Incidence, microbiological agents and predictors of surgical site infections following open surgeries at Muhimbili National Hospital, Otorhinolaryngology department

Abstract

ABSTRACT Background: Surgical site infection is the most common complication of surgery across all surgical disciplines. It has been associated with increased hospital stay, readmission, increased cost burden to both patients and the health care facilities, re-operation, and death. Adherence to surgical preventative strategies generated from modifiable risk variables significantly reduces the burden of surgical site infections. The magnitude, microbiological agents, and predictors of surgical site infections in the otorhinolaryngology department at Muhimbili National Hospital and Tanzania at large are unknown. Objective: To determine the incidence, predictors, and microbiological agents of surgical site infections among open surgeries done at Muhimbili National Hospital in the otorhinolaryngology department. Methodology: This was a hospital-based prospective cohort study, whereby all patients who had undergone open surgeries were assessed for signs and symptoms of surgical site infections 48 hours after an operation during a change of dressing, 7th day from the day of operation which was a day of follow-up and stitch removal and lastly the patients were interviewed at 30th day via phones for the symptoms of surgical site infections, clinically diagnosed SSI cases, swabs were taken for microbiological agents identification through culture, Gram stain and biochemical tests. Twenty four hours following culture; colony morphological characteristics such as margin, color and shape were assessed, followed by Gram staining and finally biochemical tests were carried out, such as using catalase for Gram-positive bacteria; to differentiate streptococci from staphylococcus, coagulase test for differentiating Staphylococcus aureus from other Staphylococci and APE20 and oxidase for specific Gram-negative bacterial identification. Data were collected through a structured data collecting tool with mixed questions and a checklist, and the interview started the day before the operation to obtain demographic data and other pre-operative risk factors. Data were entered in STATA version 15.1 for analysis and version 12.0 for graphing, the Chi-square test/Fischer exact test was used to test the statistical significance difference of SSI occurrence among different categorical variables, and the robust Poisson regression test for bivariable analysis based on crude risk ratio (cRR) and multivariable analysis based on adjusted risk ratio (aRR) was used to determine the strength of the relationship between independent and dependent variables. vi Results: A total of 89 post-open surgery patients, whose ages ranged from 13 to 78 years, were enrolled in the study. The median age was 44.5 years, and the interquartile range of (36 59). The majority (34.8%) of the study participants were in the age group (36–53), with an overall female preponderance of 1.12:1. The overall incidence of surgical site infections found in this study was 22.5%. About 13 (72.2%) of the bacterial species isolated were Gram negative. Pseudomonas aeruginosa 7 (38.9%) followed by Staphylococcus aureus 3 (16.7%) were the most isolated bacterial species in this study. On bivariable robust regression analysis, factors such as alcohol drinking habits (RR 7.33, 95% CI 3.41-15.72, P<0.0001), human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) comorbidity (RR 5.2, 95% CI 2.84-8.86, P<0.0001), diabetes mellitus (RR 3.19, 95% CI 1.29-7.87, P=0.012), those who didn’t receive antibiotic prophylaxis (RR 12.18, 95% CI 4.53-32.77, P=0.0001), high American Society of Anaesthesiologists (ASA) score (III and IV) (RR 6.56, 95% CI 2.16-19.87, P=0.001), and pre-operative waiting time of > 1 day (RR 3.47, 95% CI 1.71-7.04, P=0.001) significantly predicted occurrence of SSI. Whereas, on multivariable robust regression analysis, factors such as alcohol drinking habits (RR 1.71, 95% CI 1.01-2.94, P=0.048), HIV/AIDS comorbidity (RR 1.87, 95% CI 1.16-3.00, P=0.001) and those who didn’t receive antibiotic prophylaxis (RR 9.92, 2.16-45.51, P=0.003), independently (i.e. without effects of confounders) predicted occurrence of SSI in this study. Conclusion: The findings of this study revealed high incidence (22.5%) of surgical site infections (SSI) in the otorhinolaryngology department caused mainly by Pseudomonas aureginosa and Staphylococcus aureus. Surgical site infections occurrences were mostly predicted by alcohol use, HIV/AIDS comorbidity, and not using antibiotic prophylaxis in patients who had undergone open surgery. However, the predictors identified in this study can be prevented thus reducing the seemingly high incidence of SSI in the department. Recommendation: Abstinence from alcohol intake 4 to 8 weeks before surgery for surgical patients should be enforced to reduce the incidence of SSI. Antibiotic prophylaxis is strongly recommended in most otorhinolaryngology procedures since they are class II to IV wounds (83.1%) of all surgeries during the index investigation. In the same vein those patients who lose 1.5litres or more of blood or the procedures which take 1-2 times long half-life from the first dose of antibiotic prophylaxis, antibiotic redosing must be done. The surgical patients with HIV/AIDS comorbidity should have CD4 levels over 350 cells/μ L tested within 12 months for elective surgeries as mandatory preoperative requirement, but for emergence surgeries may be a relative indication. Many other variables, including wound class, American Society of Anesthesiologists (ASA) scores, pre-op length of hospital stay, smoking, diabetes mellitus, antibiotic redosing, operation time, and body mass index, were found to be ineffective in predicting the incidence of SSI, contrary to previous studies, thus, additional research with big sample size and a long study period is recommended.