A prospective randomised trial of isolated pathogens of surgical site infections (SSI)

Every surgical wound is colonized by bacteria, but only a small percentage displays symptoms of infection. The distribution of pathogens isolated in surgical site infections has not significantly changed over the last decades. Staph. Aureus, Coag(-) Staphylococci, Enterococcus spp and E. Coli are the main strains appearing. In addition, a continuously rising proportion of surgical site infections caused by resistant bacterial species (MRSA, C. Albicans) has been reported.

This prospective and randomized clinical study was performed in the 1st Surgical Clinic of Sismanoglion General Hospital of Athens, from February 2009 to February 2015. Patients undergoing elective surgery in the upper or lower digestive system were randomized to receive antimicrobial treatment as chemoprophylaxis. Each patient filled a special monitoring form, recording epidemiological data, surgery related information, surgical site infections (deep and superficial), as well as postoperative morbidity (urinary and respiratory infections included). The monitoring of patients was carried by multiple visits on a daily basis during their hospitalization and continued after they were discharged via phone to postoperative day 30.

Our overall SSI incidence was 4,3% (31patients out of a whole of 715 patients). Specifically, the incidence of SSIs for scheduled surgery of the upper GI tract was 2,2% (11 out of 500 patients) and for the lower GI tract was 9,3% (20 out of 215 patients). Seven main pathogens were isolated from patients with SSIs: Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Pseudomonas aeruginosa, Bacteroides fragilis, Staphylococcus aureus and Enterococcus faecalis. Their growth rates were respectively: S. Aureus (17,3%), E. faecalis (19,5%), P. aeruginosa (10,5%), B. Fragilis (13,4%) E. coli (20,4%), Enterobacter cloacae (9,1%) and K. Pneumoniae (9,8%). In addition, all the SSIs were found to be multimicrobial. Several studies have already revealed that patient characteristics and coexisting morbidities such as obesity, smoking, heart or renal failure, pre-existing localized infections and patients' age (especially if age exceeds 65) seem to be independent prognostic factors for surgical field infections. Additionally, classification of the surgical wound, surgical operation complexity, preoperative hospitalization, prolongation of surgical time and need for transfusions have been proved to differentiate the incidence of SSIs.

In conclusion, surgical site infections are important complications affecting the healthcare services, the cost of hospitalization and the patient himself. Future thorough studies are expected to reveal much more data, regarding predisposing and precautionary patient and hospital characteristics.