This study has attempted to estimate the burden of SSI by determining not only its incidence and risk factors, but also the etiological bacterial agents associated with SSI and their antimicrobial susceptibility pattern at a referral and tertiary healthcare institution in Rwanda. To our knowledge, this is the first SSI surveillance study in Rwanda, which describes incidence and associated risk factors of SSI using CDC definitions and 30-day follow-up surveillance.
The finding of this study are based on operated cases, of which, the majority (73.8%) were made of orthopedics cases and cases for general surgery and urology were represented 22.4 and 3.7%, respectively. In this study, the overall incidence of SSI was 10.9%, which is comparable to the average of 11.8% in developing countries [4, 16].
The incidence reported here appears to be also of the same magnitude as that reported in a study in India (11%) . However, the incidence rate was higher than those of several developed countries. For example, incidence rates were 1.9% in the United States, 2.2% in Europe, 1.6% in Germany, 1.4% in England, 1.6% in France, and 2.0% in Portugal .
The difference observed in the incidence rate of SSI in developed countries compared to developing countries, including Rwanda, may be due to several reasons. These reasons include poor set-up of hospitals (lack of equipment and materials necessary to maintain strict guidelines for asepsis), poor hygiene of patients increasing colonization of skin by bacterial flora, late presentation of patients to healthcare system leading to contaminated wounds, and overwhelmed emergency services due to population burden.
The present findings seem to be consistent with other research which highlighted some SSI risk factors, which are discussed below, such as age, ASA class, wound classification, skill and experience of the surgeon, duration of surgery, blood transfusion and emergency surgery [4, 17]. SSI incidence rate increased with age, which may be due to a poorer immune response and coexistence of other comorbidities. ASA score of 2 or was significantly associated with higher rate of SSI, which may be due to the severity of systemic illness which hinders immunological response in these patients.
SSI incidence rate was higher in contaminated and dirty wounds, not surprisingly, because numerous bacteria, which are the source of the infection, thrive in contaminated/dirty wounds. Consistent with the finding of this study, the skill and grade of the surgeon has been shown to directly affect the incidence of SSI. The more senior and experienced the surgeons, the less likely it was for the patient to develop an SSI.
Two other major risk factors found to be associated with a high incidence of SSI were duration of surgery, which is due to a prolonged exposure of tissue to the environment, prolonged hypothermia and declining levels of antibiotics; long hospital stay, which can be explained by a prolonged stay providing further opportunity for bacterial colonization. Higher rates of SSI in patients who were transfused during surgery can be explained by a reduced Hemoglobin in these patients which may cause hypoxia and impairment in surgical and traumatic tissue oxygenation and healing to favor wound infection.
Emergency surgeries have also been associated with increase in the incidence rate of SSI due like inadequate preoperative preparation, lack of proper control of other medical comorbidities (such as uncontrolled diabetes). Higher frequency of contaminated or dirty wounds in emergency surgeries could also be a contributing factor. Although there was no significant difference in the incidence of SSI in the relation to other potential factors such as timing of prophylactic antibiotic, smoking, BMI, sex, number of staff during, SSI rates seem to be somehow affected by these factors.
In other study, for example, patient factors (smoking, BMI, life style, nutritional status) are associated with resistance of body to germs after operation; similarly, surgical complexity would influence operation duration and exposure possibility [19, 20].
Finally, the microorganisms causing SSI and their antimicrobial resistance patterns were evaluated. Klebsiella ssp with an incidence of 55%, followed by Escherichia coli (15%) and Proteus ssp (12%) were the predominant isolate which is in contrast with the finding of other studies. In these studies, S. aureus, has been found to be the predominant cause of SSI, which is can be explained by its presence in the skin as normal flora and can thus enter to deep site during surgery. However, the results of this study agree with the findings of other studies, in which, Klebsiella ssp was found to be the predominant bacteria isolated [21, 22].
This difference in the distribution of SSI bacteria may be due to variation in common nosocomial pathogens inhabitant, difference in policy of infection control and prevention between countries and hospitals. Although there are no clear explanations of about high prevalence of Entero-bacterial isolates in the current study, but faecal contamination due to poor personnel hygiene or due to post procedural contamination and outbreaks could be the possible reasons.
High resistance rates to commonly used antibiotic, ranging from 53.3 to 98.8%, were observed in bacterial isolates causing SSI in our study. Not surprising, 53.3% of SSI showed resistance to ceftriaxone, which was prescribed as prophylaxis to all who undergoes surgery. Amikacine and Imipinem were the only effective drugs as 100% of SSI bacterial exhibited very high sensitivity.
The presence of multidrug resistant bacteria isolated in SSI has also been described in other studies in developing countries. This remarkably higher resistance may be due to their easily availability and inappropriate use of the drugs in our hospitals.