comorbidity, SAP timing, and presence of HEPA filters with SSI occurrence. A p-value < 0.05 was considered statistically significant. Where appropriate, odds ratios (OR) and 95% confidence intervals (CI) were calculated to estimate the strength of association

Table 1. Overview of Surgical Site Infection (SSI) Cases

Interpretation:
SSIs were predominantly noted among female patients and elective procedures, reflecting the high surgical load in obstetrics and gynaecology. The majority of infections manifested around the 10th postoperative day, consistent with typical SSI timelines.

Table 2. Distribution by Specialty

Interpretation:
The infection burden was highest in orthopaedic and gynaecological surgeries, likely due to extensive tissue handling, prosthesis use, and improper postoperative wound management.

Table 3. Age Group-wise Distribution

Interpretation:
The elderly (>60 years) represented the largest group with SSIs (35.3%), correlating with age-related immune compromise and comorbidities such as diabetes and hypertension.

Table 4. Comorbidities Associated with SSI

Fig 1: Comorbidities Associated with SSI

Interpretation:
Nearly half of the SSI patients were diabetics, confirming diabetes as a major independent risk factor. Hypertension and advanced age were also frequently observed.

Table 5. Microbiological Profile

Interpretation:
The predominant isolates were MRSA and E. coli (17.6% each), followed by Klebsiella spp.. A significant proportion (35.3%) showed no growth, possibly due to prior empirical antibiotic therapy.

Table 6. Identified Root Causes (Multiple causes possible)

Interpretation:
Environmental and procedural breaches—notably lack of HEPA filters and poor CSSD sterility—were leading contributors to SSIs, highlighting infrastructure-related risk factors.

Table 7. Corrective & Preventive Actions (CAPA) Implemented

Summary Interpretation

• SSI incidence was predominantly in elderly diabetics undergoing orthopaedic and gynaecologic surgeries.
• Gram-positive (MRSA) and Gram-negative (E. coli, Klebsiella) organisms predominated.
• Infrastructural lapses (HEPA absence, CSSD decontamination failures, dressing handling) were repeatedly implicated.
• Statistical analysis confirmed SAP timing and diabetic status as significant predictors of SSI.

Table 8. Association of Risk Factors with Surgical Site Infection (n = 17)

Summary Interpretation

• Significant determinants of SSI were:
• Diabetes Mellitus (p = 0.040)
• Delayed SAP (>2 hours before incision) (p = 0.048)
• Absence of HEPA filters (p = 0.024)
• Inadequate CSSD decontamination (p = 0.049)
• Non-significant factors: Age, gender, and type of surgery.
• Culture positivity (64.7%) suggests active infection despite partial antibiotic coverage.

Major contributing factors were both patient-related (DM) and infrastructure-related (CSSD, HEPA)—pointing to systemic preventive needs.

The present study provides a one-year surveillance overview of surgical site infections (SSIs) in a tertiary care hospital, highlighting key patient-related, procedural, and environmental determinants contributing to infection risk. The overall number of SSIs reported during the study period was relatively low, yet the findings emphasize persistent modifiable factors that can significantly impact surgical outcomes. In our study, the majority of SSI cases occurred among elderly patients (>60 years) and those with comorbid conditions, particularly diabetes mellitus (47.1%). This aligns with multiple reports identifying diabetes as a significant and independent risk factor for SSI development (10,11). Poor glycaemic control compromises leukocyte function, delays collagen synthesis, and impairs wound healing, predisposing to infection (12). Similar findings were noted in studies by Singh et al. and Bhatia et al. from North India, where diabetes and advanced age were strongly associated with postoperative wound infections (13,14). SSIs were more frequent when SAP was administered more than two hours prior to incision, confirming the importance of adhering to standard protocols recommending antibiotic administration within 60 minutes before incision (15). Comparable results were observed in a prospective study by Shinde et al., which demonstrated a twofold increase in SSI risk(16).

Environmental and infrastructural factors such as absence of HEPA filters, inadequate CSSD decontamination, and improper dressing material handling were also found to play critical roles. In our data, 88.2% of SSI cases occurred in OTs lacking HEPA filters, indicating the relevance of maintaining positive pressure and air filtration to reduce microbial load. Studies by Allegranzi et al. and Ousey et al. similarly highlight the role of environmental control measures—including ventilation systems and aseptic maintenance—in reducing SSIs in low-resource settings (10,17).

The microbiological profile in this study was dominated by Staphylococcus aureus (including MRSA), Escherichia coli, and Klebsiella species, reflecting both Gram-positive and Gram-negative aetiology. This spectrum closely resembles previous Indian surveillance findings, where S. aureus was responsible for up to 30–40% of SSIs, followed by E. coli and Pseudomonas spp. (13,15,16). The predominance of MRSA underscores the ongoing need for rational antibiotic use and routine antimicrobial susceptibility monitoring, as inappropriate empirical therapy contributes to resistance proliferation (12). Our data also revealed a mean SSI detection interval of 10.6 ± 4.2 days, consistent with the postoperative infection window reported in other studies (11,14). The relatively delayed onset may indicate environmental contamination or secondary wound infection rather than intraoperative inoculation.

Importantly, a substantial number of cases (35.3%) yielded no bacterial growth probably due to anaerobic organisms and also likely due to prior empirical antibiotic use before culture collection, a common limitation noted in Indian studies (10,14,17). This highlights the need for proper sample collection protocols and avoidance of unnecessary antibiotic exposure prior to microbiological sampling. The corrective and preventive actions (CAPA) implemented—such as surgeon sensitization on SAP timing, HEPA filter installation, CSSD decontamination, and patient education on wound care—represent crucial components of a sustainable infection control framework. Regular auditing and feedback mechanisms by the Hospital Infection Control Committee (HICC) can further help reduce SSI rates through continued adherence to evidence-based guidelines (17).

Our findings are in accordance with the WHO’s global SSI prevention guidelines and Indian surveillance reports, emphasizing that a combination of aseptic discipline, antimicrobial stewardship, environmental control, and patient optimization is necessary to achieve measurable reduction in SSI incidence (10,12,17). The integration of SSI surveillance data with continuous quality improvement practices will be vital to improving surgical safety in tertiary care hospitals, particularly in resource-limited settings.

Surgical site infections continue to be a significant cause of postoperative morbidity in tertiary care settings. Diabetes mellitus, delayed antibiotic prophylaxis, and poor OT sterility were key risk factors identified. Staphylococcus aureus (including MRSA) and E. coli were the most common isolates. Timely SAP administration and strict aseptic measures are vital for SSI prevention. Improved CSSD practices and HEPA-filtered ventilation significantly reduce infection risk. Continuous surveillance and adherence to infection control guidelines can sustainably lower SSI incidence.

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