Prevalence of Anaerobic Bacteria from Surgical Site Infections in Eastern Nepal

Surgical site infections (SSIs) are classified as superficial, deep and organ incisions. This study was conducted to determine the prevalence of anaerobic bacteria in SSIs in Nepal.

Total 641 patients were recruited from general surgery, orthopaedics, obstetrics and gynaecology units from October 2020 to December 2022. Surgical wound specimens from suspected SSIs were collected and processed for anaerobic culture for bacterial isolation from pus, fluids and tissues with the help of conventional and rapid methods. The odds ratio for logistic regression for categorical variables was used to determine the significance of association of host risk factors with blood parameters. The antimicrobial resistance of anaerobic bacteria was observed by agar dilution method.

The overall rate of SSIs was 311 (48.52%) where only anaerobic SSIs was 61 (9.52%). The anaerobic bacterial isolates from pus 43 (70.5%), fluid 14 (22.9%), tissues 4 (6.55%) from postoperative wounds accordingly. Infection rate in elective surgery cases were higher 38 (62.3%) than in the emergency surgery cases 23 (37.2%). Comorbidities and site of infections were significantly associated (p< 0.05) with anaerobic culture positive SSIs. Predominant isolates were Bacteroides fragilis 19 (31.15%), Bacteroides thetaiotamicron 12 (19.67%), Clostridium perfringens 12 (19.67%) followed by Peptoniphilus asaccharolyticus and Peptoniphilus anaerobius 5 (8.20%) each. Clostridium sporogens, Prevotella melaninogenica, Porphyromonas gingivalis and Propionibacterium isolates were 2 (3.28%) each. Metronidazole resistance was seen the highest numbers 33 (54.09%) of the isolates.

Susceptibility test is essential for proper prescription of antibiotics for anaerobic bacterial infections highlighting the urgent need to revise antibiotic regimens to improve the treatment of SSIs.