Clinico-microbiological evaluation of post-cesarean surgical site infections

INTRODUCTION

Cesarean section (CS) is a widely performed procedure in modern obstetrics aimed at enhancing maternal and neonatal outcomes when vaginal delivery is deemed risky or unfeasible. Despite its intended purpose, the global surge in CS rates, particularly in India, has raised concerns.^[1] The World Health Organization suggests an optimal CS rate of 10–15%, yet India’s rates escalated from 8.5% in 2005–2006 to 21.5% in 2019–2021, as reported by the National Health Systems Resource Center (NHSN).^[1-3] The escalating CS rates bring about an inevitable rise in post-operative complications, notably surgical site infections (SSIs), contributing to maternal morbidity, mortality, psychological distress, extended hospital stays, increased treatment costs, and strain on health-care facilities.^[4]

Various risk factors contribute to the occurrence of SSI, encompassing maternal pre-existing comorbidities, obstetrical factors (parity, preterm rupture of membranes, prolonged labor, meconium-stained liquor, chorioamnionitis, gestational diabetes mellitus [GDM], anemia, previous CS, excessive vaginal manipulation), socioeconomic status, and illiteracy. Factors such as the type of ward, emergency or elective procedures, type of anesthesia, abdominal incision type, and overall procedure duration also impact SSI rates. Low socioeconomic status and illiteracy heighten infection risks due to overcrowded living conditions and lack of awareness regarding surgical site care.

SSI, occurring within 30 days post-CS, is categorized by the Centers for Disease Control and Prevention (CDC) into superficial incisional SSI, deep incisional SSI, and organ/space infections. It manifest with symptoms such as purulent discharge, pain, erythema, induration, local temperature elevation, and fever.^[5] Common pathogens associated with SSI include Staphylococci, Streptococci, Enterococci, Lactobacilli, Diphtheroid, Escherichia coli, Anaerobic Streptococci, Bacteroides, and Fusobacterium species depending on the factors responsible for infection and prevalence of microbes in a particular health-care facility or area.^[6,7]

The consequences of SSI extend beyond immediate health implications, encompassing indirect costs such as loss of productivity, patient dissatisfaction, litigation, and diminished quality of life. Preventing SSI involves addressing predisposing risk factors and understanding the microbial spectrum and antibiotic sensitivity in a healthcare setting, thereby improving prognosis and reducing morbidity associated with CS.

MATERIALS AND METHODS

This study was a prospective longitudinal hospital-based study that aimed to calculate the incidence of SSIs after CSs and evaluate the various determinants of post-CS SSI, their clinical spectrum, prevalent microbiology, and their susceptibility and resistance patterns. The study was conducted in the Department of Obstetrics and Gynecology in collaboration with the Department of Microbiology at Government Medical College and Hospital (GMCH) sector-32, Chandigarh. Optimum sample size was calculated on the basis of 7% incidence of SSI after CSs.^[6] Assuming 95% confidence level and 10% precision, the sample size came out to be 385. We planned to take at least 385 subjects who complete the follow-up at 6 weeks. The study lasted 18 months from April 2021 to September 2022. Seven hundred patients were enrolled, out of which 688 patients completed the follow-up. The condition of their surgical scar/wound was assessed. The inclusion criteria for the study were patients undergoing CS at GMCH, who gave consent for the study and follow-up and SSI occurring within 42 days of CS.

The exclusion criteria were patients undergoing CS outside GMCH, patients having uterine rupture, patients undergoing peripartum hysterectomy, immunocompromised patients, and patients who refused to give consent for the study and follow-up.

