Bacterial Aetiological Agents in Infected Orthopaedic Implants - A Cross Sectional Study from Andhra Medical College, Visakhapatnam

Abstract

BACKGROUND Orthopaedic implant site infection is one of the major problems of surgical site infection associated with high morbidity and mortality. As implants are commonly used in orthopaedic procedures and especially when preceded by trauma, orthopaedic procedures are more prone for surgical site infections. We wanted to study the aerobic bacterial aetiology of infected orthopaedic implants. METHODS This was a cross sectional study carried out over a period of one and half years. The study group comprised of 100 patients who had undergone orthopaedic prosthetic implant surgeries and presented with signs and symptoms of infections. The demographic data were recorded, type of surgery, the time of infection during postoperative period and risk factors were noted. Serous / purulent discharge adjacent to infected implants were processed in the laboratory as per the standard protocol. RESULTS Among the 100 samples studied, 79 % were culture positive and 21 % culture sterile. 55.7 % were Gram-positive cocci isolated in pure, 29.1 % were Gramnegative bacilli (GNB) isolated in pure and 15.2 % were a mixture of Gram-positive cocci and Gram-negative bacilli. Staphylococcus aureus 45 (80.4 %) was the predominant isolate followed by Coagulase Negative staphylococci 11(19.6 %). Among the GNB (35), the predominant isolate was Pseudomonas aeruginosa 10 (28.6 %) followed by Klebsiella pneumoniae 8 (22.9 %). Infections occurred during the early post-operative period in 63 % cases. Methicillin resistant Staphylococcus aureus were 53.4 % and 35 % were extended spectrum beta lactamases (ESBL) among Enterobacteriaceae strains. CONCLUSIONS Orthopaedic implant site infections are common during early post-operative period. Methicillin resistant staphylococcus and ESBL strains were high. This study of aerobic bacterial analysis and their current antibiogram of orthopaedic implant infections would greatly help the orthopaedic surgeons in selecting appropriate antibiotics for prophylaxis as well as better management of patients. KEYWORDS Orthopaedic Implants, MRSA, ESBL, Orthopaedic Implant Infections, Biofilm