Factors such as age, parity, background, socioeconomic status, education level, preterm rupture of membranes, prolonged labor, GDM, overt diabetes mellitus, anemia, previous CS, multiple vaginal examinations, emergency or elective case, post-partum hemorrhage, type of anesthesia, type of abdominal incision, meconium staining of liquor, chorioamnionitis, duration of surgery, malnutrition, obesity, hypertension, and any chronic disorders were noted. The surgical wound was examined at the time of first dressing, at 8–12 days post-cesarean, as and when required, and on day 42 of CS. Diagnosis of SSI was made according to the CDC standards, which involve infection that occurs within 30 days (extended to 42 days for this study).^[5] After taking the wound swabs, where indicated, patients were treated according to ideal standard of care, which involved antibiotics, dressings, debridement, resuturing, readmission, etc. Swabs were sent for culture and sensitivity to microbiology laboratory. Isolation and susceptibility testing of culture isolates was done in our clinical microbiology laboratory using standard methods.^[8] Antimicrobial susceptibility of culture isolates was done using Kirby-Bauer’s disk diffusion method according to recent Clinical and Laboratory Standards Institute (CLSI) guidelines.^[9]

RESULTS

A total of 700 post-CS patients were enrolled out of which ten patients lost to follow-up and two patients expired. Hence, 688 patients were studied and follow-up was done till 42 days after CS. Twenty-four patients developed SSI making the incidence to be 3.49%. Various determinants of post-CS SSIs were studied. GDM and thrombocytopenia were among the maternal factors which had significant association with SSI. Maternal obstetric factors such as chorioamnionitis, prolonged labor, and multiple per vaginum examinations also significantly increased the risk of SSI. Prolonged surgery, post-partum hemorrhage, and blood product transfusions also were major risk factors for developing SSI. The following table depicts various determinants studied and their association with the risk of developing post-cesarean SSI [Table 1]. Mean time of detection of SSI was 11.75 ± 3.232 day. Out of 24 patients, 18 had purulent discharge whereas four had serous discharge. Fifteen patients had pain and tenderness, eight had induration and swelling, five were febrile, and two developed erythema. Only six patients developed dehiscence of wound, as evident [Table 2]. Twenty-two out of 24 were superficial SSI, whereas two patients had deep SSI.

DISCUSSION

The incidence of SSI in the study was 3.49% in 688 post-CS patients and it was found to be lower than some past studies due to the strict antibiotic policy and asepsis in the operation theatre of the tertiary care center where the study was conducted. The incidence of SSI has also decreased over the past decade as per the literature review.^[6,7,10-12]

The study found that maternal medical factors such as obesity, GDM, and thrombocytopenia were associated with a higher risk of SSI, but the association with obesity was not statistically significant. The study did not find any association of SSI with hypertension, pre-existing medical illnesses, or anemia. The conflicting relationship with anemia could be explained by sufficient availability of blood and blood components and adequate build-up of patients in the preoperative period, which improves the general condition of the patient, and also good antibiotic coverage, which reduces the rate of bacterial proliferation. Maternal obstetric determinants such as preterm CS, previous CS, preterm pre-labor rupture of membranes, duration of rupture of membranes, and meconium-stained liquor have been found to increase the incidence of SSI as shown by Gomaa et al. but this study did not find any such correlation.^[13] Chorioamnionitis emerged as a significant risk factor with 8.5 times increased risk of developing SSI. The study also found that patients with prolonged labor (>12 h duration) and multiple per vaginum (PV) examinations (≥5) had significantly higher risk of SSI. Surgery and anesthesia related factors such as use of general anesthesia, emergency procedures compared to electives, vertical skin incision, and general ward stay have been found to increase the risk of developing SSI in other studies, but this study did not find any significant association of rates of infection with these factors.^[10,14] Patients with duration of surgery more than 2 h had significant increase in risk of developing SSI. The study also found that patients with post-partum hemorrhage had 3.237 times higher incidence of SSI. The study also evaluated the impact of blood transfusion and antibiotic prophylaxis on the incidence of SSI. Patients who received transfusions were found to have a 2.308 times increased risk of developing SSI, which was statistically significant. Whereas, no significant difference in incidence of SSI was found between the patients receiving antibiotics within or before 60 min of incision.

CONCLUSION

Post-caesarean surgical site infections (SSI) present a significant challenge, with this study pinpointing risks such as gestational diabetes and thrombocytopenia, etc. Despite GMCH’s tertiary care status, a 3.49% SSI incidence is attributed to a comprehensive treatment approach. Staphylococcus aureus prevails, and linezolid is suggested as empirical treatment pending culture results. Continued research should prioritize identifying and modifying risk factors for improved maternal health, stressing routine analysis for timely diagnosis and effective SSI management.